Abstract: Boundary Conditions of Foreland Fold-Thrust Belt
Deformation from 3-D
Reconstruction of a Curved Segment of the
Southern Appalachian Basement Surface and Base of the Blue
Ridge-Piedmont Thrust Sheet: Progress Report and Initial
Results
HATCHER, ROBERT D. JR.1, PETER J. LEMISZKI2, and CAMILO MONTES3
1Department of Geological Sciences,
University of Tennessee-Knoxville and Environmental Sciences
Division, Oak Ridge National Laboratory
2Tennessee Division of Geology;
3Department of
Geological Sciences, University of Tennessee-Knoxville
Summary
New contour maps have been constructed of the upper and lower
bounds of the deformed wedge of Paleozoic sedimentary rocks the
southern Appalachian foreland fold-thrust belt from AL to VA.
Industry, academic, and U.S./state geological survey seismic
reflection and surface geologic data have been used, along with
crustal seismic lines in the more internal parts of the orogen for
these preliminary 2-D and 3-D
reconstructions. The basement surface
(lower bound) in our reconstruction dips gently SE in the TN
embayment from VA to GA and contains several previously
unrecognized rift-related large and small-displacement
Neoproterozoic-earliest Cambrian normal faults. Several important
previously unknown features related to the base of the Blue
Ridge-Piedmont sheet (upper bound) have also been recognized as a
result of this reconstruction. Frontal duplexes obliquely
overridden along the leading edge of the BRP sheet at present
erosion level are traceable for considerable distances beneath the
sheet; and several internal isolated domes probably also formed by
interactive footwall-duplex arching of the overlying thrust sheet.
Boundary conditions include temperatures <200°C and
pressures < 3 kb over most of the belt. Presence of low grade
metamorphic rocks in a large reentrant exposed beneath the sheet in
GA., but not in windows farther north or along the frontal edge in
TN, may indicate the up-dip westward palinspastic limit of the BRP
sheet is near its present-day trace and that the sheet was also
relatively thin in TN, whereas in GA it may have extended as much
as 30 km farther west and was much thicker than the frontal 30 km
in TN.
AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas