CATCHMENT PROCESSES AND THE QUANTITY AND COMPOSITION OF SEDIMENT DELIVERED TO TERMINAL BASINS

Although the quantities of sediment exported to the sea by large river s are relatively well known, information on mineralogical and geochemi cal characteristics is less readily available. Quantity and compositio n are strongly influenced by tectonic environment and also by both pre sent and past climate. An analysis of diagenetic processes in fine-gra ined clastic sediments suggests that bed-parallel changes in the inten sity of diagenetic modification (reflected in phenomena such as cemens tone horizons) and marked changes in authigenic mineral assemblages (s ulphides, carbonates, silicates) could be explained by changes in sedi ment supply rate driven by climatic fluctuations. It is less easy to e xplain fluctuations in detrital sediment composition: diagenetic reorg anization would appear to be the most common cause of marked local com positional contrast in mudstones.