福岡県宗像市の筑豊炭田基底から発見された汎歯類化石の産状と堆積環境

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A coryphodontid pantodent fossil was discovered from the basal part of the Ooyake Formation on the middle Eocene Nougata Group at Takaroku, Munakata City, Fukuoka Prefecture. The fossil was collected from coarse-grained arkose pebbly sandstone 5 m above an unconformity between the Cretaceous granitic rocks and basal conglomerate of the Ooyake Formation. A 20m-sequence above the basal conglomerate consists of cyclic sediments of cross-stratified pebbly sandstone, massive dirty variegated sandstone and variegated red-purple and green-gray siltstone and shale. The former sedimentary facies shows their deposition in fluvial erosional channel and point-bar, and the latter indicates their deposition on natural levee and floodplain of meandering river under subtropical climatic condition. The subtropical clirriatic inferred from the sediments conforms with the climate suggested by previous studies of fossil, plant and pollen from the middle Eocene formations in Takashima, Chikuhou and Ube Coalfield.