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Exhumed fault rock of the central Alpine Fault Zone (South Island, New Zealand) shows extensive clay mineralization, and it has been the focus of recent research that aims to describe the evolution and frictional behavior of the fault. Using Quantitative X-ray powder diffraction, 40 Ar/ 39 Ar geochronology, hydrogen isotope (δD) geochemistry, and electron microbeam analysis, we constrain the thermal and fluid conditions of deformation that produced two predominant clay phases ubiquitous to the exposed fault damage zone, illite and chlorite. Illite polytype analysis indicates that most end-member illite and chlorite material formed in equilibrium with meteoric fluid (δD = −55 to −75‰), but two locations preserve a metamorphic origin of chlorite (δD = −36 to −45‰). Chlorite chemical geothermometry constrains crystal growth to T = 210–296 °C. Isotopic analysis also constrains illite growth to T < 100 °C, consistent with the mineralogy, with Ar ages <0.5 Ma. High geothermal gradients in the study area promoted widespread, near-surface mineralization, and limited the window of clay authigenesis in the Alpine Fault Zone to <5 km for chlorite and <2 km for illite. This implies a significant contrast between fault rock exposed at the surface and that at depth, and informs discussions about fault strength, clays and frictional behavior. [ABSTRACT FROM AUTHOR]

Leaf wax n -alkanes are often extracted from modern plant material to describe their natural occurrence and understand the factors determining their potential as biomarkers for climate reconstruction. Despite several studies on the topic no standardised approach for n -alkane extraction from leaves has been yet devised. A common issue is the necessity to work on leaf subsamples to reduce co-extraction of unwanted polar compounds (e.g. chlorophyll), as they often interfere with individual steps involved in post-extraction, wet-chemical isolation of leaf wax n -alkanes. However, subsampling can generate biases regarding n -alkane distribution, concentration, and isotopic composition due to heterogeneities along the leaf sheath. Therefore, we propose and test an optimised extraction approach. Using leaves of Cladium mariscus and Typha angustifolia , we compared the effect on n -alkane extraction of two solvent mixtures, two extraction techniques and two sample preparation modalities. We found similar results for the two modes of sample preparation (intact vs. shredded leaf), while the use of the two solvent mixes and the two extraction techniques produced significantly different results. n- Hexane/dichloromethane 9:1 was almost twice as efficient (+97%) than the more commonly used dichloromethane/methanol 9:1, producing higher n -alkane yields while reducing co-elution of highly polar compounds. The best results, both for yield, sample processing time and solvent consumption, were achieved in combination with the accelerated solvent extraction technique, averagely +49% more efficient than ultrasound assisted solvent extraction. Alongside, we investigated the distribution of n -alkanes along the leaf sheath of C. mariscus . [ABSTRACT FROM AUTHOR]

The Mediterranean region is highly sensitive to climate change, particularly with regard to warming and increasing aridity. Understanding its past climate history during periods similar to the Holocene is key to understand the long-term dynamics that accompany anthropogenic climate change. Marine Isotope Stage (MIS) 11 (ca. 424–367 ka BP) is considered one of the best Holocene analogues. Despite detailed insight from Atlantic marine records and European continental records, MIS 11 temperature and rainfall evolution in the Mediterranean remains poorly understood. We present a detailed record of MIS 11–10 climate change at Tenaghi Philippon, a telmatic peatland in NE Greece. We use microbial membrane lipids (brGDGTs), the δD of n -C 29 (δD wax) and distribution of n -alkanes derived from plant leaf waxes, and levoglucosan concentrations to reconstruct changes in temperature, rainfall sources and vegetation burning. Glacial-interglacial temperature patterns indicate strong Atlantic influence in the Eastern Mediterranean region. Low δD wax values and high temperatures indicate a predominance of Atlantic-sourced winter precipitation during MIS 11, and vice versa during MIS 10. The latter is attributed to a suppression of the Mediterranean storm track, probably due to a persistent high-pressure cell over most of the European continent, mainly in response to an extended ice cover during the glacial. The levoglucosan record is consistent with rapid change to drier conditions and increased vegetation burning from MIS 11 to 10. Millennial-scale oscillations allow to characterise cooling episodes previously recorded at other sites, with conditions of decreased winter precipitation, while suggesting increased seasonality during the interglacial optimum. • MIS 11 consistently marked by abundant winter Atlantic sourced precipitation. • MIS 11c optimum marked by enhanced summer aridity. • Millennial-scale variability during MIS 11b–11a highlighted by rainfall shifts. • Continental air temperatures follow Atlantic sea-surface temperature dynamics. • Levoglucosan marks MIS 11–10 interglacial to glacial shift in fire incidence. [ABSTRACT FROM AUTHOR]

Combined geochronological and stable isotope data of quartzite mylonite from the footwall of the Raft River detachment shear zone (NW Utah, USA) reveal that an important phase of ductile deformation and infiltration of meteoric water in the shear zone occurred in Miocene time. 40 Ar/ 39 Ar release spectra are complex, and plateau ages decrease systematically from 31.1 ± 0.8 Ma at the top to 20.2 ± 0.6 Ma at the bottom of the quartzite mylonite section, capturing a segment of the ∼40–15 Ma geochronologic record that has been documented regionally and is likely related to partial to total overprinting of Eocene white mica 40 Ar/ 39 Ar ages in the Miocene. Hydrogen stable isotope values of syn-kinematic muscovite range from −123‰ to −88‰ and suggest that meteoric water infiltrated the detachment shear zone during mica (re)crystallization and mylonite development. Bulk stable isotope analyses from fluid inclusions in quartz support a meteoric origin for the fluid (low D/H and 18 O/ 16 O ratios). Quartz and muscovite oxygen isotope analyses show varying degrees of 18 O depletion, suggesting spatially variable time-integrated interaction of meteoric fluids with recrystallizing shear zone minerals. The overall pattern of D/H and 18 O/ 16 O ratios indicates that fluids were channelized along restricted layers or shear zones within the deforming detachment system. The variability in 18 O/ 16 O ratios of both quartz and muscovite and the fluid-rock isotopic exchange results can be explained by variations in the shear zone permeability (confined versus diffuse flow) along with strain variations along the transport direction (from flattening to constriction). [ABSTRACT FROM AUTHOR]

Holocene climate dynamics have strongly influenced precipitation patterns in the Eastern Mediterranean region. This holds particularly true for the ‘8.2 kyr BP climatic event’, arguably the strongest perturbation of early to mid-Holocene climate. Here we present a biomarker record of leaf wax-derived n -alkane distributions and stable isotopic composition of total organic carbon (δ 13 C TOC ) along with palynological data from the fen peat archive of Tenaghi Philippon (TP), NE Greece, spanning the interval from 8.7 to 7.5 kyr BP. Our record documents the response of in situ vegetation within the Philippi peatland to changing hydrological conditions, and addresses the applicability of organic proxies such as the ‘aquatic index’ ( P aq ), average chain length (ACL) and δ 13 C TOC as indicators of peat surface moisture conditions at the study site. The long chain n -alkanes ( n -C 27 , n -C 29 and n -C 31 ) typical of vascular terrestrial plants, dominated the peat sequence. A period of relatively dry surface conditions, indicated by low values of P aq and elevated ACL values, in concert with elevated δ 13 C TOC values, preceded the 8.2 kyr BP climatic event from ca. 8.7 to 8.2 kyr BP. Slightly wetter, more humid conditions, suggested by an increase in P aq as well as reduced ACL and δ 13 C TOC values, characterized the interval of the 8.2 kyr BP climatic event. Notably, the increase in surface wetness, as indicated by the biomarker record, coincided with a marked rise in fern spore proportion as well as increasing proportion of pollen from aquatic taxa. Following the 8.2 kyr BP event, a distinct change in paleohydrology at TP became apparent from ca. 7.9 kyr BP onward. An increase in the abundance of the mid-chain length n -alkanes ( n -C 23 and n -C 25 ), indicative of an increased contribution from aquatic plants to the sediment, together with a steep increase in P aq and a decrease in ACL, as well as variation in δ 13 C TOC , imply considerably elevated surface moisture levels, likely caused by the increased activity of the karstic system of the surrounding mountains. Collectively, the biomarker proxies and pollen data reveal a concise picture of changing moisture conditions at TP in response to the 8.2 kyr BP climatic event. [ABSTRACT FROM AUTHOR]

Topographically complex regions on land and in the oceans feature hotspots of biodiversity that reflect geological influences on ecological and evolutionary processes. Over geologic time, topographic diversity gradients wax and wane over millions of years, tracking tectonic or climatic history. Topographic diversity gradients from the present day and the past can result from the generation of species by vicariance or from the accumulation of species from dispersal into a region with strong environmental gradients. Biological and geological approaches must be integrated to test alternative models of diversification along topographic gradients. Reciprocal illumination among phylogenetic, phylogeographic, ecological, paleontological, tectonic, and climatic perspectives is an emerging frontier of biogeographic research. [ABSTRACT FROM AUTHOR]

Various studies have demonstrated that the stable hydrogen isotopic composition (δD) of terrestrial leaf waxes tracks that of precipitation (δD precip ) both spatially across climate gradients and over a range of different timescales. Yet, reconstructed estimates of δD precip and corresponding rainfall typically remain largely qualitative, due mainly to uncertainties in plant ecosystem net fractionation, relative humidity, and the stability of the amount effect through time. Here we present δD values of the C 31 n -alkane (δD wax ) from a marine sediment core offshore the Northwest (NW) African Sahel covering the past 100 years and overlapping with the instrumental record of rainfall. We use this record to investigate whether accurate, quantitative estimates of past rainfall can be derived from our δD wax time series. We infer the composition of vegetation (C 3 /C 4 ) within the continental catchment area by analysis of the stable carbon isotopic composition of the same compounds (δ 13 C wax ), calculated a net ecosystem fractionation factor, and corrected the δD wax time series accordingly to derive δD precip . Using the present-day relationship between δD precip and the amount of precipitation in the tropics, we derive quantitative estimates of past precipitation amounts. Our data show that (a) vegetation composition can be inferred from δ 13 C wax , (b) the calculated net ecosystem fractionation represents a reasonable estimate, and (c) estimated total amounts of rainfall based on δD wax correspond to instrumental records of rainfall. Our study has important implications for future studies aiming to reconstruct rainfall based on δD wax ; the combined data presented here demonstrate that it is feasible to infer absolute rainfall amounts from sedimentary δD wax in tandem with δ 13 C wax in specific depositional settings. [ABSTRACT FROM AUTHOR]

Throughout the Holocene, the climate of the Mediterranean region has been strongly influenced by variability in the atmospheric circulation of the high and low latitudes. A prominent example for such Holocene climate perturbations is the ‘8.2 kyr B.P. climatic event’. Reorganization of Northern Hemisphere atmospheric circulation patterns resulted in variations of temperature and precipitation distribution across the Mediterranean. The effects of changing high- and low-latitude atmospheric circulation on Mediterranean climate in relation to the 8.2 kyr B.P. climatic event are, however, not well understood. Here we present a high-resolution record of stable hydrogen isotope composition of plant-wax n -alkanes (δD wax ) across the 8.2 kyr B.P. climatic event from the Tenaghi Philippon peat deposit (NE Greece) in order to characterize patterns of precipitation and changes in atmospheric circulation in the Eastern Mediterranean region. Our record reveals pronounced changes in δD wax that correlate closely with previously published palynological data. A long-term decline in δD wax values characterizes the lower part of the section. The 8.2 kyr B.P. climatic event itself is connected to two distinct positive δD wax excursions: a minor shift in δD wax around 8.2 kyr B.P. and a major shift in δD wax between ca. 8.1 and 8.0 kyr B.P.. The upper part of the section shows a progressive trend towards higher δD wax values. We link shifts in δD wax to changes in Mediterranean air mass trajectories supplying precipitation to NE Greece caused by variations in the relative contributions of northerly-derived, D-depleted moisture and southerly-derived, D-enriched moisture. Possible control mechanisms for alternating air mass trajectories include changes in the influence of the Siberian High and differences in the influence of the African and Asian monsoon circulation on anticyclonic conditions in the Mediterranean region as well as regional inflow of moist air masses from the Aegean Sea. [ABSTRACT FROM AUTHOR]

A total of 141 samples mostly located in the Coastal Chain and the Sila Massif of Northern Calabria have been collected from 125 different springs and analyzed chemically and for the isotopic ratios 2 H/ 1 H and 18 O/ 16 O of water, with the ultimate aim to investigate isotope–elevation relationships for local meteoric waters. The Small Springs Method (SSM) has been adopted for this purpose. The hydrogeological characteristics of the watersheds of interest indicate that the sampled springs are discharged from water circuits hosted in alluvial and colluvial deposits rather than in the underlying rock substrata. The chemical characteristics of the sampled waters suggest that they are immature and related to shallow and short water circuits, in spite of the variable degree of chemical evolution. The spring waters of relatively high Total Ionic Salinity (TIS >12.5 meq/L) and those from watersheds of comparatively large elevation range (>650 m) and relatively large areas (>17 km 2 ) have been excluded from the analysis of elevation–isotope relationships. An oxygen isotope lapse rate of −0.194 ‰/100 m has been found for the spring water samples of Northern Calabria as a whole, whereas the obtained hydrogen isotope lapse rates are −1.23 ‰/100 m for the Coastal Chain and −1.45 ‰/100 m for the Sila Massif based on measured isotope values and optimized elevation. The following O-isotopes equation is recommended to estimate the average elevation ( H i in m) of the recharge areas of Northern Calabria aquifer systems: δ O 18 = − 0.00194 · H i − 5.91 (1) The maximum estimated uncertainty due to variations in the δ 18 O value over time is 202 m. Use of H isotopes is not recommended for constraining average recharge elevations due to important local variations, reflecting in different relations for the Coastal Chain and the Sila Massif. Assuming that Equation (1) holds true throughout Northern Calabria, an iso-distribution map of the δ 18 O value in rainfall has been drawn for this area. [ABSTRACT FROM AUTHOR]

We document the interplay between meteoric fluid flow and deformation processes in quartzite-dominated lithologies within a ductile shear zone in the footwall of a Cordilleran extensional fault (Kettle detachment system, Washington, USA). Across 150 m of shear zone section, hydrogen isotope ratios (δD) from synkinematic muscovite fish are constant (δD ∼ −130‰) and consistent with a meteoric fluid source. Quartz-muscovite oxygen isotope thermometry indicates equilibrium fractionation temperatures of ∼365 ± 30 °C in the lower part of the section, where grain-scale quartz deformation was dominated by grain boundary migration recrystallization. In the upper part of the section, muscovite shows increasing intragrain compositional zoning, and quartz microstructures reflect bulging recrystallization, solution-precipitation, and microcracking that developed during progressive cooling and exhumation. The preserved microstructural characteristics and hydrogen isotope fingerprints of meteoric fluids developed over a short time interval as indicated by consistent mica 40 Ar/ 39 Ar ages ranging between 51 and 50 Ma over the entire section. Pervasive fluid flow became increasingly channelized during detachment activity, leading to microstructural heterogeneity and large shifts in quartz δ 18 O values on a meter scale. Ductile deformation ended when brittle motion on the detachment fault rapidly exhumed the mylonitic footwall. [ABSTRACT FROM AUTHOR]

Assessing the geochemical signature and the role of fluids in a key Variscan detachment zone demonstrates the link between crustal deformation, thermo-mechanical events and Variscan mineralization. We document meteoric fluid infiltration into the ductile segment of the Late-Carboniferous Quiberon detachment zone (QDZ), when synkinematic muscovite and tourmaline crystallized and equilibrated with deuterium-depleted surface-derived fluids during high-temperature deformation. Titanium-in-muscovite thermometry supported by microstructures indicate that syntectonic isotope exchange between fluids and hydrous minerals occurred above 500 °C. 40Ar/39Ar muscovite data (∼319–∼303 Ma) and U(–Th)/Pb geochronology on zircon, monazite and apatite (∼318–∼305 Ma) from syntectonic leucogranites together with microstructural and geochemical (U and REE contents) data suggest that meteoric fluid-rock-deformation interaction started at ∼320 Ma and played a major role in leaching uranium at ∼305 Ma. U–Th/Pb data (∼330–∼290 Ma) from migmatites located below the QDZ strengthen the idea that meteoric fluid infiltration, detachment activity, syntectonic leucogranite emplacement and migmatization were coeval and allowed the development of a sustained hydrothermal system. • δD values of synkinematic hydrous minerals document the presence of 300 Ma-old meteoric fluids in a key Variscan detachment zone. • Meteoric fluid-rock interactions occurred during high-temperature deformation (>500 °C) in the Quiberon detachment footwall. • Coeval detachment activity, leucogranite emplacement and migmatization maintained the hydrothermal system for ∼17 Myr. [ABSTRACT FROM AUTHOR]

The central Menderes Massif in western Turkey is a bivergent metamorphic core complex characterised by two detachment faults that operated with opposite sense of shear. Here, we present K–Ar ages and hydrogen isotope data for fault gouge as well as fission track and (U–Th)/He ages for apatite and zircon from bedrock samples to constrain the timing of detachment faulting. Comparison of the K–Ar ages and low-temperature thermochronologic ages indicates brittle faulting at temperatures between ~240 and ~70 °C. At the western termination of the Gediz detachment, K–Ar ages between ~12 and ~5 Ma suggest rather continuous faulting since the mid-Miocene; a Pliocene phase of rapid slip is mainly recorded in the eastern part of this detachment. In contrast, K–Ar ages from the Büyük Menderes detachment cluster at 22–16 and 9–3 Ma and provide evidence for two phases of faulting, which is in accordance with new and published low-temperature thermochronologic data. Hydrogen isotope ratios of −76 to −115‰ indicate infiltration of meteoric water during detachment faulting and gouge formation. The youngest K–Ar ages and cooling histories for hanging and footwall rocks imply that the activity of both detachments ended ~3 Ma ago when the currently active grabens were established. • K–Ar ages of fault gouge record detachment faulting in a bivergent core complex. • Two detachment faults were active diachronously between ~22 Ma and ~3 Ma. • The Büyük Menderes detachment experienced two phases of faulting since ~22 Ma. • The Gediz detachment was active continuously from mid-Miocene to late Pliocene. [ABSTRACT FROM AUTHOR]