| Description: |
The North American rift margin includes of a series of Triassic rift basins along the eastern seaboard of the United States and Canada. This continent-scale rift basin system is comprised of complex and variable geometries that can be generalized into regions with similar structural, deformational, and sedimentary characteristics. Rift basins provided accommodation space for organic-rich Triassic age sediments that may be source rocks for natural gas and petroleum. Most of the known basins are exposed at the surface and relatively easy to access, but a few buried basins have been identified beneath coastal plain strata. I used primarily geophysical methods to study a buried Triassic rift basin in Bertie County, North Carolina, recently discovered from a deep core sample that documented Triassic sedimentary rocks buried underneath approximately 300 meters of Cretaceous and younger, sediments and sedimentary rock. Approximately 30 meters of Triassic strata were recovered from the well, but basement rock was not reached leaving the overall thickness of the basin undetermined. I used a gravity survey to constrain the dimensions and geometry of the basin and surrounding rock bodies at depth. Data processing, modeling, and integration with preexisting data was accomplished using Oasis:Montaj software. The buried basin creates a maximum gravity anomaly of approximately 7 mGal. Modeling of the data suggests the basin is generally elongate, SW to NE, and has maximum dimensions of approximately 15 km wide, 50 km long, and as much as 2.5 km deep (basin infill). In cross section, the basin is asymmetrical and wedge-shaped, with a NW margin that dips steeply SE and a SE margin that dips more shallowly NW. The Bertie basin is deepest to the south and was likely hydrogeologically open in that direction. Previous datasets have been derived from analysis of the cores at the North Carolina Geologic Survey and include whole rock geochemical analysis, thin sections, and magnetic susceptibility. Interpretation of the geochemical ... |