Geological Society of America

T117 Deep-Time Carbon Cycles, Redox Changes, and the Evolution of the Biosphere II

Wednesday, 28 October 2020
10:00 AM - 12:00 PM
Meeting Rooms

A TROPICALLY HOT AND SALTY WESTERN INTERIOR SEAWAY (USA) SPANNING CRETACEOUS OCEANIC ANOXIC EVENT 2

Paper number: T117-3
Program: Technical Sessions
Time: 10:30 AM – 10:45 AM

Authors

Matthew M. Jones Presenting Author
University of Michigan, Ann Arbor, MI
Allison N. Curley
University of Michigan, Ann Arbor, MI
Sierra Petersen
University of MichiganEarth and Environmental Sciences Dept., Ann Arbor, MI

Abstract

The Cretaceous Thermal Maximum (KTM) is considered Earth’s warmest sustained interval for at least the past 100 Ma. Oceanic Anoxic Event 2 (OAE2) – a 600-800 kyr interval of widespread ocean deoxygenation linked to large igneous province (LIP) volcanism – has been hypothesized to represent a hyperthermal event punctuating the KTM, beginning at ~94.5 Ma. Here, to quantify paleotemperatures in the Western Interior Seaway (WIS) of North America spanning OAE2, we present new carbonate clumped isotope geochemical analyses (Δ₄₇) of fossil marine oysters. Diagenetically altered specimens are screened from the dataset using trace element contents and a calcite preservation index from SEM images. Following screening, mean Δ₄₇ temperatures of precipitation for oyster calcite range from 28-40˚C in the pre- and syn-OAE2 specimens of the WIS, quantitatively signifying the extreme regional and global warmth during OAE2 and the broader KTM. Additionally, values of δ¹⁸O_w (~-2 to +0.5‰ SMOW), derived from Δ₄₇ temperatures and δ¹⁸O_carb values, indicate a dominantly marine salinity regime in the WIS with implications for longstanding interpretations of biotic assemblages and water mass circulation in the vast epicontinental seaway.

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

doi: 10.1130/abs/2020AM-354767

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