USING MARINE BARITE ACCUMULATION RATES TO CONSTRUCT A PALEOPRODUCTIVITY RECORD FOR THE MID-MIOCENE

Nearly ubiquitous in seawater, marine barite is regionally dispersed in deep-sea sediments accumulating particularly in sediments underlying high biological productivity regions (Paytan and Griffith, 2007 and references therein). As a result of its unique formation mechanism (i.e.,within sinking organic matter), the amount of marine barite forming in the water column and accumulating in sediments is strongly related to the organic carbon export flux and the biological productivity of the overlying water column (Paytan and Griffith, 2007). The high preservation potential of barite and its resistance to diagenetic alteration after burial in oxic settings make this authigenic mineral favorable for studies of paleoproductivity.

With this in mind, sediment samples were taken from two equatorial Pacific Ocean cores (DSDP Leg 85: sites 573B and 575B) at a resolution of better than 250,000 years. The samples span in age from ~12-18 Ma. Marine barite is extracted from deep sea sediment using a sequential leaching process (Paytan et al., 1993) and screened for purity. Barite accumulation rates have been determined for both cores, and these rates will be correlated to global changes in climate for the corresponding time period. Size fraction analyses have also been performed on the samples to determine the levels of carbonate dissolution due to changes in water corrosiveness and their relationship to changes in productivity.