Abstract

A stratigraphic cross section from Roanoke, Virginia, to Alabama shows the formations and facies of the easternmost Valley and Ridge outcrops. This cross section, coupled with 3-dimensional insights on facies changes, siliciclastic sources, and regional unconformity patterns, delimits stratigraphic expectations directly beneath the metamorphic over-thrust of the Blue Ridge-Great Smoky-Piedmont terrain as far east as the Brevard zone. These strata are in the Saltville structural block south of central Tennessee and in the Pulaski block to the north.

The stratigraphic column in the block directly beneath the metamorphic overthrust is up to 5,100 m (17,000 ft) thick and contains Upper Precambrian (Chilhowee Group) to middle Mississippian beds. The Chilhowee in the block beneath the metamorphic overthrust is probably less shaly and thinner than equivalent Chilhowee exposed along the leading edge of the metamorphic overthrust block. The Shady Formation becomes less dolomitic eastward, passing into dark, shaly limestone east of the carbonate bank edge. Rome-Conasauga siliciclastics change to carbonates eastward and northeastward. The Knox Group changes to limestone beneath the overthrust, and the post-Sauk unconformity probably disappears. Middle Ordovician siliciclastics coarsen eastward toward the Blount delta. The Wallbridge discontinuity expands eastward, so that Silurian and Lower Devonian strata probably do not occur beneath the metamorphic overthrust. The pre-Upper Devonian unconformity truncates more section eastward, so that Chattanooga Shale locally rests on Middle Ordovician Bays Formation in southeastern Tennessee. In Tennessee, Georgia, and possibly North Carolina, Mississippian strata include sandstone, dark shale, limestone, and bedded chert passing beneath the Great Smoky-Cartersville fault.

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