越後平野東縁部,笹神丘陵で発見された鮮新-更新統中の七浦不整合とその意義

概要

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A new outcrop of unconformity was found in the Pliocene Annogawa Formation at the Sasagami Hills located to the east of the Niigata Plain. This unconformity is named the Nanaura Unconformity. The Annogawa Formation is divided into two formations, namely the Sasagami-Dainichi and Sasagami-Nanaura Formations in ascending order. These formations consist of marine muddy sediments. The Sasagami-Dainichi Formation ranges from late Miocene to late Pliocene in age according to diatom biostratigraphy. Though maker diatom fossils were not yet obtained in the Sasagami-Nanaura Formation, its geological age is probably in Pleistocene, judging from the occurrence of some planctonic foraminiferal maker beds in several wells around the Sasagami Hills, The Nanaura Unconformity indicates a local upheaval movement had occurred in the Niigata sedimentary basin during Plio-Pleistocene age. It proposes new point of view for exploration of oil and natural gas in the subsurface strata of Echigo Plain.
地学団体研究会の論文
2006-11-25