Processes Controlling Characteristics of Surficial Sand Sheet, U.S. Atlantic Outer Continental Shelf: ABSTRACT

Abstract

A surficial sand sheet covers almost the entire Atlantic outer continental shelf of the United States. Until recently, the processes controlling the characteristics of this sheet were inferred mainly from the texture and composition of bottom grab samples and from the bathymetry. Studies of these aspects outlined the general nature and age of major processes, but they were necessarily limited in scope. With the advent of leasing of the outer shelf for petroleum exploration, many process-oriented studies were initiated by the U.S. Geological Survey. These studies included measurements of the velocity of bottom currents, the frequency of bottom-sediment movement, the kinds and amounts of suspended sediments in near-bottom waters, and the acoustic and sedimentary characteristics of the shallow subbottom strata. These new measurements, when used in conjunction with previous data, show that attributes of the surficial sand sheet such as the thickness, volume, composition, texture, and internal structure have been controlled by a variety of ancient and modern processes. Ancient processes include those associated with glaciers, ancestral rivers, nearshore-marine environments, and subaerial solution and erosion. Modern processes include tidal-, wind-, and wave-driven currents, internal waves, movement of water masses, regional circulation patterns, sediment bioturbation, latitudinal changes in biogenic components, and bottom fishing. A knowledge of the various factors effecting the sand sheet is fundamental to (1) an understanding of its general geologic history; (2) the paleoenvironmental interpretation of ancient sand strata; (3) a determination of the distribution and fate of anthropogenic sediments and pollutants; and (4) an evaluation of potential sand resources and geologic hazards. End_of_Article - Last_Page 733------------