18 Actualistic Paleontology: Learning from the Modern to Better Interpret the Past (Posters)

Thursday, 7 April 2022
1:30 PM - 5:30 PM
Junior Ballroom B

REFINING A ∆47 PALEOTEMPERATURE CALIBRATION USING MODERN AND FOSSIL MERCENARIA SPP. (BIVALVIA) TO RECONSTRUCT DEEP-TIME SEASONALITY

Paper number: 18-2
Program: Theme Sessions
Time: 1:30 PM – 5:30 PM

Authors

Abstract

Traditional oxygen isotope (δ18O) measurements in biogenic carbonates have been the dominant seawater (sw) temperature proxy in marine archives since the 1950s and have been used to reconstruct Cenozoic climate. However, temperature reconstructions 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. This study tests the viability of ∆47 as a paleothermometer in the marine/estuarine bivalve Mercenaria mercenaria from coastal NC, USA. We analyzed δ18Oshell values of 4 live-collected shells from UNC-Wilmington’s marine sanctuary providing sub-monthly snapshots spanning the past 15 years. Values ranged from +2.3‰ to −2.2‰ (VPDB). We calculated predicted δ18Oshell values using in situ water data (temperature, salinity, and published salinity-δ18Osw relationship) measured from a nearby location and an equilibrium fractionation equation for aragonite. Predicted values and the commonly used “wiggle matching” approach allowed us to assign dates to δ18Oshell values and estimate measured water temperature for the ∆47 calibration. We found shells track maximum daily temperatures and do not record winter temperature below ~10ºC. Our ∆47 sampling strategy targets peaks and valleys along the δ18Oshell time-series to capture average maximum summer (30.8±0.7°C) and average minimum winter (7.2±2.2°C) temperatures recorded in the shells. A total of 27 ∆47 samples will be used to construct the calibration. Once constructed, our calibration will be compared to several published ∆47 constructions using an ANOVA statistical test. We will compare ∆47-derived paleotemperatures to published δ18O-derived paleotemperatures recorded in fossil Mercenaria spp. shells from the Mid Pliocene Warming Interval (Duplin Formation) and subsequent cooling in the early Pleistocene (Waccamaw Formation). Temperatures derived from our ∆47 analysis of fossil shells, along with measured δ18Oshell values, will allow us to validate previously published δ18Osw values based on global ice volume estimates.

Geological Society of America Abstracts with Programs. Vol. 54, No. 4

doi: 10.1130/abs/2022NC-375474

© Copyright 2022 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.