T89 The Cretaceous-Paleogene (K-Pg) Boundary Interval: From Large-scale Geological Events to Mass Extinction Mechanisms

Monday, 23 September 2024
8:00 AM - 12:00 PM
204C

HIGH-RESOLUTION TEMPERATURE RECORD ACROSS THE K-PG BOUNDARY (67.1 TO 65.9 MA) USING CLUMPED ISOTOPES IN GAR SCALES FROM NORTH DAKOTA, USA

Paper number: T89-15
Program: Technical Sessions
Time: 11:35 AM – 11:50 AM

Authors

Abstract

We report a stratigraphically well-constrained terrestrial climate record from the Late Maastrichtian to the earliest Danian with a duration of 1.2 Myr. We apply a new clumped isotope calibration for the carbonate in vertebrate bioapatite (Gray and Brandon, in review). The calibration is based on the bioapatite in modern gar scales collected from a latitudinal transect across northern North America. Gars are useful as isotope thermometers because their scales grow throughout their multiyear lifespan, they do not migrate, and they live in shallow freshwater settings (< 3 m depth). As a result, they provide a time-averaged record of the local water surface temperature. We account for seasonal temperature variations by calculating an effective temperature, Te, which is the equivalent steady temperature that would result in the same Δ47 value as that produced by a gar with a variable temperature history. Our Te results more accurately represent the climate for continental interiors, particularly those at high latitudes with large seasonal changes in temperature. The prediction error for the calibration has a 95% confidence interval of ± 2.5 °C.

We report 12 temperatures for samples collected from the Hell Creek and Fort Union formations in North Dakota, USA, at a paleolatitude of ca. 52 °N. The stratigraphic sequence encompasses the recession of the Western Interior Seaway and mainly consists of fluvial deposits with minor lignite. Te values are 16.8 °C at 67.1 Ma, reach a maximum of 35.6 °C at 66.3 Ma, and decrease to 22.6 °C at the K-Pg boundary. We find a Te rise of 13 °C prior to the K-Pg boundary, coincident with the main eruption phase of the Deccan Traps, as determined by other studies (Hull et al., 2020). Overall trends in our data are also consistent with those from paleosols (Zhang et al., 2018), and freshwater mollusks (Tobin et al., 2014). These temperature estimates correlate well with the moderate atmospheric CO2 GCM experiments (Niezgodski et al. 2017).

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-405504

© Copyright 2024 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.