RAPID CHANGES IN ORGANIC CARBON PRESERVATION IN SEDIMENTS FROM COASTAL BAJA CALIFORNIA ARE LINKED TO GLOBAL CLIMATIC CHANGES

Continental margin sedimentation reflects both continental and oceanic processes. Among the most interesting of the oceanic processes influencing continental margins are changes in oxygen content of bottom water as reflected in laminated and bioturbated sediments. These changes may occur on a decadal timescale and are thus of societal relevance. Laminations of this type have been observed in sediments of the Santa Barbara Basin off Southern California (Behl and Kennett, 1996). The timing of these alternations closely matches the pattern of changes observed in the Greenland Ice cores (e.g. Grootes, et al., 1993) and North Atlantic sediments (Bond and Lotti, 1995). Other teleconnections between shallow marine sediments and Greenland ice cores have been observed in Antarctica (Brook, et al, 1996) and the OMZ of the Arabian Sea (Schultz, et al, 1998).

During the fall of 1999, gravity and piston cores were collected off the Baja California Coast in water depths ranging from 200-1250m with the objective of monitoring changes in the intensity and location of the OMZ. Shipboard spectrophotometer measurements were taken with a Minolta CM-2022 spectrophotometer at 1 cm spacing on freshly split core surfaces. Post-cruise R-Mode factor analysis reveal three factors which account for >95% of the data set variation. Preliminary worn suggests that Factor 1 is indicative of sediment carbonate content, Factor 2 corresponds to sediment iron oxide, and Factor 3 reflects sediment organic carbon. In several of the cores where the data has been processed, Factor 3 shows a remarkable similarity to the oxygen isotope record from the Santa Barbara Basin and/or the Greenland ice cores. Thus using rapid, cost-effective, and non-destructive techniques, these NE pacific continental margin sediments allow us to monitor changes in the intensity and location of the OMZ and suggest teleconnections with worldwide climate reorganization. Since laminated, high organic carbon sediments have the potential to become black shales, the historical record of these sediments may indicate previous episodes of rapid climate change.