Abyssal Basin Sedimentation: ABSTRACT

Abstract

Clastic sands and silts transported and deposited by turbidity currents have created the vast abyssal plains of the ocean basins and have constructed the abyssal cones and natural levee systems of the continental rise. Clastic silts and lutites, largely transported by ocean currents, have created much of the continental rise and the outer ridges which parallel the continental margins. Biogenous sediment, resulting from near-surface productivity, more or less redistributed by currents, has created the rolling abyssal swales of productive mid-oceanic areas and has contributed to the continental rise and marginal trench sediments. Although turbidity currents are responsible for the leveling of the abyssal plains, turbidites constitute less than one-third of the sediments beneath the plains. Horizontal size grading in turbidites away from source areas is detectable but small. Apparently a much more important control on size is imposed by the lower courses of the major rivers. Turbidity currents originate near the mouths of several major rivers at the rate of 50 per century but in many other likely areas none have occurred for thousands of years. End_of_Article - Last_Page 344------------