Transactions and Proceedings of the PaJaeontological Society of Japan New Series No. 96 Palaeontological Society of Japan December 20, 1974 Editor: Hiroshi UJIIE Associate editors: Ikuwo OBATA, Yasuji SAITO Officers for 1973 - 1974 Honorary President: Teiichi KOBAYASHI President: Tatsuro MATSUMOTO Councillors (*Executive): *Kazuo ASAMA, Kiyoshi ASANO, *Kiyotaka CHINZEI, *Taka· shi HAMADA, *Tetsuro HANAI, Kotora HATAI, *Itaru HAY AMI, *Kametoshi KANMERA, Tamio KOT AKA, *Tatsuro MATSUMOTO, Tokio SHIKAMA, Tsugio SHUTO, *Yokichi TAKAYANAGI, Toshimasa TANAI, *Hiroshi UJIIE Executive Committee: General Affairs: Itaru HAYAMI, Yasuhide IWASAKI Membership: Kazuo ASAMA, Kazuhiko UEMURA Finance: Takashi HAMADA, Naoaki AOKI Planning: Tetsuro HANAI, Saburo KANNO Publications Transactions: Hiroshi UJIIE, Ikuwo OBATA, Yasuji SAITO Special Papers: Kametoshi KANMERA, Ienori FUJIY AMA, Tomowo OZAWA " Fossils" : Yokichi T AKAYANAGI, Toshiaki TAKAYAMA All communications relating to this journal should be addressed to the PALAEONTOLOGICAL SOCIETY OF JAPAN c/o Business Center for Academic Societies, Japan. Yayoi 2-4-16, Bunkyo-ku, Tokyo 113, Japan Sole agent: University of Tokyo Press, Hongo, Tokyo Trans. Proc. Palaeont. Soc. Japan, N. S., No. 96, pp. 411-426, pI. 56, December, 20, 1974 639. CARBONIFEROUS CONODONTS FROM THE ITSUKAICHI DISTRICT, TOKYO, JAPAN* HISA YOSHI IGO Department of Geoscience, University of Tsukuba, Nihari.gun, Ibaraki 300-31 and FUMIO KOBAYASHI Institute of Geology and Mineralogy, Faculty of Science, Tokyo University of Education, Tokyo 112 JiO?:'ffll1l.Bm:ttl!.1JO)El!R*::1 / F:/ r: 1l.Bm~t1JK.lt, Vt;*~x.I?;h,-c\"t-:J: IJ~<::=: 1!l:*~El!R*tM};{ffL-C\":Q;:'ciJ~~IjIj/jLko 4@Ht, ::;::tR, l'ii!:;f;:, :j;[.tRtJ:cK·7.t;{ff-t:QE ER:!6-~7- -V - rIC 13""i;h,:Q El!R*O) ::1 / r:/ r ~~Gtx; L, -to)1liff\;~~1fB 1.:t-:o ::1 / r:/ r f¥ ~ltJ1jfIB=-"":);5IJ, IB;JtIlO)tO)lt~b¥:0)7-.:r.7-3<" -ME :toJ:Lf 3 - P ://{O)""f$ :rA-lvMEO) t O)vc%jJt ~;h" J1jf;Jtllo) t 0) It ~t*O)"":/ ~/jv/~ =- 7 *Jll""f$ C 3 - P :/ /{O)J::$-.r A -IV MElcJt~--e~:Qo tJ::toliZl:m~ (1973), tmJE8~- (1973) O)¥an-: l::..-1i-i!to)JUi"@~~~..@ ~IH$~I?O)IB;JtIlO)::1 / F:/ rf¥~~{ftJ: 5iJ;, lliff\;ffiflilc"":)\"-Clt-3&~--r, ~l?ltJji].s;; I?O)J!MJ: 1J~~J1jfL\"Iliff\;U6ffifliLko ~#lll~~. IH*)(~ graphy and geologic structure. He Introduction . proved more extensive distribution of Triassic and Carboniferous strata than Upper Paleozoic and Mesozoic forma· the previously published geologic maps. tions occur as several narrow belts Many Triassic conodonts were found in trending northwest and southeast in the the chert members which were treated Itsukaichi district, southeastern part of as the Permian by the previous authors. the Kanto Massif. FUJIMOTO (1932,1936), KOBAY ASH! also collected many Carboni­ SAKAGAMI (1956, 1958) and others con· ferous fusulinaceans and conodonts from :::. i.e.': .;eology and some paleontolo­ limestones outcropped at Yozawa, Mi­ gical aspect of this district, but detailed tsuzawa, Tamanouchi, Takimoto, Mitake stratigraphy and paleontology remained and Hossawa (Text-fig. 1). These limes­ unknown. Comprehensive field study of tones bear primitive fusulinaceans, such the Itsukaichi district has been made as Millerella, Eostaffella, and Profusuli­ by the junior author during the spring nella. field season of 1971-1972. As a result, Limestone exposed at Mitsuzawa, ap­ he found many new evidence of strati- proximately 3 km northwest of Itsukai­ * Received March 2, 1974: read January chi is particularly noteworthy because 16, 1973 at Sendai. of the occurrence of interesting bryo- 411 412 Hisayoshi leo and Fumio KOBAYASHI Hossawa• h;."j t-----J-I~--+-\-36' Hlnod,yam. ) A ~ J 902 Takimoto 14t -------/ . Mltsuzawa .: Locality of Carboniferous Fossil 5 ASOUc'lA • 788 ~~ /";"\ Tamanouchi Komiyosan A 810 Itsukaichi ~ I (km.) MusaShii'U~ichi Text-fig. 1. Map showing the localities of Carboniferous fossils in the Itsukaichi district. zoans, corals, brachiopods, mollusks and age. conodonts. SAKAGAMI (1972) was the The purpose of the present paper is first to recognize them as the Lower to discuss geologic age and descriptions Carboniferous. He described Mourlonia of the conodonts from Mitsuzawa, Taki­ and concluded that this gastropod is moto and Hossawa. These conodonts very similar to the specimens from are very important to settle the cono­ Uzura, Akiyoshi Limestone (SAKAGAMI, dont biostratigraphy near the boundary 1973). Also, YANAGIDA (1973) described between the Lower and Middle Carboni­ several brachiopods and advocated that ferous of Japan. Detailed geologic ob­ the fauna is apparently of Visean in servations of this district will be pre- 639. Carboniferous Conodonts from Itsukaichi 413 sen ted at a later date. ting thin layers of limestone in middle Acknowledgements: Here the authors part ...................... 15 m thick. record their cordial thanks to Dr. To­ shio KOIKE of Tokyo University of Both the upper and lower limits of Education and Mr. Hisaharu IGO of this sequence are in contact with Tri­ Tokyo Gakugei University for their assic sediments by pronounced faults. discussion in the field and laboratory. These lithologic units trend to N30·W The junior author's field survey was and dip 40· to the northeast. The lower carried out under the supervision of tuff is red, green and partly variegated Drs. Mosaburo KANUMA and Atsushi and becomes calcareous upward. The ISHII of Tokyo Gakugei University. Dr. calcareous part of this tuff comprises Haruyoshi FUJIMOTO, Professor Emeritus fragments of crinoid stems, other cal­ of Tokyo University of Education and careous materials and oolites. Nodular Dr. Sumio SAKAGAMI, Professor of Ehime shaped limestones are various in shape University gave us valuable field infor­ but mostly subspheroid. Averaged dia­ mation. Miss Hiromi KANASUGI, Messrs. meter of them is about 30 cm. They T. KUSANO, M. GOKAN and N. MATSUSE contain abundantly crinoid stems, corals, of Tokyo Gakugei University helped our bryozoans, gastropods, brachiopods and field survey and laboratory work. The rarely goniatites. Fossils described by authors are grateful to these individuals. SAKAGAMI (1973) and YANAGIDA (1973) We are also indebted to the Chichibu were collected from this level (158B in Cement, Buko Mining and Mitsubishi Text-fig. 2). Limestones yielding corals Kogyo Cement Companies, Ltd. for and bryozoans have almost the same generous financial assistance. lithology. The corals are Lithostrotion (Siphonodendron), Diphyphyllum and other Rugosa. These corals are cemented Geologic Setting mostly by fine-grained lime mud, subor­ The Mitsuzawa Limestone outcrops dinate fossil fragments and detrital along a small valley in the south of calcite and partly filled with clear Mitsuzawa. The following succession sparry calcite. Brachiopodal and gas­ is measured along the Mitsuzawa Valley tropodallimestones are highly bioclastic. in descending order. These fossils are cemented by fairly large fragments of biogenetic calcite Chert; thin-bedded, pale gray, green and which are mostly originated from partly reddish .. more than 20 m thick. crinoid. Interstitial cement of clean Limestone; well-bedded, intercalating calcite is also recognized, and partly thin layers of chert and dolomitic interlocking these fragments of bioge­ layers .................... 9 m thick. netic calcite. Chert; bedded, pale gray and reddish The upper limestone beds are almost .......................... 7m thick. barren in megafossils except for small Tuff; red, green and variegated, calca­ fragments of crinoid and shells,. but reous, intercalating nodular lime­ they contain smaller foraminifers and stones and limestone layers, upper other microfossils. The lower part of part grades laterally into chert .... this limestone is thin-bedded, laminated .......................... 8m thick. and intercalating thin dolomitic layers. Tuff; red, partly variegated, intercala- This rock consists of fine-grained lime 414 Hisayoshi IGO and Fumio KOBAY ASH! mud with the admixture of smaller fora­ of Mitake Railway Station. Limestone minifers and fragments of biogenetic layer interbedded with green chert, calcite which are mostly echinoderms. about 10-15 cm in thickness yields nu­ Minute shell fragments in varying abun­ merous conodonts. These conodonts are dance are also recognized, but what the same with those from the type sec­ kind of fossil shells they represent is tion of the Mitsuzawa Limestone. difficult to determine. Small dolomitic rhombs are scattered in the particular laminae as single individuals. These Appraisal of Conodont Fauna components frequently show graded lamination in a small scale. Conodonts were recovered from 1 to The upper remainder of this limestone 2 kg limestone samples by ordinary unit intercalates chert layers of about acetic acid method. Samples embedded 10 cm thick. Lithology of this part of in chert were observed by very thin limestone is almost similar to the lower slices and chips under the transmitted part, but dolomitized and laminated light. Hydrofioric acid was supplemen­ parts become obscure. Chert layers tarily used for chert samples. All of the intercalated within this limestone are samples shown in Text-fig. 2 are pro­ sometimes discontinuous and their upper ductive. The assemblage of conodont and lower surfaces show irregular wavy does not show any remarkable difference bedding plane. throughout the calcareous facies of the The uppermost chert is thin-bedded, measured section, but each species about 5 to 10 cm thick, intraformation­ varies in individual