GRAVITY AND MAGNETIC STUDY OF THE DAN RIVER BASIN, VIRGINIA

The Dan River basin is a northeast-trending, early Mesozoic rift bain located in south-central Virginia and north-central North Carolina. It formed during a regional extensional event that marked the beginning of the Pangean plate breakup. The basin developed along pre-existing structures including regional faults and foliation patterns that are pre-Mesozoic in origin and most likely formed during the Allegehanian orogen. The basin is filled with Late Triassic sediments of the Newark Supergroup and include the Stoneville, Cow Branch and Pine Hall Formations. Structurally, the basin is bounded on the northeast by a normal fault zone and on the southwest by an unconformity and localized normal faults. To determine the geometry and depth of the basin, a gravity and magnetic analysis was conducted that included the construction of Bouguer gravity anomaly and magnetic intensity maps, wavelength filtered residual anomaly maps, edge enhancement maps and a series of east-west trending two and one-half dimensional gravity and magnetic models. A preliminary Bouguer gravity anomaly map indicates that the basin lies on a regional gravity gradient that parallels the Appalachian orogen and masks most of the anomaly due to the basin sediments. The only gravity evidence of the basin is the slight bending of the contour lies that represent the thick sequence of clastic sediments within the basin.