Diatom assemblages indicative of the lower part of the Crucidenticula kanayae Zone were found in three carbonate concretions collected from the basal part of the Miocene Kamikineusu Formation in southern central Hokkaido. In spite of the fact that the formation has been correlated with the Middle Miocene Kawabata Formation in central Hokkaido on the basis of molluscan evidence, the diatom analysis clarified that the geologic age of the basal part of the formation is 16.9 to 16.7 Ma, latest Early Miocene. The new age data of the Kamikineusu Formation provides some geochronological constraints on the geological history in southern central Hokkaido. Firstly, in the southern part of the Hidaka belt, a part of the Hidaka Supergroup became exposed by an uplift by the latest Early Miocene. Secondly, a transgression occurred in the latest Early Miocene when the sedimentary basin of the Kamikineusu Formation was formed. Thirdly, at least the basal part of the Kamikineusu Formation is correlated with the Takinoue Formation in the Yubari district.

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New and useful reactions utilizing the characteristics of gem-dihalocyclopropanes and halocyclopropanes are developed from the many-sided cationic approaches toward versatile benzannulations. Regioselective and alternative naphthalene-benzannulations of aryl (gem-dihalogenocyclopropyl) methanols and Aryl¹ (aryl²) (gem-dichlorocyclopropyl) methanols were performed for the syntheses of various types of both “symmetrically” and “unsymmetrically” substituted and α-and β-halogenonaphthalenes by choosing either the order of the reaction sequences or the catalysts. Sequential and regioselective Friedel-Crafts reactions (naphthol-benzannulations) of gem-dichlorocyclopropanecarbonyl chlorides produced various 4-aryl-1-naphthol derivatives straightforwardly (in a one-pot manner) via significantly different mechanisms from the related naphthalene-benzannulations. These utilities could be demonstrated by the total synthesis of five natural lignan lactones and their analogs. A related 2, 5-diaryl-furan syntheses, a novel cyclopropane-shift type benzannulation, and a unique chirality transfer from optically active gem-dichlorocyclopropanes into atropisomeric 1-arylnaphthalenes were also described. The variation in a variety of reactions is unequivocally due to the high degree of site-selectivity in the cyclopropane-ring-openings of the three bonds (bonds A, B, and C).

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The collision of the Kuril arc against the Northeast Japan arc has made a conspicuous crustal structure from the Hidaka mountain range to the Ishikari-Tomakomai lowland, Hokkaido, Japan, since Miocene. Recent advance of deep seismic reflection studies has revealed that the Kuril arc lithosphere is delaminated at about 23km deep in the lower crust in the Hidaka collision zone. The upper half of the lithosphere (upper crust+upper portion of the lower crust) is thrust westward on the Northeast Japan arc, whereas the lower half (lower portion of the lower crust+upper mantle) descends down. The wedge of the Northeast Japan arc lithosphere intrudes eastward into the delaminated Kuril arc lithosphere. The structure is called as a “delamination-wedge structure”. In the western foreland area of the Hidaka mountain range, the west-verging fold-and-thrust belt occurs more than 70km wide involving the pre-Tertiary strata. The activity of the belt has shifted westward since the initiation of the collision. The shortening length in the foreland fold-and-thrust belt is about 60km, which is nearly equal to the delamination-wedge length toward the colliding direction. The two lines of evidence mentioned above, the westward shift of the activity and the coincidence of both lengths, indicate that the fold-and-thrust belt has been growing associated directly with the formation of the delamination-wedge structure.

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東北日本弧と千島弧の間に形成された日高衝突帯の前縁部では，ジュラ紀末～白亜紀の前弧海盆堆積物および付加体が広い面積を占める．これらは，初生的には広域的かつ低角なパイルナップ構造をとっていたと考えられる．ナップユニットは，一部に横ずれデュープレックスが形成されたほかは，主として褶曲による構造再配列を被っている．2つの主要な背斜構造のそれぞれで，軸を挟んで非対称な岩相分布を示すことから，これら背斜構造の地下に剥ぎ取り衝上断層のランプが推定される．イドンナップ帯周辺では未成熟な前弧地殻がめくれ上がっていると考えられ，落差10 km近い大規模なランプによって持ち上げられたと推察される．日高主衝上断層は，このランプから派生したのであろう．一方神居古潭帯周辺では，恐らく落差4～5 kmのランプにより，低温高圧変成を受けた付加体と被覆層がアンチフォームを形成したと考えられる．

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Interpretation of a seismic reflection profile across a metamorphic belt based on acoustic impedance measurements of exhumed metamorphic rocks is illustrated with an example of the Hidaka metamorphic belt, where a part of the cross section through the ancient Kuril-arc crust (Hidaka crust) is exposed. A combined seismic reflection profile across the Hidaka metamorphic belt reveals the strongly reflective and laminated lower Hidaka crust as well as the relatively transparent upper Hidaka crust. The exposed Hidaka crust, i.e., Hidaka metamorphic Main Zone, is composed of amphibolite- to greenschist-facies felsic rocks in its upper main part, while mainly of granulite-facies amphibolite frequently intercalated with felsic rocks in its basal part. Acoustic impedance values of representative rock samples of the exposed Hidaka crust show an overall similarity in the upper main part, but significant fluctuations in the basal part due to interlayering of amphibolite and felsic rocks. The seismically transparent upper Hidaka crust is therefore attributable to the dominance of felsic rocks, while the strongly reflective and laminated lower Hidaka crust is likely due to interlayering of amphibolite and felsic rocks, which is verified by 1D seismic reflection modeling based on the acoustic impedance structures of the exposed Hidaka crust.

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The western offshore area of the Oki Islands is evaluated as one of promising area for oil and gas exploration, because of the thick accumulation of sedimentary rock based on the results of seismic surveys. To establish the chronostratigraphic framework with high resolution in the area, the biostratigraphic study of fossil diatoms was carried out for the samples collected from the Miocene Kumi and Tsuma Formations mainly exposed in the national park in Dogo, Oki Islands, Shimane Prefecture.

The Crucidenticula kanayae Zone (16.6 - 17.0 Ma) was recognized from the samples about 10 m above the lowermost lacustrine Kumi Formation in the Kumi River, which indicates that the geologic evidence of the first marine invasion related to the Japan Sea spreading was recorded in the northern part of Dogo. The Zone including the biohorizon D33, the last occurrence of C. kanayae (16.7 Ma), was found in the Nogoshi section exposed in the northwestern part of the island. The stratigraphic change of diatom assemblage suggests a gentle transgressive trend through the C. kanayae Zone. The specimens of C. kanayae yielded from the Kumi Formation are identified as C. kanayae var. kanayae showing a wide range of morphological variation. The shallow marine sandstone is expected to be a good reservoir rock distributed in the lowstand systems tract correlated with the layer just above the C. kanayae zone.

The Crucidenticula nicobarica, Denticulopsis praedimorpha and Denticulopsis dimorpha Zones were recognized from the Kumi Formation in an about 10 m thick section in the Nagu Peninsula area of the southwestern part of the island. This suggests a condensed sequence developed from late Middle to early Late Miocene in the area. The sequence which is correlative with the black mudstone, the Utagi Mudstone Member, seems to have the highest source rock potential in the area. The lower Neodenticula kamtschatica Zone was recognized from the Igo Mudstone Member along the Nakanoura shore of the northern part of the Island. The Tsuma Formation showing lateral lithofacies changes in Dogo indicates low possibility of the cap rock existence for the unconformity play of the uppermost Kumi Formation.

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北海道中央部，トムラウシ地域の日高累層群中には，チカプペツ層と呼ばれる周囲の地層とは固結度の大きく異なる泥岩主体の地層の存在が知られていた．今回，チカプペツ層中の酸性凝灰岩とシイ十勝川層（新称）のタービダイト砂岩からジルコン粒子を分離し，ジルコンU-Pb年代を測定した結果，19.5±0.1Maと22.5±0.7Ma（前期中新世）を示す年代値が得られた．また，前者の石灰質ノジュール1試料から前期中新世を示す珪藻化石群集が得られたことから，その堆積年代は23-19Maと理解された．これまでも日高帯分布域には，後期漸新世の堆積年代を示す襟裳層や立牛層の挟在が明らかにされており，この時期に大規模な右横ずれ変位が開始されていたことが判明している．チカプペツ層やシイ十勝川層は，前期中新世に，同様の右横ずれ変位に伴って発生した海成層と考えられる．

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産炭地であった夕張は様々な地層と岩石が分布し地質学的魅力にあふれ，さらに日本における地質学の発展に大きな貢献をしてきた地域である．なかでも20世紀前半の夕張炭田地質構造の解明とクリッペ・ナッペの発見は，20世紀後半に日高造山論として結実し発展した．さらに，現在では地殻深部の探索，活構造や地形形成との関連，白亜紀以降の地球環境変遷と地層・資源形成の関連などが追及されている．
この見学コースでは，白亜系の最上部から夾炭層である古第三系をへて新第三系までの堆積岩を堆積学とシーケンス層序学の視点から観察する．

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