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A Cenozoic terrestrial paleoclimate record from He dating and stable isotope geochemistry of goethites from Western Australia

Hayden B. D. Miller, Paulo M. Vasconcelos, John M. Eiler and Kenneth A. Farley
A Cenozoic terrestrial paleoclimate record from He dating and stable isotope geochemistry of goethites from Western Australia
Geology (Boulder) (October 2017) 45 (10): 895-898

Abstract

Supergene goethites from the Hamersley region of Western Australia were analyzed for delta (super 18) O and the results combined with both new and previously published (U-Th)/He ages to assess the paleoenvironmental signal recorded by surficial goethite in a long-term continental archive. delta (super 18) O (sub goe) values increase monotonically by approximately 3 ppm between 71 Ma and 5 Ma and appear little affected by changes in temperature or other characteristics of depositional environment. The temporal trend likely reflects the isotopic composition of meteoric water from which the goethite formed, which varied as Australia migrated approximately 3000 km northward over the Cenozoic. Translating age to paleolatitude reveals that the delta (super 18) O (sub goe) data are consistent with a latitudinal gradient in the delta (super 18) O (sub precip) that, throughout the Cenozoic, remained largely unchanged from the modern gradient. There is a 5 ppm offset between the latitudinal trends of delta (super 18) O (sub goe) and modern precipitation, approximately as expected from the water-goethite fractionation factor. Temporal variation in the delta (super 18) O of local meteoric water arising from changes in moisture source or pathway are not evident in the goethites, at least in part because topography is subdued and has evolved little in this tectonically quiescent landscape. Our results provide evidence that the efficiency of water transport from equator to pole that governs the latitudinal delta (super 18) O gradient of precipitation has been roughly constant over southern temperate latitudes for the entirety of the Cenozoic.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 45
Serial Issue: 10
Title: A Cenozoic terrestrial paleoclimate record from He dating and stable isotope geochemistry of goethites from Western Australia
Affiliation: California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA, United States
Pages: 895-898
Published: 201710
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 21
Accession Number: 2018-024390
Categories: StratigraphyIsotope geochemistry
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2017293
Illustration Description: illus. incl. 1 table, sketch map
S23°30'00" - S22°00'00", E116°30'00" - E120°30'00"
Secondary Affiliation: University of Queensland, AUS, Australia
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 201806
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