著者

横山 芳春 安藤 寿男 大井 信三 山田 美隆

出版者

The Sedimentological Society of Japan

雑誌

堆積学研究 (ISSN:1342310X)

巻号頁・発行日

vol.54, no.54, pp.9-20, 2001-12-25 (Released:2010-05-27)

参考文献数

25

被引用文献数

2

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茨城県石岡-鉾田地域における下総層群“見和層”を対象に詳細な堆積相解析, 侵食面・火山灰鍵層の追跡を行った結果, 2回の堆積サイクルの存在が確認できた. 下位のサイクル1は西部の大規模な谷地形を充填する開析谷埋積システムと, これを覆って調査地域全域に分布する外浜-海浜システムの堆積物からなる. サイクル2ではバリアー島・潟システムの堆積物が特徴的に発達し西部で厚く保存されているが, 東部では外浜-海浜システムの堆積物がこれを覆って分布している. 常総層は主に河川システムの堆積物からなるが, 調査地域東部では下部に海成層が認められた. シーケンス層序学的解釈を行った結果, サイクル1にはシーケンス境界 (SB1), 内湾ラビンメント面 (BRS1), 波浪ラビンメント面 (WRS1) の3枚の侵食面が認められ, サイクル2にはSB2, BRS2, WRS2, SB3の4枚の侵食面が認められた. それぞれの堆積サイクルにはTST, HSTが認められ, 2回の相対海水準変動に伴う堆積シーケンスを構成していることが判明した.

著者

大森 光 安藤 寿男 村宮 悠介 歌川 史哲 隈 隆成 吉田 英一

出版者

一般社団法人 日本地質学会

雑誌

地質学雑誌 (ISSN:00167630)

巻号頁・発行日

vol.129, no.1, pp.105-124, 2023-02-22 (Released:2023-02-21)

参考文献数

70

被引用文献数

1 2

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いわき市アンモナイトセンターの双葉層群足沢層大久川部層(コニアシアン下部)のアンモナイト(主に径40-60 cmのMesopuzosia yubarensis)密集層と直下にある炭酸塩コンクリーション濃集層の,堆積相・産状観察と地球化学分析から形成過程を考察した.M. yubarensisは,沖合いの生息場から死後浮遊で沿岸に達した軟体部の失われた殻が,ストーム波浪で住房部が破壊され,分級・集積・運搬され,下部外浜沖合い側で癒着HCS極細粒砂層のハンモックマウンドに沿って急速に埋積した.炭酸塩コンクリーションは,多様なサイズ(径15-194 cm)の長-扁球形で,密集しながらも比較的一様に分布する.コンクリーションの形成は,ストーム波浪で運搬された有機物と底質中のベントス遺骸の分解に伴って堆積物の浅所で始まり,その後,埋没に伴い堆積物深所におけるメタン生成帯での有機物分解が生じるまで継続した.

著者

横山 芳春 大井 信三 中里 裕臣 安藤 寿男

出版者

The Sedimentological Society of Japan

雑誌

堆積学研究 (ISSN:1342310X)

巻号頁・発行日

vol.55, no.55, pp.17-28, 2002-11-20 (Released:2010-05-27)

参考文献数

34

被引用文献数

3

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茨城県東茨城台地西部において下総層群“見和層”及び涸沼段丘礫層を対象に堆積相解析, 火山灰鍵層の対比および地形学的考察を行った結果, 以下のことが判明した. 本地域の層序は,“見和層”サイクル1,“見和層”サイクル2, 涸沼段丘礫層に区分することができる.“見和層”サイクル1は泥質なエスチュアリー成堆積物から形成され, 古涸沼川が形成した開析谷とその埋積物からなる.“見和層”サイクル2は, 上位段丘面を構成し. 東茨城台地西部で内湾成の堆積相が, 東部で外洋成の堆積相が発達することから, 潟・バリアー島システムによって形成された可能性が高い. 潟・バリアー島システムを反映した堆積相分布は, 離水後の微地形や水系発達に大きな影響を与えた. すなわち, バリアー島内湾側では潟の泥質堆積物が保存され, 広く浅い谷が形成された. さらに, 泥質堆積物は水系分布を制約し, 扇状の分岐や大きく屈曲する水系が形成された. 一方, 外洋側では浜堤平野を形成した浜堤列群が保存され, 北東から南西方向の浅い谷の凹地と微高地の凸地が発達したものと解釈される.

著者

安藤 寿男 勢司 理生 大島 光春 松丸 哲也

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.104, no.2, pp.284-303, 1995-04-25 (Released:2009-11-12)

参考文献数

38

被引用文献数

14 23

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The Futaba Group is the Lower Coniacian to Lower Santonian, fluvial to shallow-marine sedimentary succession distributed in the southern Abukuma Belt in north Honshu. Fifteen depositional facies were discriminated. They include alluvial fan, meandering river, braided river, transgressive lag and upper shoreface to inner shelf sediments. It is divided into three formations, the Ashizawa (the Asamigawa and Obisagawa Members), Kasamatsu and Tamayama Formations in upward sequence. Each formation consists of a third-order depositional sequence (DS).The first depositional sequence (DS 1) has a lowstand systems tract (LST) as the lower main part of the Asamigawa Member distributed in the northern half of the area. It is lithologically characterized by upper alluvial fan conglomerate and mid to lower fan sandstone and siltstone nonconformably overlying lower Cretaceous granite (sequence boundary 1 : SB 1). In the southern periphery of the distributed area the member contains talus or upper fan angular conglomerate. The upper part of the member distributed over the area is interpreted to be transgressive conglomerate with a sharp base called a ravinement surface (RS 1) which was formed by transgressive shoreface erosion. It may represent transgressive systems tract (TST). The following highstand systems tract (HST) is represented by the upper shoreface to inner shelf, medium to fine sandstone of the Obisagawa Member.The Kasamatsu Formation (DS 2) unconformably (SB 2) overlying the preceding depositional sequence (DS 1), is substantially characterized by fluvial upward-fining successions composed of channel sandstone and flood plain siltstone. The third sequence (DS 3) is characterized by thick fluvial (braided river) sandstone of the lower to middle part of the Tamayama Formation interpreted as LST and the upper shoreface to inner shelf sandstone of the upper Tamayama interpreted as HST. The sudden lithofacies change between the Kasamatsu and Tamayama Formations implies some large-scale changes in fluvial depositional systems by sea-level fall (SB 3). The transgressive conglomerate just above RS 2 in the basal part of the upper Tamayama Formation represents a thin TST. The upper sequence boundary (SB 4) of DS 3 shows the conspicuous clinounconformity between the Futaba Group and the Paleogene Shiramizu Group.

著者

横山 芳春 安藤 寿男 橋本 聡子

出版者

日本古生物学会

雑誌

化石 (ISSN:00229202)

巻号頁・発行日

no.76, pp.32-45, 2004-09-22

被引用文献数

1

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Large oyster shell beds are contained in incised-valley fill deposits of the Cycle 1 of the Miwa Formation, Shimosa Group, Lake Kasumigaura area, Ibaraki Prefecture . This paper describes taphonomic processes of large oyster shell beds well exposed in three localities . Six shell bed types can be recognized on the basis of their lithology, sedimentary facies, mode of fossil occurrence and associated fossils : 1) autochthonous aggregated, 2) autochthonous scattered, 3) parautochthonous aggregated, 4) cross-bedded aggregated, 5) crossbedded scattered and 6) shell-fragment aggregated types. The large oyster shell bed higher than 5 m and wider than 30 m at east Hama (Loc. 1) is characterized by type 1 with two layers of type 3 five to 20 cm thick that seem to have formed by sudden storm events. The second shell bed at west Hama (Loc. 2) shows two mounds 3 m high and or wider than 7-10 m composed of type 1 and covered by massive muddy sediments. This means that the oyster banks were buried under estuary mud. The last example at Sakihama (Loc.3) is the largest oyster shell bed in this area with height of 5m and width of 70m. It can be divided into three unit bounded by two erosional surfaces. The unit I is composed mainly of type 1 representing in situ oyster reefs, and subordinately of 3 formed by reworking through tidal current. The unit II composed of types 4 and 5 forms a shallow channelfilled structure that seems to have been formed as a tidal channel. The overlying unit III above a flat erosional surface mostly consists of type 6. Reworked oyster shell fragments might have concentrated intermittently and condensed through muddy sediment bypassing within tidal flat to embayment.

著者

大井 信三 横山 芳春 西連地 信男 安藤 寿男

出版者

一般社団法人 日本地質学会

雑誌

地質学雑誌 (ISSN:00167630)

巻号頁・発行日

vol.119, no.7, pp.488-505, 2013-07-15 (Released:2013-11-02)

参考文献数

47

被引用文献数

1 2

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茨城県常陸台地を構成する下総層群の層序区分については,房総半島との対比が確立されておらず,研究者の意見の一致をみていない.本論では特に層序的な問題が多い木下層について,テフラの岩相と岩石記載,屈折率や火山ガラスの主成分化学組成を分析し,それらに基づいて給源火山域および鹿島沖海底コア(MD01-2421)中のテフラと広域対比を試みた.対比および対比の可能性のあるテフラは,ArPはNk-Yt,OiPはNk-Nm,ObはTAu-9,KtPと鹿島沖海底コアTephra20(1)である.広域対比の結果,ArP,TAu-9がMIS 5e前期,OiPがMIS 5e最盛期,KtPがMIS 5d初期に降灰したとみなされる.これによって,木下層剣尺部層の堆積年代がMIS 6~MIS 5e,行方部層がMIS 5d初期であると解釈される.

著者

安藤 寿男

出版者

一般社団法人 日本地質学会

雑誌

地質学雑誌 (ISSN:00167630)

巻号頁・発行日

vol.112, no.1, pp.84-97, 2006 (Released:2006-05-01)

参考文献数

95

被引用文献数

7 8

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関東平野東端には下部白亜系銚子層群,最上部白亜系那珂湊層群,古第三系大洗層が孤立して分布し,東北日本,西南日本の地帯構造を考える上で重要な情報をもたらす.3つの地層群の研究の現状をまとめた上で,それらの地質学的意義を考察した.東北日本の蝦夷堆積盆の北上および常磐亜堆積盆における上部アプチアン以上の白亜系~古第三系には,時代・層序・堆積相の上で3地層群に比較可能な地層は見られない.銚子層群は層序分布から関東山地北部の西南日本外帯秩父帯の山中白亜系の東方延長と見なされる.那珂湊層群は西南日本内帯南縁の和泉層群との共通性が高い.大洗層は礫の放射年代,植物化石などから白亜系ではなく古第三系の可能性が高い.那珂湊層群と大洗層は棚倉構造線の南方延長の破砕帯に含まれた古期岩類の断層隆起地塊をなしており,西南日本の要素と見なされる.大洗層は,関東山地北部の寄居層および神農原層とに対比できる可能性がある.

著者

国府田 良樹 小池 渉 安藤 寿男 上野 輝彌 碓井 和幸

出版者

日本古生物学会

雑誌

化石 (ISSN:00229202)

巻号頁・発行日

vol.81, pp.1-2, 2007-03-30 (Released:2017-10-03)

参考文献数

2

被引用文献数

1

著者

平野 弘道 安藤 寿男

出版者

石油技術協会

雑誌

石油技術協会誌 (ISSN:03709868)

巻号頁・発行日

vol.71, no.3, pp.305-315, 2006-05-01 (Released:2007-11-01)

参考文献数

63

被引用文献数

4 2

---

Thirty years passed since the Cretaceous Oceanic Anoxic Events were proposed by Schlanger and Jenkyns (1976). Three events, OAE1 to 3 were recognized at the beginning of the research. Nowadays, however, OAE1 is subdivided into four subevents, OAE1a, b, c, and d. The OAE1b subevent is further subdivided into three components, Jacob, Paquier, and Leenhardt. The existence of Mid-Cenomanian Event (MCE) between OAE1d and OAE2 is drawing attentions of world scientists. A concise review of the researches on these events and subevents is followed by more detailed descriptions of the synonymy (local names), geographic distribution, age, stable carbon isotope fluctuations, extinction and/or radiation of fossils, major synchronous events, characteristics including the duration and the types of kerogen, and their causal factors. It is recognized that all OAEs do not have the same causal factor. The western part of the Tethys and the narrower early Atlantic were rather closed basins, where anoxic to dysoxic conditions easily occurred through the stratification of water column by run off, like the Sapropel event 1 in the Holocene Mediterranean Sea. The Cretaceous global OAEs may have occurred either by the stagnation of the deep water associated with the global warming or by propagation of marine organisms. Due to a large amount of input of terrestrial siliciclasitics, the regional influence of OAEs in the Japanese Cretaceous strata may differ from that of the Tethyan/Atlantic region, even if the occurrence of OAEs is ocean wide or globally synchronous.

著者

横山 芳春 安藤 寿男 橋本 聡子

出版者

日本古生物学会

雑誌

化石 (ISSN:00229202)

巻号頁・発行日

vol.76, pp.32-45, 2004

参考文献数

52

被引用文献数

1

---

Large oyster shell beds are contained in incised-valley fill deposits of the Cycle 1 of the Miwa Formation, Shimosa Group, Lake Kasumigaura area, Ibaraki Prefecture . This paper describes taphonomic processes of large oyster shell beds well exposed in three localities . Six shell bed types can be recognized on the basis of their lithology, sedimentary facies, mode of fossil occurrence and associated fossils : 1) autochthonous aggregated, 2) autochthonous scattered, 3) parautochthonous aggregated, 4) cross-bedded aggregated, 5) crossbedded scattered and 6) shell-fragment aggregated types. The large oyster shell bed higher than 5 m and wider than 30 m at east Hama (Loc. 1) is characterized by type 1 with two layers of type 3 five to 20 cm thick that seem to have formed by sudden storm events. The second shell bed at west Hama (Loc. 2) shows two mounds 3 m high and or wider than 7-10 m composed of type 1 and covered by massive muddy sediments. This means that the oyster banks were buried under estuary mud. The last example at Sakihama (Loc.3) is the largest oyster shell bed in this area with height of 5m and width of 70m. It can be divided into three unit bounded by two erosional surfaces. The unit I is composed mainly of type 1 representing in situ oyster reefs, and subordinately of 3 formed by reworking through tidal current. The unit II composed of types 4 and 5 forms a shallow channelfilled structure that seems to have been formed as a tidal channel. The overlying unit III above a flat erosional surface mostly consists of type 6. Reworked oyster shell fragments might have concentrated intermittently and condensed through muddy sediment bypassing within tidal flat to embayment.

著者

安藤 寿男 近藤 康生

出版者

日本古生物学会

雑誌

化石 (ISSN:00229202)

巻号頁・発行日

vol.45, pp.35-38, 1988-12-15 (Released:2017-10-03)

著者

安藤 寿男 田口 翔太 森野 善広

出版者

一般社団法人 日本地質学会

雑誌

地質学雑誌 (ISSN:00167630)

巻号頁・発行日

vol.128, no.1, pp.475-499, 2022-12-29 (Released:2022-12-29)

参考文献数

55

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相馬中村層群中ノ沢層(上部ジュラ系)の館ノ沢砂岩部層は,砂質河川成の栃窪層に波浪ラビンメント面を介して重なる海進残留相から始まり,外洋浅海から内湾-ラグーンに至る上方浅海化を示す,海退性の砂質堆積物であり,数回の小規模な振動を伴う相対海水準の緩やかな上昇期に,珪質砕屑性堆積システムが前進することによってできた.小池石灰岩部層は,珪質砕屑物供給が停止することで成立した炭酸塩バリア-ラグーンシステムとして,東西数 km南北10 km超の炭酸塩プラットフォームを構成していた.分布全域に追跡される5層の上方細粒化堆積相累重(層厚数-10数m)は,バリア浅瀬→浅瀬後背→ラグーンへの変化をもたらした,5回の小規模な相対海水準変動による海退-海進の繰り返しで形成された.中ノ沢層はキンメリッジアンからチトニアン前期の第2オーダー高海水準期に,第3オーダー海水準変動周期に対応して形成された可能性が指摘される.

著者

横山 芳春 七山 太 安藤 寿男 大塚 一広

出版者

日本古生物学会

雑誌

化石 (ISSN:00229202)

巻号頁・発行日

vol.74, pp.7-17, 2003-09-20 (Released:2017-10-03)

参考文献数

30

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伊予灘海域で採取された下灘コアの層相および軟体動物化石群を検討した結果は, 以下の4つにまとめられる.1.下灘コアの層相およびこれに含まれる軟体動物化石の解析結果に基づき, DU-A〜Eの5つの堆積ユニットを識別した.このうち最下位のDU-Aを除く上位4ユニットには, 海成粘土層が発達する.2.下灘コア中に認められる軟体動物化石群は, 松島(1984)の区分した感潮域, 干潟, 内湾停滞域, 内湾泥底および沿岸砂泥底の5つの群集の構成種からなる.さらに土石流堆積物には複数の群集構成種が混合した化石群が認められる.3.堆積ユニットごとに見ると, DU-Bには感潮域化石群, DU-Cには感潮域化石群および干潟化石群が認められ, 縄文海進に伴って感潮域〜干潟が拡大したことを反映しているものと解釈される.DU-Dは内湾停滞域化石群が認められ, 水塊の交換に乏しい内湾の停滞水域下で堆積したものと考えられる.DU-Eには内湾泥底〜沿岸砂泥底化石群が認められ, 下位より潮通しの良い内湾環境下で堆積したものであろう.4.下灘沖において海水が侵入し, エスチュアリー〜干潟環境が成立, 感潮域群集の構成種が出現した年代は約12000〜11000年前以前であろう.約10000年前には急激な相対海水準上昇が生じたため, 感潮域群集および干潟群集が内湾停滞域群集へ急速に群集変化したのであろう.これは地震イベントに伴って, 下灘沖の地溝帯が急激に沈降したことによる可能性が高い.約10000年〜8000年前には, 内湾停滞域群集が発達する閉鎖的な内湾停滞域が形成され, 周囲の河川から流入した細粒物質が大きな堆積速度をもって沈積していた.約8000年前以降は内湾泥底〜沿岸砂泥底群集が生息する潮通しの良い内湾環境へと変化したが, これは地溝帯の埋積と同時に瀬戸内海の成立に伴ったものである可能性が示唆される.

著者

安藤 寿男

出版者

日本古生物学会

雑誌

化石 (ISSN:00229202)

巻号頁・発行日

vol.96, pp.41-43, 2014

著者

平野 弘道 安藤 寿男

出版者

石油技術協会

雑誌

石油技術協会誌 (ISSN:03709868)

巻号頁・発行日

vol.71, no.3, pp.305-315, 2006-05-01

参考文献数

63

被引用文献数

2 2

---

Thirty years passed since the Cretaceous Oceanic Anoxic Events were proposed by Schlanger and Jenkyns (1976). Three events, OAE1 to 3 were recognized at the beginning of the research. Nowadays, however, OAE1 is subdivided into four subevents, OAE1a, b, c, and d. The OAE1b subevent is further subdivided into three components, Jacob, Paquier, and Leenhardt. The existence of Mid-Cenomanian Event (MCE) between OAE1d and OAE2 is drawing attentions of world scientists. A concise review of the researches on these events and subevents is followed by more detailed descriptions of the synonymy (local names), geographic distribution, age, stable carbon isotope fluctuations, extinction and/or radiation of fossils, major synchronous events, characteristics including the duration and the types of kerogen, and their causal factors. It is recognized that all OAEs do not have the same causal factor. The western part of the Tethys and the narrower early Atlantic were rather closed basins, where anoxic to dysoxic conditions easily occurred through the stratification of water column by run off, like the Sapropel event 1 in the Holocene Mediterranean Sea. The Cretaceous global OAEs may have occurred either by the stagnation of the deep water associated with the global warming or by propagation of marine organisms. Due to a large amount of input of terrestrial siliciclasitics, the regional influence of OAEs in the Japanese Cretaceous strata may differ from that of the Tethyan/Atlantic region, even if the occurrence of OAEs is ocean wide or globally synchronous.

著者

横山 芳春 安藤 寿男 橋本 聡子

出版者

日本古生物学会

雑誌

化石 (ISSN:00229202)

巻号頁・発行日

vol.76, pp.32-45, 2004-09-22 (Released:2017-10-03)

被引用文献数

1

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Large oyster shell beds are contained in incised-valley fill deposits of the Cycle 1 of the Miwa Formation, Shimosa Group, Lake Kasumigaura area, Ibaraki Prefecture . This paper describes taphonomic processes of large oyster shell beds well exposed in three localities . Six shell bed types can be recognized on the basis of their lithology, sedimentary facies, mode of fossil occurrence and associated fossils : 1) autochthonous aggregated, 2) autochthonous scattered, 3) parautochthonous aggregated, 4) cross-bedded aggregated, 5) crossbedded scattered and 6) shell-fragment aggregated types. The large oyster shell bed higher than 5 m and wider than 30 m at east Hama (Loc. 1) is characterized by type 1 with two layers of type 3 five to 20 cm thick that seem to have formed by sudden storm events. The second shell bed at west Hama (Loc. 2) shows two mounds 3 m high and or wider than 7-10 m composed of type 1 and covered by massive muddy sediments. This means that the oyster banks were buried under estuary mud. The last example at Sakihama (Loc.3) is the largest oyster shell bed in this area with height of 5m and width of 70m. It can be divided into three unit bounded by two erosional surfaces. The unit I is composed mainly of type 1 representing in situ oyster reefs, and subordinately of 3 formed by reworking through tidal current. The unit II composed of types 4 and 5 forms a shallow channelfilled structure that seems to have been formed as a tidal channel. The overlying unit III above a flat erosional surface mostly consists of type 6. Reworked oyster shell fragments might have concentrated intermittently and condensed through muddy sediment bypassing within tidal flat to embayment.

著者

安藤 寿男

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.99, no.3, pp.247-262, 1990-06-25 (Released:2009-11-12)

参考文献数

49

被引用文献数

1

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The depositional sequence concept was established in newly developed sequence stratigraphy, as an unconformity-bounded stratigraphic unit formed during one complete sea-level cycle. This paper reviews general meanings of “sequence”, the definition of depositional sequences, their hierarchial patterns and recognition, and sequence boundaries problems, from a viewpoint of sedimentary geology based on outcrops and bore-hole samples.Though the word, “sequence” has many meanings generally applied to successive geologic events and processes in chronologic order, a depositional sequence is defined in a special sense, as “a relatively conformable succession of genetically related strata bounded at its top and base by unconformities and their correlative conformities”. The depositional sequence as one of hierarchial transgressive and regressive units (T-R units), has the first- to forth-order operational units, that is, the megasequence, supersequence, sequence and parasequence in descending order. A sequence boundary with a significant hiatus (=unconformity) is formed by subaerial exposure, concurrent subaerial erosion and partly submarine erosion during eustatic falls or low-stand sea level.The latter half of this paper emphasizes the difference between sequence boundaries and ravinement surfaces. The ravinement surface formed as one of diastems or “transgressive surfaces”, is an erosional surface by shoreface retreat during the following transgression after a sea-level fall. In general, it is lithologically more distinct than the underlying sequence boundary. The right recognition of the difference leads correct reconstructions of sedimentary history.

著者

安藤 寿男

出版者

一般社団法人 日本地質学会

雑誌

日本地質学会学術大会講演要旨 第104年学術大会(97'福岡) (ISSN:13483935)

巻号頁・発行日

pp.340, 1997-09-30 (Released:2017-08-24)

著者

安藤 寿男

出版者

The Sedimentological Society of Japan

雑誌

堆積学研究会報 (ISSN:18844715)

巻号頁・発行日

vol.38, no.38, pp.45-52, 1993-03-30 (Released:2010-05-27)

参考文献数

22

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The Hakubuchi Group is the uppermost unit of the Yezo Supergroup, a forearc basin sediment distributed along the meridional zone of Hokkaido, Japan. The group in the Sorachi Anticline represents the western marginal facies of the basin, showing conspicuous lateral facies changes. It is subdivided into three formations, Hk1, Hk2 and Hk3, based on the facies distribution. The upward shallowing succession of Hk1 and Hk2 in the eastern limb of the anticline, which is composed of inner shelf to delta plain facies through shoreface, foreshore and beach facies, is interpreted to be a lowstand delta on a conformable sequence boundary. The massive conglomerate facies constituting very thick Hk2 in the western limb and only the uppermost of Hk2 in the eastern limb, may be a transgressive systems tract. The base of the conglomerate in the wester limb corresponds to an erosional sequence boundary. A highstand systems tract is represented by Hk3 distributed widely in both limbs. The upper two parasequences of the three recognized in Hk3 had been partly eroded away under a sequence boundary (clinounconformity) with the Eocene coal measures, Ishikari Group. Therefore, the Hakobuchi Group constitutes a depositional sequence during 10m.y. (Lower Camapanian-Lower Maastrichtian).

著者

安藤 寿男 栗原 憲一 高橋 賢一

出版者

一般社団法人 日本地質学会

雑誌

地質学雑誌 (ISSN:00167630)

巻号頁・発行日

vol.113, pp.S185-S203, 2007

被引用文献数

3

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北海道中軸部の空知-蝦夷帯に広く分布する蝦夷層群は,白亜紀アプチアン~古第三紀暁新世の間に,サハリン南部から本州中部鹿島沖にまで続いた長大な前弧堆積盆にもたらされた堆積物で,北東アジアの海成層の模式層序となっており,当時の古環境変遷を復元するには重要な地層である.この巡検では,蝦夷層群が層序的に厚くかつ広域に分布する三笠-夕張地域において,陸海断面方向や時間層序学的にどのような堆積相変化を示すのかに注目して,セノマニアン~チューロニアン階の三笠層と佐久層,およびカンパニアン~暁新統の函淵層を中心に見学する.三笠層と函淵層では,様々な堆積構造を観察した上で,河川~浅海成堆積相や堆積シーケンスの特徴を把握する.また,三笠層の浅海生軟体動物群集やそのタフォノミーについても注目する.一方,東方同時異相である佐久層では,沖合成の泥質岩相やタービダイト相に加えて,セノマニアン/チューロニアン境界の海洋無酸素事変層準やアンモナイト群集の特徴も取り上げる.さらに,白亜紀のアンモナイトコレクションを三笠市立博物館で,古第三系始新統石狩層群の石炭層を夕張市石炭博物館で見学する.