RHEIC TRAILING MARGIN CHRONOSTRATIGRAPHY: BATTLEGROUND & BLACKSBURG FORMATIONS, KINGS MOUNTAIN TERRANE, SOUTHERN APPALACHIAN OROGEN, U.S.A

The Kings Mountain terrane is the westernmost terrane of Carolinia in the southern Appalachian Piedmont. The Battleground and Blacksburg Formations comprise the Kings Mountain terrane. The terrane represents the Middle Cambrian (Series 3) trailing edge of the Carolinian Rheic trailing margin based on detrital zircon geochronology of epiclastic units and a preliminary δ¹³C profile of the uppermost carbonate (marble member at Dixon’s Branch). We sampled metaconglomerates and metasandstones of the Battleground and Blacksburg Fms in a detrital zircon study. The stratigraphically lowest horizon at Dixon’s Gap-Stepp’s Gap yielded the youngest grains, as young as 503.2 ± 11.7 Ma. Pooling the ages + errors of the six youngest grains suggests the age of the source of these grains was 514.9 - 510.3 Ma (Stage 4, (latest) Series 2, Cambrian). 50% of sampled grains were Ediacaran-Cambrian in age; the remainder sample Mesoproterozoic Amazonian craton age provinces. Near the top of the Battleground Fm the Draytonville metaconglomerate lies at or above the Rheic rift-drift transition. Three dolomitic marble units within a dominantly epiclastic section have been described from the Blacksburg Fm: the lowest is associated with the Kings Mountain Au mine and is known from drill core; above this is the Gaffney marble; and highest stratigraphically, the marble member at Dixon’s Branch. We prepared a carbon isotope profile from the base of the Gaffney marble and the entire Dixon’s Branch marble member. δ¹³C values ranged from -2 < x < 0 for roasted, H₂O₂ -treated samples. We interpret the entire Blacksburg section to be Middle Cambrian (Series 3) in age based on published Cambrian-Ordovician carbon isotope stratigraphy (i.e., Montañez et al, 2000, Shergold & Cooper, Cooper & Sadler, in Gradstein et al, 2004). Our survey did not recognize SPICE. We conclude that the entire preserved rift-drift sequence (3900-5000m) was deposited over some part of Cambrian Series 3 time (509-497 Ma).