8 Structural Geology and Tectonics (Posters)

Wednesday, 3 April 2002
1:00 PM - 5:00 PM

PARIS MOUNTAIN PROJECT, PART 2: GEOLOGY OF THE NORTHERN HALF OF MAULDIN 7.5-MINUTE QUADRANGLE, GREENVILLE COUNTY, SOUTH CAROLINA

Paper number: 8-5
Program: Technical Sessions
Time: 1:00 PM – 5:00 PM

Authors

Abstract

This study is the second part of a regional study of the Paris Mountain thrust sheet in the Inner Piedmont. The field area, the northern half of Mauldin 7.5-minute quadrangle (MQ), covers part of greater Greenville, South Carolina, and lies southeast of Paris Mountain. Five major lithologies within the Six Mile thrust sheet were mapped in MQ. Map patterns and cross sections indicate the following stratigraphic order: quartzo-feldspathic gneiss, biotite-sillimanite schist, biotite gneiss, biotite augen gneiss, and metagranite. Quartzo-feldspathic gneiss (biotite <10%) is the lowermost unit and defines the cores of NW-vergent, map-scale anticlines. Biotite-sillimanite schist directly above quartzo-feldspathic gneiss has the widest distribution. It displays both well-defined schistosity and polyphase deformation. Biotite gneiss (biotite >15%) overlies the schist and is found in the core of an overturned syncline at Roper Mountain. Biotite augen gneiss intrudes the schist, and contact relations indicate that this gneiss is a sheeted body. Coarse-crystalline metagranite intrudes all other rock units.

Mapping shows that quartzo-feldspathic gneiss, biotite-sillimanite schist, and biotite gneiss have been affected by an older, northwest-verging, inclined fold set striking N20°E. Examples are the Hartness anticline and the Roper Mountain syncline. These folds are part of a regional pattern mapped in adjacent quadrangles. In MQ, the regional pattern is refolded by northwest-striking, northwest-plunging, upright, close folds. Mesoscopic observations and steroplots also show that northwest-striking axes refold older, isoclinal, recumbent folds that are part of the first set.

Northwest-striking, southwest-directed thrusts duplicate schist and metagranite in the northwest corner of MQ. These thrusts are similar to other thrusts identified in Taylors and Paris Mountain quadrangles. If the MQ thrusts are part of that thrust system, the structural boundaries of the Paris Mountain thrust sheet need to be re-examined.