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Abstracts: Ultra-High Resolution Stratigraphic Methods for Paleoclimatic and Paleoceanographic Studies


Quaternary paleoceanographic and paleoclimatic studies have recently come full circle by incorporating data from traditional sedimentological studies or newly developed lithostratigraphic techniques, in addition to stable isotopic or micropaleontological analyses. In most cases, stratigraphic analysis must be accomplished at very high resolution (approx. cm-scale) in order to understand rapid environmental change or to correlate exceedingly brief climatic events. The investigator is faced with deciding between making numerous, time-consuming analyses or using easily collected proxies for standard sedimentologic parameters. Both "low-tech" and "high-tech" methods can be useful. The three following methodologies have proved to be extremely valuable in Quaternary stratigraphic research: 1) Cm-scale visual assessment of ichnofabric or bioturbation indices in a 200 m core from the Santa Barbara Basin (ODP Site 893) discovered approximately 18 anoxia events during the past 60 kyr that correlate exactly with brief, rapid warming events known as Dansgaard-Oeschger interstadials in the Greenland ice cores. This method is best employed in intermittently laminated sediments for ultra-high stratigraphic resolution (<10 yr increments). 2) Computed tomographic X-radiographic analysis (CAT-sans) is being used in cores from the California margin (ODP Leg 167) to determine paleoenvironmental changes in nonlaminated sediments by quantifying burrow diameters and percentage bioturbation at 5 cm (approx. 200 yr) increments. 3) Variations in relative reflectivity (grayscale analysis) in a series of cores from the Cariaco Basin, Venezuela, provided and permitted intercore and intercontinental correlation of decadal- to century-scale climatic variation.

Search and Discovery Article #90945©1997 AAPG Pacific Section Meeting, Bakersfield, California