The regional extent of the ca. 600 Ma Virgilina deformation: Implications for stratigraphic correlation in the Carolina terrane

Abstract

We present a regional stratigraphic and structural architecture of the southern Appalachian Carolina terrane, based on new field studies in central North Carolina. The Virgilina deformation is interpreted to be a regional feature. Stratigraphic units include an older (ca. 700 to 600 Ma), calc-alkalic volcanic (Hyco and Virgilina Formations) and intra-arc rift(?) epiclastic (Aaron Formation) sequence, folded and faulted by the Virgilina event. Unconformably overlying the older stratigraphy, there is a younger (ca. 600 to 540 Ma, bimodal volcanic-sedimentary sequence (Uwharrie Formation and Albemarle Group). Some present models imply that the effects of the Virgilina deformation are not wide-spread throughout the Carolina terrane. This misconception arose because the northern slate belt stratigraphy (Hyco, Aaron, and Virgilina Formations) was miscorrelated with central slate belt units (Uwharrie Formation and Albemarle Group). A re-evaluation of the physical stratigraphic similarities and temporal constraints of Ediacarian fauna in these units indicates that the two sequences are not equivalent. Stratigraphic and structural data from the study area document the Virgilina deformation and its associated unconformity in the central North Carolina portion of the Carolina terrane. Stratigraphic and map evidence indicates that the Uwharrie Formation unconformably overlies the Hyco Formation. The unconformity between the older and younger stratigraphic units is a boundary between discordances in lineations, fold axial traces, and fold tightness. The Virgilina deformation appears to be coeval with the Monian and Cadomian events of Europe and with the Pan-African orogeny of west Africa. The stratigraphic and tectonic sequence presented herein provides a terrane characterization for the Carolina terrane that may be of use in reassembling Avalon, if Avalon was ever a single entity.