Pleistocene Stratigraphy and Eustatic History Based on Cores at Waimanalo, Oahu, Hawaii

Abstract

Eight recently drilled core holes (totaling 2200 feet) in the Waimanalo coastal plain of Oahu, Hawaii, have yielded significant stratigraphic and lithologic evidence of a series of eustatic risings and fallings of sea level in the Central Pacific Basin during Pleistocene time. Four major regressions and four major transgressions of the sea have been recognized and correlated with the major glacial and interglacial stages on the basis that each stratigraphically. recognized major regression corresponds to a major glacial stage. The depositional environment that produced this remarkable geologic record was set in a broad, flat, windward island fringe fronting a drowned amphitheater-headed valley. Reef limestones, calcareous clays, lithified calcareous dune sands, littoral sands, and terrigeneous deposits comprise the bulk of the sediments penetrated. The transgressive and regressive stratigraphy corresponds to major eustatic changes in sea level and provides convenient lithologic grouping of four formations: the Kahuku Point (Transgression I, Aftonian?, and Regression II, Kansan?), Kaena (Transgression II, Yarmouth), Bellows Field (Regression III, Illinoian), and Waimanalo (Transgression III, Sangamon). Stratigraphic evidence indicates that the Koolau Volcano of Oahu ceased its activity, was deeply incised by amphitheater-headed valleys, and subsequently drowned and partly filled with sediments during late Tertiary time.