<国立科博専報>紀伊半島下部白亜系西広層産の植物化石

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The Cretaceous System and its fossils contained in the Yuasa district, Wakayama Prefecture is summarized as follows in descending order (HIRAYAMA & TANAKA, 1956; KIMURA & KANSHA, 1978; MATSUMOTO, 1947a, b, 1954; OBATA & OGAWA, 1976; OBATA et al., 1977; this paper) : Upper Cretaceous System fault Nishihiro Formation Brackish shells (locality and horizon : 02 in Figs. 1 and 2) Plants (locality and horizon : 01) : Cladophlebis distans, C. geyleriana, Onychiopsis elongata and Coniopteris sp. disconformity Arida Formation Echinoid (locality and horizon : 04) : Aphelaster serotinus, index fossil of Aridan. Ammonites (Lower part of Upper Barremian to Upper part of Lower Barremian) Plants : Gleichenites yuasensis, Nilssoniopteris cfr. vittata, Ptilophyllum ex gr. pecten, Nageiopsis angustifolia, etc. Yuasa Formation Plants : Cladophlebis acutipennis, C. ex gr. denticulata, C. geyleriana, Sphenopteris elegans, S. ex gr. goeppertii, Adiantopteris yuasensis, Onychiopsis elongata, Ptilophyllum ex gr. pecten, Zamites buchianus, Cycadolepis kiiensis, Nilssonia densinervis, N. ex gr. schaumburgensis, etc. unconformity Paleozoic System The Nishihiro Formation, the youngest strata of the Lower Cretaceous in the Yuasa district, consists of the basal conglomerate, the lower sandstone, the lower shale, the upper sandstone, and the upper shale members. Plant fossils were obtained from the lower shale member. Four species, Cladophlebis distans, C. geyleriana, Onychiopsis elongata and Coniopteris sp. are described for the first time from this formation. Moreover, some floristic implications are noted, comparing them with the plants from the Yuasa Formation and also Late Jurassic-Early Cretaceous of Japan. Some bennettitales, which characterize the Ryoseki flora, are expected from the Nishihiro Formation. Occurrences of the Onychiopsis Series (e.g. such species as Cladophlebis exiliformis, Onychiopsis elongata etc.) from the Lias and the Ryoseki elements from the Dogger and Malm in the Toyora area (TAKAHASHI, 1957) are noted. In connection with this, the Toyora ammonoid fauna are characterized and distinguished by the eminent Mediterranean elements in the Domerian Substage from other faunas in Japan (HIRANO, 1973). Thus, influences of paleogeography and paleocurrent to the floristic elements are stressed. Plants of Onychiopsis Series probably derived from the Mediterranean area through the Toyora area in the Early Jurassic to the whole areas in the Late Jurassic-Early Cretaceous times.
1979-12-01

<国立科博専報>紀伊半島下部白亜系西広層産の植物化石

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