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Stratigraphy and Whole-Rock Amino Acid Geochronology of Key Holocene and Last Interglacial Carbonate Deposits in the Hawaiian Islands

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Title:Stratigraphy and Whole-Rock Amino Acid Geochronology of Key Holocene and Last Interglacial Carbonate Deposits in the Hawaiian Islands
Authors:Hearty, Paul J.
Kaufman, Darrell S.
Olson, Storrs L.
James, Helen F.
Date Issued:Oct 2000
Publisher:University of Hawai'i Press
Citation:Hearty PJ, Kaufman DS, Olson SL, James HF. 2000. Stratigraphy and whole-rock amino acid geochronology of key holocene and last interglacial carbonate deposits in the Hawaiian Islands. Pac Sci 54(4): 423-442.
Abstract:We evaluated the utility of whole-rock amino acid racemization
as a method for the stratigraphic correlation and dating of carbonate sediments
in the Hawaiian Islands. D-alloisoleucine/L-isoleucine (A/I) ratios were determined
for carbonate sand and sandstone samples from 25 localities in the archipelago.
The superposition of A/I ratios within stratigraphic sections and the regional
concordance of ratios within geological formations support the integrity
of the method. To correlate the A/I ratios with an absolute chronology, comparisons
were made with previously published uranium series dates on corals
and with 14C dates on carbonate sand and organic material, including several
new dates reported herein. The A/I mean from four marine isotope stage (MIS)
5e U-series calibration sites was 0.505 ± 0.027 (n = 11), and 12 "test sites" of
previously uncertain or speculative geochronological age yielded an A/I mean
of 0.445 ± 0.058 (n = 17). Similarly, extensive Holocene dunes on Moloka'i
and Kaua'i were correlated by a mean A/I ratio of 0.266 ± 0.022 (n = 8) and
equated with a 14C bulk sediment mean age of 8600 yr B.P. Our results indicate
that the eolian dunes currently exposed in various localities in the Islands originated
primarily during two major periods of dune formation, the last interglacial
(MIS 5e) and the early Holocene (MIS 1). MIS 5e and MIS 1 A/I ratios
from the Hawaiian Islands show close agreement with previous whole-rock
studies in Bermuda and the Bahamas. We discuss these results in terms of their
relevance to models of lithospheric flexure and to imposing constraints on the
time frame for the extinction of fossil birds.
Appears in Collections: Pacific Science Volume 54, Number 4, 2000

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