·MESOZOIC FLORAL SUCCESSION OF NAGATO MOUNTAINLAND, WESTERN JAPAN EITARO TAKAHASI Geological Institute, Yamaguchi University, Japan ABSTRACT the Mesozoic formations were carried out by Floral succession in Triassic and Jurassic forma• Kobayashi (1941), Matsumoto (1949), tions of Nagato mountainland, western Japan were Rase ( 1951) and others. Fortunately, the carried out by the author and determined the strati• Triassic plant beds are alternated with graphical boundary between the horizons of DiEt yo• marine shell-bearing beds and the Jurassic phyllum Series and Onychiopsis Series of Oishi exists at some limited horizon between the upper• plant beds are intercalated with marine most of Higashi-Nagano formation and the middle ammonite beds; hence the exact geological of Nishi-Nakayama formation of the Toyora ages of the plant horizons are decided. As it Group. was mentioned previously by Kobayashi ( 1938, 1942), the ages of the Mesozoic floras of our country are older than those of Europe; NAGATaJapan hasmountainlandbeen famousof fortheMesozoicwestern namely the ages of the floras of Rhaeto• plant fossils since the palaeobotanical Liassic aspect go down to the Noric Carnic works of Yokoyama ( 1891, 1905) and Yabe and Ladonic, and the ages of the floras of ( 1922). In this mountainland there de• Upper Jurassic type go down to the Middle veloped Triassic and Jurassic plant beds of and Lower Jurassic. In the early years the various stages,. some of them have been writer made efforts to settle the precise worked as coalfields. In the recent three geological position of the plant fossils already decades Oishi ( 1932-40), Konno, the present described or reported by the above-mentioned writer (TAKAHASI,1950-51) and Rozioka palaeobotanists in the Mesozoic formations ( 1938) took up their palaeobotanical works and also added numerous fossil species. on the plant fossils from this mountainland. Geological ages of the Mesozoic formations On·the other hand, stratigraphical works on of this mountainland are settled as follows: GEOLOGICAL AGES GEOLOGICAL SYSTEMS Yahata Group (Upper ........ ...",.......",...~..",......"......."...~...,.....,.. I Middle Cretaceous Kammon group ~rShimonoseki subgroup 1 Lower } l Wakino subgroup I .....•..• .."..~~..."......"........,....,......,.......,......"......".. lLow. Most 'I Toyonish group ~rYoshimo formation j LKiyosue formation * rUppeI' -""'-""~ ...,.. ....-~~..."... Jurassic 1 Middle ~rUtanoNishi-Nakayamaformation*formation* lLower { Toyora group LHigashi-Nagano formation* .....•..••..••..• ...".... .....•..•.....•..• ~~~-"""-"""~ ........• r Noric r Kamosho for. r r Aso for.* I Carnic ~l YamNakatsukaanoi for.for.* * Triassic ~L Mine (or Habu ) group ~l MomonokiHirabara for.for.** 1 r Idenoue for.* lLadonic r rKumanokura for.* ~ ~l Atsu (or Tsubuta) group ~LHongo for. LHiramatsu for.* Omine region Tsubuta region. *Plant-bearing formations. 155 156 THE PALAEO BOTANIST X At this place we must pay special atten• TSUBUT(1)X IdenoueA FOSSIL FLORAXXxX xXX ConiferalesPlantaeFilicalesPityophyllumS.DietyophyllumD.GinkgoaceanSwedenborgiaCyeadoearpidiumC.EquisetitesT.(L.&H.)( Brongn.)Nath.)sp.sp.n.sp.sp.sp.?? (Seed)incertaeP.takaianusPhoenieopsisStenoraehisD.Cladophlebis(conesp.longifoliumm.s.)sp.nathorstisp.japonieumEquisetalesswabiisedisor ThaumatopterisKonnoelegansZeill.dentieulataNath.angustifoliaYok. OishiFormationsp.?Heer FormationPodozamites laneeolatus bed toGinkgophytasome hori~ons.· (1) Kiyosue plant P.E.C.NRhipidopsisElatocladusClathropterissp.haiburnensissp.Taeniopteriseoealamitessp.sp.sp.earrerei(minensisL.indet.Hiramatsu& H.)( Zeill.)Oishi tion of Oishi is divided stratigraphically by an unconformity into two parts; Toyora group, the lower and Kiyosue formation of Toyonishi group, the upper; (2) fossil localities of Tsubuta of ()ishi belong to Idenoue formation, not to Yamanoi form• ation. Next are presented the tables of Triassic and Jurassic plant fossils. It is noticeable that the Gondwana element Rhipidopsis occurs in the lower part of Hiramatsu formation, Thinnfeldia comes in the middle part of Hirabara formation and Palaeozoic type Plagiozamites survives in the lower part of Momonoki formation. Stratigraphical boundary between the horizons of Dictyophyllum series and Ony• chiopsis series of ()ishi ( 1940) has become very clear, namely Nilssonia brevis (Brongn.), belonging to the former series comes out from the uppermost horizon of Higashi-Nagano formation and Zamites toyoraensis Oishi and Cycadites sp., both belonging to the latter series, come out from the middle horizon of Nishi-Nakayama formation. So we can clearly say that the boundary between the two series exists at some limited horizon between the uppermost of Higashi-Nagano formation and the middle of Nishi-Nakayama formation. (2) MINE FOSSIL FLORA Y AMANOI F. HIRABARA F. MOMONOKI F. Aso F. Bryophyta H epatieites Oishii X Huzioka & Tak. (m.s.) X EquisetalesOishiwilliamsoni( (3,m.s.)Oishi( Brongn.)X (( ZeiIl.)Miinst.)X ?X *NakatsukaXX f. X XX X X T.N eoealamitesreeurvatus earrereiHarris ( m.s.)~ X EquisetitesE.N. naitoihoerrensisKonnomultidentata(Schimp.)E.PhyllotlzeeaClathropteris"LobatannulariaC.(m.s.)*sp.obovatasp. IX,OishiOishisp.meniseoidesensifolia HalleBrongn.E. n. E.sp. n. sp. IX Filicales AToditesnnulariopsisgoeppertianusinopinata Zeill. TAKAHASI - MESOZOIC FLORAL SUCCESSION OF NAGATO MOUNTAINLAND 157 Y AMANOI F. HIRABARA F. MOMONOKI F. Aso F. C. sp. x Dictyophyllum japonicum Yok. x X D. nalhorsti Zeill. X X D. sp. X D. sp. indet. X X Thaumalopleris kochibei (Yok.) X Hausmannia denlala Oishi X H. sp. X Cladophlebis denliculala (Brongn.) X X X C. haiburnensis (L. & H.) X x X C. nebbensis (Brongn.) X X X C. pseudodelicalula Oishi X C. cfr. pseudodelicalula Oishi X C. raciboyskii Zeill. X C. cfr. j'aciborskii Zeill. X X C. raciborskii integra Oishi & Tak. X C. cfr. raciborskii inlegra Oishi & Talc X C. williamsoni (Brongn.) X C. n.sp. ex, Oishi (m.s.) X C. n. sp. ~, Oishi (m.s.) X C. n. sp. y, Oishi (m.s.) X C. sp. X Cycadophyta Ctenis ? sp. X Nilssonia acuminata Presl X N. inouyei Yok. X X N. simplex Oishi X N. sp. X Plerophyllum yamanoiensis Oishi & Tak. X P. sp. X P. ? sp. indet. X Zamites n. sp. Oishi (m.s.) X Z. n. sp. Oishi (m.s.) X Plagiozamiles minensis Tak. X Sagenopteris nilssoniana (Brongn.) X Thinnfeldia sp. ? X Gink~ophyta Baiera elegans Oishi X B. muensleriana (Presl) X B. pauciparlila Nath. X X B. sibirica Heer X B. sp. X Ginkgoiles digilata hultoni Seward X Czekanowskia rigida Heer X X C. sp. X C. ? sp. X Phoenicopsis sp. X X Coniferales Podocarpiles ushioi Naito (m.s.) X Elalocladus sp. X N ageiopsis rhaelica Oishi X Araucarioxylon sp. X Pilyophyllum longifolium (Nath.) X X X Podozamiles alsuensis Tak. X X P. concinnus Oishi & Huz. X P. cfr. dislanlinervis Font. X P. lanceolalus (L. & H.) X X X P. nagaloensis Tak. X X P. oishii Tak. X P. schenkii Heer X X P. n. sp. Oishi (m.s.) X P. sp. X X Cycadocarpidium erdmanni Nath. X C. swabii Nath. X C. sp. X 158 MOMONOKIHIRABARA?AsoF.F.F.F. X X OishiHeerNath.X X THEX PALAEOX BOTANISTX X T.Cfr.sp.minensisT. nabaensisOishiSwedenborgiaTaeniopte"isOishi lanceolatuscryptomeroidesStachyotaxus elegansStenorachisT.Cfr.richthofenin.LeptostrobusNath.sp., Oishielegans(Schenk)(m.s.)laxifloraOishi Plantae incertae sed is Pachypteris sp. C. sp. YAMANOI (3) TOYORA AND TOYONISHI FOSSIL FLORAS -----_._----"--._---------..,TOYORA G. TOYONISHIG. Higashi- Nishi- Utano f. Kiyosue f. Nagano f. Nakayama f. Bryophyta Thallites yabei ( Krysht.) X X Equisetales Equisetites endoi Konno (l11.s.) X Filicales Phlebopteris takahasii Huzioka X Coniopte"is burejensis (Zall.) X C. hymenophylloides (Brongn.) X Onychiopsis elongata (Geyl.) X X X A diantites sewm'di Yabe X X A. toyoraensis Oishi X Sphenopteris goepperti Dunk. X X Cladophlebis denticulata (Brongn.) X X C. deZtifolia Oishi X C. exiliformis (GeyL) X C. (Klukia?) koraiensis Yabe X C. lobifolia (PJ:1il1-J X C. toyoraensis Oishi X X C. sp. X X Cycadophyta Nilssonia b,'evis (Brongu.) X N. densinerve (Font.) X N. compta (PhiIL) X N. nipponensis Yok. X N. orientalis Heer X X X N. schaumburgensis parvula Yabe X N. sp. X X Cfr. Pseudoctenis brevipennis Oishi X P. sp. X Dictyozamites falcatus (Morris) X D. kawasakii Tateiwa X D. sp. X Otozamites beani (L. & H.) X X O. klipsteinii (Dunk.) X X Cycadiles sp. X Pseudocycas sp. ? X Pterophyllum propinquum Goepp. X X P sp. X Ptilophyllum pecten (Ph ilL) X P. pachyrachis Oishi X TAKAHASI - MESOZOIC FLORAL SUCCESSION OF NAGATO MOUNTAINLAND 159 TOYORA G. TOYONISHIG. ,- A... -., Higashi- Nishi- Utano L Kiyosue f. _Tagano f. Nakayama L P. sp. x Zamiophyllum buchianum (Ett.) X Cfr. Z. megaphyllus (Phill.) X Cfr. Z. Hoheneggeri (Schenk) Z. toyorae!,sis Oishi Z. yabei Oishi Sagenopteris petiolata Oishi Ginkgophyta Ginkgoites digitata (Brongn.) G. sibi rica (Heer) X C;;ekanowskia rigida Heer Pltoenicopsis sp. Coniferales A rauca.1·ites cutchensis Feist. 13rachypltyllum e:rpansum (Sternb.) X B. toyomensis Tak. B. sp. Elatocladus constricta (Feist.) Palissia sp. Nageiopsis longi/olia Font. Cfr. Podozamites distantinervis Font. P. sp. REFERENCES BASE, A. (1951). Triassic system of Yamaguchi Idem (1940). The Mesozoic floras of Japan. prefecture. (Geology of Triassic system of Ibid. 5(3-4): 123-454. Japan.), Rep. Geol. Surv. Japan. Spec. 1: OISHI, S. & TAKAHASI,E. ( 1936). Rhaetic plants 72-89. from Provo Nagata, Japan. A supplement. HUZIOKA, K. (1938). On the occurrence of a new Ibid. 3(2): 113-133. species of Phlebopteris in Japan. Jour. Fac. Sci. TAKAHASI,E. & NAITO, G. (1950). Dictyozamites Hokkaido. Imp.