The Kuma formation of Kyusyu is the type of the Kuman series, the highest stratigraphical division of the Permian System of the Japanese Islands. It has a characteristic fusulinid fauna including highly evolved forms and quite free from
Neoschwagerina remains ; the
Yabeina yasubaensis-Lepidolina toriyamai zone, with this fauna, is the highest fusulinid zone in the Permian System in Japan. This is the view maintained by R. Toriyama and K. Kanmera and supported by many followers. This Kuman series seems originally to have had an extensive geographical distribution, since the remains of its fauna are found from several localities wide apart one another, not only in the Outer Zone of Southwest Japan, but also in its Inner Zone (the Mainzuru group) and even in Northeast Japan (the Takagami conglomerate of Tyosi Peninsula).
Notwithstanding such an extensive distribution of the Kuma formation during the Later Permian, it does not exist, remarkably to say, along the Permian-Triassic boundary in the Takatiho district, Nisi-Usuki-gun, Miyazaki Prefecture, Kyusyu., where according to N. Kanbe, the limestone with a Skytic fauna, at the base of his Kamura formation is continuous downwards, through a 10 meters thick unfossiliferous limestone, to another with
Neoschwagerina megasphacricaDeprat,
N. margaritae Deprat,
Yabeina cfr. katoi (Ozawa) at the top of his Iwato formation. This faunule differs evidently from the Kuma fauna and is rather closely similar to the
Yabeina shiraiwensis fauna geochronologically, the uppermost limestone with this faunule of the Iwato formation may be as old as, or rather somewhat younger than the
Yabeina shiraiwensis zone.
Then, the Kuma formation some 900 meters thick, of slate, sandstone, conglomerate, and poor in limestone, is entirely lacking between the two formations, unless it is represented by the 10 meters unfossiliferous limestone-an interpretation which seems to the writer hardly convincing.
By way, it will be mentioned that the writer now suspects the approximate contemporaneity of the
Yabeina globosa-Y. shiraiwensis subzone of
Neoschwagerina-Verbeekina zone and
Yabeina yasubaensis-Lepidolina toriyamai zone in Toriyama's scheme of the Permian stratigraphy of Japan.
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