New Zealand Journal of Geology and Geophysics abstracts

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⁴⁰Ar/³⁹Ar age of a young rejuvenation basalt flow: implications for the duration of volcanism and the timing of carbonate platform development during the Quaternary on Kaua‘i, Hawaiian Islands

Paul J. Hearty

School of Earth and Environmental Sciences
University of Wollongong
Wollongong, NSW 2522, Australia
paulh@uow.edu.au

Daniel B. Karner

Department of Geology
Sonoma State University
1801 East Cotati Avenue
Rohnert Park, CA 94928, USA

Paul R. Renne

Berkeley Geochronology Center
2455 Ridge Road
Berkeley, CA 94985, USA

and

Department of Earth and Planetary Sciences
University of California
Berkeley, CA 94720, USA

Storrs L. Olson

National Museum of Natural History
Smithsonian Institution
Washington DC, 20560, USA

Siobhan Fletcher

School of Earth Sciences
James Cook University
Townsville, Queensland 4811, Australia

Abstract  Remnants of an extensive carbonate platform crop out along the southeast coast of Kaua‘i, Hawaii. A basalt flow within this succession has a whole-rock ⁴⁰Ar/³⁹Ar step-heating plateau age of 375 ± 4 ka. The plateau age, which we interpret as the eruption age, indicates that rejuvenation volcanism persisted on Kaua‘i for considerably longer (c. 200 000 yr) than previously thought, and also that published whole-rock K-Ar determinations may not accurately reflect eruption ages. The succession of younger sedimentary deposits and age of the basalt imply that the eruption occurred near the end of marine isotope stage (MIS) 11. Preservation of limestone dune assemblages and extensive paleosols above present-day sea level indicates that Kaua‘i underwent a period of emergence during the early and middle Pleistocene, probably due to passage over the lithospheric arch or forebulge created by crustal loading of Maui Nui. The presence of at least eight major limestone-soil “couplets”, together with extrapolated ages from the ⁴⁰Ar/³⁹Ar dating, make this the oldest surficial record of limestone formation in the Hawaiian Islands. This work provides a framework for further interpretation of the stratigraphy and paleoecology of Kaua‘i and the tropical Hawaiian Islands.

Keywords  lithospheric flexure; carbonate platform; bioclastic dunes (“eolianite”); argon dating; basalt flow; Quaternary; stratigraphy; Hawaiian Islands

G03032; Received 19 September 2003; accepted 18 October 2004; Online publication date 25 May 2005
New Zealand Journal of Geology & Geophysics, 2005, Vol. 48: 199–211
0028–8306/05/4802–0199© The Royal Society of New Zealand 2005

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