千々石湾茂木沖の海底堆積物の砂粒組成

概要

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The shallow water sediments in the north-western part of the Chijiwa Bay off the Mogi coast were analysed by the coarse fraction method which was devised by Shepard and Moore (1954). The average percentage for the constituents in four sediment types which are subdivided into six areal distribution are illustrated in Figure 3. Type IIa sediments are somewhat poorly sorted sand and are characterized by their preponderant content of terrigenous minerals. Type IIb sediments contain a small amount of silt and clay (15 to 17 per cent of total sample), and a half of the total sample is constituted by terrigenous materials. Shells, Foraminifera and fragments of echinoids are more abundant in silty sand which are classed to Type IIIa, especially in offshore sediments, than the other sediment types. Type III sediments are sandy silt with a dominant amount of silt and clay (65 per cent of total sample) and are characterized by the peculiar organic composition. In this class, the 1/2-1/4 mm size group contain abundant Ostracoda and wood fibers and the 1/8-1/16 mm size group contain many tests of Diatom and planktonic Foraminifera.
長崎大学学芸学部の論文