Geology and depositional environment of strata in the vicinity of Jacob's Creek Quarry, Denton, NC: Implications for the stratigraphy and age of the Albemarle Group

Abstract

The Albemarle Group is one of the major defining stratigraphic units of the Carolina terrane, the best-known division of the southern Appalachian peri-Gondwanan block of Carolinia. As such, the group has been recognized as important for correlating Carolinia with other peri-Gondwanan Appalachian blocks. Until recently, it had been considered a conformable sequence of mainly Late Neoproterozoic age; however, this age assignment has been in question due to reports of Paleozoic (Late Cambrian and younger) fossils from two quarries in the group. To accommodate the reported fossil finds, significant revisions to the stratigraphy and structure of the group were proposed. This study focused on resolving the stratigraphy and structure of the group in the vicinity of Jacob’s Creek Quarry, one of the reported Paleozoic fossil locations. Measurement of a 20-meter stratigraphic section across the Cid mudstone and Flat Swamp member contact, recently proposed as a regionally significant thrust, identified an intercalation of mudstone, greywacke, epiclastics and tuffaceous siltstone indicative of a conformable and gradational contact. No significant tectonic structures, other than a weak regional cleavage that is observed throughout the study area, were observed. Facies associations also suggest that the Cid and Floyd Church Formations form part of a conformable, coarsening upward sequence. In addition, field and facies evidence did not reveal evidence of Paleozoic outliers. Therefore, the rocks in the vicinity of Jacob’s Creek Quarry are considered Neoproterozoic and changes to our understanding of the stratigraphy and structure of the Albemarle Group are unwarranted. A secondary objective of this investigation was to compile in digital geospatial format, geological field maps produced by previous graduate students from North Carolina State University that are contiguous to the area studied herein. This was done by direct digitization of paper maps produced as part of unpublished theses. The product is a geological map of contiguous portions of the Morrow Mountain, Badin and Handy quadrangles.