SPATIAL AND TEMPORAL RELATIONSHIPS BETWEEN DIKES, THERMAL SPRINGS, AND DRAINAGE DIVIDES IN THE APPALACHIAN VALLEY & RIDGE AND THE CHESAPEAKE BAY IMPACT STRUCTURE

Spatial and temporal patterns between the Chesapeake Bay impact structure and geologic features in the Virginia Valley and Ridge suggest possible genetic relationships. Most of the Eocene intrusions centered in Highland County, Virginia are apparently older than the impact. However one basaltic plug, Trimble Knob, has an anomalous age that corresponds with the age of the impact structure. This suggests that Trimble Knob may have resulted from reactivation of crustal fractures during impact. Trimble Knob is approximately 330 km from the impact site.

Most of Virginia’s thermal springs occur in Bath County, Virginia, in close proximity to the Eocene dike swarm. These warm springs, and others that occur regionally, lie along a circle centered on the Chesapeake Bay crater. The radius of this circle is approximately 330 km, and also passes through Trimble Knob. The age of the thermal springs, and associated travertine deposits, are unknown.

Trimble Knob also lies on the drainage divide between the James and Potomac Rivers, and is about 10 km from the divide between these rivers and the Ohio River basin. These and other drainage divides are situated in radial and concentric patterns around the impact site. Drainage divides between the Susquehanna, Potomac, James, Roanoke, and Cape Fear Rivers form a radial pattern relative to the impact site, like spokes of a wheel. The divides between these five drainage basins and those of the Ohio and Peedee Rivers lie along a circle with an approximate radius of 340 km centered on the impact site.