Complex Deformation of Cretaceous Trench Deposits, Southwestern Alaska

Abstract

Research Article| June 01, 1973 Complex Deformation of Cretaceous Trench Deposits, Southwestern Alaska J. CASEY MOORE J. CASEY MOORE 1Board of Studies in Earth Sciences, University of California, Santa Cruz, California 95060 Search for other works by this author on: GSW Google Scholar Author and Article Information J. CASEY MOORE 1Board of Studies in Earth Sciences, University of California, Santa Cruz, California 95060 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1973) 84 (6): 2005–2020. https://doi.org/10.1130/0016-7606(1973)84<2005:CDOCTD>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 J. CASEY MOORE; Complex Deformation of Cretaceous Trench Deposits, Southwestern Alaska. GSA Bulletin 1973;; 84 (6): 2005–2020. doi: https://doi.org/10.1130/0016-7606(1973)84<2005:CDOCTD>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 A Cretaceous turbidite sequence, a probable trench deposit, forms the central portion of a Triassic to early Tertiary deep-water sedimentary and igneous sequence exposed along the Shumagin-Kodiak shelf, southwestern Alaska. The Cretaceous turbidite sequence was deformed initially in a partially lithified state with the development of axial plane slaty cleavage. Fold axes parallel the existing continental shelf edge, trending northeast and west-northwest in the outer Shumagin and Sanak Islands, respectively. Folds are predominantly overturned seaward, axial surfaces dipping landward. Locally, units may be described as broken formations, though no mélanges were observed. The style of this early folding is consistent with, but not diagnostic of, gravity gliding. Alternatively, the rocks may have been deformed by underthrusting at the trench inner wall. At strain rates of 10−13 to 10−14 per sec (calculated assuming underthrusting), the trench sediments may have undergone “strain hardening” (caused by increasing internal grain friction and cementation during dewatering) allowing transmission of an externally applied stress.Thick homoclinal sections dip toward the continent, suggesting tilting independent of folding. This tilting was probably associated with uplift along major high-angle faults trending parallel to the continental margin. The early folding, tilting, and uplift was followed by a second, minor, brittle deformation apparently associated with regional granodiorite and quartz diorite intrusions 60 m.y. ago. 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.