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Volume 46, Issue 546
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Reikyoku CHOH1939 Volume 46 Issue 546 Pages 113-116
Published: March 20, 1939
Released on J-STAGE: April 11, 2008
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Haruyosi HUZIMOTO1939 Volume 46 Issue 546 Pages 117-126
Published: March 20, 1939
Released on J-STAGE: April 11, 2008
JOURNAL FREE ACCESSThe Sambagawa and Mikabu systems are two important formations in the Japanese islands which have long been believed to reveal independent stratigraphic units among the older formations., The former consists of various crystalline schists, while green schits, or so-called "clastopyroxenite" by KOTO, are the leading members of the latter, to which several other metamorphosed rocks are found associated in one system., Because of barren of fossil the stratigraphic positions of these systems have been laid on the debatable ground., The current opinions on the moot question which have so far been established by Japanese geologists may be classified into the following three : a., The Sambagawa, Mikabu and Titibu systems are successively disposed in an order of geological age, among which the last one is the oldest fossillferous formation in Japan, and accordingly the other two below the Titibu must be pre-Carboniferous., b., The three systems are in the same order mentioned above, but they are separated from one another by two unconformities., Because each unconformity implies tremendous time-gap, the age of the Sambagawa could be as old as pre-Cambrian., c., The sambagawa and Mikabu systems are nothing but the metamorphosed Titibu system., Lately the writer made a renewed study on the sambagawa and Mikabu systems in the northeastern part of the Kwanto Mountainland where the systems are typically developed., As his results are summarized below, he came to the conclusion which is different from all of those opinions referred to above., Untiring effort of the writer for the determination of their geological agds was frustrated with the find of the fact that the two systems are in tectonic contact with the Titibu, wherever they are found together., More precisely, the Sambagawa and Mikabu systems apparently capping the Titibu in the surveyed area are in fact the Nappe of the two systems upon the Titibu., Moreover, the sambagawa system, in so far as can be seen, merges with the Mikabu and no definite boundary can be drawn between., The superposition of the Mikabu on the Sambagawa system may be a general status, but the reverse relation is met with at some places and a part of one system is in the heteropic relation to another part of the other system., Therefore the view of the two systems as independent stratigraphic units established by previous works no longer possesses raison d'etre., Furthermore, these formational names simply imply the metamorphosed facies of one or more formations., In other words, Sambagawa and Mikabu cannot stand as names of independent stratigraphic units., However, it is advisable that such classical names as Sambagawa and Mikabu are applicable to designate these kinds of metamorphosed facies, as the Ryoke metamorphics are used by the Japanese geologists in a similar way., As has been reported lately, the writer diseovered Radiolarian remains in certain parts of the Sambagawa metamorphics., Judging from these Radiolarians, it is certain that the fossiliferous rocks are Jurassic., On the other hand, it should be noted that the original rocks of the Sambagawa and Mikabu metamorphics are as a whole more allied to the assemblage of the Titibu rocks than to that of the Jurassic rocks in the Kwanto Mountainland., Bringing these evidences together, the writer led at length to the contention that both of the Jurassic and Titibu systems are comprised in the Sambagawa and Mikabu complexes, and that, if the two complexes are tied up in one, it reveals the metamorphosed facies of a series of formations ranging from Carboniferous to Jurassic., For this the writer intends to propose "Nagatoro system, " because the system bears not only a profound tectonic meaning but distinguishing petrographic characteristics, although several stratigraphc questions still remain unsolved. [the rest omitted]View full abstractDownload PDF (1346K) -
Masaru KATAYAMA1939 Volume 46 Issue 546 Pages 127-141
Published: March 20, 1939
Released on J-STAGE: April 11, 2008
JOURNAL FREE ACCESSThe Upper Triassic Mine and Atsu series are rspectively developed on the west and southwest sides of Akiyoshi plateau, Yamaguchi Prefecture., The Upper Palaeozoic Chichibu series of the plateau is unconformably overlain on its west side by the Mine series which is in turn generally monoclinal to the northwest except its western marginal part where the series forms a syncline and is delimited by a fault from the phyllitic rocks of Toyogatake in further west., The stratigraphic succession of the Mine series is shown in the table given below : [table] The Hirabara stage begins with the basal limestone conglomerate and consists of clay, shale, sandstone and conglomerate in alternation., A few coal seams are intercalated in its top and basal parts., The lower part of the Momonoki stage is composed of the alternation of thick conglomerate, sandstone and shale with intercalations of main coal seams ; its upper part consists in the main of thick sandstone., The Aso stage consists of the alternating beds of clay, shale, sandstone and a few coalseams in the lower part and mainly of thick massive sandstones in the upper., While the Momonoki stage overlies the Hirabara conformably or slightly para-unconformably in the southern part, the former, overlapping the latter, covers the Upper Palaeozoic Chichibu series directly in the northern part., As may be seen in the following lists, the Aso and Hirabara stages yield marine and brackish shells in various horizons, while the Momonoki contains no shells but a number of plants., FAUNA: Hirabara stage - Trigonia (Minetrigonia) hegiensis SAEKI, Halobia charlyana, Oxytoma zitteli (TELLER), Lima naumanni, Rhynchonella nasai, "Pleurophorus" sp., aff., P., perlongus, Edentula ozawai KOBAYASHI, Cardinia sp., Gervillia sp., Anodontophora sp., Syncyclonema sp., Aso stage- Pecten suzukii KOBAYASHI, Lima naumanni, Pseudomonotis sp., aff., P., spitzbergensis, Anodontophora sp., Pecten sp., Flora: Hirabara stage- Neocalamites carrerei (ZEILLER), Cladophlebis haiburnensis L., and H., Taeniopteris minensis OISHI, Cycadocarpidium swabii NATHORST, Pityophyllum longifolium (NATHORST), Podozamites lanceolatus(L., and H., ), P., schenki HEER, Nageiopsis raetica OISHI., Momonoki and Aso stages- Neocalamites carrerei (ZEILLER), Cladophlebis haiburnensis L., and H., C., nebbensis (BRONGN., ), C., raciborskii ZEILLER, Taeniopteris minensis OISHI, Pityophyllum longifolium (NATHORST), Podozamites lanceolatus (L., and H., ), P., schenki HEER, Cycadocarpidium swabii NATHORST (Momonoki stage), Ginkgoites digitata (BRONGN., ) var., huttoni SEWARD (Momonoki stage), Stenorachis elegans OISHI (Momonoki stage), Dictyophyllum japonicum YOKOYAMA (Aso stage), Nilssonia inouyei YOKOYAMA (Aso stage)., Judging from this floral assemblage the Mine flora corresponds as a whole to that of the Rhaetic of the world., On the other hand Halobia charlyana, Lima naumanni and Rhynchonella nasai which are the significant elements of the Hirabara fauna, occur commonly between the Hirabara stage and the Carnic Halobia bed in the Sakawa basin, province Tosa; Oxytoma zitteli and Trigonia (Minetrigonia) hegiensis are found commonly between the Hirabara stage and the Oxytoma bed in the Sakawa basin; the age of the latter may be Carno-Noric or Lower Noric., Among the Aso fauna, Lima naumanni is contained in the Halobia bed and Pecten suzuki in the Oxytoma bed., Pseudomonotis spitzbergensis is reported from the Carnic bed on Bear Island and the Noric bed at Spitzbergen., Further, it is a noteworthy fact in determining the age of the Aso stage that the fossiliferous sandstone of the Aso strikingly resembles a reddish micaceous sandstone at Kamosho which is located at a distance of about 15 kilometers from the fossil localities of the Aso stage, and the age of the Kamosho sandstone is decided at Noric with the find of Pseudomonotis ochotica in it. [the rest omitted]View full abstractDownload PDF (2355K) -
Hisakatsu YABE, Toshio SUGIYAMA1939 Volume 46 Issue 546 Pages 145-148_1
Published: March 20, 1939
Released on J-STAGE: April 11, 2008
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JOSEPH A. CUSHMAN1939 Volume 46 Issue 546 Pages 149-154
Published: March 20, 1939
Released on J-STAGE: April 11, 2008
JOURNAL FREE ACCESS
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