Catchment processes and the quantity and composition of sediment delivered to terminal basins

Abstract

Although the quantities of sediment exported to the sea by large rivers are relatively well known, information on mineralogical and geochemical characteristics is less readily available. Quantity and composition are strongly influenced by tectonic environment and also by both present and past climate. An analysis of diagenetic processes in fine-grained clastic sediments suggests that bed-parallel changes in the intensity of diagenetic modification (reflected in phenomena such as cemenstone horizons) and marked changes in authigenic mineral assemblages (sulphides, carbonates, silicates) could be explained by changes in sediment supply rate driven by climatic fluctuations. It is less easy to explain fluctuations in detrital sediment composition: diagenetic reorganization would appear to be the most common cause of marked local compositional contrast in mudstones.