Devils hole calcite was precipitated at ±1°C stable aquifer temperatures during the last half million years

  • Abstract: Subaqueous carbonates from the Devils Hole caves (southwestern USA) provide a continuous Holocene to Pleistocene North American paleoclimate record. The accuracy of this record relies on two assumptions: That carbonates precipitated close to isotope equilibrium and that groundwater temperature did not change significantly in the last 570 thousand years. Here, we investigate these assumptions using dual clumped isotope thermometry. This method relies on simultaneous analyses of carbonate ∆47 and ∆48 values and provides information on the existence and extent of kinetic isotope fractionation. Our results confirm the hypothesis that calcite precipitation occurred close to oxygen and clumped isotope equilibrium during the last half million years in Devils Hole. In addition, we provide evidence that aquifer temperatures varied by less than ±1°C during this interval. Thus, the Devils Hole calcite δ18O time series exclusively represents changes in groundwater δ18O values. Plain Language Summary: The oxygen isotope composition of cave carbonates records changes in Earth's climate. However, the reliability of such records depends on how stable the carbonate precipitation environment was. Here, we use a novel method called dual clumped isotope thermometry that can provide simultaneous information on a carbonate's growth temperature and whether any additional fractionation processes affected its oxygen and clumped isotope signatures. Specifically, we investigated the Devils Hole caves, which provide a reference oxygen isotope time series for North America. We find that groundwater temperature did not change significantly in the last half-million years. Variations in the oxygen isotope composition of the deposited carbonates solely reflect variations in the oxygen isotope composition of the groundwater.
Author:David Bajnai, Tyler B. Coplen, Katharina Methner, Niklas Löffler, Emilija Krsnik, Jens Fiebig
Parent Title (English):Geophysical research letters
Place of publication:Hoboken, NJ
Document Type:Article
Date of Publication (online):2021/06/01
Date of first Publication:2021/06/01
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2022/04/05
Tag:desert; drip-water; epikarst; rainfall; semi-arid
Issue:11, art. e2021GL093257
Page Number:10
First Page:1
Last Page:10
J.Fiebig acknowledges funding through D.F.G. grants “INST 161/871-1,” “FI-948-11/1,” and “FI-948-13/1,” K.Methner recognizes support through the Alexander von Humboldt Foundation. We thank Jordan Wostbrock, Hagit P. Affek, and an anonymous reviewer for their constructive reviews. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the US Government. Open access funding enabled and organized by Projekt DEAL.
Institutes:Geowissenschaften / Geographie
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 55 Geowissenschaften, Geologie / 550 Geowissenschaften
Licence (German):License LogoCreative Commons - Namensnennung 4.0