FAULT-RELATED FOLDING AND ITS CONTROL ON BASIN DEPOSITION, DEEP RIVER TRIASSIC RIFT BASIN, NORTH CAROLINA

Geologic mapping (1:24,000-scale) in the southern portion of the Durham basin extended lithofacies and lithofacies associations previously mapped in the central Durham basin. The Durham basin, a component of the Deep River Triassic basin, is one of the southern-most exposed basins in the Newark Supergroup, a series of continental rift basins formed during the breakup of Pangea. Mapping also extended and refined the trace of the previously reported Bonsal-Morrisville fault. In addition, mapping identified several unreported map-scale anticlines and synclines. These folds appear spatially and kinematically related to intrabasinal and basin-bounding normal faults. Although extensional folding is well documented in other continental rift basins, the folds identified in this study are smaller in magnitude and may not have the same mechanism of formation as those larger basin-wide folds.

In order to examine possible mechanisms for generating these folds, several models of fault-related extensional folding were applied to a portion of the Deep River basin. In addition to established models of fault-related folding (i.e., longitudinal, transverse, and relay-ramp folding), a variation of the traditional fault-bend fold model was developed. An important concept of all these models is syndepositional faulting, which not only deforms previously deposited sediment, but also controls the location of developing depocenters. When comparing schematic fold models to geologic maps of the Deep River basin, these models predicted the general locations of fold axes and depocenters. This study suggests that fault-related fold models can be used to predict depositional patterns, especially in areas of poor geologic exposure, thereby more effectively targeting costly surface and sub-surface investigations, such as drilling or seismic profiling.