230Th/234U Dates of Pleistocene Deposits on Oahu
Authors: Easton, W. H.; Ku, T. L.
Source: Bulletin of Marine Science, Volume 31, Number 3, July 1981 , pp. 552-557(6)
Abstract:Coral-algal reefs and calcarenite comprise offshore deposits contemporaneous with shoreline conglomerates of the Waimanalo stand of sea level at 7.6 m, but at lower elevation. The mean value of 23 earlier measurements of Waimanalo deposits is 122,000 ± 7,000 years by the 230Th/234U method.
Coralline limestone 1 m thick at 2.8 m elevation at Honolulu Airport is dated at 135,000 ± 6,000 years.
Reef limestone at 0.5 m on Mokuauia Island is dated at 120,000 ± 9,000 years.
Semilithified calcarenite and conglomerate 3.7 m thick overlies a pitted surface of Waimanalo reef limestone at 2.1 m on Ulupau Head at the type locality of the Ulupau stand. A coral boulder between 4.0 m and 5.8 m is dated at 122,000 ± 11,000 years. Available radiometric dates of the Ulupau and Waimanalo stands lie within the range of analytical errors and cannot be used alone to differentiate these events.
Pebbly bioclastic sand and conglomerate between 9.8 m and 11.6 m at Kahe Point are dated at 142,000 ± 12,000 years, only slightly older than Waimanalo age. The elevation corresponds with the Waialae stand but the latter is supposed to be much older than Waimanalo age. Either sea level stood at the Waialae level twice, or the Waialae stand is much younger than hitherto thought.
Four samples of Porites from the Ewa Core Hole No.1 between −13.4 m and −20.7 m are all older than 300,000 years. These samples seem to represent an offshore facies at least as old as the Kaena stand.
Document Type: Research Article
Publication date: July 1, 1981
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