Structural style and kinematics of an underplated slate belt, Kodiak and adjacent islands, Alaska

Research Article| July 01, 1987 Structural style and kinematics of an underplated slate belt, Kodiak and adjacent islands, Alaska JAMES C. SAMPLE; JAMES C. SAMPLE 1Earth Sciences Board, University of California, Santa Cruz, California 95064 Search for other works by this author on: GSW Google Scholar J. CASEY MOORE J. CASEY MOORE 1Earth Sciences Board, University of California, Santa Cruz, California 95064 Search for other works by this author on: GSW Google Scholar Author and Article Information JAMES C. SAMPLE 1Earth Sciences Board, University of California, Santa Cruz, California 95064 J. CASEY MOORE 1Earth Sciences Board, University of California, 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 (1987) 99 (1): 7–20. https://doi.org/10.1130/0016-7606(1987)99<7:SSAKOA>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 JAMES C. SAMPLE, J. CASEY MOORE; Structural style and kinematics of an underplated slate belt, Kodiak and adjacent islands, Alaska. GSA Bulletin 1987;; 99 (1): 7–20. doi: https://doi.org/10.1130/0016-7606(1987)99<7:SSAKOA>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 The Kodiak Formation, composed of coherent Maastrichtian turbidites, is a slate belt whose dominant structures developed during underplating to an accretionary wedge in the latest Cretaceous. It consists of about 80% coherent landward-dipping thrust packets; zones of disrupted sandstone associated with a scaly argillite matrix constitute the remainder. About half of these disrupted sandstone zones are related to pre-accretion deformation, and the rest formed along late-stage, strike-slip faults that postdate development of slaty cleavage. The formation is divided into three structural belts. The landward and seaward belts include steeply dipping structures, and the central belt contains shallowly dipping structures and rocks that have experienced the highest strain. The central belt probably acted as a low-angle, southeast-verging, floor thrust zone beneath the landward belt. The structural history of the Kodiak Formation includes (1) early soft-sediment disruption; (2) tectonic stratal disruption; (3) thrust faulting, slaty cleavage (S1) development, and folding (F1); (4) intrusion of granodioritic plutons, dikes, and sills and associated normal faulting; (5) development of crenulations (F2) and crenulation cleavage (S2); (6) thrust faulting; and (7) development of right-lateral, strike-slip faults. Event 3 produced the dominant northwest-dipping structural grain and caused the greatest amount of shortening; the timing of event 7 relative to events 5 and 6 is not certain.The dominant structures of the Kodiak Formation are interpreted as developing during underthrusting, underplating, and intra-wedge shortening during latest Cretaceous time within an accretionary wedge. The maximum time from deposition to emplacement was about 12 m.y., and the timing is constrained by the maximum depositional age (74 m.y.) and the age of plutonic rocks (62 m.y.) that crosscut the dominant fabric. Pre-cleavage zones of stratal disruption reflect deformation on the lower plate during underthrusting. Slaty cleavage, thrusts, and F1 folds developed during underplating that also resulted in the formation of duplexes. Crenulations are probably related to post-underplating subhorizontal shortening of sediments within the accretionary wedge. Syn-deformation dynamic recrystallization of quartz, minimum syn-accretion metamorphic temperatures between 205 and 250 °C, and pressures of at least 2.65 kb recorded during the earliest stages of deformation suggest underplating at >10 km. 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.