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Distribution and mechanisms of strain within rocks on the northwest ramp of Pine Mountain block, southern Appalachian foreland: A field test of theory

1985; Geological Society of America; Volume: 96; Issue: 4 Linguagem: Inglês

10.1130/0016-7606(1985)96 2.0.co;2

1943-2674

David V. Wiltschko, Donald A. Medwedeff, Henry E. Millson,

Geological formations and processes

Research Article| April 01, 1985 Distribution and mechanisms of strain within rocks on the northwest ramp of Pine Mountain block, southern Appalachian foreland: A field test of theory DAVID V. WILTSCHKO; DAVID V. WILTSCHKO 1Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109 Search for other works by this author on: GSW Google Scholar DONALD A. MEDWEDEFF; DONALD A. MEDWEDEFF 1Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109 Search for other works by this author on: GSW Google Scholar HENRY E. MILLSON HENRY E. MILLSON 1Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1985) 96 (4): 426–435. https://doi.org/10.1130/0016-7606(1985)96 2.0.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation DAVID V. WILTSCHKO, DONALD A. MEDWEDEFF, HENRY E. MILLSON; Distribution and mechanisms of strain within rocks on the northwest ramp of Pine Mountain block, southern Appalachian foreland: A field test of theory. GSA Bulletin 1985;; 96 (4): 426–435. doi: https://doi.org/10.1130/0016-7606(1985)96 2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Fractures, faults, stylolites, and strain determined from an analysis of twinning in calcite in the Mississippian Newman Limestone at the base of the Pine Mountain block show that deformation was accomplished primarily by a combination of bedding-plane slip and layer-parallel shortening. Poles to joints are either parallel to strike of the thrust sheet or are in the transport plane. Small slip surfaces with syntaxial calcite fibers lie either parallel to bedding or parallel to the strike of the Pine Mountain block and dip steeply. Movement along the former is in the direction of transport of the block, whereas movement on the latter is approximately along strike. Tectonic stylolites are rare but appear to be controlled by subtle changes in lithology. Wackestones contain more stylolites than do packstones. Strains in calcite from closely spaced samples show the converse relationship. They are highest in units without stylolites (maximum shortening strain, e1 = −10.4%) and lowest in units with stylolites or small faults (e1 = −2.0%). The maximum principal shortening-strain directions, however, are identical within the error and are parallel to both bedding and the transport direction. A sequence of events in this portion of the Pine Mountain block is (1) layer-parallel shortening producing tectonic stylolites and a strong preferred orientation of compression axes; (2) development of fractures parallel to the strike of the block on the lower hinge of the ramp to accommodate stretching parallel to the transport direction (these strike- parallel fractures can also be interpreted as having occurred quite late); (3) during (2) above and continuing, the start of bedding-plane slip marked by syntaxial calcite fibers which trend in the direction of transport; and (4) complications, such as shear parallel to the strike of the Pine Mountain fault, as a result of motion of the entire block between bounding tear faults. Events (2) through (4) most likely overlapped in time. These data suggest that the acquisition of dip of the rocks on the ramp was primarily accomplished by bedding-plane slip on the slip surfaces which experienced a shear stress of < 100 bars. Bending strains in units between slip surfaces were too small to alter the pattern of layer-parallel shortening preserved in the Newman Limestone. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.