15 Piedmont Geology: New Mapping and New Perspectives (Posters)

Thursday, 24 March 2011
1:30 PM - 5:30 PM
Exhibit Hall

DEFORMATIONAL AND METAMORPHIC HISTORY OF CAMPOBELLO 7.5-MINUTE QUADRANGLE, TUGALOO TERRANE, INNER PIEDMONT, SOUTH CAROLINA

Paper number: 15-3
Program: Theme Sessions
Time: 1:30 PM – 5:30 PM

Authors

Abstract

New geologic mapping of Campobello 7.5-minute quadrangle, Inner Piedmont of SC, traces the Seneca fault and a complex system of brittle faults and interference folds of the Six Mile thrust sheet east and south from adjacent Tigerville, Saluda, and Landrum quadrangles. Mineralogic and petrographic analyses of rocks of the Tallulah Falls Formation gneiss unit and the structurally overlying schist unit indicate prograde amphibolite and localized retrograde greenschist facies metamorphic conditions. The extensive lower unit includes diverse amphibole-garnet-biotite-quartzo-feldspathic and calcsilicate gneisses, amphibolite, and schist. Remnants of the upper unit of migmatitic mica schist and muscovite-biotite gneiss are preserved locally in overturned synforms and on the downthrown sides of faults. A 3 x 0.5 km body of hornblende metagabbro with amphibolite dikes (?) at Holly Springs is partly truncated by ENE faults. Plagioclase in thin section is altered to epidote and scapolite.

Geologic map patterns and stereoplot structural analysis of mesoscopic folds encountered along streams indicate at least five fold generations. Isoclinal F1 folds were refolded by macroscopic and mesoscopic scale, inclined to overturned F2 folds of NE to easterly trends. The macroscopic Campobello F2 synform deforms the Motlow Creek F1 isocline outlined by the schist unit. Inclined to overturned F3 folds trend NW, warping F1 and F2. The Campobello F2 synform is cross folded by F3 folds. Mesoscopic F4 and F5 gentle folds of NE and NW trend produce Type 1 interference patterns in stream pavements. F2 tight chevron folds in schist deform aligned sillimanite needles produced during F1.

Brittle fault orientations in Campobello and adjacent quadrangles are mostly N71°-75°E, N40°-55°W and N6°-10°W. Cross-cutting relationships indicate the fault chronology is: NE (oldest), northerly, NW, and ENE to easterly (youngest, after silicified breccia development related to the Pax Mountain fault).