Late quaternary stratigraphy and evolution of a Korean tidal flat, haenam bay, southeastern yellow sea, Korea

Abstract

Sediment cores from a tidal flat in the southeastern Yellow Sea, Korea, contain two major depositional units, a Holocene unit (Unit I) and an underlying late Pleistocene unit (Unit II). Unit I (up to 15 m thick) is a middle to late Holocene, coarsening-upward transgressive deposit. Unit II (about 10 m thick) is interpreted as tidal-flat deposits from the last interglacial period (probably oxygen-isotope stage 5e), based on its many tide-influenced signatures such as laminated silt/clay, tidal rhythmites, fossil crab burrows, authigenic minerals (pyrite and halite), clay mineral composition and a dinoflagellate cyst assemblage comparable to that of Unit I. Units I and II are separated by a regional unconformity which is highlighted by a yellow 'oxidized layer' in uppermost Unit II. The layer contains abundant evidence of subaerial exposure, including a yellowish sediment color, semi-consolidation, desiccation cracks, cryoturbation structures, and high degree of magnetic susceptibility. Two major interglacial highstands (Units I and II) and one glacial lowstand (uppermost oxidized layer of Unit II) thus characterize coastal to nearshore tidal deposits along the eastern margin of the Yellow Sea (western Korea). (C) 2002 Elsevier Science B.V. All rights reserved.