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Eocene atmospheric CO (sub 2) from the nahcolite proxy

Elliot A. Jagniecki, Tim K. Lowenstein, David M. Jenkins and Robert V. Demicco
Eocene atmospheric CO (sub 2) from the nahcolite proxy
Geology (Boulder) (December 2015) 43 (12): 1075-1078


Estimates of the atmospheric concentration of CO (sub 2) , [CO (sub 2) ] (sub atm) , for the "hothouse" climate of the early Eocene climatic optimum (EECO) vary for different proxies. Extensive beds of the mineral nahcolite (NaHCO (sub 3) ) in evaporite deposits of the Green River Formation, Piceance Creek Basin, Colorado, USA, previously established [CO (sub 2) ] (sub atm) for the EECO to be >1125 ppm by volume (ppm). Here, we present experimental data that revise the sodium carbonate mineral equilibria as a function of [CO (sub 2) ] and temperature. Co-precipitation of nahcolite and halite (NaCl) now establishes a well-constrained lower [CO (sub 2) ] (sub atm) limit of 680 ppm for the EECO. Paleotemperature estimates from leaf fossils and fluid inclusions in halite suggest an upper limit for [CO (sub 2) ] (sub atm) in the EECO from the nahcolite proxy of approximately 1260 ppm. These data support a causal connection between elevated [CO (sub 2) ] (sub atm) and early Eocene global warmth, but at significantly lower [CO (sub 2) ] (sub atm) than previously thought, which suggests that ancient climates on Earth may have been more sensitive to a doubling of [CO (sub 2) ] (sub atm) than is currently assumed.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 43
Serial Issue: 12
Title: Eocene atmospheric CO (sub 2) from the nahcolite proxy
Affiliation: Binghamton University, Department of Geological Sciences and Environmental Studies, Binghamton, NY, United States
Pages: 1075-1078
Published: 20151222
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 38
Accession Number: 2016-002011
Categories: StratigraphyIsotope geochemistry
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2015357
Illustration Description: illus. incl. geol. sketch map
N39°30'00" - N40°00'00", W108°30'00" - W108°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 201601
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