TECTONIC EVOLUTION OF THE GOOCHLAND TERRANE, VA-NC

1. (> 1045 Ma) Shallow marine sedimentation: shale with minor carbonate and dirty sandstone. Intermediate igneous Old Bandana and mafic Sabot were intruded into or extruded onto this sequence.
2. (1045-1000 Ma) State Farm bi-hbd granite and Montpelier anorthosite intrusions were accompanied by Grenvillian convergent medium pressure granulite-facies metamorphism, producing opx-plag in Old Bandana, and migmatization of silli-Kspar metapelite producing silli-gar peraluminous leucogranite.
3. (650-570 Ma) Major erosional event followed by rifting, indicated by intrusion of shallow A-type to peralkaline granites between Richmond and Raleigh.
4. (400-280 Ma) Acadian-Alleghanian convergence at relatively high pressure produced metamorphism ranging from greenschist facies to ky-Kspar granulite facies, with gar-ky leucogranite. (315 and 285Ma) Intruded by abundant Alleghanian bi-hbd granites.
5. (285-245 Ma) Transition to right-lateral strike-slip with a component of uplift, exhuming the amphibolite facies Raleigh antiform in the south and the ky-Kspar granulites of the northern Goochland. Several authors suggest more than 100 km southwestward translation of the Goochland at this time.
6. (Mesozoic) Exhumation continued with rifting. Bounding ductile to brittle strike-slip faults were reactivated as brittle normal faults, forming Triassic-Jurassic rift basins to the west in NC and to the east in VA. The region was beveled by the Cretaceous unconformity, over which was draped the Atlantic Coastal Plain sediments.
7. Field mapping and petrography does not support the alternative interpretation that all granulite facies metamorphism is confined to Acadian-Alleghanian.