3-D STRUCTURE BENEATH THE MIDDLE ORDOVICIAN TELLICO-SEVIER SYNCLINORIUM, SE AND NE TENNESSEE

The Tellico-Sevier synclinorium of SE and NE TN is a simple structure in map view that consists of one or more synclines preserving the greater than 3-km thick Middle Ordovician Taconian clastic wedge. The youngest rocks in the synclinorium are Mississippian clastic rocks that unconformably overlie the Ordovician. Some intervening anticlines in Cocke and Jefferson Counties are locally faulted at the surface, but no major faults are evident at the surface throughout this structure. Anticlines mostly expose the Knox at the present erosion level, but a faulted anticline SW of White Pine exposes the entire Knox Group (Upper Cambrian-Lower Ordovician) and the upper Conasauga Group (Middle-Upper Cambrian). From stratigraphic thickness considerations alone and accurate knowledge of depth to basement, this simple deformational style cannot prevail throughout the sedimentary section between the surface and the basement. Industry seismic reflection data in Cocke County clearly image this simple deformation style in the near surface and homoclinally dipping Rome Formation resting on the SE-dipping basement surface at depths of 6 to 7 km. In the intervening section, the seismic reflection data reveal a complex array of ramps, flats, duplexes, imbricates, and folds. Most structures verge to the NW, but a few thrusts and folds verge SE; one such thrust is traceable, using a combination of surface and seismic-reflection data, for close to 20 km. Most of the thrusts that form the anticlinal culminations, however, increase dip and decrease displacement upward to terminate before displacing surface rocks. The entire stratigraphic section from the Rome through the Middle Ordovician is repeated several times in this complex. Hints of greater complexity at depth have been obtained previously from the few areas of detailed mapping that exist in this part of the Valley and Ridge by subdivision of the Knox and Chickamauga Groups. Any solution to the structure here, however, would be impossible without the existence of the industry seismic-reflection data.