4 Paleoclimatology, Paleoecology, and Conservation Paleobiology: Old Tools and New Tricks for Unraveling the Past and Informing the Future

Monday, 15 April 2024
8:00 AM - 12:00 PM
Swannanoa

COMPARING SEASONAL SEA SURFACE TEMPERATURES FROM OXYGEN ISOTOPE RATIOS AND CLUMPED ISOTOPES RECORDED IN MERCENARIA SPP. SHELLS DURING THE PLIO-PLEISTOCENE

Paper number: 4-4
Program: Theme Sessions
Time: 8:45 AM – 9:05 AM

Authors

Abstract

Seasonal sea surface temperature (SST) reconstructions from deep-time archives can potentially provide insight into the nature of the climate system on sub-annual scales during critical climate states such as the Mid Piacenzian Warm Interval (MPWI) and subsequent early Pleistocene cooling. Traditional oxygen isotope (δ18O) measurements in biogenic carbonates have been the dominant seawater (sw) temperature proxy in marine archives but can be complicated by assumptions made to constrain δ18Osw values. Clumped isotope geochemistry (∆47) shows promise as a novel paleothermometer, as it does not rely on constraining the δ18Osw value. In this study, we validate that Mercenaria shells do not require a species-specific ∆47 paleotemperature calibration by comparing ∆47 values recorded by modern Mercenaria from coastal NC and recorded water temperature to the universal ∆47 paleotemperature calibration. We then compared seasonal SSTs during the MPWI, subsequent early Pleistocene cooling, and today using δ18Oshell values to seasonal SSTs derived from ∆47 values. Local maxima and minima within the δ18Oshell timeseries were targeted to collect 1.5-2mg of carbonate powder for ∆47 analysis to capture the largest range of recorded temperature. Oxygen isotope ratios record average summer and winter temperatures of 28±1°C and 18±2°C during the MPWI, 22±1°C and 11±3°C during the early Pleistocene, and 30±4°C and 15±7°C in modern shells. Preliminary analyses were conducted for 3 annual maxima/minima pairs (n = 6 per shell) on 3 modern shells. Values of ∆47 range from 0.645‰ to 0.733‰ and SST estimates based on available calibration studies of inorganic and organic carbonates were compared to SST estimates from δ18Oshell values. Based on these preliminary data, results suggest that ∆47-based temperature estimates from M. mercenaria are consistent with both observational data and existing δ18O calibration estimates.

Geological Society of America Abstracts with Programs. Vol. 56, No. 2

doi: 10.1130/abs/2024SE-398393

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