Sedimentology and Depositional Environments of the Wadesboro Sub-Basin, Eastern Piedmont, North Carolina: Implications for hydrocarbon resource potential

Brazell, Seth; Diemer, John

The Mesozoic rift basins of the Newark Supergroup formed during the breakup of Pangea ~225Ma and are present, both exposed and buried, along the east coast of North America from Florida to Nova Scotia. The basins comprising the Newark Supergroup provide valuable sedimentary records for the breakup of Pangea in Triassic and Jurassic times along with containing valuable economic resources including: oil, coal, natural gas, uranium, and industrial aggregates. The Deep River Basin is the largest Mesozoic rift basin in North Carolina and spans from the NC/SC border near Wadesboro, NC to north of Raleigh, NC and is composed of three sub-basins, the Wadesboro, Sanford, and Durham separated by cross-structures of Costal Plain sediments. The Sanford and Durham sub-basins have known deposits of coal, oil, and natural gas and all sub-basins are actively mined for clays used in brick-making. The southermost Wadesboro sub-basin is the least studied member of the Deep River Basin and as a result little is known of the lithologies comprising the basin fill, the environments of deposition for those lithologies, or the potential for hydrocarbon resources. This study is investigating the depositional history of the central portion of the Wadesboro sub-basin by means of sedimentologic and petrographic analysis and geologic mapping. Preliminary results indicate the Wadesboro sub-basin is dominated by laterally variable sandstone, siltstone, and mudstone units interpreted as being deposited in alluvial and fluvial environments with short-lived lakes on the floodplains of meandering streams. Gray to black organic rich shales (Cumnock Formation equivalents) have been identified near the western margin of the sub-basin. Additionally, a detailed sedimentologic and stratigraphic study of a clay pit that exposes a spectacular 87 meters of continuous stratigraphic section containing organic rich shales is being used as a fingerprint to interpret the nuanced but generally poor exposures found throughout the basin. Previous attempts at geologic mapping have characterized the entirety of the Wadesboro Sub-basin rocks as Pekin Formation (undifferentiated conglomerate, sandstone, siltstone, and mudstone) but do not map the complex yet valuable record of Mesozoic deposition. Mapping the occurrence and extent of organic rich shales in the sub-basin is the first step towards understanding the hydrocarbon resource potential of the Wadesboro sub-basin.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013