T183 Assessing the Fidelity of Geochemical Signals in Deep Time: Primary, Authigenic, and Diagenetic Signals in Proxy Data

Thursday, 29 October 2020
10:00 AM - 12:00 PM
Meeting Rooms

MULTI-PROXY SEASONALITY INVESTIGATION OF THE MID-CRETACEOUS WESTERN INTERIOR SEAWAY USING OYSTER MACROFOSSILS

Paper number: T183-7
Program: Technical Sessions
Time: 11:30 AM – 11:40 AM

Authors

Abstract

Quantifying ocean temperatures during geologic intervals of extreme warmth, like the Cenomanian and Turonian stages (~100-90 Ma), has implications for paleocirculation patterns, paleoecology, and thermal thresholds in the development of ocean anoxia. Strata deposited in the shallow, expansive Cretaceous Western Interior Seaway (WIS) of North America preserve a rich archive of climate and environmental information from a past greenhouse interval and can teach us about natural limits within the Earth system. The use of traditional oxygen isotope paleothermometry in the WIS is challenging due to known but unquantified variations in the oxygen isotopic composition (δ18Ow) and salinity of seaway waters. Here, we analyze oyster macrofossils distributed across the WIS to reconstruct paleoceanographic and paleoclimatic conditions during the mid-Cretaceous thermal maximum using multiple geochemical proxies. High-resolution sclerochronologic (sub-annual) 𝛿18O and 𝛿13C isotope analyses of oyster macrofossils from the genera Exogyra and Pycnodonte measure paleoseasonality in the mid-latitudes of the WIS. When combined with carbonate clumped isotope paleotemperatures of the fossil specimens, the degree of temperature and δ18Ow seasonality is quantified during the hothouse climate of the mid-Cretaceous. These are among the first isotope-derived estimates of Cenomanian-Turonian seasonality, including the Ocean Anoxic Event 2 hyperthermal interval.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-359010

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