Structural and paleomagnetic considerations of Alleghanian deformation around the Pennsylvania salient
- Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Geological Sciences
- Bucknell Univ., Lewisburg, PA (United States). Dept. of Geology
Paleomagnetic studies from the central Appalachian fold and thrust belt have shown that many rock units, especially the clastic redbeds, contain two ancient magnetizations; a primary characteristic magnetization and a late Paleozoic chemical remagnetization related to mobilization of orogenic brines during the Alleghanian orogeny. From careful analysis of these two magnetic components across and along the strike of the Appalachian orogen several important conclusions can be established: (1) folding progressed from the hinterland toward the foreland; folding was synchronous on the northeastern and southwestern limbs of the Pennsylvania salient; (3) the mean age of folding was in middle Permian time; (4) there was no significant syn- or post-orogenic bending of the salient. Detailed structural analysis of the Pennsylvania Anthracite region, on the northeastern limb of the salient, also reveals several important results: (1) these rocks record five stages of progressive Alleghanian deformation; (2) fiber analysis of antitaxial veins shows that at least the first three deformational stages were continuous; (3) orientation analysis of cross-cutting structures from these five stages document a progressive 30[degree] clockwise rotation in shortening directions. This rotation of shortening directions is opposite to that observed on the southern limb of the salient. Given these paleomagnetic and structural results the development of the salient cannot be explained in terms of oroclinal bending or overprinting of discrete tectonic deformational phases. Alternative ideas that will be considered include tectonic models in which previously accreted terranes were remobilized during Alleghanian compression and kinematic models that take into account impingement on an irregular North American plate margin.
- OSTI ID:
- 5806511
- Report Number(s):
- CONF-921058-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 24:7; Conference: 1992 annual meeting of the Geological Society of America (GSA), Cincinnati, OH (United States), 26-29 Oct 1992; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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