Paper No. 11-12
Presentation Time: 8:00 AM-12:00 PM
A STRUCTURAL GEOLOGIC TEST OF THE TECTOGRAPHIC ORIGIN OF EDIACARAN SPECIMENS, DURHAM COUNTY, NORTH CAROLINA: UNDERGRADUATE RESEARCH ON NEOPROTEROZOIC LIFE PART I
Seilacher et al. (2000) claimed that Vermiforma antiqua specimens found along the banks of the South Fork of the Little River, Durham County, NC, were “tectographic” pseudo-fossils, and of tectonic rather than biologic origin. These convolute, worm-like features (25-30 cm along their long axes) observed on bedding planes of laminated volcaniclastic strata of the Late Neoproterozoic Hyco arc were proposed to be the result of bedding-plane flexural slip during Late Neoproterozoic Virgilina deformation. Comparison of the orientation of the long axes (raking S55W on beds oriented N15E, 22 NW; Cloud et al. 1976) with regional structural geologic data from the Rougemont quadrangle suggest that a flexural-slip origin for V. antiqua would require interbed slip primarily subparallel to regional fold axes. New structural geologic data, collected at the site in January 2018 by University of South Carolina undergraduate students in collaboration with the North Carolina Geological Survey, is designed to test the tectonic origin of the V. antiqua specimens. Measurements were taken in a ~100 x 50 m area of exposed bedrock, which included the original bedding surface from which the V. antiqua slab was removed in the 1970’s. The measurements collected focused on the orientations of bedding surfaces, axial planar(?) cleavage, and a prominent joint set. More than 180 individual measurements were collected at more than 45 individual stations. Bedding surfaces strike consistently NNE and dip moderately NW, suggesting these rocks sit within the eastern limb of a regional, east-vergent, overturned syncline. Cleavage is typically steeply dipping, and strikes consistently NNE. Joints thought to be associated with Mesozoic rifting strike generally NW and are sub-vertical. These local data will be compared with regional data to re-evaluate the tectographic interpretation of V. antiqua.