Abstract: Field analysis shows that fault cores of brittle, extensional faults at a medium to mature stage of development are commonly dominated by lozenge-shaped horses (fault-core lenses) characterized by a variety of lithologies, including intact, mildly to strongly deformed country rock derived from the footwalls and hanging walls, various types of fault rocks of the protocatalasite and breccia series, breccia, fault gouge and clay smear. The lenses are sometimes stacked to form complex duplexes. These structures are commonly separated by high-strain zones of sheared cataclasite, and/or clay smear/clay gouge. The geometry and distribution of clay gouge in high-strain zones sometimes display evidence of intrusion, indicating high fluid pressure. Although the sizes of the horses vary over several orders of magnitude, they frequently display a length:thickness (a:c) ratio of between 1:4 and 1:15. The high-strain zones of fault rocks commonly constitute unbroken, 3D membranes that are likely to constrain fluid communication both across and along the fault zone. There are significant contrasts in fault core architecture that are probably related to processes associated with contrasting fluid pressure, strain intensity and strain hardening/strain softening. Faults associated with strain softening are characterized by less abundant brittle deformation products and are less likely to be conduits for fluid flow compared to those that are affected by strain hardening.

This paper presents an overview of the Till-Tweed project, an Aggregates Levy Sustainability Fund–sponsored geoarchaeological assessment of archaeological and paleoenvironmental records in a major northern UK river basin. The project methodology employed a suite of geomorphological, paleoecological, and archaeological techniques to identify, define, and delimit landform, sediment, and archaeological associations over 358 km 2 of the Till and lower Tweed Valleys. These associations were integrated in a geographic information system (GIS), establishing a baseline audit of the heritage resource that is driving the development of both heritage management and research frameworks in these river valley settings. Particular attention is paid to the new perspectives on landscape development, land use, and settlement that are being derived from analysis of associations between landforms, paleoenvironmental records, and enhanced archaeological data sets. The utility of this approach is illustrated by a case study of the Breamish–Till River at New Bewick, near Powburn, Northumberland. This landscape exhibits a wide range of documented archaeological records, including upstanding monuments, crop marks, and lithic scatters, as well as the potential for alluvial burial of remains that have yet to be discovered. Elements of particular interest are extensive areas of terraced sand and gravel associated with late Devensian deglaciation that are shown to host persistent, multiperiod occupation dating from the Mesolithic period. Numerous infilled kettle holes in these surfaces offer the prospect of long paleoenvironmental records, while paleochannel fills preserved on the adjacent Holocene alluvial valley floor have been shown to locally date from the fourth millennium B.C. and have yielded paleo-ecological evidence of episodic Anglo-Saxon and later woodland clearance, pastoral activities, and cereal cultivation in the immediate vicinity of the archaeological sites. We conclude that the integration of these geoarchaeological data sets into a GIS platform not only brings clear practical benefits to heritage managers and developers, but constitutes a valuable research tool by permitting more sophisticated and systematic analyses of links between the modern landscape, the environmental record, and the archaeological data set.

Abstract Organic-rich shale contains significant amounts of gas held within fractures and micropores and adsorbed onto organic matter. In the USA shale gas extracted from regionally extensive units such as the Barnett Shale currently accounts for 6% of gas production and is likely to reach 30% by 2015. Shale gas prospectivity is controlled by the amount and type of organic matter held in the shale, its thermal maturity, burial history, microporosity and fracture spacing and orientation. Potential targets range in age from Cambrian to the late Jurassic, within the main UK organic-rich black shales: younger shales have been excluded because they have not reached the gas window, but they may possess a biogenic gas play. A geographic information system, showing the distribution of potential reservoir units, has been created combining information on hydrocarbon shows, thermal maturity, fracture orientation, gas composition, and isotope data to identify potentially prospective areas for shale gas. Some of these data are shown as graphs and maps, but crucial data is lacking because earlier exploration concentrated on conventional reservoirs. The prospects include Lower Palaeozoic shale basins on the Midland Microcraton (a high risk because no conventional gas has been proved in this play), Mississippian shales in the Pennine Basin (the best prospect associated with conventional fields and high maturity), Pennsylvanian shales in the Stainmore and Northumberland Basin system (high risk because no conventional gas discoveries exist) and Jurassic shales in Wessex and Weald basins (small conventional fields signify potential here).