Abyssal Dunes of Foraminiferal Sand on the Carnegie Ridge

Abstract

Research Article| November 01, 1974 Abyssal Dunes of Foraminiferal Sand on the Carnegie Ridge PETER LONSDALE; PETER LONSDALE 1University of California at San Diego, Marine Physical Laboratory of the Scripps Institution of Oceanography, La Jolla, California 92037 Search for other works by this author on: GSW Google Scholar BRUCE MALFAIT BRUCE MALFAIT 2Oregon State University, School of Oceanography, Corvallis, Oregon 97331 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1974) 85 (11): 1697–1712. https://doi.org/10.1130/0016-7606(1974)85<1697:ADOFSO>2.0.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation PETER LONSDALE, BRUCE MALFAIT; Abyssal Dunes of Foraminiferal Sand on the Carnegie Ridge. GSA Bulletin 1974;; 85 (11): 1697–1712. doi: https://doi.org/10.1130/0016-7606(1974)85<1697:ADOFSO>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 field of sand dunes was discovered by the side-looking sonars of a deep-towed geophysical instrument package at a water depth of 2.65 km on the north flank of the Carnegie Ridge in the eastern equatorial Pacific. The dunes are moving down the flat floor of an erosional valley that has been excavated through calcareous ooze to a resistant, manganese-encrusted chalk stratum. Transverse dunes (mean wave length 20 m) anc barchans (length 6 to 80 m) are arranged in long, narrow belts. Stereo photographs (875 oriented pairs) of the dunes and of the current-swept rock floor show that average dune height is —0.6 m, the steep (25° to 30°), lee side is generally smooth, and the upstream slope is covered with short-crested current ripples. A core from a transverse dune recovered moderately sorted sand, composed of broken fragments (70 percent) and intact tests of Quaternary age Foraminifera. Photographs and side-looking sonar records both indicate a northwestward, down-valley sediment transport. The dunes are thought to be formed and propelled by fast (>30 cm/sec) currents of dense water, which spill episodically over the Carnegie Ridge into the Panama Basin. 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.