著者

石村 大輔 吉永 佑一 山田 圭太郎 原口 強 遠田 晋次

出版者

日本第四紀学会

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.56, no.6, pp.265-270, 2017-12-01 (Released:2018-02-17)

参考文献数

23

被引用文献数

2

著者

五十嵐 八枝子 五十嵐 恒夫 大丸 裕武 山田 治 宮城 豊彦 松下 勝秀 平松 和彦

出版者

Japan Association for Quaternary Research

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.32, no.2, pp.89-105, 1993-05-31 (Released:2009-08-21)

参考文献数

38

被引用文献数

31 37

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北海道北部の剣淵盆地と中央部富良野盆地で14C年代の測定と花粉分析により約32,000年間の植生変遷史を復元した. 25,000~32,000yrs BPはエゾマツ/アカエゾマツを主とし, グイマツを混じえたタイガ, 16,000~25,000yrs BP (極相期) は現在のサハリン北部に見られるステップとグイマツ, ハイマツを主とする疎林 (北部) およびグイマツ, ハイマツを主とするタイガ (中央部)が発達した. 12,000~16,000yrs BPは北部でグイマツが衰え, エゾマツ/アカエゾマツとカバノキを主とする森林が発達した. 10,000~12,000yrs BPに著しい寒さの戻り (剣淵亜氷期) があり, グイマツは極相期の規模に回復した. 8,000~10,000yrs BPにグイマツは絶滅し, 8,000yrs BPにコナラ属が急増して現在の森林が形成された.

著者

西村 裕一 宮地 直道 吉田 真理夫 村田 泰輔 中川 光弘

出版者

Japan Association for Quaternary Research

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.39, no.5, pp.451-460, 2000-10-01 (Released:2009-08-21)

参考文献数

31

被引用文献数

11 10

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北海道東部の霧多布湿原において,湿原堆積物の掘削調査から泥炭層中に連続する層厚3cm以下の砂層を発見した.この砂層は,海側から内陸側に向かって層厚や粒径を減じ,比較的層厚の大きな地点では級化構造を呈する.また,乾燥化や塩分濃度の低下に伴って発生する珪藻化石を産出することから,この砂層を津波堆積物と認定した.砂層の下位には泥炭層を挾み,1739年の樽前a火山灰(Ta-a)と1694年の駒ヶ岳C2火山灰(Ko-c2)の2層の火山灰層が確認された.これらの火山灰層の年代をもとに泥炭の堆積速度を求めたところ,この砂層の年代はおよそ1810~50年代と推定された.1843年に,北海道東部の厚岸を中心に46名の犠牲者を出した北海道南東岸沖地震津波の歴史記録があり,この津波の前後に規模の大きな津波が霧多布湿原一帯に押し寄せた記録はないことから,本砂層は1843年の津波によりもたらされた堆積物と考えられる.

著者

大森 博雄 柳町 治

出版者

Japan Association for Quaternary Research

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.30, no.1, pp.1-18, 1991-02-28 (Released:2009-08-21)

参考文献数

24

被引用文献数

1 1

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The subalpine zones on the mountains south of the Tohoku mountains in the Japanese Islands are normally occupied by coniferous forests dominated by Abies mariesii, A. veitchii, Picea jezoensis var. hondoensis and Tsuga diversifolia. But there are many mountains where the subalpine coniferous forest does not exist; the thermometrical subalpine zones on such mountains are replaced by subalpine and/or montane deciduous broad-leaved forests. Especially in the Tohoku mountains, the subalpine zone without A. mariesii forest is called the “pseudo-alpine zone”, where Quercus scrub usually dominates. The origin of the pseudo-alpine zone is discussed here based on the thermal conditions of subalpine main tree species and the rise in temperature during the Hypsithermal climax phase.The thermometrical zone for A. mariesii is divided into four ranges as shown in Fig. 5-b. The mountains whose peaks are thermometrically in zones B and C can be regarded as mountains where A. mariesii is alternatively indigenous or not indigenous under the present thermal conditions. On the mountains whose peaks are in zone A, A. mariesii is expected to be indigenous. Thus, the mountains in zone A but without A. mariesii forest are called the “A. mariesii-lacking mountains” and are examined here.For the “A. mariesii-lacking mountains”, the thermal conditions at their peaks were out of zone A and into zones B and/or C during the Hypsithermal climax phase, when the mean summer temperature rose to be 2.5°C higher than that at present in Japan. During the high-temperature period of the Hypsithermal, the habitat of A. mariesii was pushed over the mountain peak due to the upward migration of vegetation zones. Thus, the principal cause of the pseudo-alpine zone is the ‘pushing-out effect’ caused by the rise of temperature. The origin of the subalpine zones without subalpine coniferous forest in West Japan is also considered to be the same process as the pseudo-alpine zone in the Tohoku mountains. The lacking of a tree species on a mountain depends on a process in which the thermal conditions suitable for the species disappeared from the mountain during a period in the history of climatic changes and, since the event, the thermal habitat of the species has been isolated from the surrounding mountains with forests of the same species. The present features of distribution of the subalpine tree species which grow under cold climatic conditions on high mountain areas in Japan have been affected by the small changes (2 or 3°C) in temperature during the Holocene, reflecting the topographical mosaic built up by many small mountain blocks and inter-lowlands.

著者

貝塚 爽平

出版者

Japan Association for Quaternary Research

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.23, no.2, pp.55-70_1, 1984-07-31 (Released:2009-08-21)

参考文献数

98

被引用文献数

19 18

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Landforms in and around the South Fossa Magna, which are shown in Figs. 2 and 3, and the history of their growth during the late Cenozoic are described. The pattern of the tectonic landforms and the history of their growth are explained by a tectonic model shown in Fig. 5.The South Fossa Magna consists mainly of strongly folded and thrust Neogene and Quaternary strata along the subduction and collision zone between the overriding Eurasian plate (or the Eurasian and North American plates) and the subducting Philippine Sea plate. The collision occurred on the north of the Izu Peninsula during the past 1-0.5 Ma. The characteristic landform in the folded zone is flights of elongated domes or ridges, called outer ridges.There are three areas with different topography and tectonic history in central Honshu to the north of the plate boundary; they are, from west to east, 1) the Akaishi Mts-Tokai lowland and offshore area, 2) the Kanto Mts-Misaka Mts-Tanzawa Mts area, and 3) the Kanto Plain-Miura-Boso Hills and their offshore area. To the south of the plate boundary, there are three different belts in the northeastern part of the Philippine Sea (PHS) plate; they are, from west to east, i) the Shikoku Basin, ii) the inner volcanic arc (Izu Inner Bar), and iii) the outer non-volcanic arc (Izu Outer Bar) of the Izu-Bonin arc.The PHS plate moved to the north after the spreading of the Shikoku Basin (30-15 Ma BP), and different physical property and somewhat different speed of movement of the three belts gave different tectonic features to the three areas in central Honshu as is shown in Fig. 5 (A). Then the PHS plate collided with Honshu on the northern side of the Izu Peninsula, and changed the direction of movement to the northwest in 1-0.5 Ma BP. Quaternary uplift of the Akaishi, Tenshu, Misaka, and Tanzawa Mts thus started, while the processes of making the outer ridges ceased under a rather extensional stress field in the Miura-Boso Hills and their offshore area of southern Kanto as shown in Fig. 5 (B). Collision between the northeast Japan arc (on the North American plate) and the Southwest Japan arc (on the Eurasian plate) may have occurred along the Fossa Magna in the Quaternary Period.

著者

中島 礼 伊藤 光弘 兼子 尚知 樽 創 利光 誠一 中澤 努 磯部 一洋

出版者

日本第四紀学会

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.43, no.3, pp.225-230, 2004-06-01

参考文献数

12

被引用文献数

1

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茨城県つくば市東部を流れる花室川の中流域から,<i>Palaeoloxodon naumanni</i> (Makiyama)の臼歯が発見された.産出層準は,最上部更新統である桜川段丘堆積物に相当する緩斜面堆積物で,約2.7万年前より新しい年代を示す.歯種は左上顎第3大臼歯であり,歯冠長は331mm,咬板数は1/2・22・1/2と,これまでに報告された臼歯の中でも大型であり,特に咬板数は最大であることがわかった.この標本の産出は,<i>P.naumanni</i>の時代的な形態変異を明らかにする上で重要である.

著者

藤根 久 小坂 和夫

出版者

Japan Association for Quaternary Research

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.36, no.1, pp.55-62, 1997-02-28 (Released:2009-08-21)

参考文献数

42

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生駒山地西麓地域(東大阪市河内地域)から産出する縄文時代後期および晩期の土器の中には,その胎土が暗褐色~茶褐色を呈し,角閃石類を多量に含むという特徴を有する土器群があることが知られている.これらの特徴を有する土器は,“河内の土器”と一般的に呼称されており,他地域の土器とはもちろん,この地域のほかの土器とも容易に識別される.これらの土器について,土器薄片を作成し,偏光顕微鏡下において観察と記載とを行った.その結果,(1)これらの胎土中の粒子の大きさ分布は5μmから250μmの範囲で,破砕物が一般的に示すフラクタル性(スケーリング則)を有すること,(2)粘土の質・量とも断層内物質の一般的特徴を有すること,(3)粘土は一般的に用いられていたものとは異なり,接着性が非常に高い特異なものであることが明らかになった.さらに,鉱物・岩石片からなる粒子には,破片状の尖った外形を呈するものが多く,断層岩に特徴的な粒内微小断層や微角礫状組織あるいはカタクラサイト状組織を呈するものもあり,顕著な不連続的波動消光や双晶面のたわみ・キングバンドや機械的双晶という変形岩・断層岩を特徴付ける組織が多いこと,が明らかになった.以上のような土器胎土の特徴から,その材料として断層内物質が用いられた可能性がきわめて大きいと考えられ,胎土材料としてほかの材料を考えることは困難である.その産地としては,岩石学的・地質学的特徴から生駒山地西縁を南北に走る生駒断層の破砕帯が最も可能性が高いものとしてあげられる.

著者

工藤 雄一郎 小林 謙一 山本 直人 吉田 淳 中村 俊夫

出版者

日本第四紀学会

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.47, no.6, pp.409-423, 2008-12-01 (Released:2012-03-26)

参考文献数

48

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石川県御経塚遺跡から出土した縄文時代後・晩期の土器付着物と漆の14C年代,炭素・窒素安定同位体比,C/N比の測定を行い,土器で煮炊きされた内容物と各土器型式の年代学的位置づけについて検討した.その結果,後期の内面付着炭化物は,動物資源を煮炊きしたものが炭化して残ったものと考えられ,このうちのいくつかは海洋リザーバー効果の影響を受けている可能性を指摘した.晩期の土器付着物の14C年代は,周辺地域の研究成果と対比しても整合的であった.そこで,晩期の土器付着物の14C年代をIntCal04で較正し,晩期中葉の中屋式,晩期後葉の下野式および長竹式の較正年代を提示した.晩期最終末の長竹式の年代は,北陸地域における環状木柱列の形成時期とも関係することが明らかとなり,これは縄文時代から弥生時代への移行期の問題を検討する上で,きわめて重要な成果である.

著者

藤井 理行

出版者

日本第四紀学会

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.37, no.3, pp.181-188, 1998-07-31

参考文献数

20

被引用文献数

2 1

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グリーンランド氷床のコアの安定酸素同位体組成の解析により,Dansgaard-Ocschgerサイクルと呼ばれる氷期における24ものinterstadials(亜間氷期)が明らかとなった.interstadialsは,数十年間で5~7℃の急激な温暖化とその後500~2,000年の緩やかな寒冷化で特徴づけられる気温変動である.また,Dansgaard-Oeschgerサイクルを束ねたBondサイクルと呼ばれる気温変動は,ローレンタイド氷床から北大西洋への氷山群の流出(ハインリッヒイベント)後に急激な温暖化で始まることが,海底コアとの対比で明らかとなった.本論では,氷期における北大西洋深層水(NADW)の消長による海洋での熱塩循環の変動が,地球規模での気候を支配してきたことを示すとともに,気候システムには2つの安定なモードがあることを指摘する.さらに,現在進行中の温暖化に伴う降水量の増加により,北大西洋海域の塩分濃度が低下し,熱塩循環が止まり,現在とは別の気候モード(寒冷化)が引き起こされる可能性を紹介する.

著者

新井 房夫 小林 国夫 直良 信夫

出版者

Japan Association for Quaternary Research

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.10, no.4, pp.191-201, 1971-12-25 (Released:2009-08-21)

参考文献数

36

被引用文献数

1 1

著者

松下 勝

出版者

Japan Association for Quaternary Research

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.27, no.4, pp.273-278, 1989-03-31 (Released:2009-08-21)

参考文献数

38

被引用文献数

1 1

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In carrying out archaeological excavations and studies on remains of rice paddy fields, many problems cannot be solved without the help of the methods and techniques of natural science. Several such problems of considerable importance are detecting the sites, analyzing for what purpose they were used, clarifying the system for their utilization, establishing their chronology, estimating the harvest, determining the factors allowing for the existence of the rice paddy fields, their surrounding environment, and the effects of their cultivation on the natural environment.Observation of the soil section combined with pollen analysis has been successfully used in detecting the horizon of the site. Investigation of macro-remains of culture plants and other weeds contributed to recognition of the difference between rice paddy fields and dry agricultural fields, or to determining whether a rice field was dry or wet. Conventionally, in estimating a rice harvest, not only archaeological, but also bibliographical or agricultural methods have been applied. Analysis of plant opal, developed in recent years, reveals itself as a method superior to these conventional ones. To analyze the factors which made possible the establishment of the site, the methods mentioned above-for example, reconstruction of paleo-vegetation based on the pollen analysis-have been used. Recently, a method which could be referred to as micro-scale topographyenvironment analysis has been used successfully in investigating the relationship between rice field cultivation and topography and water supply.The number of branches of archaeology in which methods of natural science can be used successfully will increase also in the future. We should be aware, however, that analysis of archaeological material seldom yields any positive result unless the archaeologist, in consultation with the natural scientist, has a clear aim in utilizing such analyses. Establishing a data base to accumulate the archaeological data yielded by methods of natural science is necessary; such a data base may be useful for many disciplines in archaeological studies. More important, however, is the careful observation of sites in situ to establish the correct chronology of multi-layered archaeological sites and to estimate the time gap between succeeding layers, because the factors controlling the duration of cultivation of a rice field are multidimensional.

著者

森脇 広 岩田 修二

出版者

Japan Association for Quaternary Research

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.31, no.4, pp.229-241, 1992-10-31 (Released:2009-08-21)

参考文献数

48

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最終氷期のアイスランドは, その主要部を一続きの氷床に覆われていたが, 周辺部の山岳地帯は周辺部が薄いアイスドームからなっていた. 晩氷期末の最高位旧汀線の高度分布はこの氷河分布に対応し, 島の主要部は一続きの広い曲隆域となり, 北西地域に小曲隆部がある. 晩氷期以後, 古ドリアス期と新ドリアス期の再拡大期 (ほぼ同規模) があった. その後氷河は大きく縮小したが, ネオグレシエーション以後拡大し, 現在のようになった. 氷河融解にともなう隆起は完新世初期には終了した. 後期更新世末から完新世初期にかけての隆起量は最大150mに及ぶ. 現在の海岸地域は完新世中期以降は全体としては沈降している.

著者

吉川 虎雄

出版者

Japan Association for Quaternary Research

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.7, no.4, pp.157-170, 1968-12-20 (Released:2009-08-21)

参考文献数

37

被引用文献数

9 4

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The Pacific coast of Southwest Japan has been attacked by violent earthquakes accompanied by remarkable crustal deformation at intervals of 100 to 150 years in the historical period. At the most recent great earthquake in 1946, promontories protruding south into the Pacific Ocean were upheaved by about one meter, being tilted northwards, and inland mountainous regions were subsided. The mode of recent crustal deformation, including seismic one, of Shikoku has been revealed with precise levellings, as shown in Figs. 1-3.In the southern part of Shikoku runs a hinge line of the recent crustal deformation, which was subsided at the seismic time and upheaved in the inter-seismic periods. The coastal areas south of the hinge line were tilted southwards in the inter-seismic periods and remarkably northwards at the seismic time, while the mountainous region north of the line was quite reversely deformed.In the vicinity of Muroto Promontory, the southeastern tip of Shikoku, a characteristic process of post-seismic crustal deformation was clarified with precise levellings carried out seven times for six years after the great earthquake in 1946 (Okada et al., 1953). Immediately after the earthquake, Muroto Promontory was rapidly tilted southwards, and then the rate of southward tilting exponentially decreased to become as constant as in the pre-seismic period. The post-seismic crustal deformation (Fig. 3) is nearly reverse to the seismic one (Fig. 2) and is different in its mode from the pre-seismic one (Fig. 1), while similar minor features are found in their mode. It is, therefore, inferred that the post-seismic crustal deformation was chiefly caused by seismic after-effect and the pre-seismic crustal deformation resulted from secular tectonic movement and decelerated seismic after-effect.From this inference secular crustal deformation of Shikoku was tentatively estimated, by subtracting the post-seismic vertical displacement from the triplicated pre-seismic one. Although there is no definite reason for triplicating the latter, the estimated secular crustal deformation (Fig. 6) is nearly concordant with the patterns of geomorphological and geological structure of the mountains, and is negatively correlated with Bouguer's anomalies of gravity (Geogr. Surv. Inst., 1966).Resultant crustal deformation of Shikoku in the seismic and inter-seismic periods was also obtained from results of precise levellings (Fig. 7), assuming that great earthquakes accompanying crustal deformation of similar mode have occurred at intervals of about 120 years. Coastal terraces on the south coast descend northward and their heights have a positive correlation with the resultant deformation (Fig. 9). Topographic features of various types caused by subsidence are found along the hinge line, which is inferred to have been subsided as a result of the seismic and inter-seismic crustal deformation. Heights of the mountains north of the hinge line show positive correlations with the resultant deformation, except in the central part of the western Shikoku Mountains, and coefficients of regression are larger in higher mountains than in lower ones (Figs. 10 and 11). In the coastal areas south of the hinge line, however, correlation between heights of the mountains and the resultant deformation are negative (Figs. 9 and 11). This means that the mountains have been upheaved by tectonic movement of similar mode to the recent crustal deformation including seismic one, which probably dates from before the formation of coastal terraces and at least after the evolution of the lower mountains.A quite similar relation between the recent crustal deformation and the geomorphic features is also found in Kii Peninsula, east of Shikoku.

著者

中西 利典 木村 治夫 松山 尚典 ホン ワン 堀川 義之 越後 智雄 北田 奈緒子 竹村 恵二

出版者

日本第四紀学会

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.58, no.2, pp.163-173, 2019-04-01 (Released:2019-06-04)

参考文献数

29

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中央構造線活断層系の西端に位置する別府湾は,およそ5Maから沈降場にある.その南縁の府内断層は同堆積盆を構成する主要な正断層である.その活動性を評価するために,断層を挟んで掘削された7本のボーリングコア試料を用いて,堆積相解析,珪藻化石の群集組成解析,合計17試料の陸源植物片と4試料の海生炭酸塩の放射性炭素年代測定を実施した.それらの解析結果を基にして,デルタフロント相,デルタプレーン相,人工盛土相を認定した.これらの堆積構造と変形構造は地中レーダ探査によって可視化された.これらの結果,デルタプレーン相の最上部の泥層の堆積年代と珪藻化石群集を基にして800~400calBPの最新活動を認定した.デルタフロント相の泥層の上下変位量を基にして2,100calBP頃の活動も認定した.これらからおよそ1,700年の再来間隔が計算できる.

著者

岡口 雅子

出版者

Japan Association for Quaternary Research

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.15, no.3, pp.97-108, 1976-10-30 (Released:2009-08-21)

参考文献数

22

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The Oita district is a standard area for the Cenozoic stratigraphy in West Japan. Above all the Tsurusaki hills is regarded as the most important area including the type sections of three formations. Main parts of the Takio, the Higashiwasada and the Tsurusaki formations are distributed respectively in the central to north area, in the south and north extremity. They are overlain by the higher terrace sediments. In the south of the hill, the gravels of the Higashiwasada formation, the Takio formation and the higher terrace sediments are developed in intricate pattern and their stratigraphic relation is misleading suggesting that some of these are possibly contemporaneous. While the known index fossil from the formation is only Stegodon orientalis from the basal part of the Tsurusaki formation. Accordingly the supposed ages of the Takio and Higashiwasada formation based on an indirect correlation is not accurate. Therefore it is important to clarify their ages.For settling these problems, the fission track age determination of the accessory zircon from pyroclastic rocks from above mentioned formations were done after a systematic field survey.In norder to observe fission tracks easily and correctly, the etching procedure was examined and the condition was finally settled as following; the etchant was 2:1 mixture of 48%HF and 98% H2SO4 and etching is carried out under pressure at 250°CThe Shikido pyroclastic rock member of the Higashiwasada formation and the Hada pyroclastic rock member of the Takio formation were selected for examination. The age of the Shikido and the Hada pyroclastic rock members are (6.52±1.34)×106 year and (1.44±0.28)×106 year, respectively.The age of the Shikido pyroclastic rock member is comparable with some volcanic rocks in Central Kyushu, for example biotite andesite in Kitatakaki District, Nagasaki Prefecture (5.7m.y.B.P.), biotite hornblende rhyolite in Hirado City (5.8m.y.B.P.), etc. Considering sporadical distribution, in Central Kyushu of volcanic rocks with similar lithology to those of the Higashiwasada formation, it must be concluded that the volcanic activity of this age is more extensive than has been supposed.The Hada pyroclastic rock member is correlative with the Meisei tuff bed at MaO horizon of the Osaka group. Comparing the relative position of the Hada pyroclastic rock member and the Stegodon orientalis horizon in the Oita group with the relative position of the Meisei tuff bed and the Stegodon orientalis horizon in the Osaka group, the writer conclude that the Takio formation correspons to the lower and middle parts of the Osaka group.

著者

堀部 純男

出版者

Japan Association for Quaternary Research

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.6, no.4, pp.180-185, 1967-12-30 (Released:2009-08-21)

参考文献数

12

被引用文献数

2 2

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Principle and experimental method of paleotemperature analysis were reviewed. The temperature coefficient of equilibrium constant of exchange reaction of oxygen atom between water and carbonate is large enough to enable us to calculate temperature of formation of carbonate in water. By the recent development of mass spectrometric and experimental techniques for the measurement of isotopic ratio of oxygen, paleotemperature can be measured within the experimental error of ±0.5°C and the development is completely attributed to the effort of Urey group. Japanese mass spectrometer such as Hitachi RMU-6 and RMS-4 can be used satisfactorily for this purpose. The development of other temperature scale such as phosphateand silicate-scale is strongly desired to eliminate the hypothesis that the old ocean water had the same oxygen-18 content as that of the present day.

著者

川幡 穂高 氏家 宏 江口 暢久 西村 昭 田中 裕一郎 池原 研 山崎 俊嗣 井岡 昇 茅根 創

出版者

Japan Association for Quaternary Research

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.33, no.1, pp.19-29, 1994-02-28 (Released:2009-08-21)

参考文献数

31

被引用文献数

4 4

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海洋における炭素循環の変動を調べるために, 西太平洋に位置する西カロリン海盆の海底深度4,409mから堆積物コアを採取して, 過去30万年にわたり平均1,000年の間隔で無機炭素 (炭酸カルシウム) と有機炭素の堆積物への沈積流量を詳細に分析した. その結果, 炭素カルシウムの沈積流量は過去32万年にわたって大きく変動し, 極小値が約10万年の周期をもっていることが明らかとなった. また, 有機炭素の沈積流量は, 主に氷期に増大したが, これは基礎生物生産が高くなったためであると考えた. 無機炭素と有機炭素の形成・分解は, 海洋と大気間の二酸化炭素のやりとりに関しては, 逆の働きをしている. そこで, 堆積粒子に含まれる両炭素の沈積流量の差を用いて, 大気中の二酸化炭素の変動と比較した. その結果, 約5万年前の炭酸カルシウムの沈積流量が非常に増加した時期を除いて, 大気中の二酸化炭素濃度の変動と堆積粒子中の有機・無機炭素沈積流量の変動は第一義的に一致しており, 大気中の二酸化炭素の変動と海底堆積物とが何らかの関連をもっていたことが示唆された.

著者

早田 勉 八木 浩司

出版者

Japan Association for Quaternary Research

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.30, no.5, pp.369-378, 1991-12-25 (Released:2009-08-21)

参考文献数

40

被引用文献数

8 8

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Stratigraphic studies of local tephras distributed around the foot of Quaternary volcanoes in Northeastern Honshu, Japan have been carried out since the beginning of the 1969's. Since the discovery of the AT tephra in Fukushima Basin in 1976, a total of seven late Quaternary widespread tephras have been found, interbedded at many localities with local tephras. These are the B-Tm, K-Ah, AT, DKP, Aso-4, Pm-I and Toya tephras, in descending order. They link the stratigraphy of local tephras throughout the late Pleistocene with those in the central and southern parts of Japan. Consequently they are useful in studies of late Quaternary tectonic movements, geomorphic history relating to climatic change, volcanic activities and archaeology in Northeastern Honshu.Ignimbrites of the Lower and Middle Pleistocene have been found in the vicinity of Mt. Hakkoda, along the upper course of the Tama River, Onikobe and Shirakawa areas. Widespread tephras, predating the last interglacial, have not been discovered there yet. It is necessary to find them to support the development of geochronology and other related studies of the Middle Pleistocene in Northeastern Japan.

著者

松井 愈 松澤 逸巳

出版者

Japan Association for Quaternary Research

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.23, no.4, pp.233-244, 1985-01-31 (Released:2009-08-21)

参考文献数

17

被引用文献数

8 7

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The purpose of this paper is to report the stratigraphy, age and tectonic movement of the Pliocene-Late Pleistocene deposits on the Makubetsu Plateau in the central region of the Tokachi plain on the basis of the geological relations of these deposits and K-Ar age data of the pyroclastic materials and obsidian pebbles collected from 8 horizons in these deposits.1. The Tokachi Super Group, Pliocene-Early Pleistocene, distributed in this Plateau, is divided into the Ikeda and the Osarushinai Formations in ascending order. According to the molluscan and foraminiferal fauna, paleomagnetic stratigraphy and K-Ar age data, the age of the Ikeda Formation is correlative to the latest Pliocene, and the Osarushinai Formation to Early Pleistocene. The Osarushinai Formation, composed of clastic and pyroclastic materials, was accumulated in shallow sea and terrestrial basin formed subsequently by the westerly shifting of the center of the Ikeda depositional basin.2. The Makubetsu Plateau was transformed into an upheaving area after the deposition of Osarushinai Formation, while the Obihiro Basin remained as a relatively subsiding area. Along the western margin of the Makubetsu Plateau runs an active tectonic line called Oribe Fault.3. It is noticeable that the thick fanglomeratic deposits, the Kochien Gravel Bed, prevail throughout this Plateau. The lithofacies of this Gravel Bed suggest that the western hinterland, Hidaka Belt, was eroded away vigorousely in Middle Pleistocene. Some younger gravels and pyroclastic deposits cover the dissected Kochien Gravel Bed. Those younger gravel deposits are fan-surface deposits formed by erosion and resedimentation of the older thick gravel bed.4. The areal changes in the altitudes of both the upper surface and the basal level of the Kochien Gravel Bed in and around this area have been critically analyzed to detect the Late Pliocene to Holocene tectonic movements which displaced and deformed this gravel bed. It has been disclosed as a result of this study that the activity of the Oribe Fault has a right-lateral strike-slip component and shows a vertical component decreasing gradually since Early Pleistocene. Moreover, it is worth notice that the Oribe active fault appears to have originated along the boundary between the Hidaka and Tokoro belts.

著者

安田 喜憲

出版者

Japan Association for Quaternary Research

雑誌

第四紀研究 (ISSN:04182642)

巻号頁・発行日

vol.21, no.3, pp.255-271, 1982-10-31 (Released:2009-08-21)

参考文献数

43

被引用文献数

30 36

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Pollen analytical examination is carried out using the 32.2m core taken from a bottom of the Lake Mikata which is located in Fukui Prefecture (35°33′32″N.L.. 135°53′40″ E.L.). From the result of pollen analysis, 10 local pollen zones can be distinguished that is from lower upward MG (I, II, III), FG (I, II, III, IV, V), L and R. Each local pollen zone is sub-divided into several sub-zones.MG I and II zones (ca. 50, 000-41, 000B.P. years) are characterized by stabilized high values of Cryptomeria and Alnus suggesting cool and damper climate. This period is correlated with Port Talbot Interstadial in North America.MG III zone (ca. 41, 000-35, 000B.P. years) starts with short cold epoch which is defined by temporal increase of Tsuga. After this temporal cold epoch, frequency values of Cryptomeria shows unstability decreasing upward, on the other hand, Tsuga increases upward. This period is a transitional period from Interstadial to Pleniglacial.FG zone (ca. 35, 000-15, 000B.P. years) is marked by a decline of Cryptomeria with increase of Tsuga, Abies, Picea, Pinus Haploxylon and grass pollen like Artemisia, Thalictrum, Polygonum and Compositae indicating cold and dry climate. This zone is roughly subdivided into three characteristic periods.FG I zone (ca. 35, 000-31, 000B.P. years) is characterized by high values of Tsuga and other sub-alpine coniferous trees suggesting cold and dry climate.FG II zone (ca. 31, 000-24, 000B.P. years) is defined by increase of pioneer trees like Betula, Salix and Alnus replacing Tsuga. This zone occupies a relatively warm epoch and correlates with Plum Point Interstadial in North America.FG III, IV, V zones (ca. 24, 000-15, 000B.P. years) are dominated by Tsuga, Picea, Abies and Pinus Haploxylon indicating cold and dry climate. But the climate at FG IV zone (ca. 20, 000-18, 000B.P. years) shows wetter condition than those of FG III (ca. 24, 000-20, 000B.P. years) and FG V (ca. 18, 000-15, 000B.P. years) zones.L zone is defined by the decrease of Tsuga, Picea, Abies and Pinus Haploxylon with increase of Quercus and Alnus suggesting a climatic ameriolation. The opening of this zone is dated at 15, 000B.P. years.R zone is characterized by the sudden decrease of Tsuga, Picea, Abies and Pinus Haploxylon with the sudden increase of temperate trees like Fagus, Quercus, Juglans and Carpinus. Grass pollen also decreases suggesting the development of dense temperate broad-leaved forest under warm and moist climatic condition. The opening of this R zone is dated in 10, 000B.P. years.