地向斜におけるいわゆるフリッシュ

Abstract

The present state of knowledge on clastic sediments of "Flysch-type alterneeion" as "turbidite" is reviewed and commented. Mineralogical composition, grain-size distribution and other characteristics of Palaeozoic, Mesozoic and Palaeogene sandstones in Japan are at first systematically discussed in terms of geosynclinal sediments. Sedimentary structures of the sediments of the Shimanto geosyncline, Southwest Japan, ranging from the late Mesozoic to Palaeogene in age, are especially taken into account as the turbidite features. Remarkable results of researches made by BOUMA (1964) and VAN STRAATEN (1964) on the internal features of the recent sediments in the San Diego trough and the Adriatic Sea are also referred to for comparison. Useful information is still scarce in Japan on the relationships among various characteristics of sediments such as sedimentary facies, internal and external structures of strata, grain-size distribution of each lamina or sedimentation unit [e.g. interval of BOUMA's (1962) model] and mineralogical composition. In order to clarify the mechanism and the condition of sendimentation of turbidites and Flysch-type sediments in geosyncline, further systematic studies are needed on the basis of the hydrodynamics and sedimentary petrology.