Paper No. 4
Presentation Time: 2:30 PM
SNOWBALL'S CHANCE IN DIXIE: I. EVALUATING THE LITHOSTRATIGRAPHIC EVIDENCE FOR MARINOAN- VARANGIAN OR GASKIERS GLACIATION IN THE BATTLEGROUND AND BLACKSBURG FORMATIONS OF SOUTH CAROLINA AND ADJACENT NORTH CAROLINA, U.S.A
Distinctive dolomitic marbles, (stratiform?) barites, and manganiferous schists and gondites overlie latest Precambrian metavolcanic rocks in northwestern SC. The age of volcanism is pre-ca. 580 Ma to perhaps ≥ ca. 628 Ma. The association of sea floor barites, BIFs / MnFs, and dolomitic cap carbonates is typical of Marinoan (ca. 635 Ma) and Sturtian (ca. 710 Ma) global glacial events. Primarily metavolcanic Battleground Formation is interpreted to be overlain by metasedimentary rocks of the Blacksburg Fm. The contact between the fms is obscured by later shearing. Both fms include unusual members. In the Battleground these include metaconglomerates (e.g., Draytonville) and quartzites, Jumping Branch Mn mbr, and massive and disseminated barites. Blacksburg Fm is dominated by epiclastic phyllites and siltstones, and includes the Gaffney and the Dixons Branch marble mbrs. Deposition in the upper part of the Battleground Fm was coeval with either the Marinoan or Gaskiers glaciation (ca. 580 Ma, has been recognized only on the Avalon peninsula). The seafloor barite / BIF/MnF association is ancient, and is generally restricted to Paleoarchean (>3.2 Ga) rocks (e.g., North Pole, Pilbara). The association yields particular inferences regarding atmospheric [O2] and chemical stratification of the ocean at that time. In the Cryogenian, the association is interpreted to represent loss of atmospheric O2 and loss of communication between the ocean and the atmosphere through pack ice. The marbles of the Blacksburg Fm may comprise the cap carbonate deposited as an inorganic precipitate at the close of the global glacial event. Caveats to these interpretations include 1) the lacks of variety in lithology and size of clasts in metacongl mbrs probably precludes their being glaciogenic; 2) while barites, Mn schists and gondite are interpreted as signature mineral deposits of the infracambrian glaciations, other well known mineral deposits of the Kings Mountain belt (e.g., Au, kyanite/ sillimanite) are purely volcanogenic (or are much younger i.e., spodumene pegmatite, Sn) with no paleoclimatic significance; 3) volcanic activity, epiclastic deposition, soft sediment deformation, and tectonic deformation occurred throughout deposition of barite-MnF and cap carbonate.