Surface carbonate and land-derived clastic marine sediments from southern Chile: mineralogical and geochemical investigation

Surface carbonate and land-derived deposits in the sea off southern Chile w ere investigated for their mineralogical and geochemical composition. The d ata were related to environmental features and compared with those of simil ar temperate and polar carbonate deposits from Tasmania, New Zealand, Arcti ca, and Antarctica. The mineralogy of the siliciclastic fraction is typical of cold areas and is mainly composed of chlorite, mica, quartz, feldspars and amphibole. The CaCO3 content varies from 30 to 90%; carbonate mineralog y is made up of low-Mg calcite, high-Mg calcite and minor amounts of aragon ite. The Ca, Mg, Sr, Fe, and Mn contents of bulk carbonates and some select ed skeletal hard parts are comparable to those of carbonates from Tasmania. The elemental composition is mainly related to carbonate mineralogy, skele tal components, and seawater conditions. The delta C-13 and delta O-18 valu es of carbonates are positive, and their field falls between the "seafloor diagenesis" and "upwelling water" trend lines, because the sediments are li kely to be in equilibrium with waters of Antarctic origin. The mineralogica l, elemental, and isotopic compositions of carbonates from southern Chile s how better similarities with the "temperate" carbonates from Tasmania and N ew Zealand than with the "polar" carbonates from Arctica and Antarctica. Ca rbonate deposition is allowed by the low terrigenous input, the low SPM con centration and, probably, the upwelling of seawater from Antarctica. (C) 20 00 Elsevier Science Ltd. All rights reserved.