Terrigenous sediment supply along the Chilean continental margin: modern regional patterns of texture and composition

The regional patterns of texture and composition of modern continental slop e and pelagic sediments off Chile between 25 degrees S and 43 degrees S ref lect the latitudinal segmentation of geological, morphological, and climati c features of the continental hinterland. Grain-size characteristics are co ntrolled by the grain-size of source rocks, the weathering regime, and mode of sediment input (eolian off northern Chile vs fluvial further south). Bu lk-mineral assemblages reveal a low grade of maturity. Regional variations are governed by the source-rock composition of the different geological ter ranes and the relative source-rock contribution of the Coastal Range and An des, as controlled by the continental hydrology. The relative abundance of clay minerals is also predominantly influenced by the source-rock compositi on and partly by continental smectite neoformation. Latitudinal variations of illite crystallinities along the Chilean continental slope (and west of the Peru-Chile trench) clearly reflect modifications of the weathering regi me which correspond to the strong climatic zonation of Chile.