Examination of Chronostratigraphy of the Bisan-seto Group, beneath Bannosu Reclaimed Land, Kagawa Prefecture, southwest Japan

摘要

For the purpose of examination of sedimentary ages, the author describes lithofacies and volcanic glass shards of eighteen drilling-cores samples from beneath the Bisan-seto Strait, Seto Inland Sea, southwest Japan. In addition, some AMS radiocarbon ages of molluscan fossils in the samples are measured. Some of volcanic glass shards in the samples can correlate with wide spread volcanic ashes. Sedimentation of Tsuchinoto-seto Formation continued before 530ka or 520ka, which may show shallow marine facies. The middle to upper part of the Syaminose Formation mainly comprises marine sediments and age of formation is ranging the late Pleistocene between 95ka and 70ka. The Lower Member of Bannosu Formation began to form before 80ka or 48ka and deposited until 15ka as non-marine sediments. The Upper Member of Bannosu Formation, Holocene sediments, have formed after 15ka or 7.3ka.