Modification of Linear Sand Ridges by Bed-Form Migration--Bering Sea and United States Atlantic Shelf: ABSTRACT

Abstract

Linear sand ridges are a dominant topographic feature of the United States mid-Atlantic shelf and the northeastern Bering Sea, as well as other coastal plain shelves of the world. Similarities in geometry, lithology, and stratigraphy of ridges in these two areas of markedly different oceanographic environments reflect a similarity in the processes that modify and shape these ridges. The best development of ridge topography occurs on the Atlantic shelf off Maryland where all stages of formation and modification can be identified. Progressive changes in ridge shape and relief and in bed-forms occur from onshore to offshore. Side slopes of ridges demonstrate characteristic trends related to water depth, and textural properties are 90° out of phase with topography. Historical documentation, seismic reflection and vibracore data, and sonographs of migrating sand waves all indicate southward migration of ridges, the dominant direction of storm-directed bottom flow. Ridges in the Bering Sea are exposed to a strong unidirectional and continuous flow of water northward into the Bering Strait. Repeated surveys of these features show that families of large north-facing sandwaves undergo migration infrequently. These periods of transport occur only when the strong oceanic flow is reinforced by northward storm-driven currents. End_of_Article - Last_Page 706------------