Geological Society of America

T282 Chemostratigraphy: Physical and Temporal Applications (Posters)

Wednesday, 25 September 2019
9:00 AM - 6:30 PM
Hall AB, North Building

THE IMPORTANCE OF SAMPLING DEPTH AND SPATIAL VARIABILITY ON TERRESTRIAL δ13CORG VALUES ACROSS THE K-PG BOUNDARY

Paper number: T282-15
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Jacob W. Honeck Presenting Author
University of Alabama, Tuscaloosa, WA
Thomas Tobin
University of Alabama, Tuscaloosa, AL
Michael L. Tuite
California Institute of Technology, Pasadena, WA
David M. Flannery
Queensland University of Technology (QUT), Brisbane, QLD
Isabel Fendley
University of California, Berkeley, Berkeley, WA
Luke Weaver
University of Washington, Seattle, WA
Courtney J. Sprain
University of Florida, Gainseville, FL

Abstract

Organic carbon isotope (δ¹³C_org) analysis of organic material has the potential to produce precise correlations in terrestrial environments. A negative δ¹³C_org excursion recognized worldwide has been also been observed at the Cretaceous-Paleogene (K‑Pg) boundary in the intensely studied Hell Creek area of Montana. The K-Pg boundary in this region coincides very closely with a lithological contact between two formations, and thus provides an ideal location at which to test the use of δ¹³C_org in high-resolution stratigraphy. Previous studies have produced stratigraphic records of δ¹³C_org across the K-Pg boundary in the area (Arens et al., 2014; Arens and Jahren, 2000). However, modern organic contamination, lithological control, and local spatial variability may affect δ¹³C_org values.

To test the effects of modern contamination and lithological control, we collected samples from a traditional hand trench, a coring device, and a deep (>1m) trench dug using a backhoe. Samples obtained using each method are collected across the same stratigraphic interval within 20 m (geographically) of each other, so their relative reliability can be assessed. Results show that core samples values are more negative, but the general trends, including the negative K-Pg excursion, are preserved in all sampling methods. There does not appear to be a significant lithological bias to δ¹³C_org values. Additionally, samples were also collected from hand trenches over a greater, but still fairly small (<10 km²) area to compare the effects of local spatial variability in δ¹³C_org signals. Results of these samples will be presented at the conference.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-337892

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