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This paper contains a result of a sedimentological study of the Sakamotozawa Formation, the type sequence for the Lower Permian Sakamotozawa Series of Japan, giving precise descriptions of limestones ...and sandstones of the formation. The Sakamotozawa Limestone is petrographically classified into twelve lithologic-types. The cyclic features of the limestone display a gradual change of depositional environments from a shallow sea of a restricted water (probably a lagoonal one), with an intermittent desiccation of water at time, to a slightly deepened somewhat off-shore sea. The cyclic pattern of the Sakamotozawa Limestone is of a reversed order as compared with that of a typical cyclic sequence from a transgressive phase to regressive one in the sediments on the stable shelf. The peculiar pattern of the cycle may be related to a mode of a provincial tectonic movement. Sandstone belongs to arenite with a small amount of matrix, and is divided into four types. With regard to major framework constituents of sandstones a serial change is recognized twice in the entire sequence, one from basal to upper Sa and the other from Sc-Sd to the Kanokura. The rock fragments and heavy mineral assemblages of all the sandstone types indicate sources which were mainly composed of chert and shale on one hand and andesite and dacite on the other. Concluding remarks are given on the sedimentary environments and the tectonic significance of the sediments. The sediments have not the characters of "molasses" and had not been derived from the backgrounds which were rapidly rising by the orogenic movement. They have the characters of the sediments deposited on the island shelf.続きを見る
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1.Introduction 2.Notes on the stratigraphy of the Sakamotozawa Formation 3.Sedimentology of the Sakamotozawa Limestone 4.Sedimentology of the sandstones of the Sakamotozawa and Kanokura Formations 5.Conclusion 6.References
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Mendeley出力
19_03_p331