36 Insights from Microfossils, from Terrestrial to Marine Environments (Posters)

Tuesday, 22 March 2016
8:00 AM - 12:00 PM
Convention Hall

NEW EVIDENCE OF A WARMER BOTTOM WATER MASS LEADING UP TO THE PALEOCENE EOCENE THERMAL MAXIMUM: STABLE ISOTOPE RECORDS FROM DSDP LEG 22 SITE 215

Paper number: 36-3
Program: Theme Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

Moderately-high resolution (20 kyr) stable isotope (δ13C and δ18O) records were developed from the Deep Sea Drilling Program Indian Ocean Site 215 to investigate paleoceanographic changes during the late Paleocene (54.8-59 Ma) leading up and including to the Paleocene-Eocene Thermal Maximum (PETM). Site 215 was drilled in water depth of 5,300 meters in ponded sediments of the Ninetyeast Ridge, in the central Indian basin at 8° 12’S, 86° 50’E. This site was chosen to study the Paleocene because of the thin overlying sediment cover. This occurred due to the site subsiding below the CCD by the Early Eocene. As a result, Paleocene sediments are only buried by 100 meters of sediments, making Site 215 an ideal site to recover well-preserved foraminifera. A total of 195 stable isotopic measurements from benthic foraminifera were analyzed in this study that spanned between 54.8 Ma and 59 Ma. A chronostratigraphic framework was developed using foraminiferal biostratigraphic data and converted to the Gradstein et al. (2012) timescale.

The results from Site 215 showed similar trends as previous studies, with a long-term warming trend seen in the δ18O isotope record and progressively lighter δ13C values leading up to the PETM. A significant difference between our record and other global records (e.g., ODP Site 1209) is that bottom water temperatures (BWT) appear to increase sooner at Site 215, starting about ~ 1 myr earlier, resulting in a more gradual increase in BWT leading up to the PETM. This results in an δ18O offset of about 0.5‰ or about 2˚ C. As this is the deepest water site with stable isotope records, we speculate that a warm bottom water mass began to bathe deepest parts of the world’s oceanic basins leading up to the PETM.

Geological Society of America Abstracts with Programs. Vol. 48, No. 1

doi: 10.1130/abs/2016NE-272613

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