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Research Article| January 01, 1970 Equatorial Atlantic Deep-Sea Arkosic Sands and Ice-Age Aridity in Tropical South America JOHN E DAMUTH; JOHN E DAMUTH Lamont-Doherty Geological Observatory, Palisades, New York 10964 Search for other works by this author on: GSW Google Scholar RHODES W FAIRBRIDGE RHODES W FAIRBRIDGE Department of Geology, Columbia University, New York, New York 10027 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1970) 81 (1): 189–206. https://doi.org/10.1130/0016-7606(1970)81189:EADASA2.0.CO;2 Article history received: 14 Oct 1968 rev-recd: 09 Jul 1969 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation JOHN E DAMUTH, RHODES W FAIRBRIDGE; Equatorial Atlantic Deep-Sea Arkosic Sands and Ice-Age Aridity in Tropical South America. GSA Bulletin 1970;; 81 (1): 189–206. doi: https://doi.org/10.1130/0016-7606(1970)81189:EADASA2.0.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 Arkosic sands of latest Wisconsin age from deep-sea piston cores taken in the Guiana Basin off northeast South America between lat 20° N. and lat 10° S. support previous conclusions that an arid to semiarid climate dominated large portions of equatorial South America during the Pleistocene glacial phases in complete contrast to the present-day and Pleistocene interglacial humid tropical climate. Thirty-nine cores showed stratigraphic relations that characterize the transition from Wisconsin to Holocene. Sand beds from 23 of the cores were of latest Wisconsin age and contained 25-60 percent feldspar. In contrast, a sample of Holocene sand taken from the continental shelf northeast of the mouth of the Amazon River contained only 17—20 percent feldspar.The Quaternary history of Brazil appears to have been climatically controlled by a repeated displacement of the South Atlantic high-pressure cell by some 1500 km—northward during the glacial phases and southward during the interglacial phases. It was further influenced during glacial phases by a lowering of the snow line in the Andes by about 1000 m. In consequence, the glacial phase climates of the lower Amazon Basin were marked by cold, dry, southerly winds while the South Atlantic trade winds were deflected off the northeast coast. A semiarid to and climate ensued, coupled with a eustatic drop of sea level that caused degradation of the principal river valleys near the coast. In this way unweathered feldspars, chlorite, and other relatively coarse elastics were transported into the tropical Atlantic in contrast to the usual lateritic clays (gibbsite and kaolimte) of interglacial stages. 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.
Damuth et al. (Thu,) studied this question.