Geology and tectonic evolution of a juvenile accretionary terrane along a truncated convergent margin: Synthesis of results from Leg 66 of the Deep Sea Drilling Project, southern Mexico

Abstract

Research Article| September 01, 1982 Geology and tectonic evolution of a juvenile accretionary terrane along a truncated convergent margin: Synthesis of results from Leg 66 of the Deep Sea Drilling Project, southern Mexico J. CASEY MOORE; J. CASEY MOORE 1Earth Sciences Board and Center for Coastal Marine Studies, University of California, Santa Cruz, Santa Cruz, California 95064 Search for other works by this author on: GSW Google Scholar JOEL S. WATKINS; JOEL S. WATKINS 2Gulf Oil Exploration and Production, Gulf Building, Houston, Texas 77001 Search for other works by this author on: GSW Google Scholar THOMAS H. SHIPLEY; THOMAS H. SHIPLEY 3Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 93697 Search for other works by this author on: GSW Google Scholar KENNETH J. McMILLEN; KENNETH J. McMILLEN 4Gulf Oil Exploration and Production Company, P.O. Box 1342, Bakersfield, California 93302 Search for other works by this author on: GSW Google Scholar STEVEN B. BACHMAN; STEVEN B. BACHMAN 5Department of Geological Sciences, Cornell University, Ithaca, New York 14853 Search for other works by this author on: GSW Google Scholar NEIL LUNDBERG NEIL LUNDBERG 1Earth Sciences Board and Center for Coastal Marine Studies, University of California, Santa Cruz, Santa Cruz, California 95064 Search for other works by this author on: GSW Google Scholar Author and Article Information J. CASEY MOORE 1Earth Sciences Board and Center for Coastal Marine Studies, University of California, Santa Cruz, Santa Cruz, California 95064 JOEL S. WATKINS 2Gulf Oil Exploration and Production, Gulf Building, Houston, Texas 77001 THOMAS H. SHIPLEY 3Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 93697 KENNETH J. McMILLEN 4Gulf Oil Exploration and Production Company, P.O. Box 1342, Bakersfield, California 93302 STEVEN B. BACHMAN 5Department of Geological Sciences, Cornell University, Ithaca, New York 14853 NEIL LUNDBERG 1Earth Sciences Board and Center for Coastal Marine Studies, University of California, Santa Cruz, Santa Cruz, California 95064 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1982) 93 (9): 847–861. https://doi.org/10.1130/0016-7606(1982)93<847:GATEOA>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 Email Permissions Search Site Citation J. CASEY MOORE, JOEL S. WATKINS, THOMAS H. SHIPLEY, KENNETH J. McMILLEN, STEVEN B. BACHMAN, NEIL LUNDBERG; Geology and tectonic evolution of a juvenile accretionary terrane along a truncated convergent margin: Synthesis of results from Leg 66 of the Deep Sea Drilling Project, southern Mexico. GSA Bulletin 1982;; 93 (9): 847–861. doi: https://doi.org/10.1130/0016-7606(1982)93<847:GATEOA>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 Drilling results from the Pacific margin of southern Mexico indicate that this region is characterized by a Neogene accretionary wedge, progressively emplaced against older, tectonically truncated continental crust. Accretion has occurred by both offscraping of sediments at the base of the trench slope and underplating of sediments at depth beneath the accretionary wedge and the continental crust. Mass-balance and incremental-uplift studies suggest that about one-third of the incoming sediment is subducted beneath the leading edge of the continental crust.Piston and drill cores indicate that the trench is sand dominated and flanked by slopes covered principally by mud. A large submarine canyon bypasses sediment past the shelf and inner trench slope. The volume of sediment bypassed to the trench and adjacent lower and outer slope equals 5 to 6 times that deposited on the shelf, upper slope, and mid-slope. The muddy inner slope is characterized by foraminiferan-free mud below the calcite compensation depth (CCD) and foraminiferan-bearing mud above the CCD. The upper slope accumulates laminated mud within the oxygen minimum zone. The shelf is covered by sand and mud. Quartzofeldspathic sand compositions in the Leg 66 area reflect sources in the crystalline basement complex exposed along the coast.Structural fabrics of Leg 66 cores from offscraped and overlying slope deposits show zones of inconsistent dip, stratal disruption, and scaly mudstone, characteristics of many mélange-wedges exposed on land. Deformation transgresses the boundary between the offscraped and slope deposits, demonstrating tectonic incorporation of the slope sediments into the accretionary wedge. The rate of deformation of the slope deposits diminishes rapidly landward from the trench. Deposits overlying the continental crust show dip patterns due to mesoscopic folding, as well as local spaced cleavage and faulting, but they show no stratal disruption or scaly mudstone Oblique-slip faulting predominates between the accreted wedge and the continental crust and may reflect decoupling of these two basement types.Frozen sediment, probably bearing gas hydrate, was recovered above a bottom-simulating reflector at two sites. 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.