栃木縣産第三紀化石群(其の 1)
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概要
- 論文の詳細を見る
The Tertiary formations in the vicinity of Yaitamachi, Shioya-gun, Tochigi Pref., can be divided into the Tamada, Takashio and Tadokoro formations in descending order., Judging from the Molluscan fossils, the Tamada formation may be late Miocene in age, while the Takashio and Tadokoro may belong to the middle Miocene., The Tertiary developed in the area between Tochigi-shi and Kanuma-machi is divisible into two formations, the upper, the Hukaiwa formation and the lower, the Kanuma., The former is liparitic green tuff which resembles the so-called "Oya-ishi"., The Kanuma fromation consists mainly of andesitic volcanic conglomerate and lava., but it also includes the fossiliferous Momiyama sandstone, This sandstone contains Molluscan fossils, Placopecten n., sp., etc., which seem to indicate middle Miocene., It also contains abundant Vaginulina of a more or less large type., Recently, the writer succeeded in finding several specimens of Miogypsina kotoi Hanzawa, associated with some new species of minor Foraminifera., The chronological horizon of Miogypsina kotoi is considered to be early to middle Miocene., From these facts, the age-of the Momiyama sandstone can be determined as middle Miocen., Table II is the list of the Momiyama microfauna, showing the number of individuals in 300gr, of rock sample., The writer also collected many casts and moulds of Lucina kamenooensis Otuka and minor Foraminifera from a bluish gray fine sandstone in the so-called "Terayama group" at Hachiman-yama, Ozo, Utsunomiya., This microfauna is listed in Table III., The Terayama group is generally considered to be upper Miocene in age., Judging from the microfauna, the environment under which the Momiyama sandstone was deposited was not typically warm shallow water, as shown by the coexistence of warm and cold elements., The environment of the Terayama group" in Utsunomiya is suggested to be middle neritic from the microfauna., Several fossil plants as shown in Table I were collected from Iwafune-yama, Iwafune-mura, Shimotsuga-gun, Tochigi Pref., This mountain consists mainly of andesitic to dacitic agglomerate, intercalated with thin beds of tuffaceous mud and cross-bedded sandstone containing fossil plants., This fossil flora shows a close resemblance to the mild climatic forest of the central part of Japan proper, though it contains some warmer climatic elements, such as Cyclobalanopsis acuta, Carpinus Tschonoskii, Euptelea polyandra and Tilia kiusiana., From these facts, it seems likely that the Iwafune-yama agglomerate is a member of the Kanuma formation.,
- 日本地質学会の論文
- 1950-12-05