Oxygen isotopes in terrestrial gastropod shells track Quaternary climate change in the American Southwest

Quaternary Research
By: , and 

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Abstract

Recent studies have shown the oxygen isotopic composition (δ18O) of modern terrestrial gastropod shells is determined largely by the δ18O of precipitation. This implies that fossil shells could be used to reconstruct the δ18O of paleo-precipitation as long as the isotopic system, including the hydrologic pathways of the local watershed and the gastropod systematics, is well understood. In this study, we measured the δ18O values of 456 individual gastropod shells collected from paleowetland deposits in the San Pedro Valley, Arizona that range in age from ca. 29.1 to 9.8 ka. Isotopic differences of up to 2‰ were identified among the four taxa analyzed (Succineidae, Pupilla hebesGastrocopta tappaniana, and Vallonia gracilicosta), with Succineidae shells yielding the highest values and Vgracilicosta shells exhibiting the lowest values. We used these data to construct a composite isotopic record that incorporates these taxonomic offsets, and found shell δ18O values increased by ~4‰ between the last glacial maximum and early Holocene, which is similar to the magnitude, direction, and rate of isotopic change recorded by speleothems in the region. These results suggest the terrestrial gastropods analyzed here may be used as a proxy for past climate in a manner that is complementary to speleothems, but potentially with much greater spatial coverage.

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Publication type Article
Publication Subtype Journal Article
Title Oxygen isotopes in terrestrial gastropod shells track Quaternary climate change in the American Southwest
Series title Quaternary Research
DOI 10.1017/qua.2021.18
Edition Online First
Year Published 2021
Language English
Publisher Cambridge University Press
Contributing office(s) Geosciences and Environmental Change Science Center
Country United States
State Nevada, Arizona, New Mexico, Utah, Colorado
Online Only (Y/N) N
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