CAROLINIA: DEFINITION AND RECENT FINDINGS IN CENTRAL NORTH CAROLINA

Carolinia encompasses the exposed peri-Gondwanan crustal blocks east of the Alleghanian central Piedmont shear zone in the s. Appalachians. It is commonly correlated with the n. Appalachian crustal block of Avalonia. The two main components of Carolinia are the westerly Charlotte terrane (Cht), a medium grade Neoproterozoic magmatic arc assemblage and the easterly Carolina terrane (Ct), a low grade Neoproterozoic to early Paleozoic composite magmatic arc. We have made several significant new findings in Carolinian rocks of central NC. In the Ct near Erect, NC, arc rocks of the Virgilina sequence (Vs) (c. 615 Ma) are in contact with arc volcanics of the Uwharrie Formation (UF) (c. 580-550 Ma). The unexposed contact is marked by quartz arenite and quartzite at the base of the UF that overlies the Vs; this member changes abruptly in thickness from 0 m to 100s m over short distances. These observations are consistent with the previous interpretation that this contact is a significant unconformity in the Ct. In a quarry in the Albemarle volcanic arc sequence (As) (c. 550-530 Ma) of the Ct, USGS workers reported Late Cambrian or younger fossils, which demanded significant revision to the structural-stratigraphic interpretation of the As. In the same quarry, we have recently discovered the Ediacaran fossil Aspidella. The new fossil find along with U-Pb zircon ages of c. 541-547 Ma on felsic tuffs that lie ~ 200' stratigraphically above rocks in the quarry, suggest that this portion of the As is Neoproterozoic; thus, major modification of our understanding of the As is unwarranted. Finally, the Gold Hill fault was previously thought to represent the contact between the Cht and the As of the Ct. Our recent work indicates that volcanics to the west of the fault are similar in age and Nd isotopic character to those of the Vs of the Ct, suggesting that the eastern boundary of the Cht must lie further to the west. The main motion on the fault is Late Ordovician sinistral thrusting of the Vs over the As; the fault was also active in the Neoproterozoic, and apparently remobilized at c. 377 Ma and c. 335 Ma. Our findings support the broader interpretations that Carolinia accreted to Laurentia in the Late Ordovician and that Carolinia shows a closer affiliation to the n. Appalachian crustal block of Ganderia, than to Avalonia.