Seawater Osmium Isotope Records from Pacific ODP and IODP Sites- Refining the Paleogene Curve and Dating Red Clay Sequences
MetadataShow full item record
Reconstructing ancient ocean circulation patterns contributes to a better understanding of Earth’s past climate conditions, as the two are known to be a strongly coupled system. Paleoceanographic reconstructions of the Late Cretaceous and early Cenozoic require enhanced geographic coverage, particularly in the Pacific, in order to better constrain meridional variations in environmental conditions. The challenge with the existing inventory of Pacific deep-sea cores is that they consist almost exclusively of pelagic clay with little existing age control. Recent work indicates that seawater Osmium (Os) isotope analyses provide useful age control for red clay sequences due to its relatively long residence time compared to oceanic mixing. The drawback to using seawater Os isotope stratigraphy to date Paleogene age sediments is that the compilation of existing data has some significant temporal gaps, notably between ~38 and 55 million years ago (Ma). To improve the temporal resolution of the seawater Os isotope curve, we present new data from Ocean Drilling Program (ODP) Site 865, which has excellent biostratigraphic age control over this time interval. Preliminary data indicate a seawater composition consistent with the apparent trend in the few existing data points. We also analyzed the Os isotopic composition at Integrated Ocean Drilling Progam (IODP) Site U1370 to construct an age model for this predominantly pelagic clay section. The 187Os/188Os values generally increase from 0.312 at 64.46 meters below seafloor (mbsf), likely reflecting the Os isotope minimum recorded across the Cretaceous-Paleogene boundary, to 0.531 at 28.26 mbsf, likely correlating to the Eocene/Oligocene interval.
Rolewicz, Zachary Louis (2013). Seawater Osmium Isotope Records from Pacific ODP and IODP Sites- Refining the Paleogene Curve and Dating Red Clay Sequences. Honors and Undergraduate Research. Available electronically from