Grain-size analyses and bulk chemistry determined in surface sediment samples along the Chilean continental margin in the Southeast Pacific Ocean

Physical, chemical, and mineralogical properties of a set of surface sediment samples collected along the Chilean continental slope (21-44°S) are used to characterise present-day sedimentation patterns and sediment provenance on the Chilean margin. Despite the presence of several exceptional latitudinal gradients in relief, oceanography, tectonic evolution, volcanic activity and onshore geology, the present-day input of terrigenous sediments to the Chilean continental margin appears to be mainly controlled by precipitation gradients, and source-rock composition in the hinterland. General trends in grain size denote a southward decrease in median grain-size of the terrigenous (Corganic, CaCO3 and Opal-free) fraction, which is interpreted as a shift from aeolian to fluvial sedimentation. This interpretation is supported by previous observations of southward increasing bulk sedimentation rates. North-south trends in sediment bulk chemistry are best recognised in the iron (Fe) and titanium (Ti) vs. potassium (K) and aluminium (Al) ratios of the sediments that most likely reflect the contribution of source rocks from the Andean volcanic arc. These ratios are high in the northernmost part, abruptly decrease at 25°S, and then more or less constantly increase southwards to a maximum at ~40°S.

Nannofossil biohorizons for ODP Leg 133 sites

Paleontological studies conducted subsequent to the completion of Leg 133 led to refinements of the biostratigraphy for the Leg 133 sites. These biostratigraphic refinements bear on the calculations of sedimentation rates and on the age-depth plots prepared for the Initial Reports volume for Leg 133. To make available the revised data to anyone who may wish to make use of it, the revised biostratigraphic information is presented here in tabulated form. Revised age-depth plots also are presented for all of the sites to facilitate comparison of sedimentation rate curves and to identify intervals where significant changes have been made based on post-cruise studies. The revised age-depth plots include calcareous nannofossils only, and the revised data have been taken from thechapters contributed for this volume (Gartner et al., 1993, doi:10.2973/odp.proc.sr.133.213.1993; Wei and Gartner, 1993, doi:10.2973/odp.proc.sr.133.216.1993). Planktonic foraminifer biostratigraphy revisions became available subsequently and could not be readily incorporated. The age-depth plots for Sites 812 through 818 were made with the (ADP) program provided to ODP by Dave Lazarus.