Sequence stratigraphy of the late Pleistocene Palaeo-Tokyo Bay: barrier islands and associated tidal delta and inlet
Okazaki, H.; Masuda, F. (1995). Sequence stratigraphy of the late Pleistocene Palaeo-Tokyo Bay: barrier islands and associated tidal delta and inlet, in: Flemming, B.W. et al. (Ed.) Tidal Signatures in Modern and Ancient Sediments. Special Publication of the International Association of Sedimentologists, 24: pp. 275-288 In: Flemming, B.W.; Bartholomä, A. (Ed.) (1995). Tidal Signatures in Modern and Ancient Sediments. Special Publication of the International Association of Sedimentologists, 24. Blackwell Science: Oxford. ISBN 0-86542-978-2. 358 pp., more In: Special Publication of the International Association of Sedimentologists. Blackwell: Oxford. ISSN 0141-3600; e-ISSN 2054-6610, more |
| Abstract | The Kioroshi and Joso Formations, deposited in the late Pleistocene Palaeo-Tokyo Bay, crop out in southern Ibaraki and northern Chiba Prefectures, eastern Kanto, central Japan. They form a depositional sequence which is primarily controlled by glacio-eustatic sea-level changes (c. 150-60 kaBP) and characterized by the barrier-island system of Palaeo-Tokyo Bay. ln Palaeo-Tokyo Bay, antecedent valleys were formed by rivers at the low sea-level stage of a glacial period. The subaerial unconformity cut at that time comprises a sequence boundary. During the early transgression associated with the following interglacial period, the drowned valleys were filled with estuarine and Ouvial deposits. The transgressive surface relates to an abrupt increase in accommodation, its ravinement surface caps the overlying drowned-valley fill. Subsequently, a transgressive barrier-island system consisting of beach-shoreface, tidal-delta and tidal-inlet systems migrated landwards to form a transgressive systems tract. As the rate of sea-level rise slowed, the retfeat of barrier islands ceased and was followed by emergence. During the subsequent sea-level lowering, the coastal plain prograded seawards and formed a highstand systems tract. The depositional sequence in Palaeo-Tokyo Bay thus documents a transgressive and regressive barrier system. Landward migration of the barrier system in the wake of the rising sea-level resulted in the development of Oood-tidal deltas on the lagoonal side of the barrier system and a ravinement surface on the open-sea side. Accordingly, the Oood-tidal delta and inlet-fill, which have a high preservation potential, are important as a transgressive system tract of the tidally influenced Palaeo-Tokyo Bay. |
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