Origin of the Antietam Formation (Late Precambrian?--Lower Cambrian), Central Virginia

Abstract

ABSTRACT The Antietam Formation (Late Precambrian ?-Lower Cambrian) is a succession of quartz-rich clastics which occur in the upper part of the Chilhowee Group in the Central and Southern Appalachians. In central Virginia, the Antietam consists principally of orthoquartzitic and protoquartzitic sandstone. Recrystallization and pressure solution often obscure original texture and sedimentary structures to produce quartzite. The Antietam was derived from a low-lying complex of intermixed crystalline rocks (schist, gneiss, and silicious plutons) and pre-existing sediments exposed west of the outcrop belt in the craton. Paleocurrent analysis (based principally on rarely occurring cross-bedding) shows primary dispersal by marine bottom currents flowing down a paleoslope from northwest to southeast. Reworking by longshore currents (flowing northeast and southwest) contributed little or no additional volume of sediment. No southeastern borderland source (Appalachia?) is indicated.