Tokuoka, Takao

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RIGHT:URL:CITATION:AUTHOR(S):ISSUE DATE:TITLE:Kizekkyo Sandstone andConglomerate of the PaleogeneMuro Group in the Kii Peninsula,JapanTokuoka, TakaoTokuoka, Takao. Kizekkyo Sandstone and Conglomerate of the Paleogene Muro Group inthe Kii Peninsula, Japan. Memoirs of the College of Science, University of Kyoto. Series B1966, 32(4): 335-3491966-03http://hdl.handle.net/2433/258735MEMOIRS OF      Vol.THE COLLEGEXXXII, No. 4OF SCIENCE,Geology andUNIvERSITy oF KyoTo, SERXEs B,Mineralogy, Article 5, 1966Kizekkyo SaRdstone        Muro Groupand Conglomerate ofin the Kii Peninsula,the PaleogeneJapaBByGeologica}      Takao ToKUOKAand Mineralogical Institute, URiversity of Kyoto(Received Nov. 19, 1965)                                 Abstraet   Thls paper deals with the source areas of the sediments of the Muro group with speciai referenceto the composition of conglomerates and sandstones. The Muro group may have been supplled mainlyfrom the north. The Ryoke Metamorphic Belt, the Sanbagawa Metamorphic .B.elt, the Paieozoicregions of the Chichibu Terrain, and the regions of the Sennan Acidic Rocks and Åíhe so-calledTorinosu Series may be regarded as the provenances of the Muro group. However the materialsderived frem the Sanbagawa Me!amorphic Belt are smai!er in quantlty and have been discovered onlyin the rock fragments of the sandstones.                               Introduction    The Paleogene Muro group in the southem part of the Kii Peninsula occupiesthe upper part of the Shimanto Supergroup, which is composed of geosynclinalsediments and ranges from the Mesozoic to the early Cenozoic in age. In this paperthe Muro group in tke northwestern end is described (Figure 1).    The problem of the source area, which is very irnportant in clarifying geologicdevelopments, has long been ignored in the Shimanto Terrain. The writer will refer tothe provenance of the Muro group with speeial reference to the composition of con-glomerates and sandstones. However, the precise discussion will be left to furtherstudy.          General Remarks on the'Mure Group and the Reperted Area    ThQ Muro group is composed of thick geosynclinal sedirnents, which are flysch-type alternations of sandstone and shale, frequently intercalated by conglomerates,and shows completely folded structures. The Muro group is thought to be upperQiigoceneorlpwgr Miocqne frQrn paolluscan fossil evidences (HARATA et al, l963;336 Takao ToKuol<A                          Fig. 1. Ifidex map.MATsuMoTo, in press). The folded structures have been clarified along the Hiki riverwhere the Muro group attains more than 4000m. in total thickness (ToKuoKA,l966). The Muro group in the Kii Peninsula was generally reported by T. HARATA(1964).   The Muro group in this area had once been studied by K. HiRosE (1961, unpub-lished). It is composed of alternations of sandstone and shale in the lower part. Inthe upper part it is composed of massive sandstones intercalating conglomerates.The lower part, which is ill exposed and whose geologic structure cannot be welldefined, may have isoclinally foided structures. On the contrary, the upper part dipsat about 20-40 degrees to the north and oyerlies conformably on the lower part asshown in Figure 2,Kizekkyo Sandstone and Conglomerate of the Paleogene Muro          Group in the Kii Peninsula, Japan337                             Stratigraphy   The Muro group of this area can be divided into the following three formations,i.e. the Kamiakitsu alternation, the Kizekkyo sandstone aRd conglornerate, and theFuzono alternation in ascending order.   Kamialdtsu AIternation: This is distributed along the downstream of the Aizuriver in the neighbourhood of Sugihara, and is composed of alternations of sandstoneand shale, 10 to 20 cm. bedded. The lower parts are rich in shale, while the upper partsare rich in sandstone. Several sole markings such as flute cast, load cast and biohiero-glyph can be seen commonly on the bottom surface of sandstone beds.    Kizekkyo Sandstone and Conglomerate: (a) Kizekkyo Sandstone: This is dis-tributed typically besides the gorge of Kizekkyo. It is composed mainly of massive,very coarse sandstones in which granules are contained in abundance and pebble orcobble gravels are also contained sporadically. It is rarely intercalated by thin alter-nations of sandstone and shale, 5 to IO cm. bedded. The composition of massive sand-stones, which will be described later in detail, is arkosic, and shale patches arecontained in abundance. (b) Kizekkyo Conglomerate: The Kizekkyo sandstone is fre-quently intercalated by cenglomerate beds in the upper part. They are cellectivelycalled the Kizekkyo Conglornerate. This is distributed typically in the neighbourhoodof Shimomura along the Aizu river aHd its tributary. Along theAizu riverthe con-glomerate beds are of more than l2 horizons, while along the upper reaches of theMisu river they are of 3 horizons. This is shown in Figure 3. Their constitution willbe discussed later on in detail. They are rounded or subrounded pebble, cobble andboulder gravels. The matrlx is very coarse sandstones.    Fuzono Alternation: This is distributed along the road from Kengyo to Fuzonoand along the Aizu river from Shimomura to Kagihara. It overlies conformably on theKizekkyo sandstone. It is 5 to le cm. bedded alternations of sandstone and shale richin the Iatter, and frequently is intercalated by sandstones of 20 to 10e cm. thick. Minorfolded structures are found occasionally.    Kdyadani Formation: This is seen typically around Koyadani. It is mainly com-posed of shales and rarely intercalated by fine sandstones, 2 to 5 cm. thick, and fre-quently includes calcareous nodules. It may be correlated to the Inami series at thewestern coast of Inami-Town, Wakayama Prefecture (MATsusHiTA, 1953). Its geologicage has not been clarMed, but it must be older than the Muro group. In this region theKoyadani formation is in contact with ghÅë Muro group by the Koyadani fau# QfE-W trend,8 oo10 .vsaKOYADANI'"-'ft='--'i30ili{       :1;      '.'i':1Z':.•i:.3a 'f2      ti'.'.z:'.'.:.t      t:t:tt :.i:t:1t      tttttttltttittl:ttttllje •}g,)./; rlt?oe:o"r)ditl r)"Oeq30 c t;70 "60 s      SUGIHARA'ilYt7ity0 1 2km    FaultH N x N o e 9 e R >(1 . Tanabe group,    Fig. 2. Geologic map of the northern part of the Tanabe City. Wakayama Prefecture.2. Fuzono alternation, 3. Kizekkyo saRdstone and conglomerate, 4. Kamiakitsu alternation,5. Koyadani formation)C•17o 100 200mAFig. 3..6--"r ?FC•17C•150•14B163emC•1 9, 20C..•18_-_cC•1 150mD"C•12C•1 3Route maps and columnar sections of the Muro group.-1 23 1:.lil•:.]tlii:11.i:':',t safidstofte iiii'_-:z:i Alternations of Saftdstofte and Shale i:':::':::{;. Conyfomerate  -" Stri;<e aRd Di, / FaultC•11--20 Locaiity oÅí lavestigaied CoRglofnera tes P•1--3 Locaiity of Photographs . A- D LOcaiitY of COIUMnar SeedDftSKizekkyo Sandstone          Groupand Cenglomerate ofin the Kii Peninsula,the PaleogeneJaPanMuro 339                          Geolegic Structures   Although the Muro group in general has completely folded structures, it hassomewhat gently folded or in other words somewhat basin-like structure in this area.As shown in Figure 2 the Kizekkyo sandstone has NW-SE strike in the west, E-Wstrike in the central part and NE-SW strike in the east, and as a whole takes basin-likestructure, which is cut off by the Koyadani fault. In alternations of sandstone and shaleof the Kamiakitsu and Fuzono formations, minor folded structures can be observedfrequently.   The Koyadani fault which is seen 500 m. northwest of Shimomura is the boundarybetween the Koyadani formation and the Muro group. It can be traced continuouslyto the east in Wakayama Prefecture (}IARATA, l964). The I<oyadani formation, thestructure of which has not been determined yet, has E-W trend generally and mayhave isoclinally folded structures which are in accordance with the general trend efthe Outer Zone of the Southwest Japan.               The Cempositien ef the Kizekkye Conglomerate   The study of the composition of the Kizekkyo conglomerate is significant forclarifying the provenance of the Muro group. There are more than l2 layers of con-glomerate beds in this area. Tlte writer studied their compositions at 9 localities. Ineach locality he counted 30e gravels at randoin at three points in one exposure (atone point 1OO gravels were counted). These gravels were limited to the ones larger than1 cm. in diameter. They vfere classified in the field into 6 elements by unaided eye, thatis, sandstone, shale, chert*, limestone, granltic and gneissose rocks, and acidic volcanicand dyke rocks. These are shown in Figure 4. The quantity of the gravels larger thanIO cm. in diameter is also shown by the lnner circles, whose sizes are propotional totheir total volume (for instance the quantity of the gravels larger than l0 cm. in C-l2is 160/., and in C-l3 it is 1 %). Their properties were examined microscopically withgravels of random sampling (Table l).    Figure 4 suggests the following facts.1. The gravels are classified into the above mentioned 6 elements, in which sandstone,   chert, and granitic and gneissose rocks are dominant.* Metamorphic rocks such as schistose laornfels, sandstone horBfels were included in chert. These  are yery similar with chert and cannot be discriminated from chert by unaided eye. Their quantity  rnay attain to 20 0/p or so of chert mentioned here,EIIIIIIIIis$.S$.•$'s.SandstoneSha]eGhert19 18IillllilI]gllll$ISIILmestoneGranitso and GneissoseAatdiC VO1eaRiC and Dike20RocksRocks11             17 15Fig 4 The composition of the Kizekkyo ConglomeraÅíe at 9 localities.12 13 14co pa o g tu x pt o 8 9 e g >Kizekkyo Sandstone   Groupand Conglomerate ofin the Kii Peninsula,the PaleogeneJaPanMuro 342LocalityNumberof Sections;'2gg'V3.g<z2.Ut.Iige<Biotlte GraniteMuscovite GraniteTwo Mica GraniteGnelssose Granite--  GneissGranodioriteGraphic granite,Granite PorphyryMicrogranite, ApliteGranopkyreQuartz PorphyryDacitePorphyriteRhyolite TuffC-1138E2eeEACHERT6:ft9U) ct)gg:g•S"x-.t111Muddy Limestone  lnciuding  ForaminifersMuddy Limestone  including  no ForaminiferOolitic LimestonePure LimestoneChertCalcareous SandstoReNon-Calcareous  SandstoneSchistose HornfelsSandstone Hornfels53516122C-122894211l12421C-13 C-147 l 4oil122242311l659242C-151933265C-1759536323331948C-18121112112111C-l92991361311112C-201lTotal2332417l41tIt1iI 47llllII     I  is l     j  13 i     i  12 I 55   li   3Il 8IE   ils I   I10 I 76   l   '   ''   '32   '   '   '   l19 l----- lsl 82016]rmn'iI1 36i  I  i7I  I 114iTable 1 . The properties of the  sampiing (ene section  and pure limestone).Kizekkyoshows oneConglomerate examined by gravels of raRdom gravei, excluding the cases of oolitic iimestone342 Takao ToKuo!<A2. No difference in composition is observed at each locality generally*.3. The difference of composition according to size is not so much.4. Granitic and gneissose rocks attain to 15-25 0/. of the total numbers, besides those   larger than 10 cm. in diameter attain to 4e-60 O/,.5. Limestones, in which muddy limestones are very much, are commonly contained   at each locality.   The properties of the constituent rocks are described in the following.    Sanctstone (a) Calcareous sandstone: coarse-medium, subangular-subrounded             ewith calcit  matrix. It is noteworthy that this rock contains fragments of schistosehornfeis and some schists as grains. (b) Non-caicareous sandstone: medium-fine,angular-subangular graywackes. Schistose homfels are sometimes included as in thecase of calcareous ones.   Li/mestone (a) Muddy iimestone: In fine muddy limestones, sand grains arefrequently contained. There are also some schistose homfels and quartz-schists assand grains. Undetermined smali foraminifers are frequently found. (b) Ooliticlimestone: Smaller in quantity, but these are cobbles or boulders in general and some-times attain to more than 50 cm. in diameter. It is significant that they includeabundant fossils such as corals, various small foraminifers, moiluscs, stromatoporoidsand "Cidaris" spines. (c) Pure limes'cone: The maximum diameter attains to 6e cm.These also include many fossiis such as corals, stromatoporoids, molluscs and smallforaminifers.    Limestones mentioned above, in particular b and c, are somewhat simiiar to theso-called Torinosu Limestone of the upper Jurassic and the lower Cretaceous. Coralssuch as Tk.amnastreri.a spp., Aplosmil'ia cÅí somaensis EGucHi, Di laraea2 sp. werefound in them**.    Granitic and Gneissose Rocks (a) Granite: This inciudes biotite granite, musco-vite granite and two mica granite, and among them biotite granite is most abundant.They often bear garnet. (b) Gneissose granite and gneiss: Gneissose granites form themajority. it is frequently garnet-bearing. Mosaic structure and undulose extinctionare clearly observed in quartz. Secondary twin lamellation in plagiociase felspar cancommonly be seen.    Acidic Yolcani.c and Dyke Rocks: (a) Rhyolite tuff: Flow structure and welded \' ln comparlson with the composition of conglomerates in the Hiki river area, there are many  granites and gneissose graBites, and less acidic volcanic and dyke rocks in Åíhis area. In acidic  volcan{c and dyke rocks, there at'e abundant rhyolite tuffs, in which abotit a haif are we{ded  ones, and few dyke rocks in the Hiki river area (ToKuoKA, l966). On the contrary there are  few t'hyolite tuffs and comparatively many dyke rocks in this area.** Corals were identified by N. YAMAGiwA.            Kizekkyo Sandstone and CoRglomerate of the Paieogene Muro 343                      Group in the Kii Peninsula, Japanstructure are scarcely observed, and crystals of quartz are commonly corroded.(b) Dyke rocks: Granophyre, quartz porphyry, dacite and porphyrite are included.Although their quantity is not so large, they are eommonly contained in all layers.    The above-mentioned facts lead to the following considerations.1. The granitic and gneissose rocks and schistose hornfels rnay have been suppliedfrom the Ryoke Metamorphic Belt which is situated to the north of the ShimantoTerrain.2. The limestones must have been transported from the areas where the so-calledTorinosu limestones are distributed er have once been distributed.3. The acidic volcanic and dyke rocks may have been supplied from the Sennan AcidicRocks along the southern naargin of the Ryoke Metamorphic Belt.4. The calcareous sandstones, whose quantity is about half ef the sandstone gravels,may have been derived from the so-called Torinosu series, although it is not so clear.5. The cherts may have beeR supplied from the Paleozoic rocks of the ChichibuTerrain.                 The CompositioR ef the Kizekkyo Sandstone    Massive, very coarse Kizekkyo sandstones were inyestigated. They were studiedin thin slices and their compositions were plotted to a triangle diagram based on thethree end members, quartz, felspars, and rock fragments and matrix (Figure 5).    The following facts were clarified.                            MATRIX.ROCKFRAGMENTS1.2.                  FELSPARS OUARTZ,CHERT                  Fig. 5. The composition of the Kizek.kyo                        Sandstone.Sandstones are very coarse and contain abundant granule gravels and shale patches.The grains are subangular and generally M sorted.344 Takao ToKuoKA3. They are arkosic and have very smaller amount of matrix.4. Many quartz grains show unduiose extinction, which suggests gneissose sourceareas.5. K-felspars are abundant and angular in shape, suggesting their granitic origin.6. Rock fragments are granitic rocks, acidic rocks, shales, sandstones, schistosehornfels, schists and andesitic rocks. Among them fragments of schist are noteworthy,although they are very rare. They are mostly quartz-schists, and rarely graphite-schist.* They may have been derived from the Sanbagawa Metamorphic Belt.                                Summary1. The Paleogene Muro group in the northern part of the Tanabe City was investigatedwith special reference to the composition of conglomerates and sandstones.2• The Muro group of this area is divided into the following formation, i.e. theKamiakitsu alternation, the Kizekkyo sandstone and conglomerate, and the Fuzonoalternation in ascending order.3. The composition of the Kizekkyo conglomerate was studied. There are sandstone,shale, chert, limestone, granitic and gneissose rocks, acidic volcanic and dyke rocks,schistose hornfels and others in the gravels of the Kizekkyo conglomerate. They mayhave been supplied from the Ryoke Metamorphic Belt, the region of the Sennan AeidicRocks, the Paleozoics of the Chichibu Terrain and the regions of the so-calledTorinosu series.4. The composition of the Kizekkyo sandstone was also studied. It is arkosic. In therock fragments of sandstones there are small quantities of schist in addition to all rocksfound as the gravels of the Kizekkyo conglomerate. The fragrnents of schist may havebeen derived from the Sanbagawa Metamorphic Belt.                            Acknowledgements    The writer is indebted to Prof. S. MATsusHiTA for his kindness in correcting themanuscnpt.    The writer is also indebted to Prof. K. NAKAzAwA and Ass. Prof. S. IsHiDA forvaluabie advices and encouragements and Dr. T. HARATA for the helpful discussions.He wishes to express his obligation to Dr. N. YAMAGiwA for identification of fossiis.This investigation was supported partly by the Grant in Aid for Scientific Researchof the Department of Education, for which the writer expresses his thanks.* Schists were deteffmiged by I. NAKA\AMA, to whom the writer expresses h(s thafiks.l<izekkyo SandstoRe            Groupandln Conglomerate ofthe Kii Pen!nsula,the Paieogene MurojaPan345-ReferencesEGucHi, M. (1951): Mesozoic Hexacorals from Japan. Sci. Rep. Tohoku Univ., 2nd Ser. 24, pp. 1-96.HARATA, T., ToKuoKA, T. and MATsuMoTo, E. (1963): Some Important New Facts from the Muro   Group in the South Part of the Kii Peninsula-The New Occurrence of Fossils from the Upper   Part of the Muro Group. (in Japanese witk English abstract) Earth Science, 69, pp. 20-24.HARATA, T. (1964): The Muro Group in the Kii Peninsula, Southwest Japan. Mem. Coll. Sci., Univ.   Kyoto, Ser. B, 31, no. 2, pp. 71-94.MATsuMoTo, E. : Molluscan Fossils from the Muro Group in the Southern Part of the Kii Peninsula,   Central Japan. Part 1. (in press)MATsusmTA, S. (1953): The Regional Geoiogy oÅí Japan, "Kinki District". Asakura Shoten, lrokyo.   (in Japanese)TAMuRA, M. (1961): The Torinosu Series and Fossils Theirin. The Geologic History of the Torinosu   Epoch and the Mesozoic Reef-Limestones in Japan. Japan. Jour. Geol. Geogr., 32, no. 2, pp. 219-   277.ToKuoKA, T. (1966): The Muro Group along the Upper Reaches of the Hiki River in Wakayama   Prefecture, Japan. Jour. Geol. Soc. Japait. 72, No. 2, pp. 53-61. (in Japanese witk Engiig.h   abstract)346 'irakao 1}oKuoKAFig. 1.Fig. 2.                     Explanation of PIate nMaximum granite boulder in the Kizekkyo Conglomerate (Locality C-20, Gneissose granite)Limestone boulder in the Kizekkyo Conglomerate (Locality Cl7, 0olitic limestone)Mem. Coll. Sci. Kyoto, Ser. B, Vol. XXXII, No. 4 Geol. & Min,, Art. 5, 1966 Pl. 7Fig. 1.Fig. 2.g48 Takao Tol<uoKAExplanation ef Plate 8Fig. 3.Fjg. 4.Exposure of the Kizekkyo Conglomerate at Locality Cl8Massive, yery coarse Kjzekkyo Sandstone including abun•dant shale patches (large block ofshale also inciuded at the right)Mem. Coll. Sci. Kyoto, Ser. B, Vol. XXXIr, No. 4 Geol.& Min. Art. 5, 1966 Pl.8Fig. 3.Fig. 4.

Kizekkyo Sandstone and Conglomerate of the Paleogene Muro Group in the Kii Peninsula, Japan

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Kizekkyo Sandstone and Conglomerate of the Paleogene Muro Group in the Kii Peninsula, Japan

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