Dispersal and deposition of eolian and fluvial sediments off Peru and northern Chile

Abstract

Research Article| February 01, 1982 Dispersal and deposition of eolian and fluvial sediments off Peru and northern Chile KENNETH F. SCHEIDEGGER; KENNETH F. SCHEIDEGGER 1School of Oceanography, Oregon State University, Corvallis, Oregon 97331 Search for other works by this author on: GSW Google Scholar LAWRENCE A. KRISSEK LAWRENCE A. KRISSEK 1School of Oceanography, Oregon State University, Corvallis, Oregon 97331 Search for other works by this author on: GSW Google Scholar Author and Article Information KENNETH F. SCHEIDEGGER 1School of Oceanography, Oregon State University, Corvallis, Oregon 97331 LAWRENCE A. KRISSEK 1School of Oceanography, Oregon State University, Corvallis, Oregon 97331 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1982) 93 (2): 150–162. https://doi.org/10.1130/0016-7606(1982)93<150:DADOEA>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 KENNETH F. SCHEIDEGGER, LAWRENCE A. KRISSEK; Dispersal and deposition of eolian and fluvial sediments off Peru and northern Chile. GSA Bulletin 1982;; 93 (2): 150–162. doi: https://doi.org/10.1130/0016-7606(1982)93<150:DADOEA>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 Relative abundances of quartz and feldspar in fine-grained terrigenous sediments have been used to recognize specific continental sediment sources along northwestern South America and to trace the dispersal of specific grain size fractions from these sources to adjacent continental margin and deep-sea sedimentary environments. Quartz/feldspar ratios are low (∼0.6) for all fractions of sediments derived from southern Peru and northern Chile, but such ratios increase systematically in central and northern Peru as the importance of granitic and related intrusives increases relative to more basaltic extrusives and gabbroic equivalents. Limited published analyses of dusts collected offshore (Prospero and Bonatti, 1969) are also consistent with a latitudinally varying continental sediment source. We find that clay (<4 µm) and fine silt (8–11 µm) dispersal patterns are coincident with offshore wind-driven surface currents, whereas nearly all coarser sedimentary components (32–62 µm particles) exhibit limited dispersal normal to the shoreline on the continental margin. Because of the coincidence of wind and surface current patterns, transport of clay and fine silt away from the South American continent could be caused by either mechanism. However, on crossing to the seaward side of the Peru-Chile Trench, sedimentation rates decrease dramatically, silt/clay ratios are higher than expected, and clay mineral assemblages change abruptly. We argue that the trench is an imposing physiographic barrier to the seaward near-bottom advection of suspended particulates, thereby limiting the major influence of hemipelagic sedimentation to the continental margin. Deposition of terrigenous eolian components is clearly dominant seaward of the trench. Regardless of the mechanism responsible for the horizontal transport, rapid settling is required once a terrigenous particle leaves the surface mixed layer. We propose that coarse silt particles settle out of the water column rapidly over the shelf and continental slope, while finer components are incorporated into fecal pellets by large populations of zooplankton and nekton. Our observations that planktonic organisms ingest quartz and feldspar grains in proportions similar to those found on the underlying sea floor and that fecal pellets are ubiquitous in bottom sediments where an oxygen minimum impinges on the continental slope suggest the predominance of fecal pellet transport for these components. 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.