Abstract The 295-300 Ma Petersburg batholith in east-central Virginia forms one of the largest and northernmost of the Alleghanian plutonic complexes in the southern Appalachian Piedmont. The batholith is primarily composed of granite including massive and foliated (both magmatic and solid-state fabrics) varieties. The plutonic complex intruded medium-grade metamorphosed volcanic/plutonic rocks of the Roanoke Rapids terrane. The western edge of the batholith experienced right lateral transpressional deformation associated with movement on the Hylas fault zone during the Alleghanian orogeny; this was followed by normal faulting and exhumation during the development of the Triassic Richmond basin. Much of the batholith was buried by a thin veneer of primarily Cenozoic siliciclastic sediments at the western edge of the Atlantic Coastal Plain. Granite rocks of the Petersburg batholith have long been quarried for both dimension and crushed stone. The purpose of this trip is to discuss the age, origin, and tectonic significance of the Petersburg batholith.

Abstract The Richmond basin, a rift basin of Late Triassic to Early Jurassic age in east-central Virginia, produced the first coal mined in the United States in the early 1700s. These Triassic coal beds are thick and gas-rich, and fatal explosions were common during the early history of exploitation. Since 1897, at least 38 confirmed oil, natural gas, and coal tests have been drilled within the basin. Although shows of asphaltic petroleum and natural gas indicate that active petroleum systems existed therein, no economic hydrocarbon accumulations have been discovered to-date. The Richmond basin has been assessed by the U. S. Geological Survey (USGS) as one composite total petroleum system, in which the hydrocarbon potential of the source beds (both coal and dark shale) and potential reservoirs have been combined into a single continuous tight gas assessment unit within the Chesterfield and Tuckahoe groups (Upper Triassic). Sandstone porosities are generally low (<1 % to 14 %). Thick, dark-colored shales have total organic carbon (TOC) values that range from <1% to 10%, and vitrinite reflectance (%R O ) values that range generally from about 0.3 to 1.1%, which indicates that the submature to super mature shales appear to be the source of the hydrocarbons recovered from some of the boreholes. The stratigraphic combination of these potential source rocks, tight sandstones, and hydrocarbon shows are the basis for the current USGS assessment of the technically recoverable undiscovered hydrocarbon resources of the basin. Mean values for these resources are 211 billion cubic feet of gas (BCFG) and 11 million barrels of natural gas liquids (MMBNGL).

Abstract The central Virginia Piedmont is underlain by complex igneous and metamorphic rocks, including: Paleozoic, Neoproterozoic, and Mesoproterozoic rocks of the suspect Goochland terrane; Early Paleozoic rocks of the suspect Chopawamsic arc terrane; Mid-Paleozoic successor basin deposits; and a suite of Taconic and Alleghanian plutons. Terranes are juxtaposed along a network of Late Paleozoic dextrally transpressive high-strain zones. The origin and significance of both the Goochland and Chopawamsic terranes remain a source of debate. The central Virginia Piedmont includes a distinct suite of commercial-grade mineral deposits including rutile-rich anorthosite, pegmatite, kyanite, and slate. The widely felt 2011 Virginia earthquake (M = 5.8) occurred along an unrecognized fault in the central Virginia seismic zone and demonstrates that old Appalachian structures are still active in eastern North America's modern stress field.

Abstract The story of UK onshore exploration goes back to the days of World War I and was prompted by the increasing use of oil for the war effort. The war was drawing to a close as the campaign commenced in 1918. The UK government sponsored the drilling with a budget of £1 000 000 and the work was undertaken by S. Pearson & Sons, a UK engineering company owned by Lord Cowdray (Weetman Pearson). Pearson also had oil interests and he owned the Mexican Eagle Company that had had exploration success in Mexico. Pearson hired a team of American geologists to select suitable drilling locations in the UK. The Carboniferous rocks in the area surrounding the Derbyshire Dome in England and the Midland Valley in Scotland were chosen because of their similarity to the oil-producing areas of Pennsylvania and West Virginia in the USA. Eleven wells were sunk: seven in Derbyshire, two in North Staffordshire and two in Scotland. The first well to be spudded was at Hardstoft in Derbyshire in October 1918 and it was also the first oil discovery. The geological reasoning behind the selection of the drilling sites will be compared with the actual results from 1918–22.

Abstract In 2014, the geomorphology community marked the 125th birthday of one of its most influential papers, ‘The Rivers and Valleys of Pennsylvania’ by William Morris Davis. Inspired by Davis’s work, the Appalachian landscape rapidly became fertile ground for the development and testing of several grand landscape evolution paradigms, culminating with John Hack’s dynamic equilibrium in 1960. As part of the 2015 GSA Annual Meeting, the Geomorphology, Active Tectonics, and Landscape Evolution field trip offers an excellent venue for exploring Appalachian geomorphology through the lens of the Appalachian landscape, leveraging exciting research by a new generation of process-oriented geomorphologists and geologic field mapping. Important geomorphologic scholarship has recently used the Appalachian landscape as the testing ground for ideas on long- and short-term erosion, dynamic topography, glacial-isostatic adjustments, active tectonics in an intraplate setting, river incision, periglacial processes, and soil-saprolite formation. This field trip explores a geologic and geomorphic transect of the mid-Atlantic margin, starting in the Blue Ridge of Virginia and proceeding to the east across the Piedmont to the Coastal Plain. The emphasis here will not only be on the geomorphology, but also the underlying geology that establishes the template and foundation upon which surface processes have etched out the familiar Appalachian landscape. The first day focuses on new and published work that highlights Cenozoic sedimentary deposits, soils, paleosols, and geomorphic markers (terraces and knickpoints) that are being used to reconstruct a late Cenozoic history of erosion, deposition, climate change, and active tectonics. The second day is similarly devoted to new and published work documenting the fluvial geomorphic response to active tectonics in the Central Virginia seismic zone (CVSZ), site of the 2011 M 5.8 Mineral earthquake and the integrated record of Appalachian erosion preserved on the Coastal Plain. The trip concludes on Day 3, joining the Kirk Bryan Field Trip at Great Falls, Virginia/Maryland, to explore and discuss the dramatic processes of base-level fall, fluvial incision, and knickpoint retreat.

Abstract The cliffs along the Potomac River at Stratford Hall display extensive exposures of Miocene marine strata that belong successively to the Calvert, Choptank, St. Marys, and Eastover Formations. Within the lower part of this sequence, in the Calvert and Choptank Formations, there is well-developed cyclic stratigraphy. Above the Miocene units lies the marginal marine to deltaic Pleistocene Bacons Castle Formation, which is the highest and youngest formation exposed in the cliffs. The goals of this field trip guide are to (1) show the Miocene formations exposed in the cliffs and discuss the paleoenvironments within which they formed, (2) demonstrate the cyclicity in the Miocene marine formations and discuss its origin, (3) compare and contrast the section exposed at the Stratford and Nomini Cliffs with the classic Miocene Calvert Cliffs sequence exposed to the northeast in Calvert County, Maryland, and the Miocene sequence recovered in the Haynesville cores to the southeast in Richmond County, Virginia, (4) discuss and explain why a detailed correlation among these three places has been so difficult to attain, and (5) show typical lithologies of the Bacons Castle Formation and discuss the paleoenvironments in which they formed.

Abstract The Hugh Miller collection (mainly NMS G.1859.33) held at the National Museums of Scotland, Edinburgh, consists of 591 palaeobotanical specimens, 54 of which are of type and/or figured status. A preliminary assessment of this collection, in the light of renewed interest in Hugh Miller’s works in the bicentenary of his birth (2002), has provided new insights into this remarkable Scottish geologist. Miller, through writing popular articles in both newspaper and book format, publicized the various subdisciplines of palaeontology including palaeobotany. His distinctive writing style promoted public understanding of the science, and helped his readers to grasp the concept of deep time and the intricacies of past worlds. An appendix of type and figured material based on Miller’s collection is included.