Strain decoupling across the decollement of the Barbados accretionary prism

Abstract

Research Article| February 01, 1996 Strain decoupling across the decollement of the Barbados accretionary prism Bernard A. Housen; Bernard A. Housen 1Institute for Rock Magnetism, University of Minnesota, Minneapolis, Minnesota 55455-0128 Search for other works by this author on: GSW Google Scholar Ocean Drilling Program Leg 156 Shipboard Science Party; Ocean Drilling Program Leg 156 Shipboard Science Party Search for other works by this author on: GSW Google Scholar Harold J. Tobin; Harold J. Tobin 2Earth Sciences Department, University of California, Santa Cruz, California 95064 Search for other works by this author on: GSW Google Scholar Ocean Drilling Program Leg 156 Shipboard Science Party; Ocean Drilling Program Leg 156 Shipboard Science Party Search for other works by this author on: GSW Google Scholar Pierre Labaume; Pierre Labaume 3Laboratoire de Géophysique Interne et Tectonophysique, Grenoble, Franc Search for other works by this author on: GSW Google Scholar Ocean Drilling Program Leg 156 Shipboard Science Party; Ocean Drilling Program Leg 156 Shipboard Science Party Search for other works by this author on: GSW Google Scholar Evan C. Leitch; Evan C. Leitch 4Department of Applied Geology, University of Technology, Sydney, Australia Search for other works by this author on: GSW Google Scholar Ocean Drilling Program Leg 156 Shipboard Science Party; Ocean Drilling Program Leg 156 Shipboard Science Party Search for other works by this author on: GSW Google Scholar Alex J. Maltman; Alex J. Maltman 5Institute of Earth Studies, University of Wales, Aberystwyth, United Kingdom Search for other works by this author on: GSW Google Scholar Ocean Drilling Program Leg 156 Shipboard Science Party Ocean Drilling Program Leg 156 Shipboard Science Party Search for other works by this author on: GSW Google Scholar Author and Article Information Bernard A. Housen 1Institute for Rock Magnetism, University of Minnesota, Minneapolis, Minnesota 55455-0128 Ocean Drilling Program Leg 156 Shipboard Science Party Harold J. Tobin 2Earth Sciences Department, University of California, Santa Cruz, California 95064 Ocean Drilling Program Leg 156 Shipboard Science Party Pierre Labaume 3Laboratoire de Géophysique Interne et Tectonophysique, Grenoble, Franc Ocean Drilling Program Leg 156 Shipboard Science Party Evan C. Leitch 4Department of Applied Geology, University of Technology, Sydney, Australia Ocean Drilling Program Leg 156 Shipboard Science Party Alex J. Maltman 5Institute of Earth Studies, University of Wales, Aberystwyth, United Kingdom Ocean Drilling Program Leg 156 Shipboard Science Party Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1996) 24 (2): 127–130. https://doi.org/10.1130/0091-7613(1996)024<0127:SDATDO>2.3.CO;2 Article history First Online: 02 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 Bernard A. Housen, Harold J. Tobin, Pierre Labaume, Evan C. Leitch, Alex J. Maltman; Ocean Drilling Program Leg 156 Shipboard Science Party, Strain decoupling across the decollement of the Barbados accretionary prism. Geology 1996;; 24 (2): 127–130. doi: https://doi.org/10.1130/0091-7613(1996)024<0127:SDATDO>2.3.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 SocietyGeology Search Advanced Search Abstract The interrelation between deformation styles and behavior of fluids in accretionary prisms is under debate, particularly the possibility that overpressuring within the basal decollement may enable mechanical decoupling of the prism from the subducting material. Anisotropy of magnetic susceptibility (AMS) data from sediments spanning the basal decollement of the Barbados accretionary prism show a striking progression across this structure that strongly supports the hypothesis that it is markedly overpressured. In the accretionary prism, above the decollement, the minimum AMS axes are subhorizontal and oriented nearly east-west, whereas the maximum AMS axes are oriented nearly north-south and shallowly inclined. At the top of the decollement, the minimum AMS axes orientations abruptly change to nearly vertical; this orientation is maintained throughout the decollement and in the underthrust sediments below. The AMS orientations in the prism sediments above the decollement are consistent with lateral shortening due to regional tectonic stress, as the minimum axes generally parallel the convergence vector of the subducting South American plate and the maximum axes are trench-parallel. Because the orientations of the AMS axes in deformed sediments usually parallel the orientations of the principal strains, the AMS results indicate that the incremental strain state in the Barbados prism is one dominated by subhorizontal shortening. In contrast, the AMS axes within and below the decollement are consistent with a strain state dominated by vertical shortening (compaction). This abrupt change in AMS orientations at the top of the decollement at Site 948 is a direct manifestation of mechanical decoupling of the off-scraped prism sediments from the underthrust sediments. The decoupling horizon occurs at the top of the decollement zone, coinciding with the location of flowing, high-pressure fluids. 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.