GEOLOGY OF THE SCHUYLER 7.5’ QUADRANGLE: UNDERSTANDING IAPETAN RIFTING, SEDIMENTATION, AND MAGMATISM IN THE EASTERN BLUE RIDGE, VIRGINIA

The Schuyler 7.5’ quadrangle is located approximately 30 km south-southwest of Charlottesville, Virginia on the eastern limb of the Blue Ridge Anticlinorium. The town of Schuyler has been the center of an extensive soapstone industry since the late 1800s. The goals of our study are: 1) produce a 1:12,000 scale bedrock and surficial geologic map of the quadrangle 2) decipher the origin of the contact between the basement complex and cover sequence, 3) resolve the regional stratigraphy and depositional age of the Neoproterozoic Lynchburg Group, 4) determine the age and origin of soapstone mafic-ultramafic bodies, and 5) quantify the metamorphic conditions experienced by rocks in the eastern Blue Ridge.

The bedrock geology consists of the Grenvillian basement complex that is overlain by a cover sequence of metasedimentary and metavolcanic units that includes Neoproterozoic rocks of the Lynchburg Group and Catoctin Formation, as well as the early Cambrian Evington Group. The basement complex, exposed in the northwest corner of the quadrangle, consists of Grenvillian granitoid and gneiss that is intruded by two Cyrogenian A-type plutons and their associated dikes. The basement complex is unconformably overlain by a >6 km thick cover sequence. The Lynchburg Group is primarily an arkosic sequence derived from erosion of the basement complex. We revise the stratigraphy of the Lynchburg Group and recognize five formations, many of which are bound by significant unconformities. A mafic-ultramafic complex, metamorphosed to metagabbro and soapstone/serpentinite, intrudes the basement complex and the Lynchburg Group. Tholeiitic metabasalts of the Catoctin Formation erupted during Iapetan rifting. Evington Group meta-pelites overlie the Catoctin Formation and mark the transition from active rifting to passive margin development in southeastern Laurentia. A few NNW-striking Jurassic diabase dikes cut older rocks. We quantified metamorphic conditions using Raman graphite geothermometry in the cover sequence. Proterozoic to Cambrian rocks in the Schuyler area were metamorphosed under mid-greenschist facies during regional deformation in the Neoacadian.