--> --> Use of NURE Stream Sediment Data to Determine the Provenance of Triassic Clastic Sediment in the Raleigh – Durham Area, North Carolina

Eastern Section Meeting

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Use of NURE Stream Sediment Data to Determine the Provenance of Triassic Clastic Sediment in the Raleigh – Durham Area, North Carolina

Abstract

The National Uranium Resource Evaluation (NURE) program was initiated by the Atomic Energy Commission (AEC) in 1973 with a primary goal of identifying uranium resources in the United States. The program ended in 1983. Two major phases of the program included sampling and analysis of stream sediment and groundwater in many areas of the United States. This study utilizes stream sediment data. There were 397,609 stream sediment samples collected and analyzed for the United States (Smith, 1997). Elements of interest in minus 100-mesh stream sediment include Th, REE, K, Fe, and Ti. The Durham sub-basin and the Rolesville batholith are enriched in Th, REE, and K, and depleted in Fe and Ti compared to the rocks of the Carolina, Falls Lake, Raleigh and Crabtree terranes that lie between these units. Monazite has been identified in the Rolesville batholith, and the La/Th ratios are consistent with that of monazite in both the Rolesville batholith and the Durham sub-basin. The La/Th ratio in rocks surrounding the basin are much higher, and out of the normal range of monazite. Consequently, La and Th likely reside in different minerals in these rock units. A geologic model which explains these relationships involves uplift of the Rolesville batholith resulting in erosion and formation of a clastic wedge on a pediment surface that extended to the west. During the early history of the Durham sub-basin, the clastic wedge probably extended over the entire basin, and was captured by the basin during periods of subsidence along the Jonesboro fault. So long as the clastic wedge extended over the entire basin, rock units surrounding the basin were covered and did not contribute sediment. The northern portion of the Durham sub-basin is interpreted as a principal depo-center. From here, sediment was re-transported to more southerly portions of the sub-basin along basin axial flow. Implications of these findings on the depositional, erosional, and tectonic history of the area complement recent studies on the natural gas resource potential of the Deep River basin (Reid and Milici, 2008; Reid and others, 2011).