Sedimentary fill of the Chile Trench (32–46°S): volumetric distribution and causal factors

Abstract

The Chile Trench of the convergent continental margin of Central Chile is a sediment-filled basin that stretches over 1500 km in a north–south direction. The sediment fill reflects latitudinal variations in climate as well as in the morphology and geology of Chile, but also of sediment transport processes to the trench and within the trench. We try to untangle these signals by calculating the total volume and the latitudinal volume distribution of trench sediments and by relating this distribution to a number of factors that affect this pattern. The volume calculation is based on a model geometry of the top of the subducting oceanic plate that is buried beneath trench sediments and the sea floor as measured by swath bathymetry. We obtain the model geometry of the subducting plate by interpolating between depth-converted seismic reflection profiles that cross the trench. The total volume of the trench fill between 32 and 46°S is calculated to be 46000 ± 500 km 3 . The resulting latitudinal volume distribution is best explained by a sedimentation model that alternates between (1) glacial phases of high sediment flux from Southern Chile combined with active latitudinal sediment transport within the trench and (2) interglacial phases over which sediment input is dominated by local factors. Supplementary material: Top of the oceanic basement (TOB) grid is available as ascii raw data files (xyz) at www.geolsoc.org.uk/SUP18664 .