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The areal distribution of sand layers in the basin plains of 13 modern deep ocean basins has been studied. Fundamentally, sand-layer distribution is controlled by the volume of sand input in single events relative to the basin plain size and by the areal distribution of basin entry points on the ocean basin floor. Although tectonic setting and sea level position may play a role in rate of basin infilling, these factors are relatively unimportant in the control of sand-layer geometry. A basin plain sand-layer classification has been devised. The classification is comprised of a hierarchy with three ranks or categories. The first category describes the distribution of basin entry points as being one of the following; radial, semiradial, longitudinal, or lateral. The second ategory separates basin plains with similar entry point distributions on the basis of the extent of sand coverage on the flat basin floor. Sand coverage is classified as either overall or partial. The final category further separates basin plains according to the general shape of sand bodies on the basin floor--either wedge, sheet, or axial. The classification has application to the study of both modern and ancient deposits. If the distribution of sand layer characteristics is known, it may be possible to locate probable basin entry points and to predict the size of the drainage area relative to the size of the flat basin floor. Alternatively, if the approximate size of the drainage area relative to the basin plain area and the distribution of basin entry points are known, it may be poss ble to predict the nature of the sand distribution on the basin plain.
Inherent in each basin plain type is a specific distinctive areal distribution of sand layer characteristics and particular manifestations of proximal/distal relations. For example, a basin with sand layer geometry classified as radial fill, overall coverage, and wedge-shaped (the Hispaniola-Caicos plain) would have its thickest sand and lutite (or shale) layers located around the periphery of the basin plain. The highest frequency of sand layers would probably be found in the basin plain center and the ratio of drainage area to basin plain area would be relatively large (greater than 3).
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