Late Quaternary records of organic carbon, calcium carbonate, and biomarkers from Site 1016 off Point Conception, California margin

Abstract

Total organic carbon (TOC) and calcium carbonate (CaCO 3 ) concentrations were determined for 304 samples, and biomarkers were analyzed for 101 samples from Core 167-1016C-1H. TOC varies between 1% and 2%, and CaCO 3 is typically 1%-4%, with peaks reaching 14%. Paleotemperature estimated from U 37 k' varies from 8.5° to 17.5°C. The U k 37 variation implies that Core 167-1016C-1H covers oxygen isotope Stages 1-6. Peaks of diatom-derived C 25:1 HBI alkene concentrations occur during warming intervals, suggesting intensified upwelling during deglaciation. The concentrations of haptophyte-derived alkenones and diatom-derived C 25:1 HBI alkene vary out of phase, which presumably resulted from the changes in the mode of nutrient supply to surface mixed layer. Maximal CaCO 3 contents (>10%) were observed in both warming and cooling intervals. The peak in cooling interval relates to an alkenone maximum, whereas the peaks in warming intervals do not. This implies that carbonate production is not the only factor controlling carbonate compensation depth at this site, and it suggests considering the changes in North Pacific deep-water chemistry. Petroleum-type compounds are present in Site 1016 sediments. Their concentrations are maximized in the warming intervals that correspond to the timing of destruction of a huge tar mound off Point Conception. The tarry material was presumably transported by the Arguello Fan system to Site 1016.