| 概要 |
The Paleogene to Neogene sedimentaty rocks, defined here as the Kurusuno and Shimizu Formations, representing a part of the Shimanto Supergroup, in SW Shikoku, Japan, are composed of clastic sedimenta...ry rocks. Each formation is subdivided into two lithologic facies such as chaotic facies and coherent facies. The chaotic facies is composed mainly of various blocks and clasts of sandstone, shale and rare limestone, volcanic breccia and conglomerate. The Kurusuno Formation is interpreted as a precursory olistostrome, whereas the Shimizu Formation as a composite olistostrome. The Kurusuno Formation consists mainly of sandstone and shale derived from the coherent facies deposited within the same sedimentary basin. On the other hand, the Shimizu Formation consists mainly of other different exotic blocks and clasts of older age that are derived from an uplifted accreted terranes. The sedimentary facies and bedding features are observed in each coherent facies both of the Kurusuno and the Shimizu Formations. The Kurusuno Formation is interpreted as submarine channel and overbank deposits accumulated at the base of a slope depositional setting. The Shimizu Formation is interpreted as channel sediments showing inverse grading and inverse-to-normally grades, beds indicating that they are slope or slope basin deposits accumulated near a canyon mouth. The abundant slump beds associated with pebbly mudstone within the turbidites also support that they are deposited together with this channel fill on a slope or within a slope basin. Both of the Kurusuno and Shimizu Formations are deposited as mass flows that initiate to transport reworked slope sediments or accreted trench deposits to the trench floor, commonly via small submarine canyons that head on the lower slope.続きを見る
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Mendeley出力
27_02_p075