The Augusta fault zone as a guide to Alleghanian extension in the Southern Appalachian Piedmont

Conference · Mon Mar 01 04:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5950400

Maher, Jr, H D ^[1]; Secor, D Jr ^[2]

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1. Univ. of Nebraska, Omaha, NE (United States). Geography and Geology Dept.
2. Univ. of South Carolina, Columbia, SC (United States). Dept. of Geology

The South Carolina and Georgia eastern Piedmont is in part characterized by rocks of lower metamorphic grade and earlier cooling histories structurally overlying rocks of higher metamorphic grade and later cooling histories. Contacts between these metamorphic terranes are often composed of mylonitic rocks with synkinematic intrusives and compressed metamorphic gradients. A question can be raised as to the role extension played in development of these relationships. One example of such geologic setting is the Augusta fault zone (AFZ), exposed along the SC-GA border, where low grade Belair terrane metavolcanics and metasediments structurally overly migmatitic gneisses and schists of the Savannah R. terrane. Structures and geochronology, previously described, indicate a predominant hanging-wall down movement for the Augusta fault zone, circa and post 274 Ma. The late Alleghanian age is compatible with extension due to gravitational collapse, as described by others for the Himalayas and other orogens. Magmatism could be due to extensional unloading or could trigger collapse and extension by altering the crustal strength profile. As a relatively late Alleghanian feature the AFZ can be expected to truncate earlier faults. Using the AFZ as a guide, contacts with the following characteristics might be investigated for extensional kinematic indicators: (a) inferable crustal section omission with underlying deeper rocks, (b) presence of synkinematic planar intrusions, and (c) a linear aeromag anomaly signature, weaker where the contact is moderately to shallowly dipping. The Modoc fault zone, to the NW of the AFZ, has some of these attributes, and while predominantly dextral has an extensional component, but some 20--30 Ma before that on the AFZ. Speculatively, extension may have been episodic, potentially related to episodic magmatism.

• OSTI ID: 5950400
• Report Number(s): CONF-9304188--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:4
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AGE ESTIMATION
DEVELOPED COUNTRIES
GEOLOGIC FAULTS
GEOLOGIC FORMATIONS
GEOLOGIC FRACTURES
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
GEOLOGY
GEORGIA
LITHOLOGY
MAGMATISM
METAMORPHISM
NORTH AMERICA
OROGENESIS
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SOUTH CAROLINA
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