Precambrian Hydrocarbon Rift Basin Potential, Western North Carolina
Twenty-two samples from Precambrian strata of western North Carolina were analyzed for whole rock TOC wt.%. Polished thin sections were made from field samples from these same rocks confirming graphite-bearing metasedimentary rocks within the Late Precambrian Ocoee rift basin of western North Carolina. TOC wt.% values from the samples range from 0.38 wt.% to 2.40 wt.%. Many of the sulfides are pyrrhotite containing minor pyrite. State geologic map units sampled included the Wehutty, Nantahala, Boyd Gap, Ammons, Grassy Branch, and slate of the Copper Hill. Samples were obtained in December 2018. These samples originate from the Precambrian Ocoee rift in extreme western North Carolina. We know surprisingly little of the exact depositional environment and setting of this part of the state. A wide range of apparent primary layers (including graded bedding) are affected by folding and/or cross cut by penetrative fabrics. By state law, the North Carolina Geological Survey is charged with investigating the hydrocarbon potential in this basin. Metamorphic grade in the sampled area of the southwestern part of the state is about that of garnets. Garnets dominate in several samples. Many of these samples also have iron sulfides. The graphite is interpreted to be the result of algal mats that are potential hydrocarbon source rock. The stratigraphic sections sampled are very thick (maybe as much as 15,000-ft thick or more). However, the actual the graphitic horizons within these units are probably not that thick. Slightly lower grade metamorphic rocks may occur along strike in southwest Tennessee. Additional reflected and transmitted light microscopy study is planned for these samples to increase insight to this basin’s hydrocarbon potential.
AAPG Datapages/Search and Discovery Article #90373 © 2019 AAPG Eastern Section Meeting, Energy from the Heartland, Columbus, Ohio, October 12-16, 2019