Isotope Geochemistry of Clay Minerals in Young Continental and Oceanic Sediments

Abstract

Continental erosion is affected mainly by riverine processes and, to a smaller degree, by wind and glacial activity. The debris eroded by these agents are deposited in fluvial, glacial, lacustrine and other continental depositional centers and in various parts of the oceanic basins, the latter constituing almost the bulk of the sediments deposited during the entire history of the Earth. A recent estimate given by Milliman and Meade (1983) suggested that about 13.5 × 10¹²kg of sediment are annually delivered to the oceans by the rivers and, according to Gibbs (1967), 4 × 10¹²kg of the material consist of <2 μm size particles. Assuming that nearly 60% of the <2 μm fraction consists of clay minerals, which is the same amount present in an average shale, about 2.4 × 10¹²kg of clay minerals are delivered each year to the present-day oceans by the rivers.