Abstract The Scottsville Basin in the central Virginia Piedmont forms one of the westernmost Mesozoic sedimentary basins in eastern North America. This small basin has received limited scientific attention during the past 50 years; this field trip focuses on recent stratigraphic and structural research concerning the Scottsville Basin and surrounding region. The ∼110 km 2 Scottsville Basin and adjacent ∼5 km 2 Midway Mills Sub-basin formed astride the boundary between the eastern Blue Ridge and western Piedmont. The Scottsville Basin is a half-graben, bound on its northwest margin by a segmented normal fault that places Neoproterozoic to early Paleozoic metamorphic rocks in the footwall against Triassic strata in the hanging wall. Basin strata dip to the northwest toward the boundary fault, and dip angles increase from west to east. The southeastern basin boundary, previously interpreted as a small displacement normal fault, is an unconformity with phyllitic rocks of the western Piedmont. Strata within the basin include 2–3 km of boulder to pebble conglomerate, breccia, arkosic sandstone, and siltstone. Sedimentary rocks in the Scottsville Basin were sourced primarily from Proterozoic rocks in the Blue Ridge province to the west of the basin. The age of Triassic strata in the Scottsville Basin is poorly constrained. The Midway Mills Sub-basin was originally contiguous with the Scottsville Basin, but now forms an erosional outlier. A suite of north-northwest–striking Jurassic diabase dikes crosscuts Triassic sedimentary rocks and is subparallel to the dominant extensional fracture set in basin sedimentary rocks.

Two cores at the outer margin of the Chesapeake Bay impact structure show significant structural and depositional variations that illuminate its history. Detailed stratigraphy of the Watkins School core reveals that this site is outside the disruption boundary of the crater with respect to its lower part (nonmarine Cretaceous Potomac Formation), but just inside the boundary with respect to its upper part (Exmore Formation and a succession of upper Eocene to Pleistocene postimpact deposits). The site of the U.S. Geological Survey–National Aeronautics and Space Administration Langley core, 6.4 km to the east, lies wholly within the annular trough of the crater. The Potomac Formation in the Watkins School core is not noticeably impact disrupted. The lower part of crater unit A in the Langley core represents stratigraphically lower, but similarly undeformed material. The Exmore Formation is only 7.8 m thick in the Watkins School core, but it is over 200 m thick in the Langley core, where it contains blocks up to 24 m in intersected diameter. The upper part of the Exmore Formation in the two cores is a polymict diamicton with a stratified zone at the top. The postimpact sedimentary units in the two cores have similar late Eocene and late Miocene depositional histories and contrasting Oligocene, early Miocene, and middle Miocene histories. A paleochannel of the James River removed Pliocene deposits at the Watkins School site, to be filled later with thick Pleistocene deposits. At the Langley site, a thick Pliocene and thinner Pleistocene record is preserved.

Abstract The elemental compositions of relatively unweathered Fe-Ti oxide grains, mostly ilmenite, separated from 83 samples collected from late Pleistocene to modern beach sands in Virginia and North Carolina were compared to those of 72 samples from five potential source rivers, the Roanoke, James, Potomac, Susquehanna, and Hudson Rivers. The composition of the Fe-Ti oxides from the toe of the Suffolk Scarp have a much different provenance than do younger beach deposits to the east. Based on discriminant analysis classification of the Fe-Ti oxide compositions with potential source rivers, the Suffolk Scarp beach is inferred to have been derived primarily from the James River; the younger beaches, including modern beach deposits of the Outer Banks, North Carolina, are inferred to have been primarily from the Susquehanna River with minor input by the Hudson River via longshore transport and reworking of shelf sands. The difference in provenance is due primarily to the origin of the Suffolk Scarp beach by erosion of older estuarine units in a protected-bay beach setting, whereas the younger beach deposits were derived from reworking of shelf sands, probably bay-mouth sand deposits (massifs), in an unprotected or barrier-beach setting. Subtle differences in the Fe-Ti oxide compositions among beach deposits are due to changes in the mix from the different river sources. Discrimination of the differences allows for a clearer understanding of the interrelation among those coastal-plain ridges and scarps that contain the beach sands.