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There is a limited understanding of the spatial linkage between cementation processes in shoreface/coastal plain successions and those operating in distal offshore successions. To address this, an integrated sedimentological, sequence stratigraphic and diagenetic study was undertaken on a distal shallow-marine succession, the Upper Cretaceous Kenilworth Member Book, Cliffs, Utah, USA. Laterally extensive carbonate cement is the most volumetrically significant diagenetic feature. It constitutes up to 55 vol.% of the distal lower-shoreface sandstone and sandy siltstone units beneath major flooding surfaces. During rising relative sea-level major flooding events resulted in low sedimentation, which extended residence time of sediments in early diagenetic zones and promoted enhanced cementation beneath these boundaries. Carbonate for early calcite cements was probably derived from sulphate reduction, marine water and oxidation of organic matter. Stable-isotopic composition of later ankerite (δ18O − 11.9 to − 6.0‰ VDPB, δ13C − 4.5 to − 0.3‰ VDPB) suggests precipitation during progressive burial (c. 1.7 to 3.4 km, 72 to 122 °C) from evolved marine fluids. The carbonate and other mineralizing solutes were derived, increasingly with burial, from decarboxylation of organic matter and clay mineral transformations in adjacent siltstones and shales. These interbedded, overlying and underlying facies provided an important source of mineralizing solutes that influenced the extent of pervasive cementation during burial. The combination of stratigraphic and lithofacies control resulted in laterally extensive cements that differ to shoreface successions, although are similar in form to those described for many offshore mudstone-dominated successions. Limited early concretionary ferroan dolomite beneath the expression of the sequence boundary and some flooding surfaces, however, suggests cementation by meteoric fluids at times of relative sea-level lowstand. Similar processes have been demonstrated in more proximal successions in the Book Cliffs.

Remobilisation of contaminant metals from sediments can occur by chemical, biological or physical changes. This in turn can lead to contaminant fluxes to the porewaters and ultimately the water column. The aim of the research presented here is to document post-depositional controls on metal mobility and fluxes in a heavily metal-contaminated estuary. This will allow for an improved understanding of the impact of contaminated sediments on water quality from both a short-term and long-term perspective. Dulas Bay is situated on the east coast of Anglesey, North Wales, and receives polluted waters from Parys Mountain. Metals within Dulas Bay sediments show surface enrichment and variations in mineralogical form. Diagenesis clearly plays a role in post-depositional behaviour of the metals, forming sulphides and potentially carbonates. The presence of a dominant exchangeable/carbonate fraction, and elevated porewater metals, in this sulphidic system is significant and could indicate the presence of freshwater diagenesis, or, reflect the high levels of metals in the sediment.

Laterally persistent carbonate cementation, in the form of concretions or cemented horizons, is common within shallow marine sandstones reservoirs. Understanding the distribution of such cemented zones is of immense value, as within the subsurface they may lead to reservoir compartmentalisation and associated production problems. However, the exact sedimentological and stratigraphic relationships of these cemented horizons are generally lacking as the majority of studies have been undertaken on borehole material or outcrops of limited lateral extent. In this paper the field relationships between cementation and stratigraphy from the exceptionally well-exposed Upper Cretaceous sediments in Book Cliffs, Utah-Colorado are documented. We show that laterally persistent cemented horizons consistently occur beneath major marine flooding surfaces and propose that the initial precipitation of these cemented horizons took place at periods of markedly reduced sediment accumulation rates associated with these flooding events.

This study documents a link between sea-level fall and basin-scale dolomite cementation of shoreface sandstones in the Upper Cretaceous Desert Member, Book Cliffs, Utah, by integrating sedimentology, sequence stratigraphy, and sedimentary geochemistry. Within the Desert Member shoreface sandstones, a number of high-frequency sequence boundaries formed as a result of relative sea-level falls that led to localized incised valley formation, subaerial exposure, and meteoric leaching of upper shoreface sandstones. Shoreface sandstones up to 10 km downdip from these subaerial exposure surfaces contain ferroan dolomite concretion bodies as much as 8 m thick. Basinward of this smaller (as much as 1 m in size), less abundant dolomite, concretions can be traced at the same horizons. Some δ 1 8 O data suggest that cement precipitated from porewater with a significant meteoric component, although reequilibration and recyrstallization cannot be eliminated. Some δ 1 3 C data suggest carbonate derivation from detrital dolomite leached from beneath organic-rich coastal plain strata deposited during high-frequency sequence boundary development. We propose that during high-frequency sequence boundary formation, meteoric fluids migrated basinward into shoreface sandstones as a result of the relative fall in sea level. The precipitation of dolomite cement in the shoreface sandstones was promoted by the updip dissolution and remobilization of detrital dolomite by the meteroic fluids, mixing with marine pore fluids, and the presence of detrital dolomite in the shoreface sandstones, which acted as nucleation sites for dolomite precipitation. This study illustrates the impact of stratigraphic development upon basin-scale early diagenetic cementation of siliciclastic succcesions.

A one day meeting of the British Sedimentological Research Group (BSRG), convened by K. G. Taylor and A. H. Ruffell, was held at the Postgraduate Research Institute for Sedimentology, University of Reading on 23 June 1992. The meeting set out to consider what is known about palaeoenvironments of the NW European early Cretaceous and to present current areas of new research that may significantly expand our understanding of this topic. Over 50 people attended this multidisciplinary meeting, coming from the fields of sedimentology, geochemistry, palaeontology and tectonics. There were 13 speakers and five poster presentations. Financial assistance from the BSRG to speakers from overseas is gratefully acknowledged. The Institute is also thanked for the use of their facilities. After a brief welcome by the conveners, D. J. Batten (Aberystwyth University) gave a talk reviewing his work on the palynology of NW European Wealden sediments. In this he stressed how palynological data, integrated with other available evidence, can contribute significantly to interpretations of early Cretaceous environments and should be utilized more by sedimentologists. In particular, the total recoverable organic matter in a sample should be studied, not just the identification of miospores and dinoflagellate cysts. J. Eyers (Open University) described how detailed sedimentology, grain-size analysis and gamma-ray logging have been used to correlate the Lower Cretaceous of the Bedfordshire Province. Using isopachyte maps, she was able to show that basement structures, reactivated as a result of North Sea rifting, were a major control on sedimentation. She also tentatively compared a combined

PurposeChromium, a potentially harmful element, occurs commonly within the urban sediment cascade as a result of abundant industrial and transport-related sources. The risks that Cr-bearing particles pose to ecosystems and humans depend on the solid-phase chemical speciation of Cr and its environmental mobility. In this study, we adopt an integrated geochemical approach to investigate and determine the long-term fate of Cr in the urban sediment cascade.Materials and methodsWe use bulk chemical digests, sequential chemical extraction analysis, electron microscopy, electron microprobe and microfocus XANES analysis to describe the solid-phase speciation, geochemical characteristics and potential long-term behaviour of Cr in urban particulate matter from both aquatic sediment and road dust sediment (RDS) in Manchester, UK.Results and discussionCr-bearing grains within RDS and aquatic sediment are predominantly iron oxides and alumino-silicate glass grains. Electron microprobe analysis indicates Cr concentrations up to 3300 and 133,400 μg g−1 in the RDS and aquatic grains, respectively. XANES analysis indicates that Cr(III) is the dominant oxidation state, with only trace amounts of Cr(VI). Importantly, Cr speciation does not appear to have changed between sedimentary environments and the dominance of Cr(III) suggests limited bioavailability or toxicity under predominant environmental (anoxic and neutral pH) conditions in the aquatic sediment sink. Furthermore, geochemical analyses suggest the environmental mobility of Cr in the aquatic sediment sink is low (compared to other toxic metals) due to its association mainly with alumino-silicate glass grains and its inclusion as an integral part of the glass structure.ConclusionsIndustrial glass grains are a major component of urban sediment worldwide. The speciation and geochemical investigations performed in this study suggest most Cr within the urban sediment cascade may be resistant to environmental processes that could mobilise other toxic metals.

This article presents the first part of a study on the interaction between residual stresses and crack driving force. Blunt notched CT specimens were pre-strained to introduce residual stresses at the notch, where a crack is subsequently introduced. FE modelling is used to model the specimen preload and pre-cracking. Modelling predictions are validated by two different methods. The total predicted surface residual strains are compared to image correlation measurements. The predicted residual strains were measured using neutron diffraction, both before and after fatigue cracking. The residual strain profiles show good agreement with the 3D FE model in the far field but the peak strains measured near the notch are smaller those predicted. This is a result of the low spatial resolution of the technique.

Permeabilities (k) of Lower Jurassic Whitby Mudstone samples collected from a wave-cut platform, NE England, were measured for flow of argon parallel and perpendicular to bedding across a range of effective pressures (peff) (10–70 MPa) using the oscillating pore pressure method. Petrographic analyses including X-Ray diffraction and scanning electron and optical microscopy show that samples comprise a silt-rich, clay bearing mudstone containing 2 orders of magnitude, after which permeability of samples parallel to the layering varies with peff according to: k = 4.1(±0.6)×10−19 exp(−0.034 ± 0.003 peff). Over this pressure range volumetric strain measurements showed that after the first pressure cycle pore volume changes are purely elastic and there is no permanent pore collapse. The technique of pressure cycling as part of the measurement of k reduces the time required to make a reliable measurement that is likely to represent the in-situ permeability and its relationship to peff. The impact of permeability sensitivity to pressure was evaluated by application of a simple reservoir model for dry gas. Unless the effective pressure dependent permeability is taken into account, substantial overestimation of gas flow rate and original gas in place will be made from well tests.