広島県庄原地域の底生有孔虫群集

The stratigraphic distribution of the middle Miocene benthic foraminifera from Shobara area, northeastern part of Hiroshima Prefecture, is examined. Q-mode cluster and principal component analyses reveal four biotopes such as inner bay, littoral to outer bay, middle shelf, and outer shelf to continental slope. These biotopes are characterized by following assemblages:
Inner bay, Ammonia tochigiensis Assemblage; littoral to outer bay, Ammonia tochigiensis Nonionella sp. - Hanzawaia tagaensis Assemble; Hanzawaia tagaensis - Lenticulina spp. Assemblage, and Oridorsalis umbonatus - Cibicides spp. Assemblage; outer shelf, Uvigerina segundoensis (s.l.) Assemblage.
The strata containing no foraminifera, which were deposited on upper to middle continental slope, are developed stratigraphically above the U.segundoensis (s.l.) Assemblage.
The distribution pattern of these benthic foramiinferal assemblages is smilar to that of Masuda area, eastern Shimane Prefecture, suggesting the common history of the Miocene sedimentary basin.