PERMIAN, TRIASSIC, AND JURASSIC HISTORY OF THE RALEIGH – DURHAM AREA, NORTH CAROLINA

Previously, Carpenter and Reid (2014) provided evidence that the Rolesville batholith was the principal source of sediment to the Durham sub-basin of the Deep River basin. They proposed that uplift of the batholith formed a highland area from which an alluvial fan extended at least to the western edge of the Durham sub-basin.

The present study extends this hypothesis using published geochronological and geobarometric data, and examines the uplift history of the Rolesville batholith during the Permian and Triassic periods. Key events are as follows:

1. Intrusion of Rolesville granite at 300 ma. Rocks now exposed at the surface crystallized at an estimated depth of 12 km.
2. Biotite age of 255 ma suggests that depth of crystallization had risen to 7.5 – 10 km below the existing surface. The uplift probably occurred on faults along the margin of the granite batholith.
3. Uplift continued throughout most of the Triassic, and when downdrop occurred along the eastern edge of the Durham sub-basin (this includes the Jonesboro and other faults near the eastern margin) at 235 ma, basal sediment in the alluvial fan was captured and preserved within the basin. Later, as sedimentation occurred within the basin, downdrop along the eastern margin influenced facies relationships, and lacustrine deposits formed during periods of rapid downdrop of faults along the eastern margin of the basin.
4. When diabase dikes were intruded at 200 ma, they cross cut the Jonesboro fault with no offset suggesting that downdrop had ceased along the eastern margin of the Durham sub-basin by that time. However, vitrinite reflectance data and heulandite-harmatome relationship in dike amygdules indicate that 1-3 km of additional sediment covered the basin, but has subsequently been eroded away.
5. In early Jurassic time the highland area persisted without further uplift and was subsequently eroded to the present surface configuration.