Recent investigations by the U. S. Geological Survey indicate that approximately two billion tons of sediment have accumulated in Lake Mead during its first 14 years from 1935 to 1948, inclusive. About 50 per cent of this material has been transported by turbidity currents which form at the mouths of the Colorado and Virgin Rivers. The sediment carried by the Colorado turbidity currents has been deposited along the bottom of the entire length of the lake, a distance of 120 miles, whereas the material supplied by the Virgin River turbidity currents is confined chiefly to the northern part of the inundated Virgin River valley (Overton Arm of Lake Mead). A review of the nature and history of the Lake Mead turbidity currents is presented and consideration is given to the possible applications that these studies may have to similar sedimentary processes in the ocean.
Figures & Tables
By 1951, recent studies of the sea floor were forcing drastic revisions of many of our basic geological concepts. The concept of vertical stability of the ocean basins was being challenged by the discovery of “guyots”; sea-mounts whose flat tops, now several thousand feet beneath the sea surface, give evidence of wave truncation. The belief that the deep ocean floor was essentially a flat, featureless plain was completely discredited by the discovery of fault scarps and mountain ranges comparable in size and complexity to any of those existing on the continents. One of the most challenging of recent discoveries is the finding of relatively coarse sediments (coarse silt and sand) in deep basins and on the open ocean floor at depths of several thousand feet and many miles from land. Solution of this problem was particularly difficult because the mere occurrence of these coarse sediments violates some of the traditional opinions of the day about processes operating in the oceans. This volume contains some of the first and best documented research in this area that opened a whole new way to interpret deep water deposition.