Abstract:
This study focuses on changes in ocean chemistry during the late Campanian and Maastrichtian (75-65 Ma), as inferred from elemental concentrations of Ba, Ca, Al, Sr, Mn in sediments from Deep Sea Drilling Project (DSDP) Sites 305, 384, 463 and Ocean Drilling Program (ODP) Site 690. Previous isotopic studies have shown an interval of globally high delta (super 18) O and low delta (super 13) C values between 71 and 69 Ma (Barrera and Savin, 1999). High delta (super 18) O values are attributed to the influx of cooler high latitude waters into low latitudes and to an increase in ice volume. Lower sea levels may have caused isotopically negative organic carbon to be eroded from exposed continental shelves and transported into the oceans. Results from this thesis suggest that the input and remineralization of shelfal organic carbon could have resulted in increased primary productivity. The evidence is the increased biogenic barium (Ba (super *) ) concentrations at Sites 305 and 690 between 71 and 69 Ma. At equatorial Pacific Site 305, Ba* concentrations increase from 40,000 ppm at 70.5 Ma to 80,000 ppm, where they remained until 69.5 Ma. At Southern Ocean Site 690, Ba (super *) concentrations increased from 1,000 ppm at 70.5 Ma to 14,000 ppm at 70 Ma. North Atlantic Site 384 showed no biogenically-derived barium. Equatorial Pacific Site 463 had the highest Ba* concentrations ( approximately 40,000 ppm) throughout the Late Campanian-Maastrichtian, but there was no change in concentrations during the 71-69 Ma interval. I also investigated whether the drop in sea level was accompanied by increased oceanic Sr concentrations as suggested by Stoll and Schrag (1996, 1998). Only Site 305 showed higher Sr concentrations during the proposed sea level drop. At 71 Ma, the percent Sr increased from 75% to 95% where it remained until 70 Ma. At 67-66.5 Ma, biogenic barium concentrations at Site 305 and 690 began to drop reaching values near O ppm by Cretaceous-Tertiary boundary time (65 Ma). This suggests that oceanic productivity was declining for a considerable time prior to the extinction event. My results do not support prior assertions, based on planktic foraminiferal faunas, that suggest productivity declined approximately 300,000 years before the boundary event (Keller and Lindinger, 1989).