|Southeastern Section - 54th Annual Meeting (March 17–18, 2005)|
|Paper No. 13-4|
|Presentation Time: 1:00 PM-5:00 PM|
POLYDEFORMED PROTEROZOIC BASEMENT IN THE BLUE RIDGE THRUST COMPLEX OF NORTHEAST TENNESSEE-NORTHWEST NORTH CAROLINA PART I: DECIPHERING 1 BILLION YEARS OF SOUTHERN APPALACHIAN HISTORY PRESERVED IN AN OUTCROP OF MIDDLE PROTEROZOIC ROCKS IN THE WESTERN BLUE RIDGE, NORTH CAROLINA
MERSCHAT, Arthur J., Earth and Planetary Sciences, Univ of Tennessee, 306 Earth and Planetary Sciences Bldg, Knoxville, TN 37996, firstname.lastname@example.org, BULTMAN, John G., Department of Earth and Planetary Sciences, Univ of Tennessee, 306 Geological Sciences Building, Knoxville, TN 37996-1410, and HATCHER, Robert D. Jr, Earth and Planetary Sciences, Univ of Tennessee, 306 Earth and Planetary Sciences Bldg, Knoxville, TN 37996-1410|
A ~240 m long, west–facing roadcut near milepost 5 on Interstate 26 in northwestern North Carolina exposes an assemblage of ~1.1 Ga migmatite, amphibolite, biotite granitoid gneiss, and biotite granitoids in a complex fold mullion structure cut by sugary quartz veins and intruded by two gabbro bodies. Crosscutting relationships permit the development of a detailed deformational history, although, absolute timing is based on correlation with published data. Three Proterozoic deformations are responsible for the majority of structures, fabrics, and high-grade metamorphism. Biotite granitoid gneiss and granitoids intruded migmatitic inequigranular gneiss and amphibolite at ~1.15 Ma. The rocks were then penetratively deformed at upper amphibolite facies during D1 and D2. Early D1 structures include S1 foliations preserved in amphibolite and biotite granitoid gneiss boudins and F1 intrafolial folds. These structures are transposed by D2 structures, interpreted as peak Grenville deformation. S2 foliation defined by alignment of biotite, hornblende, and metamorphic and stromatic migmatite layering trend N to WNW, and dip moderately to steeply SW. Reclined to recumbent, closed to isoclinal F2 folds plunge gently N–S. Anvil–shaped structures cored by biotite granitoid gneiss, sub–parallel to F2 folds and L2 lineations, may represent outcrop–scale sheath folds. Intrusion of the Bakersville gabbro at ~734 Ma produced contact metamorphism, M2, and local deformation, D3, of the country rocks. The contact aureole ranges from 1-20 cm wide and consists of quartz lenses and medium– to coarse–grained hornblende granofels that contain hornblende + plagioclase + quartz + chlorite + actinolite + biotite + epidote. Geometry, rim synforms, pluton–up–shear–sense, and S3 parallel to the pluton contact suggest emplacement of the Barkersville gabbro as a diapir. A penetrative foliation, S4, is recognized in one Bakersville gabbro body and is tentatively correlated with the Taconic orogeny, D4. Retrogressive Alleghanian structures, D5, minor mylonitic fabrics, slickensided brittle faults, and filled joints, are observed only locally in the outcrop. Filled joints and associated centimeter wide alteration zones commonly contain pink potassium feldspar, chlorite, epidote, quartz, and minor fluorite. Mesozoic or Cenozoic joint formation is the youngest deformation, D6, observed in the outcrop.
Southeastern Section - 54th Annual Meeting (March 17–18, 2005)
General Information for this Meeting
|Session No. 13--Booth# 17|
Structural Geology and Tectonics (Posters)
Bayview Hotel at the Grand Casino Resort: Grand Ballroom D
1:00 PM-5:00 PM, Thursday, March 17, 2005
Geological Society of America Abstracts with Programs, Vol. 37, No. 2, p. 36
© Copyright 2005 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.