Deep-sea sedimentation and sediment-fauna interaction in Cascadia Channel and on Cascadia Abyssal Plain

Abstract

The transport of sediments from shallow water by turbidity currents and their deposition within Cascadia Channel in the northeast Pacific Ocean have created a unique environment. Thick organic-rich turbidity current deposits of postglacial age in Cascadia Channel contrast markedly to the thin, less rich, hemipelagic clays overlying clean late Pleistocene sands on the adjacent abyssal plain to either side. The benthic animal population in the channel is four times as abundant as that of the adjacent plain. Burrowing organisms in Cascadia Channel have left many well-preserved burrows of distinct sizes and shapes within the successive turbidity current deposits. A variation in the depth and the frequency of burrowing within these deposits has been recognized and correlated over a distance of 65 km within Cascadia Channel. It is postulated that the turbidity flows create a unique environment in the channel and that the fauna is affected by differences in sediment size and composition and by the increased supply of utilizable organic material.