Document Type

Thesis

Abstract

Deposits of iron-oxide cemented conglomerate and coarse sandstone were recently discovered in northern Albemarle County and southern Madison County, in the eastern Blue Ridge Province of north central Virginia. These deposits are interpreted to represent remnant Mesozoic rift basins on the basis of deformational age constraints, sedimentary provenance, and lithologic similarity and proximity to other Mesozoic sedimentary rocks. Mesozoic rift basins occur along eastern North America and were formed by tensile stresses from the breakup of Pangea and the birth of the Atlantic Ocean in the mid to late- Triassic and early Jurassic. The Beautiful Run Basin (new name) in Madison County is comprised of two erosionally separated ~100-200 m wide iron-oxide cemented conglomerate and sandstone deposits bounded by a normal fault trending 040 on their NW side. The Burnley Basin (Nelson, 1962) in Albemarle County is comprised of two erosionally separated ~50-100 m wide iron-oxide cemented conglomerate and sandstone deposits. In contrast to the Beautiful Run Basin, the Burnley Basin displays structural complexity, and may occur along a right stepping segment of the same normal fault. Both the Beautiful Run and Burnley basins abut a 10-400 m belt of graphite schist. This belt of graphite schist, called the Johnson Mill Member (Allen, 1963) of the Lynchburg Group, acted as a detachment surface during Mesozoic extension and controlled basin formation. Clast assemblage analyses on the Burnley Basin and Beautiful Run Basin reveal a local provenance. Similar analyses of conglomerates of the Culpeper and Barboursville Basins depict a larger westerly source area. Restoration of the Burnley and Beautiful Run basins assuming a conservative 1.5 km of erosion shows those two basins merging with the Barboursville/Culpeper Basin in an imbricated fault block geometry.

Date Awarded

2008

Department

Geology

Advisor 1

Christopher M. Bailey

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