貝化石群集の群集構造による古水深の推定方法 : 中新統瑞浪層群産貝化石群を例として

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Paleobathymetric depth was estimated on the molluscan fauna from the early to early middle Miocene Mizunami Group by using the method based on the living depth of Recent species and genera and the analysis of community structure (species diversity and ratio of protobranch species to total bivalves). The fauna consists of many shallow and warm water species as well as some boreal species, many of which are extinct. Despite including many extinct species, the paleodepth of communities from the Mizunami Group can be estimated from the data of the Recent genera because the generic composition of the fossil community resembles the Recent one. The paleobathymetric depths estimated by both methods are concordant with each other. Thus, the community structure analysis is useful to estimate the paleobatymetic depth of molluscan community which are composed of many extinct species like as the Mizunami fauna. Moreover, this method enables us to recognize more finely subdivided depth zones of shallow water than Hickman's (1984) method in which the ratios of orders of each bivalves and gastropods are used.
2001-09-21