EXPLORING PRE-CRETACEOUS TERRANES AND BASINS BENEATH THE ATLANTIC COASTAL PLAIN

Poorly known pre-Cretaceous terranes and basins beneath Atlantic Coastal Plain sediments comprise one of the last geological frontiers in eastern North America. Local insights come from drilling for energy (hydrocarbon, geothermal) resources, environmental remediation (e.g., geophysics and drilling at Savannah River Site), and drilling to evaluate ground-water quality and availability (aquifer studies and Chesapeake Bay impact structure).

To evaluate pre-Cretaceous rocks beneath the coastal plain from VA to southern NJ, we are completing a geospatial data set of >400 boreholes (>330 have pre-Cretaceous rock descriptions); performing petrographic, geochemical, and isotopic analyses of drill samples; reprocessing aeromagnetic and gravity data (experimenting with derivatives, filters, data combinations, colors, shading); and producing a 1:500,000-scale geologic map. In this region, buried extensions of Piedmont terranes and basins are flanked progressively eastward by the Sussex mafic complex and suture(?) zone, Neoproterozoic and Paleozoic rocks of the Chesapeake zone (mostly greenschist facies), and amphibolite-facies rocks of the Cape May (Mesoproterozoic?) and Hatteras (Neoproterozoic) zones. Most early Mesozoic rift basins lack distinct magnetic and gravity anomalies, but the Taylorsville basin correlates with a gravity low and long-wavelength magnetic anomalies consistent with thick sedimentary rocks. Recurrent Cretaceous to Cenozoic movements occurred on steep coastal-plain faults rooted in basement structures such as the Hylas and Spotsylvania fault zones.

We are interested in expanding collaboration on geospatial data sets, analyses of drill samples (notably geochronology and isotopic studies), geophysical studies, geologic mapping, and syntheses of pre-Cretaceous terranes beneath the coastal plain beyond the mid-Atlantic region. In GA and SC, for example, studies are needed to test hypotheses of basement influence on coastal-plain structures, aquifers, and neotectonics; improve the geologic framework for water, energy, environmental, geohazard, and CO₂ storage applications; and decipher buried features such as the Suwannee suture, Brunswick (Charleston) terrane, fault systems, and relations of late Paleozoic transpression to early Mesozoic rift initiation.