THE EDIACARAN-CAMBRIAN TRANSITION IN THE CAROLINA TERRANE: PRELIMINARY RESULTS AND NEW DIRECTIONS
Here we report preliminary geochemical measurements from the Albemarle Group, sampled from a number of sites on the limbs of the New London Syncline, near Albemarle, NC. This succession of fine-grained, low- to medium-grade metasediments ranges from the latest Ediacaran to the late Cambrian, and is associated with the Carolina Terrane, an arc accreted to the Laurentian margin in the Paleozoic. The sediments display little to no axial-planar foliation, and preserve primary sedimentary structures suggesting deposition at or near storm wave base. They include extensive evidence of local volcanism, including pumice clasts, fiamme structures, and laminated ash horizons, as well as evidence of syndepositional tectonic activity in the form of soft-sediment deformation.
This succession may have been deposited in a restricted back-arc basin, which in Ediacaran time is likely to have been a semi-permanently anoxic environment. We would thus expect these sediments to accumulate redox-sensitive trace metals, to the extent that these metals were available in the global ocean. Global trace element inventories are expected to reflect both oxidative continental weathering and the volume of oxygenated seawater available to serve as a trace element reservoir, both of which will track the progressive oxygenation of the oceans and atmosphere.