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Communities today are increasingly vulnerable to fluvial flood events due to increased development on floodplains and climate change impacts. This prompts a need to improve flood risk management strategies. In particular, the forecasting of high flow events via hydrological modelling. In piedmont regions, where sediment supply can be substantial and variable depending on seasonal hydrology and perturbations such as landslides, geomorphic change can influence channel conveyance and thus flood risk. However, the modelling of sediment transport and its impacts on geomorphic change and flood risk is rarely incorporated into flood risk management. This thesis therefore aims to assess an end-to-end modelling framework to predict discharge, sediment transport and morphological change on a braided piedmont river. First, Structure from Motion photogrammetry was used to monitor topographic change along a braided reach of the River Feshie, Scotland, to demonstrate how morphological data can be obtained to assess numerical model performance. The coupled numerical modelling framework used for this analysis included a catchment scale rainfall runoff model (CLiDE), and a reach scale geomorphic change model (CAESAR-LISFLOOD). Model results show that the parameterised rainfall runoff model could appropriately predict base and storm flow discharges. The geomorphic change model could predict the location and magnitudes of change for one to two years of model runtime. However, after multiple floods the morphodynamic model outputs substantially degraded. As lateral erosion rapidly carved out river banks and deposited sediment in the channel, resulting in a topographically smooth reach. Despite the limitations of the reach scale model to maintain braiding over multiple events, this work demonstrates how an end-to-end modelling framework could be implemented to predict geomorphic change and contribute to updating the topography in flood risk mapping and forecasting models. Results also illustrate how repeat topographic surveys can be used as input and verification data for flood risk modelling which incorporates geomorphic change.

The existence of extensive tropical peatlands (i.e. 35,600 ± 2133 km2) was recently confirmed in Amazonia (Lähteenoja et al., 2009 a, b; 2011; Draper et al., 2014). These peatlands appear to be hydrologically intact but are at risk of degradation from anthropogenic impacts and climate change (Roucoux et al., 2017). Furthermore, their discovery represents a new potential source or sink of atmospheric gas budgets and a new component of the CH4 global map that need to be considered in future climate change scenarios. Our main interests are to test the applicability of biomarkers within these settings, to describe CH4 production in Amazonian peatlands and the changes in CH4 efflux through time, as a function of various environmental parameters, as this information is currently lacking for this area. We focused on surface and core samples from Pastaza-Marañón Foreland Basin, northern Peru with samples associated with three vegetation types, providing thus a wide view over these dynamic ecosystems. Vegetation and environment related biomarkers (i.e. n-alkanes; hopanes; GDGTs) and proxies are in agreement with changes depicted in pollen records from Quistococha and San Jorge peatland (Roucoux et al., 2013; Kelly et al., 2017). Thus, they can be used to describe shifts in vegetation or environment in the third peatland, Buena Vista. Furthermore, since present day CH4 are not predictable from a water-table depth point of view as, for example, higher effluxes occur during the dry season in black-water seasonally flooded forest (i.e. Bunea Vista; Teh et al., 2017), several biomarker groups were used to further our understanding of processes that lead to these discrepancies. Thus, short chain and monosaturated fatty acids were employed alongside hopanoids and GDGTs, in order to test and understand how the archaea and bacteria, and more specifically, methanogen and methanotroph communities, responded to changes in the ecohydrology. Furthermore, we provide new temperature and pH palaeorecords for each peatland that were previously lacking for these environments and compared them to present-day instrumental measurements in surface samples. By employing a multi-biomarker approach, we can explore the relationship between environmental parameters via direct and proxy observations of fluctuations in water table depth, changes in vegetation, hydrology and CH4 production potential, gaining a further insight into tropical peatland dynamics and carbon biogeochemical cycles within them. Finally, we encourage higher-resolution biomarker analysis and provide ideas for further research within these peatlands.

The Indian Summer Monsoon (ISM) is an incredibly influential climate system, with many developing nations and over 1 billion people reliant upon favourable monsoon conditions. A suite of organic paleoclimate proxy biomarkers was extracted from sediment core samples retrieved from Qinghai Lake, Yunnan Province, southwest China in order to reconstruct various climate parameters at high-resolution in the region throughout the Holocene. The main aim of the project is to investigate changes caused by the ISM. The upper 145cm of the core were analysed covering an age range of 8877 cal yr BP (calibrated years before present) to -16 cal yr BP (cal yr BP denotes calibrated years before present hereafter). The results indicate several distinct climatic regimes, often separated by abrupt changes in climate. From 8877 cal yr BP to 6895 cal yr BP multiple proxies imply a prolonged period of warm, wet climate and thus an intense ISM system during this period which likely represents the Holocene Climatic Optimum (HCO). Between 6895 cal yr BP and 3240 cal yr BP the climate becomes much more chaotic with several distinct drops and spikes in temperature and changes in precipitation illustrated by the average chain length (ACL) and short to long-chain acid ratio. Overall, during this period the climate was more arid with a weaker monsoon in the Yunnan province than during the HCO, but there was a high degree of variation in monsoon intensity indicated by almost all proxies with rapid changes in precipitation. ACL values sharply spiked to high values similar to the HCO period from 3540 cal yr BP to 3240 cal yr BP. Following on from 3240 cal yr BP to 1130 cal yr BP, a high value ACL plateau along with PWax/PAq, and acid ratio data indicates a warm, wet period and the return of strong monsoon intensity during the Roman Warm Period (RWP). A brief cool, dry period with a weaker monsoon followed by a rapid rise in temperature and monsoon intensity between 1133 cal yr BP-755 cal yr BP likely represents the Medieval Warm Period (MWP). Over the final 755 cal yr BP to -16 cal yr BP period of this record the ACL, carbon preference index (CPI), acid ratio and PWax/PAq record suggests progressively cooler and increasingly intense monsoon conditions during the Little Ice Age (LIA) towards the present in the Qinghai Lake region.

This work discusses the dynamic development of hydraulic fractures, their evolution and the resulting seismicity during fluid injection in a coupled numerical model. The model describes coupling between a solid that can fracture dynamically and a compressible fluid that can push back at the rock and open fractures. With a series of numerical simulations it is shown how the fracture pattern and seismicity change depending on changes in depth, injection rate, Young’s modulus and breaking strength. Simulations indicate that the Young’s modulus has the largest influence on the fracture dynamics and also the related seismicity. Simulations of rocks with a Young’s modulus smaller than 10 GPa show dominant mode I failure and a growth of fracture aperture with a decrease in Young’s modulus. Simulations of rocks with a Young’s modulus higher than 10 GPa show fractures with a constant aperture and fracture growth that is mainly governed by a growth in crack length and an increasing amount of mode II failure. This change in fracture geometry evolution has an effect on the observed seismicity. Rocks with a Young’s modulus of 10 GPa have the smallest moment magnitude while both decrease and increase of Young’s modulus value contribute to a growth of the seismic moment magnitude. The signal is further altered by non-linear change in dip and tensile angle depending on the Young’s modulus value. It is proposed that two distinct failure regimes are observed in the simulations. Below 10 GPa a fracture propagates through growth in aperture, this causes the fracture tip to be under constant extension. For rocks above 10 GPa, the aperture is small and the fracture is under compression. In this case fracture growth is driven by stress intensification at the crack tip, which causes fracture opening to have greater proportion of mode II compared to mode I. To suppliment the observations made from numerical simulations, laboratory experiments with air injection into vertically orientated Hele-Shaw cell were carried out. Strain analysis of the recorded experiments showed stress regimes that are very similar to the ones observed during numerical simulations with soft rocks. In both cases negative strain fields could be observed in front of the fracture tip. This indicates that fracture propagation for soft materials is driven by tensile failure and walls being pushed apart. Further analysis on fracture propagation mechanisms and solid media response were carried out. These results are applicable to the prediction of fracture dynamics and seismicity during fluid injection, especially since we see a transition from one failure regime to another at around 10 GPa, a Young’s modulus that lies in the middle of possible values for natural shale rocks.

Effluents produced from the coal conversion industry, particularly from coal gasification, are complex mixtures, rich in semi-volatile organic compounds (SVOCs). In the case of underground coal gasification (UCG), the production of syngas is accompanied by significant amounts of wastewater and tar, the detailed characterisation of which is required for risk assessment and disposal purposes but also for identification of components of high economic value. This characterisation is challenging as these effluents are unique, both in their physico-chemical nature and their SVOC content. Here, a close-to-exhaustive SVOC characterisation of UCG wastewater was performed, with the development of a novel micro-extraction method, which utilises three physico-chemical effects: ultrasonication, emulsification and salting-out. The delivery of ultrasound in the samples was performed using a novel system that transmits ultrasound into a vessel's contents through its wall, and was named high-intensity vessel-wall sonication (HIVS). The developed ultrasound-assisted surfactant-enhanced salting-out emulsification micro-extraction (UASESOEME) method proved to be successful in the extraction of SVOCs from UCG wastewater, overcoming limitations of previous methods. The HIVS technique was also applied in the development of a fast and precise ultrasound-assisted extraction (UAE) method for coal tar and in the development of an ultrasound-assisted derivatisation (UAD) method for derivatising extracts from both wastewater and coal tar, significantly enhancing their gas chromatographic analysis. Analytical methods for gas chromatography coupled to mass spectrometry (GC-MS) and comprehensive gas chromatography coupled to time-of-flight mass spectrometry (GCxGC-TOFMS) were also developed to analyse the extracts. The above methods were applied in the extraction of SVOCs from three time-series of samples (two from simulated ex-situ UCG experiments and another from an in-situ field-scale UCG trial) and in the extraction of a series of leachates from tar leaching experiments performed with tars of increasing weathering/processing. Analyses yielded comprehensive datasets that were processed using a custom data processing approach and analysed using exploratory and multivariate statistical analysis techniques for sample classification and marker discovery. Time-series analysis indicated several SVOCs as markers, mostly oxygen and nitrogen containing compounds, most of which are not commonly considered in gasification studies; the differences between the two matrices was also highlighted, indicating coal tar as the most representative of the two. Analysis of leachates showed that they can be classified based on their SVOC signature according to the parent tar type; also, tars were shown to continue leaching SVOCs after weathering/processing and that their solubility is dependent on the ionic strength of the leaching medium.

Predicting the geometry and continuity of clastic units within lava-dominated sequences in volcanic margin settings is problematic as they are typically laterally discontinuous, relatively thin and often poorly imaged in the subsurface. Although such sequences are well known, detailed studies of their lithofacies architecture are rare and poorly constrained, which can result in major challenges to hydrocarbon exploration in these settings. As the demand for hydrocarbons increases, exploration is being focussed on more challenging stratigraphic and tectonic settings, such as volcanic margins. Consequently, it is necessary we enhance our understanding of how petroleum systems interact with volcanic-prone sequences, in order to maximise recovery of hydrocarbons. Using a field analogue in conjunction with remote sensing datasets is fundamental to understanding these complicated systems. This study utilises the Hreppar Formation (HF) in SW Iceland as an analogue to understand elements of petroleum systems to reduce the challenges and risk associated with hydrocarbon exploration within volcanic-dominated basins. The HF at Flúðir, comprises basaltic lavas and interbasaltic sedimentary rocks of Plio-Pleistocene age (3.3-0.7Ma) and provides excellent 3D exposure. This study provides a comprehensive evaluation of the geology in this area and its relevance and importance to hydrocarbon exploration. Detailed field mapping and graphic logging have been combined with field panoramas and photogrammetry to characterise the sequence in detail and to identify the lateral (dis)connectivity of the clastic units, the main lithofacies, the different facies architectures, structural elements and drainage pathways within the HF. The detailed field data presented here are generally all below seismic resolution. In an offshore setting, with currently available technology, it is highly unlikely this level of detail can be captured using remote sensing tools alone. The advantage of using a field analogue such as that of the HF is the level of detail which can be captured. This enables the gap in scale, between field-scale and seismic¬/well-scale to be bridged. It allows models to be ground truthed, which reduces uncertainty and risk, essential to hydrocarbon exploration. This research identifies complex interaction between volcanic, glacial and fluvial systems, underpinned by a strong tectonic influence. >60% of the HF is dominated by sub-aerial basaltic lavas and predicting where lithofacies occur in these types of environments is challenging, however, through initial quantitative analysis of volcanic and sedimentary units in the HF, basic prediction in similar settings is possible. The field data collected in the HF can inform every stage of the development of a hydrocarbon field in a volcanic margin, from determining the architecture of a potential reservoir to defining the main structures and potential fluid pathways as well as deciding how to produce the field.

No abstract available.

D.E. and H.P.A. acknowledge support from Yale University and the Yale Analytical and Stable Isotope Center and from Grant 171/16 of the Israel Science Foundation. W.R. and L.J.C. were supported by NWO Grant ALW 822 01 009. The Tanzania Commission for Science and Technology (COSTECH) and the Tanzania Petroleum Development Corporation supported the Tanzania Drilling Project (TDP) which recovered the Tanzanian specimens. Laser-ablation ICPMS work at RHUL was partly funded by a 2014 Natural Environment Research Council (NERC) Capital Equipment Grant (Ref. CC073). The Research Foundation Flanders is acknowledged for financial support (to P.S.). M.Z. acknowledges support from the Netherlands Earth System Science Center and Horizon 2020 Grant MSCA-IF-2014 655073. Past greenhouse periods with elevated atmospheric CO2 were characterized by globally warmer sea-surface temperatures (SST). However, the extent to which the high latitudes warmed to a greater degree than the tropics (polar amplification) remains poorly constrained, in particular because there are only a few temperature reconstructions from the tropics. Consequently, the relationship between increased CO2, the degree of tropical warming, and the resulting latitudinal SST gradient is not well known. Here, we present coupled clumped isotope (Δ47)-Mg/Ca measurements of foraminifera from a set of globally distributed sites in the tropics and midlatitudes. Δ47 is insensitive to seawater chemistry and therefore provides a robust constraint on tropical SST. Crucially, coupling these data with Mg/Ca measurements allows the precise reconstruction of Mg/Casw throughout the Eocene, enabling the reinterpretation of all planktonic foraminifera Mg/Ca data. The combined dataset constrains the range in Eocene tropical SST to 30–36 °C (from sites in all basins). We compare these accurate tropical SST to deep-ocean temperatures, serving as a minimum constraint on high-latitude SST. This results in a robust conservative reconstruction of the early Eocene latitudinal gradient, which was reduced by at least 32 ± 10% compared with present day, demonstrating greater polar amplification than captured by most climate models. Postprint

Evidence exists for great volumes of water on early Mars. Liquid surface water requires a much denser atmosphere than modern Mars possesses, probably predominantly composed of CO2. Such significant volumes of CO2 and water in the presence of basalt should have produced vast concentrations of carbonate minerals, yet little carbonate has been discovered thus far. These ‘missing carbonates’ comprise the Mars carbonate conundrum. This thesis provides insight to the conundrum via three distinct lines of investigation. Firstly, using engineering to expand our ability to locate carbonates on the Martian surface. A Micro-Optic UltraSonic Exfoliator (MOUSE) was designed and built that was tested on a range of rock types and wavelengths. Using ultrasonics demonstrates many advantages over the rock abrasion tool currently used on Mars rovers, including a smoother grind finish and a lower rate of tool tip wear when using tungsten carbide. Secondly, carbonates present in our only samples of the Martian regolith on Earth, meteorites, were studied. Carbonates found in Martian meteorites can provide a record of aqueous and atmospheric conditions extending back over 4.5 billion years. This thesis observes carbonates in two meteorites, ALH 84001 and Lafayette, representing early Mars and more recent Mars respectively, and finds evidence for two types of carbonate replacing glass in ALH 84001. The aqueously altered minerals of these two meteorites were compared with those found in the terrestrial ophiolites of Leka (Norway), and Semail (United Arab Emirates), and these ophiolites were assessed for suitability as Mars analogues. Chemically zoned carbonate rosettes similar to those in ALH 84001 are found in the Semail ophiolite samples. No carbonates were identified in Leka samples, but extensive serpentinisation was present. Finally, this thesis sought to replicate alteration processes and products that are recorded by Martian meteorites within a Mars analogue laboratory environment. The effects of differing initial atmospheric and mineral compositions were explored, specifically the comparison of CO2 and SO2 with basalt versus CO2 with olivine. These three interdisciplinary strands of investigation provide some novel tools, ideas and evidence to help solve the Mars carbonate conundrum.

The morphologies of pyroclasts in basaltic and silicic ash deposits and tuffs in volcanic sequences have been used by previous authors to determine eruption processes in proximal settings commonly from modern eruption deposits. However, little research has been conducted on the finest tephra fraction, ash and fine-ash, in distal settings. The study of tephra in distal localities, >100 km from source, may provide important information regarding the dispersal of ash from highly explosive large-scale eruptions, for which proximal deposits are no longer present. The grain morphologies (blocky, bubble-wall, irregular and rod-like) and vesicularity of pyroclasts can be used to determine eruption processes and distinguish between ‘dry’ magmatic and ‘wet’ hydrovolcanic eruption-styles. This research is mainly concerned with the characteristics of pyroclasts in basaltic ash/tuff likely formed by highly explosive eruptions, and whether the explosivity of these eruptions was due to magma-water interactions and hydrovolcanism. This study includes a re-examination, and detailed petrographical analysis, of tuffs in the Early Eocene Balder Formation, North Sea Basin, and Harwich Formation, SE England, where the source of tephra produced by explosive volcanism and the extent of basaltic ash dispersal have been contested. Previously, these basaltic tuffs have been attributed to large-scale hydrovolcanic eruptions that occurred during initial sea-floor spreading in the NE Atlantic during the separation of Greenland from NW Europe. These tuffs are compared and contrasted with the basaltic Saksunarvatn Ash (10.3 ka BP) of Grímsvötn Volcano, Iceland, and various non-lava lithologies of the Miocene Columbia River Flood Basalt Province, USA. The primary characteristics of pyroclasts may be modified by abrasion and alteration, particularly during additional transport and deposition. Therefore, the features created directly by the fragmentation and quenching of pyroclasts need to be distinguished from features created by the reworking of this material in the sedimentary environment. It is therefore essential to determine the characteristics of pyroclastic and volcaniclastic materials, which can be achieved by comparing data on the overall deposit characteristics, grain-types, grain-size distribution and grain-morphologies. For example, pyroclastic deposits of ash-grade are dominated by up to 100% igneous/volcanic grain-types, particularly glassy pyroclasts; in thin-section the pyroclasts have smooth-edges and may have undergone limited alteration in modern deposits. In contrast, volcaniclastic deposits may contain a wide range of clast-types, including a greater number of non-volcanic grains, and sedimentary structures such as cross-stratification; in thin-section, reworked pyroclasts of ash-grade (volcaniclastic grains) often have jagged-edges, and varying levels of alteration. This study builds upon the observations and naming schemes of previous authors and proposes a scheme applicable to distal deposits of ash and fine-ash, of both basaltic and silicic composition, including highly altered material.

The search for life on Mars continues apace, however the significant cost in time and resources involved in each robotic mission, whether orbiter, lander, or even rover, necessitates the use of terrestrial Martian analogue sites. Few regions on Earth are able to accurately simulate the conditions on Mars, yet locations such as the Atacama Desert of northern Chile and McMurdo Dry Valleys of Antarctica offer invaluable opportunities to test experiments and equipment prior to missions, as well as to advance understanding of the survival of life at the limits of habitability. This study presents an exciting new analogue region in the Chilean Altiplano, offering a unique balance of Mars-like conditions not experienced in other terrestrial Mars analogues. Utilising this novel Martian analogue, the present study examines how signs of ancient life may be preserved in the soils and sediments of Mars, investigating the extent of protection afforded by soil coverage against the inhospitable conditions of the surface. In addition, this study presents a new approach to understanding the bacterial community which does survive in such a hostile environment on Earth, illustrating the effect of soil coverage on the survival of bacteria in a Mars-like environment. The rapidly-changing nature of hostile soil conditions with increasing soil depth was found have stark implications for the likelihood of success of upcoming missions such as the ESA 2020 ExoMars Rover, as well as advancing the understanding of life in extreme – and under reported – environments on Earth.

The uniquely low temperature sensitivity of the apatite (U-Th)/He system makes it an invaluable tool for studying shallow crustal processes which are not accessible through other techniques. Major advancements in both the theoretical and practical aspects of the technique have taken place over the past decade or so, however the routine application of the process is often held back by the perceived problem of single grain age ‘over dispersion’, particularly when applied to old, slowly cooled geological settings. There persists a misconception that age dispersion is indicative of a problem with the apatite (U-Th)/He system. A significant component of single grain age dispersion is inherent to the natural system, and therefore beneficial to reconstructing robust thermal histories. Variations in crystal grain size, accumulated amounts of radiation damage and changes to the helium concentration gradient within a grain due to fragmentation all contribute positively to age dispersion. Other, imposed factors such as crystal zoning and 4He implantation (which are undesirable) can also contribute to dispersion, however in the vast majority of cases their effects are negligible and only contribute noise to the inherent natural dispersion signal. The Ballachulish Igneous complex (BIC) in western Scotland has been used as a case study to demonstrate the range of age dispersion which should be expected when analysing large numbers of single grain aliquots per sample. Where 20+ grains are analysed, total dispersion will often be well in excess of 100% for old, slowly cooled samples, indeed dispersion in excess of 200% is possible. Such dispersion will often be as a consequence of outlying or apparently anomalous ages, however such ages should not be discounted unless there is sound analytical justification to do so. Apparent anomalous ages will often be ‘swallowed up’ by the data if more, or even different sized/shaped grains are analysed. Due to the competing effects of the three main causes of inherent natural dispersion, it should not be expected that large, well dispersed data sets will show any significant correlation between single grain age and either grain size or eU concentration. However a lack of correlation does not indicate poor quality data. Brown, Beucher and co-workers (Brown et al., 2013; Beucher et al., 2013) proposed a new modelling approach to account for the common occurrence of broken crystals in apatite separates, demonstrating that the additional inherent natural age dispersion arising from analysing fragments can be exploited when reconstructing thermal histories. A new inversion technique – HelFRAG was developed, based on a finite length cylinder diffusion model. The model is computationally demanding, therefore sampling based inversion methods requiring many forward model simulations become less practical. Consequently, an approximation of the finite cylinder diffusion model has been incorporated into the modelling software QTQt (Gallagher, 2012). Here, the approximation – QFrag has been demonstrated capable of returning comparable results to the full HelFRAG inversion technique when given the same synthetic data set, enabling the more routine application of the fragment model. Both QFrag and HelFRAG modelling techniques have been used to model the new BIC AHe dataset. The purpose is twofold: to demonstrate the importance of the fragment model with a real dataset, and to provide a new thermochronological interpretation for the BIC. When using this dataset, modelling samples individually shows only subtle differences (if any) between modelling broken grains correctly as fragments, verses modelling them incorrectly as whole grains. A far greater difference in the model output is seen when only modelling 3-6 grains compared to 20+, irrespective of whether fragments are treated correctly or not. When multiple samples are modelled together in a vertical profile, the fragment effect becomes much more important. A very different thermal history interpretation arises when any broken grains are modelled incorrectly as whole grains compared to when modelled as fragments. The new thermal history interpretation for the BIC involves a four stage cooling history from the time of intrusion (c. 424Ma). Very rapid cooling and uplift occurred immediately after intrusion over the first c. 20Myrs of the history (Phase 1). This brought the complex from c. 10km depths to within 2-3km of the surface. There followed much slower continued uplift between c. 404Ma and c. 300Ma, resulting in up to 1km of denudation (Phase 2). Over the next c. 150Myrs only a small volume of uplift occurred, however the geothermal gradient increased towards the end of this time period, suggesting crustal thinning (Phase 3). A final, rapid period of cooling and uplift occurred at c. 140Ma, bringing the top of the profile very near to the surface (Phase 4). No significant denudation has occurred since the end of this rapid uplift phase (10’s to 100’s of meters at most). The first two phases of cooling are interpreted as the final stages of the Caledonian orogeny, with erosion driven isostatic uplift causing continued denudation after the cessation of collisional tectonics. The end of phase three and the subsequent rapid uplift (Phase 4) are interpreted as the beginnings of crustal thinning and continental rifting which ultimately led to the opening of the North Atlantic Ocean.

Measurements of volatile abundances at the martian surface (e.g. H2O, Cl, CO2, CH4) are a priority for the latest generation of martian rovers (Curiosity and ExoMars) due to the astrobiological importance of these compounds. Mars is a prime candidate to find water as recent Mars orbiter and lander missions have revealed evidence for the presence of liquid water early in Mars’s history (e.g., Nochian ~3.9 to 4.5 Ga). Geomorphological features (e.g., fluvial valleys), water rich sediments and minerals (e.g. clays) and evaporates (e.g. gypsum) all indicate hydrological activity has occurred on Mars. However, rovers are limited to surface exploration and therefore are unable to provide insight to the volatile content of the martian interior. Martian meteorites identified on Earth consist largely of volcanic basaltic material. Therefore, the volatile contents of primary igneous minerals within these martian basalts can indicate the volatile content of the source regions at depth in the martian interior. The discovery of Northwest Africa (NWA) 7034 (and pairings) and NWA 8159 has expanded the diversity of the martian meteorites from the common Shergottite, Nakhlite, Chassignite (SNC) types observed. NWA 7034 is a polymict basaltic breccia, whereas NWA 8159 is an augite basalt. This study investigates the apatite volatile content of these two unique martian meteorites. The apatite volatile content in NWA 8159 relates to the volatile abundances of the parental melt, hence providing insight into a previously unstudied martian volcanic province. This study showed these apatites are F-rich, indicating an unusually F-rich parental melt for martian meteorites, which typically have Cl-rich apatite compositions. Results from this study confirm the presence of more Mars typical Cl-rich apatites within NWA 7034 and reveal a significant OH component within individual apatite grains. The volatile content of NWA 7034 is in fact uncharacteristically uniform for a polymict breccia (i.e., no groupings of apatite can be seen in terms of their volatile abundances (Cl: F: OH)), indicating post-crystallisation processes- possibly a thermal event have overprinted the original Cl, F and OH contents of these apatite grains. Three distinct groupings of apatites can be noted on the basis of hydrogen isotope composition, water content and texture of NWA 7034 apatite. This implies that there are at least two different apatite histories that have been recorded. Group 1 is characterised by high δD values paired with low water contents, and inferred to be the result of devolatilisation during shock and/or thermal heating. Group 2 consists of intermediate δD values and high water contents, which could be controlled by hydrothermal alteration. Group 3 is characterised by low δD values and high water contents, probably caused by terrestrial contamination, but possibly representative of a martian mantle signature.

This study investigates the seismic history of the Rocky Ledge, Old Lumber Mill and Arkwright Flat faults in the Hat Creek Graben, north east California, in order to understand the interaction of faults in this tectonically active and geologically unique area. Probabilistic seismic hazard analysis outputs are used to inform building codes in areas of tectonic activity to minimise the hazard presented by seismic shaking. Quantitative data can be used to increase the accuracy of these models, reducing the hazard. Using the well-established method of surface exposure dating of normal fault feature using cosmogenic Helium 3, a seismic history of the graben is established. Groups of calculated exposure ages at 51ka, 32ka and 12ka give a deduced possible recurrence interval of 20ka. The associated hazard curve gives a peak ground acceleration of 0.7g for a 20ka recurrence interval. The calculated exposure ages also confirm the accuracy of previously calculated 40Ar/39Ar ages for the Rocky Ledge basalt. Exposure dating of the flow top surface confirms minimal erosion since emplacement, reinforcing the accuracy of the exposure ages calculated. The study shows the importance of geomorphological tools in seismic investigations, as historical records and geophysical evidence do not often span recurrence interval time scales.

Magmatic plumbing systems of monogenetic volcanic fields comprise an interconnected network of sills, dykes and inclined sheets; however, the morphology, distribution and emplacement mechanisms of these shallow plumbing systems are often overlooked due to the lack of observable field data. Using seismic data provides an opportunity to understand these systems and integrate seismic-scale features with macro-scale observations from the field. Using a seismic dataset from the Faroe-Shetland Basin, NW Scotland, the Ben Nevis Monogenetic Volcanic Field (BNVF), this research provides an insight into how monogenetic volcanic fields are fed, and how the distribution of edifices can be primarily influenced by the structure of the substrate. By comparing the seismic data with field observations from three separate field studies, this research focuses in on the shallow, ductile zone (

The overarching science question being addressed by this research project was the geological history of the nakhlite group of Martian meteorites as representative of a young Amazonian Martian crust. This included the magmatic processes and mechanism of emplacement at the origin of the meteorites but also the nature of a young Amazonian Martian aquifer that circulated throughout the nakhlites bedrock from its chemistry, origin and longevity. Answering these questions are fundamental to understand the physical and chemical properties and chronological evolution of Mars sub-surface environment over the last billion year with implication for astrobiology and current and future Mars exploration. For this project, a large set of nakhlite meteorites (probably the most comprehensible) have been assembled. It included NWA 5790, NWA 817, NWA 998, MIL 03346, Y 000593/000749, Lafayette and Nakhla. The mineralogy and mineral texture and chemistry of each meteorite have been fully characterized at the �m- and nm-scale using Electron Microscopy techniques (SEM and TEM) and Raman Spectroscopy at the University of Glasgow and Mass Spectroscopy (LA ICP-MS) at the University of Durham. The nakhlites are differentiated basaltic rocks formed by accumulation of augite in a sub-surface environment. The chemical composition of both cumulus augites (the liquidus phase) and their multiphase and glass inclusions representing trapped magma during augite growth indicate that the parent magmas at the origin of the meteorites were not primitive but residua of progenitors that experienced cryptic fractional crystallization processes in the deep basaltic plumbing system. The nakhlites have similar mineralogy but each meteorite has mineral phases with distinct properties which indicates that the rocks experienced each their own crystallization history. The nakhlites probably crystallized within separate igneous bodies/batches. Compositional variability of the nakhlites' parent magmas cannot be explained by a differentiation of a single pulse of magma that solidified through continuous fractional crystallization of augite and olivine alone in a shallow magma chamber. Aqueous alteration of the nakhlites is limited but the presence of small quanti- ties of clay minerals from the smectite family with carbonate, sulphate, halite and Fe-oxide demonstrate the existence of briny crustal water in the young Martian basaltic crust at least at the site sampled by the nakhlites. Variations in mineral assemblages provide evidences for contrasting conditions in the aqueous environments ranging from neutral-to-acidic (with a deposition of sulfate and halite) to near neutral-to-alkaline (with a precipitation of carbonate) apparently associated with a temporal evolution of the brines' property. The texture and chemistry of the secondary mineral assemblages are consistent with a deposition from discrete aqueous events fading away over time.

Nature has a range of distinct mechanisms that cause initially heterogeneous systems to break their symmetry and form patterns. The study of pattern formation and the behaviour of non-linear systems have interested scientists across many disciplines from physics, chemistry, biology, and economics to geosciences. In study, a new mechano-chemical process that leads to the formation of complex periodic wave- or stripe-like zebra patterns in rocks will be presented. The genesis of periodically banded dolostones, which host lead-zinc mineralization, has been studied for several years, because an evolutionary relationship between the banded dolomites and mineralized areas is highly likely. To date, a complete generic model has not been formulated for the formation of these zebra rocks and there is an ongoing debate on the exact processes leading to the genesis of the pattern. In the first part of this work, new analytical findings obtained from zebra dolomites from Peru and Germany will be presented. The zebra dolomites from Germany have never been described before and represent the first known zebra dolomite deposit in Germany. Based on the analytical finding, a numerical and an analytical model were developed in the second part of this thesis. The combination of the numerical and the analytical model yields a new approach to the zebra pattern formation based on one of nature’s fundamental processes for wave-like pattern formation in geological systems. This approach also includes a new inversion routine based on the spacing of the respective pattern.

This study focuses on the Navan Deposit, County Meath, Ireland – a carbonate-hosted Zn-Pb sulphide deposit originally comprising 110Mt @ 8% Zn and 2% Pb, prior to depletion by mining. Navan belongs to the “Irish-type” deposit group – Zn-Pb deposits hosted in the Irish Ore Field that have characteristics of both MVT and SEDEX-style deposits, though cannot be easily be categorised as either. The Irish-types formed from mixing of two fluids – a metalliferous hydrothermal fluid, and a bacteriogenic-sulphide enriched brine. The hydrothermal fluid from Irish-types in the southern Irish Midlands yield a respective hydrothermal fluid homogenisation temperature and salinity range of 170-280oC and 12-18 wt.% NaCl. The Navan hydrothermal fluid was notably lower temperature at 100-140oC and had a salinity of 5-10 wt.% NaCl. Mixing of this moderate temperature fluid with a high salinity bacteriogenic-sulphur enriched brine (70-100oC, 20-25 wt.% NaCl) allowed high-grade Zn-Pb ore to precipitate along a shallow, extending sea basin at approximately 345 Ma (Lower Carboniferous). Navan ore has an average Zn/Pb ratio of 4, though low-grade, low Zn/Pb below 3 is observed in the hangingwall of the Randalstown Fault 200 metres west of the mine site – an end-Variscan reverse fault of at least several hundred metres throw and one kilometre dextral displacement. Low Zn/Pb has been previously noted in Navan and other Irish-type deposits as an indication of a nearby “feeder zone” – early-forming normal faults that allowed hydrothermal fluid upwelling. Hydrothermal fluids then mixed with downwelling bacteriogenic sulphide-enriched brines on, or close to the seafloor to produce high-grade Zn-Pb sulphide ore. Low Zn/Pb in western Navan, therefore, is of particular interest and may point to a new, unidentified feeder. In addition, Cpy- Qtz(-barite) veining has been identified in drillcore for the first time in the Navan area approximately 850 metres west of the Randalstown Fault, coinciding with the low Zn/Pb area. Notable chalcopyrite has been identified close to feeder-zone faults in other Irish-type deposits, though is absent at Navan – until this discovery. Mineralised samples were selected along four drillhole transects – The “A1 Transect” was selected trending southeast along the hangingwall of the Randalstown Fault, while the “A2 Transect” trends southeast along the Randalstown Fault footwall. The “B and C Transects” trend perpendicular and parallel to the Main Orebody, respectively. Sulphides from the Main Orebody and western Navan share a similar paragenesis, suggesting that both may have derived from the same hydrothermal fluid event. Sulphur isotope analysis constrains a δ34S range of -1.5 to 12.5‰ for Zn-Pb sulphides west of the Randalstown Fault. This range coincides with previous studies that have constrained the δ34S range for the hydrothermal fluid (-4 to 16‰) that supplied Zn-Pb to the Navan Main Orebody and is interpreted to represent hydrothermal fluid that migrated westward during early normal faulting. Fluid inclusion analyses constrain a mineralisation temperature and salinity range of 87-136.5oC, and 6.8-22.7 wt.% NaCl, respectively. This is broadly coincident with the hydrothermal fluid temperature and salinity range. Higher fluid salinity is interpreted to reflect mixing with limited downwelling seawater and/or in-situ pore water. Cpy-Qtz(-barite) veining in western Navan is hosted in a 10.5 metre thick stratal dolomite and formed from a separate mineralising fluid to the Navan Deposit. δ34S analysis of three chalcopyrites yield a range of 0.8-3.3‰, results consistent with a hydrothermal fluid origin. Fluid inclusion analysis of two-phase quartz-hosted inclusions yield a temperature range of 191-223oC, while monophase inclusions constrained a salinity range of 10.2-22.8 wt.% NaCl. The assemblage is both distinct from Navan and closer to higher temperature systems in the southern Irish Midlands – an observation supported by a mineralisation temperature range that is closer to the southern Irish-type deposit systems. The mineralising fluids were both higher temperature and more saline than the Navan hydrothermal fluid, potentially pointing to the feeder zone of a new, unidentified system.

Lava-water-sediment interaction encompasses the processes and products created as lava is emplaced over, or into sediment (and/or water). The lithologies preserved at the lava-sediment interface include pillow lavas, hyaloclastite and peperite, which are well documented within the literature. However, little work captures the full scope of the interaction between sub-aerially emplaced, invasive lava and (clastic) sediment (+/-water). Furthermore, the scales and geometries of interaction at the lava-water-sediment interface are yet to be fully understood. This research uses four field localities from a variety of environmental and tectonic settings to assess the remarkably variable, complex and intricate fragmental textures and geometries preserved at the lava-sediment interface, many of which are documented for the first time. The processes and lava/sediment properties that influence interaction are then interpreted. This research identifies a continuum of lava-water-sediment interaction, from minimal and passive interactions, to dynamic and complex interactions, predominantly between basalt lavas and siliciclastic and volcaniclastic sediments. The contiuum recognises that the variability of sedimentary properties (e.g. saturation, grain size, cohesion, compaction), rather than lava properties (e.g. effusion rates/flux, composition, temperature, viscosity, shear strength etc.), is the dominant influence on interaction products. The variability of sedimentary properties can occur on the micro- to macro- scale, producing a range of scale-invariant lava-sediment products. When sediment is partially consolidated and compacted, with relatively little to no water content, loading and passive interaction, including the formation of passive peperite, occurs. Sediment that is very fine grained, compacted, semi-saturated and only slightly consolidated, is typically more cohesive and produces coherent sedimentary inclusions. Sediment inclusions within lava and peperite domains are abundant, and interpreted as the product of lava invading and entraining fragments of more cohesive, consolidated sediment. When sediment is saturated (with pore water), unconsolidated, and uncompacted, dynamic peperite forms and sediment fluidisation occurs. Sediment fluidisation is also the main product at the interface between pillow lavas and sediment. Measurement analysis of pillow-sediment contacts establishes that pillow invasion is scale invariant. An understanding of the lateral variability of the processes and products of lava-water-sediment interaction is developed, along with the concept of individual sedimentary ‘barrier’ layers that may impede lava-invasion, and influence the geometries of the system. The geometries of lava-water-sediment domains, particularly where dynamic interaction occurs, may be further influenced by palaeoenvironment (e.g. fluvial drainage systems may focus aggressive interaction and peperite formation in channels). The products and processes of lava-water-sediment interaction, and the geometries of the lava-sedimentary systems, are presented in a series of models, all of which highlight the variable sediment properties at the time of lava invasion. The results of this research are directly applicable to the petroleum industry in aiding exploration within volcanic-rifted margins. Application of these findings is of particular importance during the development of regional and basin-scale depositional environment models. The field data is applied to wireline and borehole image log interpretations, which provides greater understanding of how potential reservoir units may be disrupted by lavas, both physically and by “compartmentalization” of the reservoir. Together, these results demonstrate how lavas have the potential to considerably fragment on interaction with sediment and/or water, informing our understanding of the interplay of volcanic and sedimentary systems.

Topography is often thought as exclusively linked to mountain ranges formed by plates collision. It is now, however, known that apart from compression, uplift and denudation of rocks may be triggered by rifting, like it happens at elevated passive margins, and away from plate boundaries by both intra-plate stress causing reactivation of older structures, and by epeirogenic movements driven by mantle dynamics and initiating long-wavelength uplift. In the Cenozoic, central west Britain and other parts of the North Atlantic margins experienced multiple episodes of rock uplift and denudation that have been variable both at spatial and temporal scales. The origin of topography in central west Britain is enigmatic, and because of its location, it may be related to any of the processes mentioned above. In this study, three low temperature thermochronometers, the apatite fission track (AFT) and apatite and zircon (U-Th-Sm)/He (AHe and ZHe, respectively) methods were used to establish the rock cooling history from 200◦C to 30◦C. The samples were collected from the intrusive rocks in the high elevation, high relief regions of the Lake District (NW England), southern Scotland and northern Wales. AFT ages from the region are youngest (55–70 Ma) in the Lake District and increase northwards into southern Scotland and southwards in north Wales (>200 Ma). AHe and ZHe ages show no systematic pattern; the former range from 50 to 80 Ma and the latter tend to record the post-emplacement cooling of the intrusions (200–400 Ma). The complex, multi-thermochronometric inverse modelling suggests a ubiquitous, rapid Late Cretaceous/early Palaeogene cooling event that is particularly marked in Lake District and Criffell. The timing and rate of cooling in southern Scotland and in northern Wales is poorly resolved as the amount of cooling was less than 60◦C. The Lake District plutons were at >110◦C prior to the early Palaeogene; cooling due to a combined effect of high heat flow, from the heat producing granite batholith, and the blanketing effect of the overlying low conductivity Late Mesozoic limestones and mudstones. Modelling of the heat transfer suggests that this combination produced an elevated geothermal gradient within the sedimentary rocks (50–70◦C/km) that was about two times higher than at the present day. Inverse modelling of the AFT and AHe data taking the crustal structure into consideration suggests that denudation was the highest, 2.0–2.5 km, in the coastal areas of the Lake District and southern Scotland, gradually decreasing to less than 1 km in the northern Southern Uplands and northern Wales. Both the rift-related uplift and the intra-plate compression poorly correlate with the timing, location and spatial distribution of the early Palaeogene denudation. The pattern of early Palaeogene denudation correlates with the thickness of magmatic underplating, if the changes of mean topography, Late Cretaceous water depth and eroded rock density are taken into consideration. However, the uplift due to underplating alone cannot fully justify the total early Palaeogene denudation. The amount that is not ex- plained by underplating is, however, roughly spatially constant across the study area and can be referred to the transient thermal uplift induced by the mantle plume arrival. No other mechanisms are required to explain the observed pattern of denudation. The onset of denudation across the region is not uniform. Denudation started at 70–75 Ma in the central part of the Lake District whereas the coastal areas the rapid erosion appears to have initiated later (65–60 Ma). This is ~10 Ma earlier than the first vol- canic manifestation of the proto-Iceland plume and favours the hypothesis of the short period of plume incubation below the lithosphere before the volcanism. In most of the localities, the rocks had cooled to temperatures lower than 30◦C by the end of the Palaeogene, suggesting that the total Neogene denudation was, at a maximum, several hundreds of metres. Rapid cooling in the last 3 million years is resolved in some places in southern Scotland, where it could be explained by glacial erosion and post-glacial isostatic uplift.

Scottish sandstone buildings are now suffering the long-term effects of salt-crystallisation damage, owing in part to the repeated deposition of de-icing salts during winter months. The use of de-icing salts is necessary in order to maintain safe road and pavement conditions during cold weather, but their use comes at a price. Sodium chloride (NaCl), which is used as the primary de-icing salt throughout the country, is a salt known to be damaging to sandstone masonry. However, there remains a range of alternative, commercially available de-icing salts. It is unknown however, what effect these salts have on porous building materials, such as sandstone. In order to protect our built heritage against salt-induced decay, it is vital to understand the effects of these different salts on the range of sandstone types that we see within the historic buildings of Scotland. Eleven common types of sandstone were characterised using a suite of methods in order to understand their mineralogy, pore structure and their response to moisture movement, which are vital properties that govern a stone’s response to weathering and decay. Sandstones were then placed through a range of durability tests designed to measure their resistance to various weathering processes. Three salt crystallisation tests were undertaken on the sandstones over a range of 16 to 50 cycles, which tested their durability to NaCl, CaCl2, MgCl2 and a chloride blend salt. Samples were primarily analysed by measuring their dry weight loss after each cycle, visually after each cycle and by other complimentary methods in order to understand their changing response to moisture uptake after salt treatment. Salt crystallisation was identified as the primary mechanism of decay across each salt, with the extent of damage in each sandstone influenced by environmental conditions and pore-grain properties of the stone. Damage recorded in salt crystallisation tests was ultimately caused by the generation of high crystallisation pressures within the confined pore networks of each stone. Stone and test-specific parameters controlled the location and magnitude of damage, with the amount of micro-pores, their spatial distribution, the water absorption coefficient and the drying efficiency of each stone being identified as the most important stone-specific properties influencing salt-induced decay. Strong correlations were found between the dry weight loss of NaCl treated samples and the proportion of pores

The East Asian Monsoon (EAM) is an active component of the global climate system and has a profound social and economic impact in East Asia and its surrounding countries. Its impact on regional hydrological processes may influence society through industrial water supplies, food productivity and energy use. In order to predict future rates of climate change, reliable and accurate reconstructions of regional temperature and rainfall are required from all over the world to test climate models and better predict future climate variability. Hokkaido is a region which has limited palaeo-climate data and is sensitive to climate change. Instrumental data show that the climate in Hokkaido is influenced by the East Asian Monsoon (EAM), however, instrumental data is limited to the past ~150 years. Therefore down-core climate reconstructions, prior to instrumental records, are required to provide a better understanding of the long-term behaviour of the climate drivers (e.g. the EAM, Westerlies, and teleconnections) in this region. The present study develops multi-proxy reconstructions to determine past climatic and hydrologic variability in Japan over the past 1000 years and aid in understanding the effects of the EAM and the Westerlies independently and interactively. A 250-cm long sediment core from Lake Toyoni, Hokkaido was retrieved to investigate terrestrial and aquatic input, lake temperature and hydrological changes over the past 1000-years within Lake Toyoni and its catchment using X-Ray Fluorescence (XRF) data, alkenone palaeothermometry, the molecular and hydrogen isotopic composition of higher plant waxes (δD(HPW)). Here, we conducted the first survey for alkenone biomarkers in eight lakes in the Hokkaido, Japan. We detected the occurrence of alkenones within the sediments of Lake Toyoni. We present the first lacustrine alkenone record from Japan, including genetic analysis of the alkenone producer. C37 alkenone concentrations in surface sediments are 18µg C37 g−1 of dry sediment and the dominant alkenone is C37:4. 18S rDNA analysis revealed the presence of a single alkenone producer in Lake Toyoni and thus a single calibration is used for reconstructing lake temperature based on alkenone unsaturation patterns. Temperature reconstructions over the past 1000 years suggest that lake water temperatures varies between 8 and 19°C which is in line with water temperature changes observed in the modern Lake Toyoni. The alkenone-based temperature reconstruction provides evidence for the variability of the EAM over the past 1000 years. The δD(HPW) suggest that the large fluctuations (∼40‰) represent changes in temperature and source precipitation in this region, which is ultimately controlled by the EAM system and therefore a proxy for the EAM system. In order to complement the biomarker reconstructions, the XRF data strengthen the lake temperature and hydrological reconstructions by providing information on past productivity, which is controlled by the East Asian Summer monsoon (EASM) and wind input into Lake Toyoni, which is controlled by the East Asian Winter Monsoon (EAWM) and the Westerlies. By combining the data generated from XRF, alkenone palaeothermometry and the δD(HPW) reconstructions, we provide valuable information on the EAM and the Westerlies, including; the timing of intensification and weakening, the teleconnections influencing them and the relationship between them. During the Medieval Warm Period (MWP), we find that the EASM dominated and the EAWM was suppressed, whereas, during the Little Ice Age (LIA), the influence of the EAWM dominated with time periods of increased EASM and Westerlies intensification. The El Niño Southern Oscillation (ENSO) significantly influenced the EAM; a strong EASM occurred during El Niño conditions and a strong EAWM occurred during La Niña. The North Atlantic Oscillation, on the other hand, was a key driver of the Westerlies intensification; strengthening of the Westerlies during a positive NAO phase and weakening of the Westerlies during a negative NAO phase. A key finding from this study is that our data support an anti-phase relationship between the EASM and the EAWM (e.g. the intensification of the EASM and weakening of the EAWM and vice versa) and that the EAWM and the Westerlies vary independently from each other, rather than coincide as previously suggested in other studies.

Permeability of a rock is a dynamic property that varies spatially and temporally. Fractures provide the most efficient channels for fluid flow and thus directly contribute to the permeability of the system. Fractures usually form as a result of a combination of tectonic stresses, gravity (i.e. lithostatic pressure) and fluid pressures. High pressure gradients alone can cause fracturing, the process which is termed as hydrofracturing that can determine caprock (seal) stability or reservoir integrity. Fluids also transport mass and heat, and are responsible for the formation of veins by precipitating minerals within open fractures. Veining (healing) thus directly influences the rock’s permeability. Upon deformation these closed factures (veins) can refracture and the cycle starts again. This fracturing-healing-refacturing cycle is a fundamental part in studying the deformation dynamics and permeability evolution of rock systems. This is generally accompanied by fracture network characterization focusing on network topology that determines network connectivity. Fracture characterization allows to acquire quantitative and qualitative data on fractures and forms an important part of reservoir modeling. This thesis highlights the importance of fracture-healing and veins’ mechanical properties on the deformation dynamics. It shows that permeability varies spatially and temporally, and that healed systems (veined rocks) should not be treated as fractured systems (rocks without veins). Field observations also demonstrate the influence of contrasting mechanical properties, in addition to the complexities of vein microstructures that can form in low-porosity and permeability layered sequences. The thesis also presents graph theory as a characterization method to obtain statistical measures on evolving network connectivity. It also proposes what measures a good reservoir should have to exhibit potentially large permeability and robustness against healing. The results presented in the thesis can have applications for hydrocarbon and geothermal reservoir exploration, mining industry, underground waste disposal, CO2 injection or groundwater modeling.

Humans have interacted with their surroundings for over one million years, and researchers have only recently been able to assess the geomorphic impacts indigenous peoples had on their landscapes prior to the onset of European colonialism. The history of human occupation of Australia is noteworthy in that Aboriginal Australians arrived ~50 ka and remained relatively isolated from the rest of the world until the AD 1788 when Europeans established a permanent settlement in Sydney, New South Wales. The southeastern Australian Tablelands landscape, west of Sydney, has seemingly undergone drastic geomorphic change since European arrival. The introduction of European grazing practices reportedly led to the occurrence of deep erosional incisions, gullies, into valley bottoms and hillslopes, releasing sediment, which is subsequently deposited over downstream wetland environments – swampy meadows. This sediment is often called post-settlement alluvium (PSA); however, the age and genesis of PSA in Australia are debated. Questions regarding the geomorphic features and processes in the Tablelands remain unanswered because few studies quantify the timing of gully incision, PSA deposition, or the pre-human rate of landscape change. Erosion rates inferred from concentrations of in situ 10Be measured in fluvial sediment (n = 11) and bedrock outcrops (n = 6) range from 2.9–11.9 mm/kyr and 5.2–13.8 mm/kyr, respectively. The two sample populations are statistically indistinguishable, suggesting no relief has been generated since 600–110 ka. The overall erosion rate in the Tablelands is 7.5 mm/kyr, equal to long-term denudation rates integrated since ~20 Ma. Aboriginal Australians have been present in the Tablelands for at least 30 kyr, ~12–26% of the cosmogenic integration time, yet widespread Aboriginal fire use did not measurably affect landscape erosion until ~5.5 ka, in sync with increased charcoal in the sediment record. Portable optically stimulated luminescence (OSL) reader data from poly-mineral and poly-grain size samples collected from gully wall profiles of PSA and swampy meadow sediment show that swampy meadow environments were buried by PSA and that PSA is alluvium derived from upstream gully erosion. No relationships between bulk OSL and sample grain size or mineralogy exist, and inferences about bulk sediment mineralogy or grain size cannot be determined from portable OSL reader data. Large variability in adjacent PSA sample replicates, however, reveals incomplete sediment bleaching conditions during PSA deposition during floods. Greater bleaching efficiency is inferred from the small variability of bulk OSL data in the uppermost 10s of cm of PSA profiles. Measured concentrations of meteoric 10Be and bulk OSL in two PSA deposits in Birchams Creek show that initial gully incision eroded into weathered sandstone regolith and not swampy meadow environments, as previously believed. Initial gully incision was shallow (

Patagonia has one of the most extensive and well preserved glacial geomorphic records of anywhere else in the world. This study provides empirical constraints of Patagonian Ice Sheet (PIS) configuration and dynamics during the last two glacial cycles and the Holocene at 49°S. In particular a chronology of palaeo-ice surface elevations, thickness changes and ice-thinning rates is developed. Cosmogenic surface exposure dating across eight mountain transects at Hielo Patagonico Sur (HPS) outlet glaciers' Viedma and Chico, and from eastern facing mountain valley glaciers, is utilised to reconstruct PIS ice-surface elevation changes through time. The earliest dated glacier ice thickness marker falls into MIS6 (Marine Isotope Stage). The last glacial cycle is characterised by continuous ice-surface elevation lowering from a maximum at MIS5a to the Antarctic Cold Reversal (ACR). Large scale PIS cover occurred between ca. 40-47 kyrs, in both the HPS outlet glaciers and the eastern mountain valleys. This regional ice-cover considerably pre-dates the global Last Glacial Maximum (gLGM). A gLGM vertical ice surface expression is absent from the study area. A minor re-advance and/or stillstand at ca. 18 kyrs is recorded by the valley glaciers, but is not evident at the HPS outlet glaciers. Glacier Viedma records a prominent ice elevation during the ACR with rapid thinning at the end of the climate perturbation. Ice-surface lowering from the ACR limit continues with acceleration toward the late-Holocene. The PIS palaeo-ice elevation and thinning record presented here is sensitive to internal PIS dynamics, local and global climate forcing acting on different timescales, with glacier response to climate perturbation strongly linked to glacier catchment size and distance from the main source of precipitation at 49°S.

Research within the last decade has revealed that meteorite impacts on our planet have the potential to create transient hydrothermal environments that are conducive to the development of extremophile microbial communities. Impact products also record the hydrologic and environmental history of a terrestrial body’s surface, making them attractive targets in the search for water and exolife on other planets and satellites. The interpretation of geologic and surface processes observed on other terrestrial bodies is based on ground-truths we recognize on Earth. Due to the recycling of crust and an active surface environment, the direct study of hydrothermal activity in craters on our planet is often obscured by pre-impact fluid episodes and non-preservation at ambient surface conditions. As a result, detailed studies focusing on water-rock interactions during the post-impact cooling period are lacking. Many mysteries still surround the development and sustainability of impact-hydrothermal activity, such as the role of target composition and paleofluid reservoirs. This study investigates post-impact hydrothermal activity within the complex, 23km diameter, marginal marine, late Triassic Rochechouart impact structure located in west-central France. Previous studies have noted a pervasive K-metasomatic overprint attributed to post-impact hydrothermal circulation; however, Rochechouart is highly weathered, and the target consists primarily of Variscan quartzofeldspathic igneous and amphibolite facies metamorphic rocks which show evidence for aqueous alteration during pre-impact events. This thesis aims to overcome the complications arising from multiple fluid event overprinting in Rochechouart by documenting secondary alteration throughout all impactites using detailed petrography, scanning electron microscopy, energy dispersive X-ray and Raman analysis combined with carbon, oxygen and sulphur stable isotope techniques to place temperature and fluid constraints on secondary carbonate and sulphide minerals within lithic impactites. Results from this study reveal that the intensity of alkali metasomatism directly correlates with host rock melt content; relatively impermeable melt rocks and melt-bearing breccias show evidence for pervasive K-metasomatism, with late-stage carbonate-sulphide mineralization concentrated in lithic breccias and autochthonous impact fractures. No pre-impact hydrothermal carbonates were detected isotopically. Isotopic data also supports the hypothesis that seawater, and possibly meteoric water, mixed with metamorphic fluids, were the contributing fluid reservoirs fuelling hydrothermal circulation within the structure; this conclusion is further supported by the strongly biological signatures of secondary sulphide minerals and the structure’s marginal marine paleogeography. The sequence of hydrothermal alteration within Rochechouart follows the following scheme; early stage alkali-saturated waters sourced from the quartzofeldspathic, impermeable melt rocks were responsible for the pervasive K-metasomatic overprint in all lithologies; intermediate stage alteration was dominated by chlorite-smectite assemblages with continued K-metasomatism, which decreases in intensity in melt-poor rocks; and relatively cool carbonate-sulphide assemblages dominate lithic impactites and basement fractures where hydrothermal fluid flow is concentrated well into the late stages of cooling. Results also reveal that the porous network of parautochthonous breccias and autochthonous impact fractures within the sub-crater environment of complex craters with a majority-crystalline target may host hydrothermal fluid circulation for relatively long periods of time. These sites may also provide an environment conducive to the development of thermophilic microbial communities.

Identifying how injected CO2 is retained underground is a fundamental challenge for carbon capture and storage. Developing tracers that are cheap and widely applicable will increase confidence that stored CO2 remains in place. This PhD examines the applicability of the isotopic composition of noble gases (He, Ne, Ar, Kr and Xe) that are present as minor natural constituents in CO2, as tracers of the fate of injected CO2. The Cranfield oil field (MS, USA), into which natural CO2 is injected for enhanced oil recovery (EOR), was developed as a site for a parallel study of carbon capture and storage, and is the focus of this research. Samples of gas from the transported CO2, and the injection and production wells were taken 18 and 45 months after the commencement of injection in July 2008. Neon isotope data are consistent with simple binary mixing between the injected and in situ natural gas. This relationship allows the Ne isotope composition of the pre-injection gas in Cranfield to be determined. Coherent correlations between Ne, He and Ar isotopes allow the natural gas end-member composition to be calculated as well. The noble gas isotopic ratios (3He/4He = 0.05 RA, where RA is the atmospheric value of 1.39 x 10-6, 20Ne/22Ne = 9.62, 21Ne/22Ne = 0.0384, 40Ar/36Ar = 836 and 40Ar*/4He = 0.09, where 40Ar* is the sum of the radiogenic and mantle derived 40Ar) of the natural gas in Cranfield are typical of natural gases derived from the continental crust. Helium isotope ratios and the 40Ar*/4He ratio notably correlate with CO2 concentrations, indicating that the noble gas fingerprints of the injected gas are preserved, and may offer utility as a tracer of the CO2. The He and Ar isotope systematics of the four sampled wells that have the lowest CO2 concentrations identify the loss of a significant amount of CO2 from the free gas phase. The amount of loss in each of the four wells can be quantified from the measured 3He/4He and 40Ar*/4He ratios and changes in the CO2/3He values. Losses vary between 22% and 96%, with good agreement between the different methods. It is notable however, that these four wells do not have significant gas production, and do not contribute significantly to the total amount of produced and re-injected gas. So, even though there is a significant loss from these wells, the total amount of CO2 lost is estimated to be only ~0.1% of the total injected gas, equivalent to 10kt gas. Notwithstanding this, the new data indicate that, across the entire field, CO2 is retained as a free phase and stratigraphic trapping is the most important storage mechanism. The fractionation of 40Ar*/4He, CO2/3He and δ13CCO2 in the CO2-poor samples is consistent with dissolution in water. The non-radiogenic noble gases (20Ne, 36Ar, 84Kr, 132Xe) originate from the atmosphere and are present in the gas, water and oil phases in the reservoir to differing degrees. It has been revealed that groundwater degassing, induced by CO2 injection plays an important role in fractionating 20Ne/36Ar, 84Kr/36Ar and 132Xe/36Ar at the early stage of injection, but a large heterogeneity in the degree of degassing has been observed throughout the reservoir. Some wells have shown 100% water degassing, while others are close to 0%. Oil degassing, and therefore the active CO2 – oil contact, became important during the later phase of injection, which is consistent with the fact that more CO2 injection was required to degas the oil than water. Temporal variations in the non-radiogenic noble gas ratios and 3He/4He are indicative of the evolution of the oil displacement efficiency. This fully agrees with the injection – production well data recorded in the field during sampling. This suggests that noble gases can also be used as a reservoir engineering tool to better understand the interaction of CO2, water and oil in the subsurface not only during CO2 storage but also to track EOR operations.

The British-Irish Ice Sheet (BIIS) is predicted to have deglaciated rapidly from ~ 18 ka, in response to rising sea level and temperature, similar forcings experienced by modern polar ice sheets. As the main conduits of ice mass loss, the reaction of ice streams to these forcings is thought to have been central in determining the mode and timing of this deglaciation. However, lack of understanding of ice stream influence on the glaciology and deglaciation of ice sheets limits confidence in ice sheet model predictions. NW Scotland is an area of the last BIIS predicted to have been dominated by ice stream onset conditions. This thesis presents results from a geomorphological and terrestrial cosmogenic nuclide (TCN) analysis study which resulted in the production of a composite ice-sheet thermal regime map and retreat chronology for the last BIIS in this region. Mapping and surface exposure dating suggest that the regional glaciology and landscape evolution was dominated by the presence of ice-stream onset zones during Greenland Stadial-2 (GS-2). Mountain top erratics were uplifted and transported to high elevation during GS-2, before 16.5 ka BP. By inference, mountain summits were covered by ice during maximal ice sheet conditions. The existence of sharp thermo-mechanical contrasts, developed in response to ice streaming, are proposed as the main controls on bedrock erosion and terrestrial sediment deposition. The interpretation of ‘trimlines’ in NW Scotland as englacial thermo-mechanical boundaries, is verified by the identification of ‘rip-offs’, a newly recognised geomorphic feature in the UK, and by quantitative demonstration of the increase in glacial erosion in the vicinity of these boundaries. Geomorphic and TCN data supports a conceptual model of thermal inversion following ice-stream cessation. The first description of ‘till tails’ in the UK provides insight into the glaciological organisation and thermal evolution of the BIIS. A dated (17.6 ka BP) terrestrial glacial limit on the north Sutherland coast indicates early ice retreat from the shelf and provides a minimum ii constraint on ice-stream cessation. This indicates rapid loss of ice extent and volume following shutdown of the Minch palaeo-ice stream. Major ice sheet reorganisation c. 15-16 ka BP is suggested by the correlation of some lateral margin ages with high elevation erratic deposition ages implying significant ice thinning and margin retreat prior to this time. Additionally, thinning of ~300 m is predicted for some areas prior to 14 ka BP.

This work is focused on carbonate-hosted base metal deposits in the Irish midlands with emphasis on the Navan ore deposit, County Meath, Ireland. The Irish ore deposits were created by the mixing of two fluids, a metal-bearing fluid and a sulfur-rich brine. Herein I aim to further the understanding of the creation, movement, and mixing of these two fluids and how they created the giant Zn and Pb deposit at Navan, as well as how post-ore genesis fluids are recorded in the rocks around Navan. The first chapter contains a summary of current knowledge and views of the deposit, local lithologies, structures, and mineralization. The second chapter is original work that examines how metal distribution patterns and 3D meshes of the paleo-surfaces can yield insights into the movement of mineralizing fluid during ore genesis. This work builds on previous work over the many years the mine has been operating. This new work shows the spatial variability in Pb and Zn concentrations and ratios and interprets these values with respect to vertical and horizontal fluid flow. It also builds on the work of others to interrogate the extent to which a major paleo-erosion event and surface has affected the mineralization found above and below this surface. This has significant bearing for the future of exploration in the area. The third chapter is original work that contains new noble gas data from Navan and deposits across Ireland that elucidate the temperature and tectonic setting that drove the metal bearing fluid that made the Irish midlands so well-endowed in base metals. Sulfides from every major carbonate-hosted base metal mine in Ireland were crushed to release noble gases trapped in fluid inclusions, which had retained 3He/4He signatures from the time of mineralization ca. 350 Ma. These 3He/4He ratios indicate a small but clear contribution of mantle-derived 3He, which reveals that mineralization occurred during an extensional event that introduced heat from the mantle. The fourth chapter is original work based on new 40Ar/39Ar geochronological results that constrain the timing of a later fluid flow event caused by the Variscan compression that inverted the local basin. This inversion event created large wrench and reverse faults and has greatly complicated the local lithology and metal extraction. The timing of this inversion event was interrogated by analyzing the 40Ar/39Ar systematics of disturbed feldspars along a large reverse fault. The 293 ± 3 Ma minimum age produced represent the first radiometric age of the Variscan compressional event in central Ireland and confirms the long held assumption that these faults are related to this large scale tectonic event. The fifth and final chapter is a combination of original and recently published work from others. It focuses on a newly discovered area of mineralization several km to the south of Navan. Mineralization, fluid inclusions, and the structural setting of this new area are evaluated and compared to ‘typical’ Navan mineralization. The new area was created by hotter hydrothermal fluid and did not mix with the surface fluid as effectively as the main deposit.

This thesis contains a selection of forty-three research papers [1-43], published by the author that investigate key processes in the formation and stabilization of continental crust. The processes are addressed at a micro-scale and linked to crustal processes at a global scale. Many of the studies included in this thesis take an integrated but novel approach, typically combining disciplines in ways different to "traditional" research on crustal rocks and/or studying mineral groups in ways not typically used to investigate crustal processes. Metamorphic equilibrium in rocks is driven by the thermodynamic forces controlling the stability of mineral assemblages, and is inhibited by kinetic inertia of mineral reactions. It is the balance between these two factors that controls metamorphic reactions. Much existing literature on metamorphic processes is concerned with assessing thermodynamically constrained equilibrium conditions. This thesis includes many studies that emphasize the importance of chemical disequilibrium preserved by individual minerals and the kinetic consequences for metamorphic processes [1,2,3,4]. Deformation and volume diffusion are recognized as key factors in allowing thermodynamic equilibrium to be established between minerals and the significance of many metamorphic changes is re-evaluated. It is within polymetamorphic rocks that the kinetic "problems" associated with metamorphic reactions are most apparent, such that only rocks that have experienced multiple events at similar temperatures reliably retain the evidence [5]. The importance of kinetic controls on equilibrium is emphasized both in their effect on major rock-forming minerals and in ground breaking petrological studies of accessory phases. Solid-state diffusion is a key to allowing chemical and isotopic transport within grains, however, communication between grains is typically controlled by the characteristics of grain boundaries such as the presence, absence or geometry of fluids. As such grain edges are probably the most important, but perhaps the least studied, "phase" present in any rock. Innovative approaches have been used to investigate the characteristics of mineral boundaries [8,9], the extent of isotopic exchange within rocks [6] and the role that highly localized fluid infiltration may have on the metamorphic responses of the crust [7,9]. Many of the studies address key factors controlling metamorphic processes and use a variety of different minerals, such as garnet [1], muscovite [2,3,7], apatite [8,9] and zircon [10,11] to assess crustal behaviour. The use of accessory minerals to directly understand a range of metamorphic processes is a unique aspect to the research. Studies included here describe zircon and apatite textures in-situ within rocks. Zircon was previously thought of as an exceptionally stable unreactive mineral, but in a series of studies is shown to be one of the most reactive and hence informative of silicate minerals capable of recording reaction histories and fluid movements through a wide range of crustal conditions [12,13,14,15,16]. In studies of crustal behaviour, time is a key component and investigations of the fundamental controls on metamorphic processes have been integrated with data from thermochronometers to provide insights into the low temperature cooling history of the crust. Rb-Sr and K-Ar geochronology on biotite and muscovite, lower temperature thermochronometers including apatite fission track, U-Th-He on apatite and zircon, together with cosmogenic isotopes are applied in a range of investigations to assess unroofing histories. The impact of spatial and temporal variability of exhumation rates is linked back to metamorphic and structural processes within the deeper crust [17,18,24]. The variation acts as a trigger to structural collapse [19], causes major diachroneity in metamorphic events [18] and facilitates significant lateral heat transfer that impacts on isograd patterns [22]. Surprising general conclusions are reached suggesting that some thermochronometers can not record erosional unroofing but may reveal the thermal influence of fluid movements [20,21]. Factors such as localized uplift, and fluid and magma movements in the crust, are explored further as effective agents for modifying lateral and vertical geothermal gradients in a range of tectonic settings and point to considerable complexity in the geothermal gradients of orogenic belts [22,23,24,25]. The exotic nature of crustal terranes in the British Caledonides is addressed in a range of collaborative studies, through a variety of isotopic determinations, constraining movements, amalgamation histories and events within crustal blocks [26,27,28]. Such studies are then integrated with petrological and stratigraphic evidence to present models for crustal evolution in the Caledonides [29,31,32] and in addition develop general models for the formation of metamorphic terranes in strike-slip environments [30]. The approach of using detailed characterization of minerals to understand metamorphic rock-forming processes is similarly applied to deciphering magmatic processes in the crust. A wealth of published research on the petrogenesis of igneous rocks focusses on bulk rock geochemical and isotopic approaches to study the origin of the melts and examples of such investigations are included here [35,36,37]. However many of the studies included in this thesis emphasise small-scale chemical disequilibrium, question this approach, and open new avenues to investigate magmatic processes. The evolution of slowly cooling granite magma chambers is studied at a range of different scales using zoned feldspars [37,38,39] and accessory minerals [42,43]. Crustal contamination [40], magma mixing [39,42,43], sub-solvus crystallization [37,38], and late stage permeability [42] are all processes that are investigated through detailed textural and geochemical characterization of magmatic minerals. The importance of inefficient diffusion is again emphasized and the controls on melt permeability during crystallization are highlighted. Such techniques may yield unprecedented details of the magmatic processes that complement traditional whole rock geochemical and isotopic investigations. Small-scale processes that operate in magma chambers are also linked to models of large-scale crustal generation processes, including the formation of the enigmatic Late Proterozoic massif anorthosites [41]. The theme throughout the thesis is integration of geological disciplines that are not commonly combined. Metamorphic processes traditionally linked to thermodynamics are investigated via kinetic controls, such as deformation and fluid access [3,4,13,16]. Denudation histories traditionally linked to surface processes are integrated with metamorphic histories and structural evolution [e.g. 18,19,25]. Magmatic systems traditionally investigated using bulk rock geochemical and isotopic approaches are instead studied using disequilibrium crystallization histories of minerals [e.g. 38,39,42,43].

The Loch Uisg Granite-Gabbro Intrusion, previously known as the Loch Uisg Granophyre and Gabbro, is a 2-component intrusion, which crops out in the south-east of the Island of Mull. It was first described in the Mull Memoir of the BGS (Bailey et al, 1924). It comprises an extensive granitic component and two smaller gabbroic units, intruded into folded basaltic lava country rocks. The latter gabbroic units are slightly different to one another in terms of their field characteristics and their mineral chemistry, but are thought to comprise one gabbroic intrusion. The granite and the gabbro were re-mapped and samples taken for optical and SEM analysis. As a result of this work, a new model for emplacement is proposed based on field relationships of the units and the mineral chemistry. Interaction between the felsic and the mafic components is considered in detail. By detailed examination of the field relationships and the mineral chemistry it is proposed that the granite was intruded first and that the gabbro was intruded soon after. Intruded into the Loch Uisg Granite-Gabbro Intrusion and the surrounding basaltic country rocks are two very different suites of mafic and ultramafic rocks. These are described in this work as the “Loch Uisg Picrite Suite” and the “Miscellaneous Minor Intrusions”. The Loch Uisg Picrite Suite comprises three intrusions: an irregular dyke-like intrusion and two sill-like intrusions of very fresh picrite, rich in magnesian olivine (up to Fo91.5). These figures place the LUPS rocks in the same category as the Baffin Island Picrites, the Horingbaai dykes from Namibia, the Gorgona komatiites, and the M9 dyke of Rum. Due to the highly magnesian nature of these rocks, these intrusions are unusual within the British Palaeogene Igneous Province. The dyke-like body, known as the Gleann Beag Intrusion after its location, displays very pronounced igneous layering. Layering is also present in the sill-like bodies. The mineral chemistry is described in detail and a petrogenetic model is proposed for the origin of these unusual rocks. Because of the unusual nature of these rocks, the igneous history of SE Mull has been re-assessed. It is proposed that ultramafic activity in SE Mull recommenced at a late stage in the overall history of the Palaeogene magmatism. Due to the freshness of the LUPS rocks, it is proposed that the emplacement of the intrusions of this particular suite may represent some of the very last igneous events in Mull. The third suite of mafic rocks is composed of several altered medium to coarse-grained dykes and dyke-like bodies which cross the area, broadly following the regional NW-SE trend where they are found cutting the Loch Uisg Granite-Gabbro Intrusion and the basalt country rocks towards the eastern end of Loch Uisg. Their geographical extent is limited to a small area of approximately 1 km2. They are distinct from the dykes of the Mull Dyke Swarm and display a wide variety of textures, mineralogy and grain size. The field relationships of these dykes are described and optical and SEM analysis provides an insight into the makeup of these rocks. All the members of this dyke suite have been extensively altered by hydrothermal action. It is proposed that they were intruded in a similar way to the Mull Dyke Swarm, from a similar basic to ultrabasic source magma. An explanation is given for the difference in grain size and mineral chemistry between these “Miscellaneous Minor Intrusions” and the dykes of the Mull Dyke Swarm.

Helium isotopes have found wide use in geoscience research, notably as chronometers of surface exposure. This thesis comprises two distinct components around the theme of cosmogenic He determinations. In the first section (Chapter 3) I test whether cosmogenic 3He can be used to determine short exposure times (

Spaceborne Synthetic Aperture Radar (SAR) sensors obtain regular and frequent radar images from which ground motion can be precisely detected using a variety of different techniques. The ability to remotely measure slope displacements over large regions has many uses and advantages, although the limitations of an increasingly common technique, Differential SAR Interferometry (D-InSAR), must be considered to avoid the misinterpretation of results. Areas of low coherence and the geometrical effects of mountainous terrain in SAR imagery are known to hinder the exploitation of D-InSAR results. A further major limitation for landslide studies is the assumption that variable rates of movement over a given distance cannot exceed a threshold value, dependent upon the SAR image pixel spacing, the radar sensor wavelength and satellite revisit frequency. This study evaluates the use of three SAR image modes from TerraSAR-X and ENVISAT satellites for monitoring slow-moving landslides in the densely vegetated Three Gorges region, China. Low coherence and episodically fast movements are shown to exceed the measureable limit for regular D-InSAR analysis even for the highest resolution, 11-day interferograms. Subsequently, sub-pixel offset time-series techniques applied to corner reflectors and natural targets are developed as a robust method of resolving time-variable displacements. Verifiable offsets are generated with the TerraSAR-X imagery and the precise movement history of landslides is obtained over a period of up to four years. The capability to derive two-dimensional movements from sub-pixel offsets is used to infer a rotational failure mechanism for the most active landslide detected, and a greater understanding of the landslide behaviour is achieved through comparisons with likely triggering factors and 2D limit equilibrium slope stability analysis.

Libya has five major Cenozoic volcanic provinces (Garian, Jabal Al Haruj al Aswad, Jabal Al Hasawinah, Jabal as Sawda and Jabal Nuqay) that have a surface area of approximately 66,000 km2. These volcanic provinces are dominated by alkali to mildly alkali basalts. The provinces are aligned NNW-SSE, typically occurring where NE-SW trending structural features intersect the main regional uplift structures. Small volumes of phonolites are associated with the basaltic volcanism at Garian and Jabal Al Hasawinah. Despite their size and relative accessibility the Cenozoic volcanic provinces of Libya have been rarely studied. In the first part of this thesis I report a new study of the petrology, geochemistry (major and trace elements, REE, Sr-Nd isotopes) and geochronology (40Ar/39Ar) of basalts and phonolites from the Garian volcanic province in north Libya. These analyses indicate that the plateau and late basalts are not distinct basalt types produced from melting of different mantle regions at different times as proposed by earlier studies. They are the product of fractional crystallisation of a common parent. There is little indication of crustal contamination. Trace element and REE data support an origin in 2 to 12 % melts of heterogeneous sub-lithosphere mantle. Trace elements and Nd and Sr isotopic composition of the Garian basalts overlap values measured in metasomatised peridotite xenoliths in the GVP. They are compositionally similar to Cenozoic volcanism of northern Libya (e.g. Jabal Al Haruj) and southern Italy (e.g. Etna and Pantelleria; European asthenosphere mantle reservoir), and they lack the influence of enriched mantle present in other North African Cenozoic basalt provinces. Compositional variation in the Garian province phonolitic magmas is dominated by extensive fractional crystallisation (50-83%) of plagioclase and alkali feldspars combined with an unusual style of assimilation (2-45%) of old upper crust typical of Pan-African shield. The new high precision age determinations of the phonolites suggest that they were produced over a very short period at ~8.1 Ma. This contrasts strongly with previous age determinations that were 40-50 Ma. In the second half of the thesis I report new Ar/Ar chronology measurements for extrusive and intrusive rocks all the major Cenozoic volcanic fields in Libya. The major pulse of basaltic volcanism in Garian in the north (from 6 to 2 Ma) overlaps in time in Jabal Al Haruj province in southern Libya. Jabal Al Hasawinah and Jabal as Sawda basalts were erupted significantly earlier (23-10 Ma). Dykes and plugs at all provinces imply basaltic volcanism started in Miocene, followed by periods of erosion. There is no systematic trend of time in Cenozoic basaltic volcanism of Libya. It appears to be related to reactivation of ancient structures during the passive rifting that has been produced in response to interaction of African and European plates since the late Mesozoic.

CM carbonaceous chondrites display a range of alteration (aqueous alteration) from slightly altered (CM2.5) to most altered (CM2.0). They are of particular interest in understanding early solar system evolution because they are made of a mixture of mineral grains that formed at high temperatures in the solar nebula with secondary minerals including phyllosilicates and carbonates whose origin is controversial. Previous studies suggest that these secondary minerals were produced by low temperature water-mediated alteration of anhydrous minerals within the asteroidal parent body of carbonaceous chondrites. Others have suggested that phyllosilicates and other secondary minerals may have formed from a nebula gas or within an earlier-formed asteroid. This study has focused on answering these questions by the study of carbonates. Results from this study are consistent with an origin of all the secondary minerals by parent body aqueous alteration. In addition to aragonite, calcite and dolomite, CM chondrites contain breunnerite and Ca-poor dolomite. This study has found a very complex sequence of mineralisation in CM chondrites, which was: aragonite ≥ (i.e. formed before or at the same time) calcite free of rims > calcite rimmed with tochilinite and/or Fe-sulphide > phyllosilicate pseudomorphs after calcite ≥ calcite replacing Mg-rich olivine > calcite veins > dolomite > calcite replacing dolomite > dolomite veins > breunnerite > Ca-poor dolomite > calcite cement. Aragonite grains record a period relatively early in the aqueous alteration history of the parent body of CM chondrites. This initial parent body water crystallized aragonite with high oxygen isotope values (average δ18O of 39.9 ± 0.57 ‰ and δ17O of 20.4 ± 1.1‰), these values falling as the water obtained oxygen from reaction with anhydrous silicates. Aragonite was probably present in all CM chondrites, but was dissolved or replaced by calcite in some moderately and highly altered CM chondrites as aqueous alteration progressed. Aragonite in less altered CM chondrites crystallized from fluids with higher concentrations of Fe than those from which the aragonite grains in the moderately altered chondrites crystallized, and whether aragonite or calcite formed was determined by the fluid Mg/Ca ratio. The majority of aragonite grains in CM chondrites have a preferred orientation, which is most likely to be the result of compression in the parent body during crystallisation. Calcite free of rims and inclusions is comparable in texture and petrographic appearance to most aragonite grains, but it exhibits more complex CL patterns, which suggests that this calcite precipitated from fluids that were less compositionally stable than those from which aragonite crystallized. Calcite grains rimmed with tochilinite and/or Fe-sulphide are present in all CM chondrites studied, and are more abundant than aragonite and calcite free of rims and inclusions. CL patterns of this calcite are more complex than those of the other carbonate generations. The most complicated CL patterns have been found in grains from less altered CM chondrites, and CL characteristics become simpler towards the highly altered CM chondrites. Rimmed calcite has lower δ18O values (average δ18O of 37.5 ± 0.65‰ and δ17O of 20.9 ± 1.3‰) than aragonite grains, and so probably formed after aragonite. It was partially replaced by phyllosilicates to leave serpentine-tochilinite rimmed pseudomorphs, which in some cases comprise 3.15 vol% of a meteorite. Tochilinite-serpentine pseudomorphs after calcite are present only in moderately altered CM chondrites, whereas Mg-rich serpentine pseudomorphs after calcite occur in the moderately and highly altered CM chondrites, indicating that solutions at later stages in the alteration sequence were richer Mg than Fe, a result of the dissolution of Mg-rich silicates; consequently new minerals rich in Mg were formed. Calcite replacing Mg-rich olivine is found in all the studied CM chondrites, but it is more abundant and coarser grained with increasing degree of alteration. Results of this study suggest that calcite after Mg-rich olivine, and Mg-rich serpentine or serpentine-tochilinite intergrowth with calcite, probably formed at the same time or immediately after each other. Fe, Mg and Si were released from Mg-rich olivine, and were used for the replacement of calcite by Mg-rich serpentine. Calcite veins in CM chondrites formed in late stages of aqueous alteration as a result of dissolution and recrystallisation of earlier formed Ca-carbonate grains. A large calcite vein (millimetres in size) in the Antarctic CM chondrite LON 94101 has average δ18O of 18.4 ± 0.3‰ and δ17O of 9.0 ± 0.5‰, and low concentrations of Fe in comparison with other calcite and aragonite grains. Petrographic observations show that shock post dated the crystallization of rimmed calcite grains and the LON 94101 vein, suggesting this calcite vein was formed by water in the parent body rather than by Antarctic weathering. Dolomite is found mainly in the highly altered CM chondrites. These rocks also contain calcite intergrown with dolomite and inclusions of dolomite within calcite. Dolomite has probably been completely replaced by calcite in the most altered CM chondrites. In common with calcite veins, dolomite veins in highly altered CM chondrites have very low concentrations of Fe and Mn, and more Mg than dolomite grains in the meteorite matrix, and may have been sourced from dissolution of earlier dolomite grains. The Antarctic CM chondrite QUE 93005 contains complex carbonate minerals consisting of bimineralic grains (i.e. dolomite-breunnerite) and polymineralic grains (i.e. breunnerite-(Ca-poor-dolomite)-calcite cement). The presence of breunnerite in this meteorite suggests an evolutionary link between CM and CI chondrites (CI chondrites are more aqueously altered than CM chondrites). Based on the results of this study, CM chondrites were probably derived from the same parent body, but from different regions that vary in ice content, porosity and permeability, and source of heating (26Al with a half-life 717,000 years).

Fault zones are ubiquitous structures throughout the Earth’s crust and as a fault evolves it can significantly influence the rheological and hydrological properties of the crust. Fluid flow through fault zones is typically associated with fault-fluid-rock interactions and these interactions can affect the mineralogy, strength and evolution of a fault zone. In this study, field mapping is combined with petro-physical and stable isotopic analyses of the fault rock to evaluate the fault-fluid-rock interactions that occur within different fault zones, and the effects of these reactions on fault zone and fault population evolution. At Passo Moro in the NW Itilian Alps, there are three sets of joints cross-cutting the granite gneiss and numerous faults have formed by reactivation of pre-existing joints. The distribution of faults at Passo Moro is ultimately controlled by the variability of joint density within the host rock and the pre-existing joint distribution also affects the likelihood of whether a fault will grow into a mature fault zone or not. Where the joint density is high, strain is unable to accumulate to significant levels to enable joint reactivation into faults, whereas where joint density is low, fault zones are isolated and thus there are no structures nearby to facilitate fault linkage. At Passo Moro the fault population has evolved in a similar way as that described by Martel (1990) whereby small faults link to form simple faults which connect to form compound fault zones. The Virgin Fault and Spaghetti Fault would be considered as small fault zones and The Ciao Ciao Fault is equivalent to a compound fault zone. All three fault zones have different fault architectures and the small faults have been affected by different fluid-rock reactions compared to the larger fault. The small faults have experienced fault zone strengthening by K-feldspar precipitation, whereas the large fault has been weakened by muscovite precipitation. The different reactions between the fault zones are primarily controlled by the water-rock ratio which in turn is governed by permeability and the volume of fluid that infiltrates the fault zone. The Virgin Fault is considered as a rock-dominated system (K-feldspar-rich) whereas The Ciao Ciao fault is a fluid-dominated system (muscovite-rich). However, stable isotopes from both fault zones record a low water-rock ratio signifying rock-dominated conditions. Therefore the mineralogy of the fault rock is not solely controlled by the permeability defined water-rock ratio. The fluid dominated conditions promoting muscovitization in the Ciao Ciao Fault were probably enabled by an open fluid system and large volumes of fluid flowing through the fault during its lifetime. Stable isotopes indicate that water-rock ratios got lower with time in the Virgin Fault implying a limited open system, whereas muscovitization and stable water-rock ratios in the Ciao Ciao Fault point towards open system behaviour. In the Ciao Ciao Fault quartz precipitation only occurs in the foliated cataclasite within the fault core. Quartz precipitation is typically associated with closed system behaviour and suggests that the foliated cataclasite periodically ceased to be open to fluids and hence experienced cycles of higher and lower permeability. Stable isotopes show that the Virgin Fault records mineral precipitation from a metamorphic-like fluid, but after fault deactivation, the fault periodically transmitted progressively more meteoric-like fluids via a micro-fracture network. The Ciao Ciao Fault records mineral precipitation from a more meteoric-like fluid compared to the Virgin Fault, and flow through micro-fracture networks is dominated by an essentially meteoric fluid. The Ciao Ciao Fault therefore does not preserve evidence of fluids from its early history. This study indicates that the geochemical reactions that occur within a fault are controlled in part by the evolutionary stage of the fault, the fault rock permeability and the volume of fluids that pass through the fault. These results have been used to propose models for how the hydraulic properties and strength of a fault (population) evolve with time. The models produced from this study help advance our understanding of the processes that occur during the timescale of the seismic cycle, and how a population of faults will evolve in terms of mineralogy, strength and fluid flow. Such information will be of use to those involved in mineralization and mining studies, the storage of nuclear waste in crystalline rock, and earthquake prediction studies.

In the past decades, engineers have started to realize the importance of the interaction between vegetation, biota and water flow, in riverine and marine environments; a discipline that has been named “Eco-Hydraulics”. Scientists have valued this coupled phenomenon for much longer than their engineering colleagues. As early as 1970, marine researchers presented the evidence that colonies of micro-organisms might alter the stability of fine cohesive sediments (Neuman et al., 1970). However traditional models of sediments transport (e.g. Shields, 1936) have been derived using abiotic sediments and did not consider that most wet surfaces would soon be colonized by micro-organisms and their extracellular polymeric substances (EPS), a combination called “biofilm” (Lock, 1993). Scientists during the 1990s, after observing this phenomenon in the field, coined the term “biostabilization”. During this period they showed that colonies of cyanobacteria and diatoms coating fine sand or cohesive sediments can increase their stability by up to 960% compared to abiotic sediments (Grant and Gust, 1987; Dade et al, 1990; Paterson 1997). Only recently have engineers started to take into consideration the effect of such increased cohesion and adhesion due to biogenic forces within the sediment transport model (Righetti and Lucarelli, 2007); yet all of those studies have low applicability because they are linked to specific environmental conditions. Moreover no data are available on the effect of biofilm on larger sediments (e.g. coarse sand and gravel). The present thesis provides experimental data carried out in a flume laboratory pertaining to biostabilization of non-cohesive coarse sand and gravels at a scale representation of a real river system (from 0.2m to 1m). Four sediment substratum (glass spheres of D50 = 1.09mm and 2.00mm; sand of D50 = 1.20mm and gravel of D50 = 2.20mm) were colonized under unidirectional flow by a cyanobacterium (Phormidium sp.) for between 1 and 10 weeks. The increase in erosion threshold for biotic sediment is then investigated using a series of different methods ranging from traditional sediment transport techniques (e.g. Yalin, 1972), to image thresholding and particle image velocimetry (PIV) assessments of flow modification due to biofilm presence. Moreover, tensile strength analysis of ex-situ biofilm/substratum specimens will be presented to understand better the mechanical property of this composite material. Data indicates that: i) biostabilization of sediments in the range of coarse sand and gravel occurs (9%-150% more shear stress required to induce entrainment compared to abiotic sediments) but to a lower extent compared to critical entrainment thresholds for fine sand and cohesive sediments (Paterson, 1997); ii) flume experimentation can be employed to control specific variables affecting biostabilization and could help to unfold the complicated interactions between environmental variables, and the affect of flow on the growth and strength of biofilm colonization over sediments; iii) strong biofilm growth generated a more uniform velocity field, with reduction in shear stress (up to 82% compared with abiotic sediments) and decreases in roughness length of the bed (up to 94% compared to abiotic sediments); iv) Composite biofilm/substratum specimens presented a clear elastic behaviour when tensile tested; v) Conventional models of sediment transport (e.g. Wiberg and Smith, 1987) do not consider the presence of biofilm and will not work in the case of bio-mats smoothing the surface of the bed; hence the need for new models which include the biofilm elasticity and the bio-mat smoothing process. This thesis suggests two theoretical examples where the biofilm action is considered at a grain to grain and bio-mat scale.

Postglacial bedrock river erosion is likely to be a major control on the evolution of deglaciated landscapes. This study provides a quantitative assessment of bedrock channel change in a postglacial, post-orogenic terrain, encompassing the long-term evolution of bedrock channel distribution, geometry and the timing and rate of fluvial incision. In the NW Scottish Highlands, fluvial incision is focused on steep valley headwalls and at knickpoints formed at inherited glacial valley-floor steps (riegels). Holocene average incision rates of 0.4 – 1.3 m/kyr were measured using cosmogenic surface exposure dating (10-Be) at five strath terrace sites. Incision rates of 0.1 m/kyr were quantified from active channel beds and are lower than the Holocene average. This finding is consistent with a paraglacial decline in sediment supply being responsible for a reduction in fluvial incision in detachment-limited channels. Further support for a paraglacial sediment influence on bedrock channels is found in the long-term increase in the proportion of bedrock-exposure, reflecting a decrease in the critical slope threshold for the alluvial to bedrock channel transition. In reaches that have undergone a switch from alluvial to bedrock channel conditions, the onset of fluvial incision into bedrock was found to lag deglaciation by 2 – 4 kyr, suggesting that a substantial reduction in sediment availability occurred within several thousand years of ice retreat. Hydraulic conditions and substrate resistance are also major controls on the distribution and geometry of bedrock channels, and the rate of fluvial incision, in the NW Highlands. The geometry of both bedrock and alluvial channels was found to be strongly hydraulically scaled, with bedrock channels significantly narrower than coarse-grained alluvial channels. Lithology also governs the critical slope for alluvial to bedrock channel-transition; resistant metasedimentary bedrock produces relatively coarse-grained bed material with a high threshold for sediment entrainment, meaning that alluvial channels occur up to comparatively steep channel slopes. Lithological resistance also constrains the process and rate of fluvial incision. A new lithological resistance index, the ratio of joint spacing to intact rock strength, successfully discriminates between abrasion and plucking dominated channels and is non-linearly related to incision rate. The pulse of postglacial incision in bedrock channels has resulted in 2 – 8 m of entrenchment into valley floors since deglaciation. Bedrock channels narrow during entrenchment, achieving a consistent hydraulic geometry when entrenched to between 1 and 2 times the bankfull flow depth. Width adjustment occurs within 8 – 17 kyr of ice retreat, but adjustment of channel slope takes considerably longer and the long profiles of NW Highland rivers remain strongly glacially conditioned. Entrenchment disconnects channels from floodplains and may have contributed to the decline in paraglacial sediment flux, suggesting that fluvial incision may be a self-limiting process in post-orogenic postglacial terrains.

Conventional methods for the determination of past soil erosion provide only average rates of erosion of the sediment's source areas and are unable to determine the rate of at-a-site soil loss. This study addresses this issue by exploring the extent to which in situ cosmogenic Be-10 and C-14 depth-profiles can be used to quantify the magnitude and timing of site-specific soil erosion events on soils of known age. The study focuses on two sites located on end moraines of the Loch Lomond Readvance (LLR) in Scotland: Wester Cameron and Inchie Farm, both near Glasgow. The LLR is well documented and several LLR moraine radiocarbon ages exist in the literature allowing for the placement of a first order age constraint on soil/till emplacement. In addition, the site at Wester Cameron is in the proximity of Croftamie, a well-studied LLR type-locality. The site near Wester Cameron does not show any visible signs of soil disturbance and so this has been selected in order to test (1) whether a cosmogenic nuclide depth profile in a sediment body of Holocene age can be reconstructed, and (2) whether in situ Be-10, C-14 and Al-26 yield concordant results. Field evidence suggests that the site at Inchie Farm has undergone soil erosion and so this was selected so as to explore whether the technique can also be applied to determine the broad timing of soil loss. The results of the cosmogenic Be-10, C-14 and Al-26 analyses in the Wester Cameron site samples confirm that the cosmogenic nuclide depth-profile to be expected from a sediment body of Holocene age can be reconstructed. Moreover, the agreement between the total cosmogenic Be-10 inventories in the erratics and the Wester Cameron soil/till samples indicate that there has been no erosion at the sample site since the deposition of the till/moraine. Further, the Wester Cameron depth profiles show minimal signs of homogenisation, as a result of bioturbation, and minimal cosmogenic nuclide inheritance from previous exposure periods. The results of the cosmogenic Be-10 and C-14 analyses in the Inchie Farm site samples show a clear departure from the zero-erosion cosmogenic nuclide depth profiles suggesting that the soil/till at this site has undergone erosion since its stabilisation. The LLR moraine at the Inchie Farm site is characterised by the presence of a sharp break in slope, suggesting that the missing soil material was removed instantaneously by an erosion event rather than slowly by continuous erosion. The results of a Monte-Carlo type analysis carried out to constrain the magnitude and timing of this erosion event suggest that the event was relatively recent and relatively shallow, resulting in the removal of ca. 20-50 cm of soil less than 1500 years BP. The results of sensitivity analyses show that the predicted magnitude and timing of the Inchie Farm erosion event are highly sensitive to the assumptions that are made about the background rate of continuous soil erosion at the site and also about the stabilisation age of the till. The results further indicate that the density of the sedimentary deposit will also affect the magnitude and timing of the predicted erosion event. All three parameters can be independently determined a priori and so despite the method presented in this study being sensitive to variations in these parameters, they do not impede future applications of the method to other localities. The results of the sensitivity analyses further show that the predicted erosion event magnitude and timing is very sensitive to the in situ cosmogenic C-14 production rate used and to the assumptions that are made about the contribution of muons to the total production of this cosmogenic nuclide. Thus, advances in this regard need to be made for the method presented in this thesis to be applicable with confidence to scenarios similar to the one presented here.

Glasgow contains many buildings made from local ‘blond’ sandstones that are showing the legacy of 150 years of urban weathering and this decay may accelerate as climate changes in the future. Most of the blond sandstones are Carboniferous in age and comprise of micaceous quartz arenites with varying amounts of diagenetic minerals including ankerite and kaolinite. Chemical decay can be visually identified in the carbonate minerals, but the combination of quantitative X-ray microanalysis (chemistry of mineral) and Raman spectroscopy (structure of mineral) also allows chemical decay to be observed in both kaolinite and muscovite. The Raman spectroscopy shows a variation in the muscovite minerals between the outermost surface and internal region (20 mm depth), demonstrating that structural decay is occurring within the micas and reduces them to an “ionic slurry state” in a relatively short time frame. The impact of microbial colonisation on the stones was also investigated. Using osmium stained polished blocks, complimented by scanning electron microscope imaging, microorganisms were found to be living cryptoendolithically in a few samples but at very shallow depths (

Many living systems produce mineral materials via organic-inorganic interactions; through a process known as biomineralisation. The formation of all biomineral structures is under exquisite biological control, concerning crystal morphology, polymorph selection and crystal orientation. The common blue mussel Mytilus edulis produces a shell structure composed of heterogeneous calcium carbonate polymorphs: an outer layer of prismatic calcite and an inner layer of aragonite nacre. The extrapallial (EP) fluid, confined to the space between the organic mantle and inner shell, is considered to be a key participant during shell growth. The existence of both organic components i.e. proteins, glycoproteins and inorganic ions in the extrapallial fluid supports such a hypothesis of functional involvement. This study screens the influence of extrapallial (EP) proteins from M. edulis on in vitro crystallisation in the laminar flow microfluidic system. In laminar flow microfluidic systems, mass exchange between adjacent streams is driven by diffusion. This principle provides opportunities to simultaneously screen protein influences in a range of scenarios by mixing with different reagents. In addition, the combination of computational modelling and real-time crystallisation demonstrates the major influence of the microenvironment on crystal formation along microfluidic channels. The simulation of protein and ion concentration profiles, as well as the supersaturation ratio, contributes to our understanding of protein influence on crystal morphology and polymorph control. In order to identify the influence of EP proteins on crystallisation, the total wild-type extrapallial (TWEP) proteins were initially used to produce oval calcite crystals. For further investigation, individual purified proteins were used to modify crystallisation, including the wild-type proteins directly extracted from living mussels and the expressed proteins provided from an E.coli expression system. Novel lemon-shaped structures precipitated in the microfluidic channel when the main wild-type 28 kDa extrapallial protein was mixed with CaCl2 solution only. Similar structures were also generated in microfluidic channel with the expressed proteins in either CaCl2 solution only or both reagent solutions. Multilayer calcite structures were induced in the microfluidic channel in the presence of biomineral proteins, mixed with Na2CO3 solution only. All of these results suggest that the extrapallial proteins influence CaCO3 crystallisation. Microcontact printing (μCP) has been used to create two-dimensional protein and polymer patterns for in vitro crystallisation. Polyacrylic acid (PAA) has been used as polymer patterns to control CaCO3 crystal formation, including precipitation and morphology. Calcite crystals, composed of nano-blocks, are the only structures precipitated in the patterned regions while PAA and calcium ions are both printed on the substrates. Although encouraging, further work is required to fully establish the protocol for protein patterning as a means of screening biomineral protein function.

The compound eyes of trilobites, which appeared in the Early Cambrian, represent one of the first preserved visual systems. Application of state-of-the-art microscopy techniques in the present study has revealed fine details of the microstructure and chemistry of these unusual calcite eyes that, until now, have been inaccessible and this has facilitated new insights into their growth and function. Six species from three families of trilobite with holochroal eyes, ranging from Early Ordovician to Middle Carboniferous, and 21 species from three families of trilobite with schizochroal eyes, ranging from Early Ordovician to Middle Devonian, were investigated. High-resolution microscopy techniques, including Electron Backscatter Diffraction, Transmission Electron Microscopy and Electron Probe Micro-analysis have made it possible to ‘see’ through the diagenesis of trilobite lenses to reveal the likely original lens microstructure and chemistry. Computer-based optical modelling has further shown how original lens microstructure and chemistry enhanced lens function. The discovery of sub-micron sized crystals that display a gradual and precise change in orientation shows that in many lenses much of the original microstructure has remained intact despite exposure to pore fluids and elevated temperatures and pressures during diagenesis. Although microstructure varies slightly with lens shape, there is often exceptionally precise crystal orientation. In holochroal eyes there is a direct relationship between lens shape and microstructure; where lens surfaces are planar, crystals are of uniform orientation, but where lens surfaces are convex, c axis orientation fans out, away from the lens axis. Several microstructural patterns have been identified in schizochroal lenses. However, a single original microstructural pattern, in which c axis orientation fans out at lens surfaces but remains parallel to the lens axis in the centre of the lens, may be applicable to all schizochroal lenses. The original chemical composition of the lenses, in particular those of schizochroal type, is less commonly preserved. However, the unravelling of a diagenetic pathway of change, through understanding the intricacies of relationships between different minerals in the lenses, has made possible a better understanding of how these lenses were altered during diagenesis. Lenses in holochroal eyes are invariably low-magnesium calcite, like the rest of the exoskeleton, as has been established for some time. The present study clarifies the original structures of schizochroal lenses and in doing so, ends the controversy over lens function; lenses were originally constructed as doublets, as suggested by Clarkson and Levi-Setti, and were not gradient index lenses, as was suggested by Campbell and Bruton and Haas. Lenses in schizochroal eyes, were constructed of high-magnesium calcite, with highest concentrations of magnesium in the lower ‘intralensar bowl’ and central ‘core’ regions of the lens. The degree of partitioning of high levels of magnesium, of up to 8 mole % MgCO3, in the schizochroal eyes is remarkable given the magnesium-poor ‘calcite seas’ in which they were formed. This is perhaps the first example of element partitioning within biominerals for a specific function. Based on the growth sequence of modern arthropod exoskeletons lenses in trilobite eyes are likely to have grown from the outer surface in, one lamella at a time, with microstructure and chemical composition controlled by an organic matrix. Assessment of the trilobite optical structures, using Code V optical modelling software, leads to the conclusions that the trilobite eyes functioned in a similar manner to the apposition eyes of modern animals. Code V modelling of holochroal and schizochroal eyes, and the subsequent determination of their resolution and sensitivity, shows that both eye types probably had a single optically isolated photoreceptor beneath each lens. Using a combination of specific lens size, shape, spacing, microstructure and composition, the schizochroal eye was adapted to low light intensities, similar to the eye of the modern isopod Cirolana. These adaptations would have provided the trilobite with light and dark detection of a resolution sufficient to identify movement, allowing it to detect prey and defend itself against predators. The birefringent properties of the calcite from which these lenses were made could be a hindrance, resulting in double refraction of light rays and the formation of ‘ghost’ images. Fascinatingly however this property provides the lenses with the refractive power required to make full use of the light available to them, vital for an organism with a crystalline lens with a fixed focal length. Study of the calcified lenses of ostracods and brittlestars and comparison to lenses in schizochroal trilobite eyes confirms that these modern organisms do not provide accurate analogues for trilobite eyes. No other organism that shares all characteristics of schizochroal trilobite eyes has yet been found; the eyes of the phacopine trilobites remain unique in the natural world.

The purpose of this research was to investigate temporal and spatial trends in the Marine Radiocarbon Reservoir Effect (MRE) on the North Sea coast of Scotland throughout the Holocene. The MRE is a 14C age offset between contemporaneous marine derived carbon and its terrestrial counterpart, owing to the extended residence time of 14C in oceanic environments. This results in marine samples being depleted in 14C relative to contemporaneous terrestrial samples and consequently, the production of 14C ages that are erroneously old. The offset between contemporaneous marine and terrestrial entities varies through space and time on a global scale and so a single correction factor cannot be universally applied. In order to gain a coherent understanding of the MRE, its variability and its full impact on the radiocarbon dating of samples containing marine derived carbon, a brief background to the fundamental principles of radiocarbon dating is presented. This is followed by a global overview of variability in the MRE before focussing on the UK coastal environment, and in particular the North Sea coast of Scotland. Using contemporaneous multiple terrestrial and marine entities from secure archaeological contexts, this thesis investigates the MRE as represented by 13 contexts from 9 archaeological sites spanning a geographical range from Aberdeen in the north to Dunbar in the south. The sites are predominantly Medieval in age, owing to sample availability, and cover a calendar age range of c. 600 – 1500 AD. This thesis recommends the use of the multiple paired sample approach for ΔR calculations and the publication of ΔR using histograms alongside weighted mean values and the standard error for predicted values in order to provide a more accurate estimate of where ΔR values measured in the future for a similar site and location may lie. In so doing, a weighted mean for the sites studied in this thesis has produced a ΔR for the period described above of -19 ± 52 14C yrs. This thesis also compared ΔR values calculated using mollusc shell with those calculated from fish bone and found that although fish bone produces a slightly increased ΔR, this offset is not significant using the standard error for predicted values. When the fish bone results are included in the weighted mean for the study region; ΔR = -29 ± 51 14C years. This thesis highlights the variability inherent within the calculation of ΔR values and places caution on drawing definitive conclusions using ΔR as a proxy for large scale changes in oceanographic/climatic regimes. It also provides new methods of interpreting and presenting ΔR values and their associated errors for publication, alongside recommending best practice statistical treatment of the data used in ΔR calculations. Previous MRE research in this geographic area is limited and therefore this thesis contributes significantly to the understanding of the temporal and spatial trends in the MRE on the North Sea coast of Scotland within the Medieval period.

Understanding the link between tectonics and climate and their consequences in landscape evolution is a major current issue in Earth sciences. Bedrock rivers are an important component of the landscape because they transmit changes in tectonic and/or climatic conditions by setting bedrock incision rates to which the landscape must be adjusted. Nevertheless, there remain unresolved issues in relation to bedrock river processes and response to perturbation. The effects caused by propagation of a knickpoint triggered by a sudden drop in base-level remain to be fully clarified. Questions about rates of knickpoint recession, the control exerted by structure and lithology, the morphological response of rivers after knickpoint recession and whether bedrock incision rates are re-established after the passage of a knickpoint, as theory predicts, are all issues that need to be clarified. Moreover, the estimation of bedrock incision, which is key to understand transience in landscapes, has relied on the stream power model, mainly tested on large fluvial settings. Whether the stream power model is valid for small bedrock rivers is not well understood. Some of these questions are tackled in this research, by studying small bedrock river catchments. The case of a knickpoint propagation on a homogeneous resistant lithology (quartzite), triggered by an instantaneous base-level lowering ( 18 m in 13.6 ka), is evaluated here, as well as the effect of structure and the morphological response of rivers to base-level fall. Two approaches were followed: (1) stream profile analysis using slope-area and distance-slope plots and (2) the analysis of terrestrial cosmogenic nuclides to obtain erosion rates. The Isle of Jura, located in the west coast of Scotland, was selected as natural laboratory because bedrock rivers incise the landscape and rapid rock uplift resulting from glacio-isostatic rebound after the Last Glacial Maximum has left the Jura landscape in transience. The present research is organised in seven chapters. In chapter 1, the motivation for this research is presented. In chapter 2, a review of theory underpinning research on bedrock rivers, landscape evolution and knickpoint generation, is detailed. The relevant studies in the field are also reviewed. The physical setting of Jura is characterised in chapter 3, as well as the morphometry of catchments, stressing the effect of Quaternary glaciation on the landscape of Jura. Unpublished exposure ages and analysis of the resultant raised beaches (~35 m OD) of Jura’s west coast are used to demonstrate a sudden drop in base-level in Jura ~13.6 ka. Chapter 4 details how stream long profiles were extracted and how the slope-area (SA) and distance-slope (DS) analyses were undertaken. This chapter 4 shows that the Jura rivers have strong imprints related to glacial processes and base-level fall, making it difficult to use SA and DS models to estimate channel incision as has been done for large fluvial settings. Chapter 5 is explains how the base-level fall knickpoints were identified and it is shown that stream discharge is a first-order control on knickpoint propagation. Structure and lithology, on the other hand, are not first-order controls on knickpoint recession. Chapter 5 also evaluates the vertical distribution of knickpoints and morphological response of rivers after knickpoint migration, with the results indicating that stream power controls the vertical distribution of knickpoints and the morphological response of rivers to base-level fall. A threshold of ~5 km2, where rivers’ ability to modify their channel, resulting in a channel convex profile, is also identified. In chapter 6 the problem of bedrock incision and the role of sediment is tackled. Based on the sampling of sediment in fieldwork, it is demonstrated that the median fraction in the rivers of Jura is ≈45 mm and grain-size neither fines nor increases with stream discharge and channel slope, strongly indicating that detachment-limited conditions are likely to control bedrock incision. In the second part of chapter 6, the incision rates upstream and downstream of the base-level fall knickpoint are obtained to test whether incision rates are re-established after knickpoint propagation. Incision rates were obtained from the concentrations of cosmogenic 10Be in samples extracted from the river bed. The results indicate that incision rates are not re-established at an expected value of ≈ 0.1 m/k yr after knickpoint migration. Rather, incision rates below the knickpoint remain somewhat elevated (≈ 0.5 m/k yr) reflecting: (1) ongoing base-level fall, and/or (2) the propagation of younger knickpoints (< 13.6 ka) in those transient reaches. The cosmogenic-derived incision rates were tested with different bedrock incision rules. The results indicate that the stream power model is a good predictor for channel incision, even for the case of small catchments. In chapter 7 the conclusions of this research are provided.

Many marine molluscs produce complex shells of calcium carbonate. These shells are formed under strict biological control to provide a range of functions to ensure the survival of the living organism. These inspiring biomineral structures can also provide an archive of environmental change via proxies such as δ18O and δ13C within the shell carbonate. However, the intimate relationship between the biological and environmental controls influencing biomineral production can often obscure the environmental signal, making it difficult to interpret environmental information from shell proxies. Understanding the design of biomineral structures will further our knowledge of biomineralisation as a whole, while understanding the controls that influence shell production will ensure that shell proxies applied to palaeoenvironmental studies are accurate. Oysters are sessile bivalve molluscs that have evolved since the Triassic and expanded to occupy a range of habitats with almost global distribution, providing an example of a highly successful biomineral system. This study investigates the ultrastructure, crystallography and stable isotope composition of the Pacific oyster, Crassostrea gigas from estuarine and marine environments. The method by which oysters adhere to hard substrates is also investigated. Both valves of the oyster shell are composed predominantly of low Mg calcite in three forms; an outer prismatic region, an inner foliated structure and chalk lenses which appear sporadically throughout the valves. Aragonite is restricted to the myostracum and parts of the hinge structure. Crystallographic analysis shows that, despite variations in structural morphology, the superimposed layers of the oyster shell maintain a single crystallographic orientation with the crystallographic c-axis orientated perpendicular to the outer shell surface. Varying crystal morphology, while maintaining crystallographic unity, may be a deliberate design to provide the oyster shell with both strength and flexibility. In general, there is no difference in the overall ultrastructure or microstructural arrangement of estuarine and marine oysters. Estuarine oysters contain significantly more chalk than marine equivalents suggesting that the appearance of chalk lenses is, to some degree, triggered by an external environmental stimulus. Stable carbon and oxygen isotope analysis of folia and chalk provides further insights into the appearance of chalk in the oyster shell structure. There is no significant difference in the isotope composition of folia or chalky layers, although patterns of δ13C and δ18O of folia and chalk reveal key differences between the two structures. Folia display a narrower range of δ18O values compared with chalk and exhibit significant interspecimen variation with respect to δ13C. Interspecimen variation, with respect to either δ18O or δ13C is absent in chalk samples. These patterns suggest that secretion of folia requires a more specific environmental stimulus and a greater input of metabolic carbon than chalk. Chalk is apparently secreted across a greater range of environmental conditions, with less metabolic regulation. Deviation from optimal environmental conditions, for example during periods of reduced salinity and/or cold or warm temperatures, may reduce metabolism causing the oyster to deliberately default from folia to chalk secretion. In general, folia and chalk in both estuarine and marine oysters is secreted in oxygen isotope equilibrium with the ambient environment. Another aspect of the oyster biomineral system is their ability to adhere tightly, and usually permanently, to a range of hard substrates by cementation of the left valve. Investigation of the contact zone between oyster shells and biological (other oyster shells) and inorganic (rock) substrates reveals the influence of both biogenic and non-biogenic processes in oyster cementation. Original adhesion is brought about by secretion of an organic adhesive which acts as a nucleating surface onto which crystals precipitate which have random orientation and are composed of high Mg calcite. The lack of orientation and elevated Mg content suggests that these crystals are nucleating outwith the biological control experienced by the shell biomineralisation process and are formed from inorganic precipitation from seawater. It is proposed that oysters do not control, or secrete, the crystalline cement but instead they secrete an organic film onto which crystals precipitate from seawater. Oysters thus provide excellent examples of both biologically induced and biologically controlled mineralisation.

In order to avoid the damaging climatic consequences of rising atmospheric CO2, and reduce current atmospheric CO2 concentrations to pre-industrial levels, anthropogenic CO2 emissions must be mitigated by capturing CO2 at power plants and storing it for thousands of years. Underground storage within deep geological formations, such as depleted gas and oil fields or deep saline aquifers, is the best understood solution for storage of CO2. In order for this method to gain more public and political acceptance it is important to characterise the potential causes, quantities and rates of CO2 release that could result if leakage were to occur from anthropogenic storage projects. This study examines two sites in the Colorado Plateau where faulted and actively leaking CO2 reservoirs provide natural analogues for failed anthropogenic storage sites. The two sites in question, the Little Grand Wash and northern Salt Wash graben faults are situated at the northern end of the Paradox Basin in Utah and represent classic three way traps due to juxtaposition of the shallow, north plunging Green River anticline against a set of east-west trending normal faults. In addition to active leakage sites in each area there are numerous fossilised travertine deposits. Along the Little Grand Wash fault the ancient mounds are restricted to the fault trace whereas ancient travertine mounds associated with the northern fault of the Salt Wash graben are far more numerous and occur up to ~530 m into the footwall of the fault. This more diffuse pattern of flow is due to the outcropping of unconfined aquifer units at the surface. A total of 45 U-Th dates from the majority of these travertine mounds provides a unique data set. The oldest deposits from the Little Grand Wash and northern Salt Wash graben faults produced ages of 113,912 ± 604 and 413,474 ± 15,127 years respectively. Repeat ages show reasonable reproducibility and analytical errors on results are of the order of 1% of the ages. The coupling of travertine elevation measurements with their radiometric ages gives an incision rate for each site. A rate of 0.342 m/ka for the Little Grand Wash fault relates directly to Green River incision and agrees with previous work on the Colorado Plateau, providing a further data point for characterisation of uplift of the province. For the northern fault of the Salt Wash graben a rate of 0.168 m/ka for the tributaries running through the area gives a robust method with which to estimate ages for un-dated mounds. The results of radiometric dating and incision rate age estimation of travertine mounds shows that leakage can last for timescales of 100,000’s of years, while high resolution U-Th dating of an individual mound demonstrated that leakage from a single point can last for a minimum of ~11,000 years. A range of travertine ages show that leakage to the surface has constantly switched location through time, while the presence of three mounds of distinct age at one location demonstrate that pathways can become repeatedly re-used over periods of ~45,000 years. There is no evidence of temporal periodicity in travertine deposition but there is a distinct spatial pattern of leakage as shown by localised similarities in the initial uranium chemistries of travertine mounds. Initial leakage is proximally located to the axial trace of the Green River anticline and subsequent leakage spreads from this central point along the fault plane in both east and west directions. The switching of fluid flow pathways to the surface can be explained by three main mechanisms: mineralisation, 3-phase interference of CO2 related fluid flow and seismically triggered alteration in dynamic strain acting upon the hydrology of the faults. These mechanisms have differing influences in each area - demonstrating that the behaviour of fluid flow switching in a system confined to damage zone fractures (Little Grand Wash fault) is different to a system leaking through an unconfined aquifer (northern fault of the Salt Wash graben). Coupling of travertine ages with estimates of their volumes provided a total worse case scenario for quantity of CO2 leakage of 6.2 x 10^6 ± 1.7 x 10^6 tonnes for the Little Grand Wash fault and 7.4 x 10^6 ± 2 x 10^6 tonnes for the northern fault of the Salt Wash graben. From these totals time averaged leakage rates of 55 ± 15 and 47 ± 13 tonnes/year were estimated for each fault. The leakage rate for the actively precipitating Crystal Geyser travertine (which is the result of anthropogenic exploration drilling) is estimated to be 3,153 ± 851 tonnes/year. These total and modern rates provide analogues for leakage via caprock failure and catastrophic wellbore failure. Applying them to large scale storage sites such as Weyburn and Gorgon revealed that for caprock failure complete leakage of these reservoirs will take place over timescales of 10^5-10^6 years, while for catastrophic failure of a single well complete leakage of these reservoirs could occur over as little as 10^3 – 10^4 years. This finding has important implications for the successful monitoring of anthropogenic storage sites.

This thesis aims to investigate the use of two materials: rockdust and greenwaste compost for use as soil fertility amendments. A field trial was conducted over three years to investigate the impact these materials had on plant yield, plant nutrient content, soil chemistry and soil microbial communities in direct comparison with chemical fertilizer and farmyard manure. There were annual applications of compost, manure and chemical fertilizer in spring with one rockdust application in the autumn prior to the first year of the trial. Two harvests were carried out each year in summer and autumn to determine differences in plant yield. The soil was analysed prior to applications to determine the baseline chemical status then was analysed at two more points through the trial. Results from the field trial showed clear effects of organic amendments on plant yield that were attributed to nitrogen addition by compost and manure. NPK chemical fertilizer produced a yield effect at an earlier point in the trial compared to manure and compost. This, and the chemical analysis of the materials showed that the organic materials required a period of mineralization of organic-N in order to replenish soil available nitrogen. The results from the field trial also showed differences in plant nutrient content (as a measure of plant quality). The organic treatments were shown to generally produce higher plant nutrient content than the NPK fertilizer showing that the increased yields of the inorganic fertilizer treatment impacted negatively on the nutrient content. No yield effects due to rockdust addition were apparent after 3 years of the field trial. In addition, rockdust did not impact on plant nutrient content nor did it affect the soil chemistry despite 3 years of weathering that was considered sufficient time to release nutrients to the soil. Samples of soil were taken in the summer after the final year of the field trial to determine long-term changes in the soil microbial communities between the treatments. Results showed that there were fewer long-term changes than were initially expected in soil microbial communites at the end of a 3 year trial of these materials. Short-term greenhouse pot trials were also conducted using 3 different test crops to investigate the use of greenwaste compost and various types of rockdust for use as growth media in comparison with a peat based control. Results showed that while greenwaste compost supported plant growth as well as the peat based media, no rockdust type increased plant growth beyond the yield in a greenwaste compost control. The short-term supply of nitrogen in greenwaste compost was as good as that of the peat based control and while the phosphate supplied by the peat based control was shown to give excessively high plant P content. Results from the pot trials showed that greenwaste compost could wholly or partially replace peat in plant growth media without negatively impacting on plant yield or quality. The likely effects of various types of rockdust on soil chemistry were investigated by carrying out nutrient extractions using increasing extractant ‘strength’. Nutrient extractions showed that a high degree of rock weathering was required to release small quantities of trace elements from rockdust samples. Sodium, calcium and to a lesser degree potassium, magnesium, iron and phosphate were supplied in greatest quantities from most rockdust samples with basic rocktypes releasing highest quantities of nutrients. As a result of the work carried out in this thesis, it is concluded that composted greenwaste could be a valuable addition to agricultural soil and that it could replace peat in some plant growth media. There are some implications to the use of composted materials – transport and application costs and the potential addition of potentially toxic elements to soil; however the potential nutrient addition and improved plant quality could make it an attractive fertility amendment in some organic farming techniques. It was concluded that rockdust was not shown to influence plant yield or quality in the agricultural setting of the field trial, nor was it shown to be a useful addition to plant growth media. Therefore rockdust could not be proven to be a useful soil fertility amendment.

Titanite is a calcium titanium silicate accessory mineral that serves as a sink for trace elements, especially the rare-earth elements and the high-field strength elements (Cerny and Rivadisa.L 1972; Groat, Carter et al. 1985; Enami, Suzuki et al. 1993; Perseil and Smith 1995; Della Ventura, Bellatreccia et al. 1999; Piccoli, Candela et al. 2000). It is also characterised by very sluggish diffusion of these elements, and as such it has the ability to resist most sub-solidus alteration. These characteristics make titanite a prime candidate for the ability to preserve a record of the petrogenetic processes which formed the igneous rocks in which it is found. In order to assess titanite’s ability to serve as a petrogenetic tool, a textural and geochemical study of titanite from different igneous environments was undertaken. The Ross of Mull Granite is an igneous complex located on the south west coast of the Isle of Mull, Scotland. It is a Caledonian age pluton that displays evidence of magma-mixing processes at depth and also contains notable amounts of titanite. Samples of different host granite and diorite enclave lithologies and relationships were documented and collected in order to asses the ability of titanite to retain evidence of magma-mixing processes within its compositional zoning. Titanite from the Ross of Mull Granite displays a large variety of textural features, both with respect to crystal shape and compositional zoning. The variation of the trace elements observed in titanite is a direct reflection of the compositional zoning pattern. Melts that are enriched in particular trace elements pass on that signature to the titanites. If melts of significantly contrasting chemistries mix or mingle, then titanite may record any significant instance of trace element diffusion between the melts. More importantly, there doesn’t need to be a transfer of trace elements between mingling/mixing melts for titanite to record evidence of the interaction. If the melts are of significantly different oxygen fugacities, then titanite may become destabilised and partially dissolve. This dissolution may only be temporary, but it may be difficult to tell if it was a product of increasing heat of the melt of if it was due to a change in oxygen fugacity. Titanite however, may record evidence of the cause of dissolution based on the nature of re-growth. As shown by some of the titanites within the Ross of Mull Granite, re-growth following a period of dissolution may be attributed to a change in oxygen fugacity if the new titanite growth is characterised by unusually low REE content. This is related to the nature of trace element incorporation in the titanite structure; REE are taken up due to coupled substitution mechanisms involving tetravalant Al and Fe. If a melt becomes reduced then the activity of ferric Fe will also be reduced, thus inhibiting the ability of titanite to take up REE by affecting the activity of the coupled substitution (Wones 1989; Piccoli, Candela et al. 2000). Titanite from the ROMG is largely characterised by compositional zoning that reflects the trace element chemistry of one of the end-member lithologies (host granite or dioritic enclaves), or has compositional zoning that reflects the changing conditions of the magmatic environment, namely: changes in melt composition, changes in temperature and pressure and changes in oxidation of the magma. In the case of the ROMG, all of these changes were wholly, or in part, brought about by magma mixing processes. Another way in which titanite reflects processes of petrogenesis is that it has been found to reflect the degree of homogenisation of the melt from which it has crystallised. To further asses the ability of titanite serve as a petrogenetic tool, a study was made of the characteristics of titanite from the volcanic environment. The Fish Canyon Tuff, from the San Juan volcanic field, Colorado, USA, was chosen as a suitable candidate for study due to its well documented nature; it is the largest known pyroclastic eruption to be documented. The Fish Canyon tuff also contains numerous phenocrysts of titanite. Eruption of the Fish Canyon Tuff is thought to have been brought about by the thermal rejuvenation of a batholith-sized magma chamber which had previously cooled to a rigid crystal mush (Bachmann and Bergantz 2003). The main conclusion from the study of titanites from the Fish Canyon Tuff and is that evidence for the thermal rejuvenation of the magma chamber by a mafic melt prior to eruption is preserved in the textural and chemical signature preserved in the compositional zoning of the titanites as dissolution and re-growth textures. This study illustrates that titanite is able to not only preserve evidence of magma mixing processes occurring at depth, but it is also able to preserve evidence of similar processes all the way through to the volcanic environment.

Understanding how faults initiate and fault architecture evolves is central to predicting bulk fault zone properties such as fault zone permeability and mechanical strength. The study of faults at the Earth’s surface and at near-surface levels is significant for the development of high level nuclear waste repositories, and CO2 sequestration facilities. Additionally, with growing concern over water resources, understanding the impact faults have on contaminant transport between the unsaturated and saturated zone has become increasingly important. The proposal of a high-level nuclear waste repository in the tuffs of Yucca Mountain, Nevada has stimulated interest into research on the characterisation of brittle deformation in non-welded to densely welded tuffs and the nature of fluid flow in these faults and fractures. The majority of research on the initiation and development of faults has focussed on shear faults in overall compressional stress regimes. Dilational structures have been examined in compressional settings e.g. overlapping faults generating extensional oversteps, or in normal faults cutting mechanical layered stratigraphy. Previous work has shown the affect mechanical stratigraphy has on fault dip angle; competent layers have steeply dipping segments and less competent layers have shallowly dipping segments. Displacement is accommodated by shear failure of the shallow segments and hybrid failure of the steeply dipping segments. As the fault walls of the shear failure segment slip past each other the walls of the hybrid failure segment are displaced horizontally as well as vertically thus forming dilation structures such as pull-aparts or extensional bends. Work on truly extensional faults has been at the kilometre scale of fissure swarms in rift systems where the focus is on fault geometry and direction of fault propagation. This study examines dilational faults with offsets of centimetres to 10’s of meters within moderately and densely welded ignimbrite units on the caldera island of Gran Canaria, Spain. Through the investigation of fault populations within different ignimbrite units I have examined how the fault architecture changes with accumulated displacement, identified the factors controlling fault core evolution and using these observations developed a new model for the initiation and growth of dilational faults in ignimbrites. The faults in this study do not have a linear correlation of increasing fault core thickness with displacement. Fault core width varies along fault dip and the largest offset faults have the narrowest fault cores. Furthermore, the damage zone joint frequency shows a limited increase with increasing displacement and faults and joints are sub-parallel. From these observations I have developed a new model for fault initiation and evolution in which the petrophysical properties of the host rock are the primary control on fault architecture. Faults initiate on existing sub-parallel joints and grow by the incorporation of material from joint surfaces and joint bound slabs. The growth of the fault depends on the joint spacing and the competency of the host rock. In densely welded ignimbrites, joint spacing is controlled by sub-layers within the ignimbrite unit which are formed by flattening and stretching of fiamme. In moderately welded ignimbrites, fiamme and lithic inclusions in the ash matrix act as sites of joint initiation; the greater the abundance of such flaws the higher the joint frequency. Whether fault growth is promoted or inhibited depends to some extent on the competency of the material. Faults cutting ash-rich friable units have narrow fault cores regardless of displacement. This suggests that the material is easily abraded in the fault core inhibiting fracturing of the host rock and incorporation of new material. Hence host rock fabric and composition have an important influence on fault architecture in these ignimbrite units. The other influence on fault evolution is the tensile stress regime in which faulting occurs. The faults in this study form by hybrid failure and so have both vertical and horizontal displacements. The dilation of existing joints causes slip on the joints and allows material to fall into the joint forming a fault core. This work identifies distinct differences between the mechanism of dilational fault initiation and resultant fault architecture compared to that of shear faults. The observations made in this study indicate that the host rock petrophysical properties, stress regime at time of faulting (tensile or compressive) and confining pressure are primary influences on fault architecture and not displacement; contradicting the widely accepted fault thickness-displacement scaling relationship. I suggest that the architecture of dilational faults can be predicted by examining the host rock properties and using the data from this study have developed a framework that illustrates how ignimbrite host rock properties may affect deformation structures. Such frameworks for individual lithologies may be more useful in predicting fault zone properties as opposed to global scaling relationships. The results of this study have implications for conceptual models of fluid flow based on fault architectures predicted using the thickness-displacement relationship.

Cosmogenic nuclide concentrations in alluvial sediment are now routinely used to estimate time and space-averaged catchment-wide denudation rates, but have the potential to offer considerably more. This is because each grain leaving a catchment has a potentially unique history of erosion, transport and storage, and so the frequency distribution of cosmogenic nuclide concentrations in large numbers of grains can provide an integrated signature of the catchment's geomorphic history. This thesis evaluates the extent to which aspects of source area geomorphology and geomorphological processes can be inferred from frequency distributions of single grain detrital cosmogenic nuclide concentrations through the use of a combination of cosmogenic Be-10 and Ne-21 analyses and numerical modelling. The Gaub River study catchment is a tributary of the ~15,500 square km Kuiseb, one of the major ephemeral river systems draining western Namibia. The geomorphology of the upper Gaub is that of a high elevation passive margin and is characterised by an extensive low relief upland region and a highly dissected, high-relief zone marking the Great Escarpment. Denudation rates in the steeper escarpment sub-catchments of the upper Gaub, based on analysis of Be-10 concentrations in 6 amalgamated sediment samples, range from 12.5±0.8 to 14.1±0.9 m/Myr. These rates are twice those obtained for 5 upland plateau sub-catchments: 3.4±0.2 to 8.0±0.5 m/Myr. The Be-10 analyses show that there is a very strong linear relationship between measured denudation rate and mean slope of a sediment sample's source catchment. The analysis of Be-10 in a sample from the outlet of the Gaub and in the 11 sub-catchment samples confirms that, despite the strong geomorphic asymmetry that characterises this catchment, sediment leaving the upper Gaub is well mixed. The denudation rates based on Be-10 are consistent with published cosmogenic nuclide data and confirm the finding that the steeper escarpment zone is eroding more rapidly than both the more gently sloping coastal plain and the upland plateau. Analyses of Ne-21 in 32 individual quartz pebbles (16 - 21 mm) collected from the outlet of the Gaub yield cosmogenic Ne-21 [(Ne-21)c] concentrations that span nearly two orders of magnitude (2.6 – 161.2 million atoms/g) and are highly skewed toward low values. These results are corroborated by a DEM-based analysis assuming a linear correlation between denudation rate and slope, inferring that the measured distribution is a signature of the slope dependence of, and hence spatial variation in, denudation rates in the study catchment. Sensitivity analyses conducted using a GIS-based numerical model of cosmogenic nuclide acquisition show that the shape of the frequency distribution of (Ne-21)c concentrations in sediment leaving a catchment is sensitive to the range of processes operating in the sediment's source areas and that this distribution can be used to infer aspects of source area geomorphology and geomorphological processes. The results also show that lithology can affect the shape of the (Ne-21)c concentration distribution indirectly by exerting control on the spatial pattern of denudation in a catchment. The results of the sensitivity analyses further indicate that although the shape of the distribution of (Ne-21)c is sensitive to the range of erosion rates that are present, this sensitivity is not sufficient to allow the use of the (Ne-21)c concentration distribution for accurately constraining the range of process rates in a catchment.