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GSA Annual Meeting in Seattle, Washington, USA - 2017

Paper No. 30-11
Presentation Time: 11:00 AM

UNTANGLING THE DIET OF HERBIVOROUS DINOSAURS FROM THE MINERALIZATION OF THEIR DUNG: A STABLE ISOTOPE ANALYSIS OF COPROLITES


PLAZA-TORRES, Stephanie, Department of Geology, University of Puerto Rico at Mayagüez, PO Box 9000, Mayagüez, PR 00681-9000, DAVIDHEISER-KROLL, Brett, Geological Sciences, University of Colorado Boulder, 2200 Colorado Ave, Boulder, CO 80309, CHIN, Karen, Geological Sciences and Museum of Natural History, University of Colorado Boulder, UCB 265, Boulder, CO 80309 and WING, Boswell, Geological Sciences, University of Colorado Boulder, UCB 399, Boulder, CO 80309, stephanie.plaza1997@gmail.com

Coprolites are fossilized feces, and provide unique records of the diets of extinct organisms. Here we study two coeval Cretaceous assemblages of herbivorous dinosaur coprolites, one from the Two Medicine Formation of Montana and another from the Kaiparowits Formation of Utah. Building on the well-characterized features of the dietary residues of these coprolites, we conducted δ13C and δ18O stable isotope analyses to better understand dinosaurian diets and the process of carbonate mineralization of the coprolites. δ13C values of carbonates sampled from the bulk samples of the predominant fabrics of different coprolite specimens ranged from approximately -17 to 10‰ VPDB, while associated δ18O values ranged from approximately -16 to -10.5‰ VPDB. Targeted sampling of carbonates from different fabrics within a single coprolite specimen revealed a correlation between coprofabrics and isotopic values: the δ13C and δ18O values of carbonates from different fabrics were varied, yet comparable coprofabrics retained similar δ13C and δ18O values. δ13C values of organic matter (bulk and kerogens) in the coprolites appear to be within a -20‰ to -24‰ VPDB range. This is consistent with histological evidence that these dinosaurs consumed C3 plants. Our results suggest that while the organic carbon in the original feces was isotopically homogeneous, the processes that transferred carbon from the organic pool to the inorganic pool (carbonate) fractionated carbon isotopes to varying degrees. However, original dietary materials that comprise minor carbon pools in the coprolite, such as crustacean cuticle (carbonate) and wood tissues (organic carbon), may preserve original isotopic signals. As this record of variable fractionation is linked to specific structures and fabrics within a coprolite, it may provide a way to disentangle the relative roles of microbial metabolisms and abiotic geochemistry in coprolite preservation.

Session No. 30

T249. New Voices in Geobiology I
Sunday, 22 October 2017: 8:00 AM-12:00 PM
Room 602/603 (Washington State Convention Center)
Geological Society of America Abstracts with Programs. Vol. 49, No. 6
doi: 10.1130/abs/2017AM-307348
© Copyright 2017 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.
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