岡山県大賀南西部の下谷石灰岩体の層位

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The Shimodani Limestone in the Oga upland in Okayama prefecture, western Japan, is composed of massive limestone with basic pyroclastic rocks at the base. This limestone is divisible into two foraminiferal zones in upward sequence : the Endothyra-Mediocris Zone and the Eostaffella-Millerella Zone. The former is characterized mainly by Endothyra exilis, E. similis, E. irinae, Endostaffella sp., Planoendothyra sp., Mediocris mediocris and M. adducta. The latter is composed of Eostaffella kanmerai, E. etoi, E. akiyoshiensis, E. mosquensis, E. ikensis, Millerella marblensis, Ozawainella japonica, Zellerinella discoidea and others. These two zones are regarded as ranging in age from the late Osagean to the early Morrowan in North America, and the early Visean to the late Serpukhovian in Russia. The Shimodani Limestone has a successive sequence without nonconformity, making a gentle basin structure, and thrust over the Upper Triassic Nariwa Group. The Shimodani Limestone is similar to the western and central parts of the Koyama Limestone in the lithofacies and the foraminiferal assemblages. Therefore, the Shimodani Limestone is considered to be the so-called klippe separated from the Koyama Limestone. This thrust fault has a large fracture zone, though the structure of the limestone is not disordered. This fact suggests that basic pyroclastic rocks of the Shimodani Limestone and coal beds of the Nariwa Group played an important role in its sliding surface.
日本古生物学会の論文
1995-06-30

岡山県大賀南西部の下谷石灰岩体の層位

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