STRATIGRAPHIC CHANGE OF THE COARSE CLASTIC ROCKS OF THE SHIMANTO SUPERGROUP IN EASTERN, SHIKOKU, SOUTHWEST JAPAN

The Shimanto Supergroup of geosynclinal facies which ranges from Cretaceous to early Tertiary in age, is widely distributed in the outermost zone of Southwest Japan. Coeval volcanic and plutonic rocks are extensively distributed in the Inner Zone. The coarse clastic rocks mainly of sandstone occupy about a half of the Shimanto Supergroup, and a stratigraphic change of sandstone and conglomerate composition is recognized in the supergroup. The amount of rock fragments, chiefly acidic to intermediate volcanic rocks, increases upward throughout the Cretaceous sequence. Additionally, acidic tuff layers are frequently intercalated in the Late Cretaceous sequence. Conglomerates in the Late Cretaceous are very dominated by acidic volcanic rock clasts. The geosynclinal sedimentation of the Cretaceous Shimanto Supergroup proceeded with the coeval volcanism which became more active in the Late Cretaceous. The clastic sediments were supplied mainly from the sites of the volcanism. The volcanism corresponds to the Cretaceous volcanic activity in the Inner Zone of Southwest Japan. The Cretaceous Shimanto Supergroup may represent a typical forearc sedimentation in an arc-trench system.Book chapterKumon, Fujio. “STRATIGRAPHIC CHANGE OF THE COARSE CLASTIC ROCKS OF THE SHIMANTO SUPERGROUP IN EASTERN, SHIKOKU, SOUTHWEST JAPAN”. Formation of Active Ocean Margins. Nasu, N. Terra Scientific Publishing Company, 1986, p. 819-833.boo

Paleolimnological studies

Book chapterKumon, Fujio. “Paleolimnological studies”. Lake Kizaki: Limnology and Ecology of a Japanese Lake. Saijo, Y. and Hayashi, H. Backhuys Publishers, 1981, p. 55-62.boo

Coarse Clastic Rocks of the Shimanto Supergroup in Eastern Shikoku and Kii Peninsula, Southwest Japan

The stratigraphy and correlation of the Cretaceous strata in eastern Shikoku and Kii Peninsula are examined based on the radiolarian biostratigraphy. As the results, the stratigraphic change of the sandstone composition was recognized. The sandstones of the late Early Cretaceous are rich in feldspar, especially of plagioclase, and poor in rock fragments. Most sandstones of the Late Cretaceous are dominant in rock fragments, especially of acidic to intermediate volcanic rocks. Most of the Paleogene sandstones are characterized by very dominant quartz and poor rock fragments. Such stratigraphic change is also supported by the change of conglomerate composition. It reflects the change of the provenance nature. The increasing trend of rock fragments consisting mainly of volcanic rocks in the Cretaceous sequences indicates that the volcanism of acidic to intermediate nature took place in the provenance to the north of the basin contemporaneously with the sedimentation of the Late Cretaceous Shimanto Supergroup, and provided a large amount of volcanic materials to the basin. This volcanism corresponds to the so~called late Mesozoic Igneous Activity in the Inner Zone of Southwest Japan. Thus, the Late Cretaceous Shimanto Supergroup represents one type of the forearc sedimentation in magmatic arc-trench system. The difference of clastic composition between the Cretaceous and the Paleogene is explained by the unroofing process of the Cretaceous magmatic terrane. Lastly, the geotectonic development of the Shimanto Belt and its provenance is discussed mainly based on the sedimentological analyses. The marginal sea setting similar to the present Philippine Sea is considered to be preferable for the Shimanto geosyncline.ArticleMemoirs of the Faculty of Science, Kyoto University. Series of geology and mineralogy. 49(1-2):63-109 (1983)departmental bulletin pape

Modal and chemical compositions of the representative sandstones from the Japanese Islands and their tectonic implications

ArticleKumon, Fujio; Kiminami, Kazuo. “Modal and chemical compositions of the representative sandstones from the Japanese Islands and their tectonic implications”. Proceedings of the 29th International Geological Congress: Part A. Kyoto, Japan, 1992-08-24/09-03, VSP, 2004, p. 135-151.conference pape

Late Pleistocene variation in lignin and fatty acids from core TKN-2004 in a small mountain basin in central Japan

We generated a record of lignin and fatty acid compositions from the TK-2004 core in Takano Basin, central Japan, during 39-162 ka by TMAH-thermochemolysis-GC/MS. We tested lignin and fatty acid compositions in the sediments of a small lake (1.88 km(2) watershed) as a paleovegetation proxy to understand the responses of terrestrial vegetation in central Japan to global climate change. Variation in terrestrial organic carbon contents estimated by C/N and Sigma 8 was parallel to the total organic content (TOC) variation, suggesting that the inflow of terrestrial organic matter was a major factor determining the TOC. The ratio of mid-chain C-20-C-24 n-fatty acids to short-chain C-14-C-18 n-fatty acids (MFA/SFA ratio) and the ratio of cinnamyl to vanillyl phenols (C/V ratio) of lignin gradually increased from mid-MIS 6 to early MIS 3. The increase in both parameters suggested increase in the contribution of submerged and floating plants as the flats were expanded in the lake margin. The ratio of syringyl to vanillyl phenols (S/V ratio) corresponded to the pollen vegetation index. This correspondence indicated that the S/V ratio reflected the relative abundance of angiosperms to gymnosperms in the Takano Basin. The consistency of the S/V ratio at the site of core TKN-2004 and the other two locations suggests that the S/V ratio in a small basin is a robust proxy for terrestrial vegetation on a regional scale.ArticleGEOCHEMICAL JOURNAL. 48(2):207-217 (2014)journal articl

Holocene climate variability as deduced from the organic carbon and diatom records in the sediments of Lake Aoki, central Japan

ln order to understand the climate ｖariability of the Holocene period, two sediment cores were extracted at the northeastern　part of Lake Aoki,an intermontane freshwater body located near the northern Japanese Alps, Central Japan. The sediments are mainly composed of silty clay with some interealation of event sediments, including a tephra known as the Kikai-Akahoya (K-Ah) that dates 7,250cal BP. The sediment chronology yields the sedimentation rate of ca. 0.16 and 0.37 mm yr⁻¹ above and below the tephra, respectively. The sediments were investigated at 0.5cm interval, providing a time resolution of 13-29 years, for total organic carbon (TOC) and total nitrogen (TN) contents. The record of the organic contents along with the diatom abundance at 50 horizons is used as limnological monitors and climate proxies. The diatom record suggests that the lake has been oligotrophic and alkaline. TOC content and diatom abundance yield close correspondence with both short- and long-term fluctuations, shifting between low-and high-values. Climate, which control surface-water temperature, appears to be the main factor to affect the variability in the proxy records in Lake Aoki. The climate is dynamic, abruptly switching from various degrees of cool to warm Conditions in centennial to millennial scale. Warm conditions prevail from ca. 750-1300, 1750-3050, 4000-5250, 6150-7250, and 8800-10000calBP, and cooling occurs during 150-750, 1300-1750, 3050-4000, 5250-6150, and 8350-8800cal BP. The period between 7250-8350cal BP is rather Auctuating.Climatic events such as the Little Ice Age (LIA), the Medieval Warm Period (MWP), the Kofun cold stage, and the Holocene Optimum (HOP) are evident, and some other warm and cool events not well recorded before in Japan and abroad are also recognized. The lake also provides a valuable window into the recent climate change and the modern hydraulic changes in the lake system.青木湖は北アルプスの山麓,標高822mにある貧栄養湖である.表層堆積物の粒度分布を検討し, 1954年以降の電源開発のための人為的水利用が堆積物の性質と堆積速度に大きな影響を与えていることを明らかにした.青木湖の北東部から採取した2.2m長のコア試料は,おもに粘土質シルトから構成されており,年代的には約1万年間をカバーしていた.この柱状試料中の有機炭素･窒素含有率と珪藻殻含有数の増減はよく一致しており,湖の生物生産性の増減が有機炭素･窒素含有率の増減に反映している. 1954年以前の青木湖の生物生産性は,気温と連動した水温の変化に支配されていた可能性が高いので,有機炭素含有率の時代的変遷を基にして完新世の気候変動を復元することができた.完新世にはそれぞれ5つの温暖･冷涼期と1つの変動期が認められた.それらの多くは,小氷期,中世温暖期,完新世最温暖期などの汎世界的な寒暖変動とはぼ一致する.climatic variability, Holocene OptimumArticle地質学雑誌 108(4): 249-265(2002)journal articl

Coarse Clastic Rocks of the Shimanto Supergroup in Eastern Shikoku and Kii Peninsula, Southwest Japan

The stratigraphy and correlation of the Cretaceous strata in eastern Shikoku and Kii Peninsula are examined based on the radiolarian biostratigraphy. As the results, the stratigraphic change of the sandstone composition was recognized. The sandstones of the late Early Cretaceous are rich in feldspar, especially of plagioclase, and poor in rock fragments. Most sandstones of the Late Cretaceous are dominant in rock fragments, especially of acidic to intermediate volcanic rocks. Most of the Paleogene sandstones are characterized by very dominant quartz and poor rock fragments. Such stratigraphic change is also supported by the change of conglomerate composition. It reflects the change of the provenance nature. The increasing trend of rock fragments consisting mainly of volcanic rocks in the Cretaceous sequences indicates that the volcanism of acidic to intermediate nature took place in the provenance to the north of the basin contemporaneously with the sedimentation of the Late Cretaceous Shimanto Supergroup, and provided a large amount of volcanic materials to the basin. This volcanism corresponds to the so-called late Mesozoic Igneous Activity in the Inner Zone of Southwest Japan. Thus, the Late Cretaceous Shimanto Supergroup represents one type of the forearc sedimentation in magmatic arc-trench system. The difference of clastic composition between the Cretaceous and the Paleogene is explained by the unroofing process of the Cretaceous magmatic terrane. Lastly, the geotectonic development of the Shimanto Belt and its provenance is discussed mainly based on the sedimentological analyses. The marginal sea setting similar to the present Philippine Sea is considered to be preferable for the Shimanto geosyncline

An oceanic fragment in the Upper Cretaceous Miyama Formation of the Shimanto Belt, Kii Peninsula, Japan

An oceanic fragment comprising a complete pelagic sequence from basalt through chert to red shale was found in the Miyama Formation of the Shimanto Belt which is a typical accretion complex in Japan. The conformable sequence, from base, consists of MORB-type basalt, micritic limestone, CCH-type chert, TCH-type chert, MCH-type chert and red shale. CCH chert is alternating beds of calcareous chert and opaque-tuffaceous layers. TCH chert is non-calcareous interbedded chert with opaque-tuffaceous parting. MCH chert is bedded chert intercalated with clay parting. Radiolarian biostratigraphy confirmed that the sequence was continuous from Hauterivian-Barremian to Turonian-early Coniacian time. There also are systematic changes in geochemistry such as decreasing of negative Ce anomaly. These continuous changes of lithology might be due to the changes of depositional regime, that is, from the mid-oceanic ridge, ridge proximal regime above CCD, a slightly distant regime from the ridge, distant regime from ridge and approaching to a contiment, and continental margin regime where hemipelagic sediments accumulated. The depositional regime had moved away from a mid-oceanic ridge to near a trench by ocean spreading in Paleopacific ocean. The complete sequence provides kcy information to reconstruct the original situations of chert and accretion complex in the Shimanto Belt. MORB型の玄武岩から, ミクライト質石灰岩・層状チャートを経て, 半遠洋性の赤色泥岩にいたる連続的な遠洋性堆積物の重なりが, 紀伊半島の上部白亜系美山層中に見いだされた。チャートは, 下位からCCH, TCH, MCHの3つのタイプに岩質上細分される。CCH型は, 石灰質チャートと不透明鉱物に富む凝灰質層との互層であり, TCH型は非石灰質のチャートと不透明鉱物に富む凝灰質層と互層である。MCH型は非石灰質チャートと粘土鉱物を主体とする泥質薄層との繰り返しである。これらの重なりは, 放散虫化石の検討により, Hauterivian-BarremianからTuronian-early Coniacianにかけての連続した堆積物であることが確認された。また, 化学組成の検討から, Ceの負異常が系統的に減少していくことも認められた。このような岩質および化学組成の系統的な変化は, もともと中央海嶺付近にあった堆積場が, 古太平洋の海洋拡大によって徐々に中央海嶺から離れ, 水深を増加させてCCDよりも深くなり, かつ, 徐々に陸域に近づいていった過程を反映したものと解釈される。この遠洋性の重なりをもった海洋地殻の断片は, 四万十帯堆積物の起源や付加過程の解明に重要な情報をもたらすものである。Article地質学論集. 48:100-109 (1997)journal articl

OCCURRENCE OF CRETACEOUS SHALLOW-SEA BIVALVES FROM THE NORTHERN BORDER OF SHIMANTO TERRAIN, KII PENINSULA, SOUTHWEST JAPAN

和歌山県清水町の湯川川下流, 湯川層砂岩よりSpondylus aff. decoratus, Plicatula aff. hanaii, Amphidonte cf. subhaliotoidea, Ostrea sp.などの二枚貝や, さんごCamalophyllia sp.が発見された。二枚貝は宮古統のものに類似し, 時代は古白亜紀とみなされる。厚殻, 付着, 固着性の二枚貝を主体とし, ごく浅い海の環境を示している。これは砂岩の堆積学的研究からも支持される。周囲はやや深い地向斜性の堆積層であるが, このような浅海性の地層の存在は, 海底地辷りによるものではなく, 海水準の相対的変化によるものと結論した。 Bivalve fossils collected from the northern border of the Shimanto Terrain are characterised by shallow marine species, such as Spondylus aff. decoratus, Plicatula aff. hanaii, Amphidonte cf. subhaliotoidea, Rastellum? sp., Ostrea sp. and others, the age of which is considered to be early Cretaceous. The fossilbearing sandstones also show a shallow shelf environment, while the surrounding sandstones indicate turbidity current origin under bathyal environment. The presence of shallow-sea sediments among the turbidite sequence is explained by sealevel change and not by submarine slide of the shallow-sea sediments.Article日本古生物学会報告・紀事 新篇. 113:15-29 (1979)journal articl