Tectonics of the Neogene Cascadia forearc basin: Investigations of a deformed late Miocene unconformity

Abstract

Research Article| August 01, 2000 Tectonics of the Neogene Cascadia forearc basin: Investigations of a deformed late Miocene unconformity Lisa C. McNeill; Lisa C. McNeill 1School of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK Search for other works by this author on: GSW Google Scholar Chris Goldfinger; Chris Goldfinger 2College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA Search for other works by this author on: GSW Google Scholar LaVerne D. Kulm; LaVerne D. Kulm 2College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA Search for other works by this author on: GSW Google Scholar Robert S. Yeats Robert S. Yeats 3Department of Geosciences, Wilkinson Hall, and College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2000) 112 (8): 1209–1224. https://doi.org/10.1130/0016-7606(2000)112<1209:TOTNCF>2.0.CO;2 Article history received: 23 Nov 1998 rev-recd: 12 Jul 1999 accepted: 04 Aug 1999 first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Lisa C. McNeill, Chris Goldfinger, LaVerne D. Kulm, Robert S. Yeats; Tectonics of the Neogene Cascadia forearc basin: Investigations of a deformed late Miocene unconformity. GSA Bulletin 2000;; 112 (8): 1209–1224. doi: https://doi.org/10.1130/0016-7606(2000)112<1209:TOTNCF>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 continental shelf and upper slope of the Oregon Cascadia margin are underlain by an elongate late Cenozoic forearc basin, correlative to the Eel River basin of northern California. Basin stratigraphy includes a regional late Miocene unconformity that may coincide with a worldwide hiatus ca. 7.5–6 Ma (NH6). The unconformity is angular and probably subaerially eroded on the inner and middle shelf, whereas the seaward correlative disconformity may have been produced by submarine erosion; alternatively, this horizon may be conformable. Tectonic uplift resulting in subaerial erosion may have been driven by a change in Pacific and Juan de Fuca plate motion. A structure contour map of the deformed unconformity and correlated seaward reflector from seismic reflection data clearly outlines deformation into major synclines and uplifted submarine banks. Regional margin-parallel variations in uplift rates of the shelf unconformity show agreement with coastal geodetic rates.The shelf basin is bounded to the west by a north-south–trending outer arc high. Rapid uplift and possible eustatic sea-level fall resulted in the formation of the late Miocene unconformity. Basin subsidence and outer arc high uplift effectively trapped sediments within the basin, which resulted in a relatively starved abyssal floor and narrower Pliocene accretionary wedge, particularly during sea-level highstands. During the Pleistocene, the outer arc high was breached, possibly contributing to Astoria Canyon incision, the primary downslope conduit of Columbia River sediments. This event may have caused a change in sediment provenance on the abyssal plain ca. 1.3–1.4 Ma. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.