Estuarine clay mineral distribution:Modern analogue for ancient sandstone reservoir quality prediction

The spatial distribution of clay minerals in sandstones, which may both enhance or degrade reservoir quality, is poorly understood. To address this, clay mineral distribution patterns and host‐sediment properties (grain size, sorting, clay fraction abundance and bioturbation intensity) have, for the first time, been determined and mapped at an unprecedentedly high‐resolution in a modern estuarine setting (Ravenglass Estuary, UK). Results show that the estuary sediment is dominated by illite with subordinate chlorite and kaolinite, although the rivers supply sediment with less illite and significantly more chlorite than found in the estuary. Fluvial‐supplied sediment has been locally diluted by sediment derived from glaciogenic drift deposits on the margins of the estuary. Detailed clay mineral maps and statistical analyses reveal that the estuary has a heterogeneous distribution of illite, chlorite and kaolinite. Chlorite is relatively most abundant on the northern foreshore and backshore and is concentrated in coarse‐grained inner estuary dunes and tidal bars. Illite is relatively most abundant (as well as most crystalline and most Fe–Mg‐rich) in fine‐grained inner estuary and central basin mud and mixed flats. Kaolinite has the highest abundance in fluvial sediment and is relatively homogenous in tidally‐influenced environments. Clay mineral distribution patterns in the Ravenglass Estuary have been strongly influenced by sediment supply (residence time) and subsequently modified by hydrodynamic processes. There is no relationship between macro‐faunal bioturbation intensity and the abundance of chlorite, illite or kaolinite. Based on this modern‐analogue study, outer estuarine sediments are likely to be heavily quartz cemented in deeply‐buried (burial temperatures exceeding 80 to 100°C) sandstone reservoirs due to a paucity of clay grade material (<0·5%) to form complete grain coats. In contrast, chlorite‐enriched tidal bars and dunes in the inner estuary, with their well‐developed detrital clay coats, are likely to have quartz cement inhibiting authigenic clay coats in deeply‐buried sandstones

Hypogene Calcitization: Evaporite Diagenesis in the Western Delaware Basin

Evaporite calcitization within the Castile Formation of the Delaware Basin is more widespread and diverse than originally recognized. Coupled field and GIS studies have identified more than 1000 individual occurrences of calcitization within the Castile Formation outcrop area, which includes both calcitized masses (limestone buttes) and laterally extensive calcitized horizons (limestone sheets). Both limestone buttes and sheets commonly contain a central brecciated zone that we attribute to hypogene dissolution. Lithologic fabric of calcitized zones ranges from little alteration of original varved laminae to fabrics showing extensive laminae distortion as well as extensive vuggy and open cavernous porosity. Calcitization is most abundant in the western portion of the Castile outcrop region where surface denudation has been greatest. Calcitization often forms linear trends, indicating fluid migration along fractures, but also occurs as dense clusters indicating focused, ascending, hydrocarbon-rich fluids. Native sulfur, secondary tabular gypsum (i.e. selenite) and hypogene caves are commonly associated with clusters of calcitization. This assemblage suggests that calcium sulfate diagenesis within the Castile Formation is dominated by hypogene speleogemesis

Coronal Magnetic Field Evolution from 1996 to 2012: Continuous Non-potential Simulations

Coupled flux transport and magneto-frictional simulations are extended to simulate the continuous magnetic-field evolution in the global solar corona for over 15 years, from the start of Solar Cycle 23 in 1996. By simplifying the dynamics, our model follows the build-up and transport of electric currents and free magnetic energy in the corona, offering an insight into the magnetic structure and topology that extrapolation-based models cannot. To enable these extended simulations, we have implemented a more efficient numerical grid, and have carefully calibrated the surface flux-transport model to reproduce the observed large-scale photospheric radial magnetic field, using emerging active regions determined from observed line-of-sight magnetograms. This calibration is described in some detail. In agreement with previous authors, we find that the standard flux-transport model is insufficient to simultaneously reproduce the observed polar fields and butterfly diagram during Cycle 23, and that additional effects must be added. For the best-fit model, we use automated techniques to detect the latitude–time profile of flux ropes and their ejections over the full solar cycle. Overall, flux ropes are more prevalent outside of active latitudes but those at active latitudes are more frequently ejected. Future possibilities for space-weather prediction with this approach are briefly assessed

Transmission electron microscopy of metamorphic reactions

2 vols; vol. 2 of this thesis has not been filmed; please apply direct to the issuing universitySIGLEAvailable from British Library Document Supply Centre- DSC:D77416 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Cross formational flow in the Paris Basin

International audienceCross formational flow of water has occurred across several hundred metres of Liassic mudstone from the Triassic Chaunoy Formation sandstone to the Middle Jurassic Dogger Formation carbonate in the Paris Basin, France. This has been demonstrated by chemical and isotopic data from rocks and formation waters, sampled on a basin scale, from the Dogger and Chaunoy formations. Present-day and palaeoformation waters in the Dogger record input of exotic water in terms of salinity and carbon and strontium isotopes. The exotic water was highly saline and contained isotopically light carbon and 87Sr-enriched strontium in comparison to the indigenous Dogger Formation water. The source of the exotic water can only have been the Chaunoy Formation. Salinity and isotope data show that present-day Dogger Formation water contains 10–15% invasion Chaunoy water. Modelling strontium isotope ratio and concentration data from mineral cements shows that over the duration of Dogger cementation, Dogger palaeoformation waters were replaced by 1–5% Chaunoy water. Cross formational flow of water must have occurred by convective mass flow, rather than diffusion, in order to preserve the characteristics of water input from the Chaunoy. Flow probably occurred via the major Hercynian fault and fracture systems that run through the centre of the Paris Basin. Upward flow in this setting is most likely in a compressional tectonic regime, the situation during much of the Tertiary in the Paris Basin. Thermodynamic modelling indicates that cross formational flow from the Chaunoy has probably caused carbonate cementation in the Dogger