Sources of Sediment in Western Basins of Atlantic Ocean: ABSTRACT

Abstract

The Mid-Atlantic Ridge divides the Atlantic Ocean into two isolated north-south troughs. The western basin is subjected to intensified north-south moving currents because of the Earth's rotation. In addition to the surface currents such as the Gulf Stream and the Falkland Current, deep western boundary currents are presently identifiable as the North Atlantic Deep Water and the Antarctic Bottom Water. These currents affect the source and distribution of sediments in the western Atlantic basin. In the western North Atlantic basin, bottom transport from high latitude sources is clearly seen by the contour of such mineral indicators as quartz, amphibole, and diagnostic mixed-layer clay minerals. The transporting agent is the North Atlantic Deep Water. In the western South Atlantic basin, bottom transport via the Antarctic Bottom Water from high southern latitudes supplies a major part of the sediments in the Argentine basin. The sediments came from glacial sources in Antarctica and from South Pacific volcanogenic sources. These volcanogenic sediments are carried eastward by the Antarctic Circumpolar Current. This is indicated in part by the mineralogy, but more so by the distribution pattern of the S87/S86 ratio in the detrital parts of the sediments. A diagnostic criterion for Antarctic glacial source relative to fluviatile sources from southern Argentina is seen in the surface texture of quartz grains. On the basis of material-balance calculations, much of the detrital sediment in the western Atlantic basin can be ascribed to high-latitude, glacially originating sources close to the continental margin; bottom transport from the shelf and slope also will contribute significant sediment. End_of_Article - Last_Page 331------------