New uranium-series ages of the Waimanalo Limestone, Oahu, Hawaii: implications for sea level during the last interglacial period

Marine Geology
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Abstract

The Waimanalo Formation (limestone) of Oahu has been correlated with the last interglacial period based on U-series dating of corals by T.-L. Ku and colleagues. The limestone consists of growth-position corals and overlying coral conglomerate. An apparent bimodal distribution of ages for the growth-position corals (mean age = 133 ka) and the overlying coral conglomerate (mean age = 119 ka) has been interpreted to represent two distinct high stands of sea that occurred within the last interglacial period. Both growth-position corals and overlying, conglomerate coral occur in an outcrop east of Kaena Point and consist mainly of Pocillopora and Porites. U-seriesages of growth-position corals that show closed-system conditions are 120 ± 3 ka and 127 ± 4 ka; overlying conglomerate corals have U-seriesages that range from 120 ± 3 ka to 138 ± 4 ka. At Kahe Point, conglomerate corals have ages of 120 ± 3 ka and 134 ± 4 ka. These data show that the growth position corals are not systematically older than the conglomerate corals; thus, there is no evidence for two distinct high stands of sea. Waimanalo deposits at Kahe Point and Mokapu Point (new U-seriesages of 134 ± 4 ka and 127 ± 3 ka) have beach deposits as high as 12.5 m and, at Mokapu Point, growth-position corals as high as 8.5 m. A last-interglacial sea-level stand of +8.5 to +12.5 m conflicts with estimates of +6 m from a number of tectonically stable coastlines and islands in the western Atlantic Ocean. We infer, therefore, that Oahu may be undergoing uplift at a low rate. This uplift may be due to compensatory lithospheric flexure, because the island of Hawaii has been subsiding throughout much of the Quaternary from volcanic loading. Because of this possible uplift, Oahu and islands like it elsewhere in the Pacific cannot be used as reference points for sealevel during the last interglacial period.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title New uranium-series ages of the Waimanalo Limestone, Oahu, Hawaii: implications for sea level during the last interglacial period
Series title Marine Geology
DOI 10.1016/0025-3227(94)90091-4
Volume 118
Issue 3-4
Year Published 1994
Language English
Publisher Elsevier
Publisher location Amsterdam, Netherlands
Contributing office(s) Geology and Environmental Change Science Center
Description 12 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Marine Geology
First page 315
Last page 326
Country United States
State Hawai'i
Other Geospatial O'ahu;Waimanalo Limestone
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