沖縄島・本部(もとぶ)半島の"古生層"
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概要
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The Mesozoic-"Taleozoic" sequences in the Motobu Peninsula of Okinawa-jima are subdivided into the following three formations, from east to west; the Wakugawa (age indet.), the "Paleozoic" and the Nakijin Formation (Triassic). But owing to two major faults with N-S to NE-SW trend, the original stratigraphic relation of these formations can not be followed. In this paper, the lithologic characters of "Paleozoic", which consists of the M Formation and Y Formation tentatively called in ascending order, are described and also discussed on the geologic age. M Foramtion: Crystalline limestone with minor mudstone, conglomerate and chert, especially in the lower part. Y Formation: It may safely be said that this formation is characterized by so called sedimentary complexes. Because, not with standing the lithological facies without any tectonic structure are continuously mappable, sedimentary lithologic units ranging from pebbly mudstone to dispersed or large bodies of harder or older rocks are piled up obliquely and joined together complicatedly. Besides, it is fact that the faunal assemblages of different age were occurred from a sedimentary lithologic unit; such as the middle Permian fusulinaceans from limestone gravels and bodies, and the upper Triassic conodonts from chert gravels and beds. More than that, the present writer finds newly the early Cretaceous (?) radiolarian fossils from the laminated siliceous mudstone-intercalation of pebbly mudstone layer of the upper part, about at 2 km east of Toguchi. Judging from the "abnormal" lithology and the fossil occurrences that overlap in age, the sedimentation of the Y Formation must be related to the re-depositonal process such as submarine sliding and debris flow.
- 日本地質学会の論文
- 1983-03-30