※一部利用できない機能があります
| 1.
図書 |
図書
|
研究代表者 長谷川卓
|
||||||
| 2.
図書 |
図書
|
研究代表者 長谷川卓
|
||||||
| 3.
論文 |
論文
|
山本, 真也 ; 長谷川, 卓 ; Yamamoto, Shinya ; Hasegawa, Takashi
概要:
金沢大学理工研究域自然システム学系<br />北海道穂別北部地域のMiddle-Upper Turonian亜階で，国際的に年代指標性のある浮遊性有孔虫が連続的に産出し，重要な浮遊性有孔虫帯境界であるHelvetoglobotruncana
…
helvetica帯上限の層序学的位置を推定することができた．更に，国際的に同種と共産するとされている浮遊性有孔虫３種との共産が確認され，鍛冶屋の沢ルートの上部がほぼH. helvetica帯最上部であることが明らかになった．同ルートの炭素同位体比の変動は，汎世界的なMiddle-Upper Turonian亜階の変動と調和的であり，浮遊性有孔虫層序から推定された年代を支持する.また，Middle Turonian亜階でArchaeoglobigerina属がH. helveticaと共産することから，同属の初出現の時期は従来の知見より古いことが示された．<br />Continuous occurrence of international planktonic foraminiferal index species was recognized in the Middle to Upper Turonian successions in the Hobetsu area, Hokkaido, Japan. It enables us to assume the stratigraphic position of the upper limit of the Helvetoglobotruncana helvetica Zone, an important planktonic foraminiferal zonal boundary. Helvetoglobotruncana praehelvetica, Marginotruncana pseudolinneiana, and Praeglobotruncana gibba, which are also internationally recognizable species, occur associated with Helvetoglobotruncana helvetica. This association indicates that stratigraphic top of the Kajiyanosawa route should be assigned to close to the top of the total range of Helvetoglobotruncana helvetica. Correlation of the carbon isotope fluctuation through the Kajiyanosawa route with that of well-studied sections supports our chronostratigraphic interpretation from planktonic foraminiferal biostratigraphyConcurrence of genus Archaeoglobigerina with Helvetoglobotruncana helvetica in the Middle Turonian of this area demonstrates that the timing of the first appearance of Archaeoglobigerina is older than previous known.
続きを見る
|
||||||
| 4.
論文 |
論文
|
山本, 真也 ; 長谷川, 卓
概要:
金沢大学大学院自然科学研究科<br />北海道穂別北部地域のMiddle-Upper Turonian亜階で,国際的に年代指標性のある浮遊性有孔虫が連続的に産出し,重要な浮遊性有孔虫帯境界であるHelvetoglobotruncana he
…
lvetica帯上限の層序学的位置を推定することができた.更に,国際的に同種と共産するとされている浮遊性有孔虫3種との共産が確認され,鍛冶屋の沢ルートの上部がほぼH. helvetica帯最上部であることが明らかになった.同ルートの炭素同位体比の変動は,汎世界的なMiddle-Upper Turonian亜階の変動と調和的であり,浮遊性有孔虫層序から推定された年代を支持する.また,Middle Turonian亜階でArchaeoglobigerina属がH. helveticaと共産することから,同属の初出現の時期は従来の知見より古いことが示された. Continuous occurrence of international planktonic foraminiferal index species was recognized in the Middle to Upper Turonian successions in the Hobetsu area, Hokkaido, Japan. It enables us to assume the stratigraphic position of the upper limit of the Helvetoglobotruncana helvetica Zone, an important planktonic foraminiferal zonal boundary. Helvetoglobotruncana praehelvetica, Marginotruncana pseudolinneiana, and Praeglobotruncana gibba, which are also internationally recognizable species, occur associated with Helvetoglobotruncana helvetica. This association indicates that stratigraphic top of the Kajiyanosawa route should be assigned to close to the top of the total range of Helvetoglobotruncana helvetica. Correlation of the carbon isotope fluctuation through the Kajiyanosawa route with that of well-studied sections supports our chronostratigraphic interpretation from planktonic foraminiferal biostratigraphy Concurrence of genus Archaeoglobigerina with Helvetoglobotruncana helvetica in the Middle Turonian of this area demonstrates that the timing of the first appearance of Archaeoglobigerina is older than previous known.
続きを見る
|
||||||
| 5.
論文 |
論文
|
長谷川, 卓
概要:
金沢大学大学院自然科学研究科
|
||||||
| 6.
論文 |
論文
|
土屋, 健 ; 長谷川, 卓 ; Pratt, Lisa M.
概要:
金沢大学大学院自然科学研究科<br />イノセラムス化石帯区分は上部白亜系の年代層序決定の手法として重要であるが,近年,本邦蝦夷層群において微化石との間に指標する年代区分に不一致が指摘されている.本論はイノセラムス化石帯に対応する炭素同位体
…
比曲線を報告する.北海道大夕張・古丹別両地域のTuronian中部～Santonianの炭素同位体比曲線はInoceramus hobetsensis帯では負方向へのシフトを見せ,I. hobetsensis帯上部及びInoceramus teshioensis帯で特定傾向を示さず安定する.その上位のI. uwajimensis帯からInoceramus amakusensis帯に向かって次第に正方向にシフトする.この炭素同位体比曲線の経時変化パターンは,英国におけるTuronian中部からSantonian下部のものと類似する.それらに加え,I. hobetsensis帯に小規模なピークも見られ,これは国際対比の鍵になる可能性がある. Although inoceramid zones are important chronostratigraphic tools for the Japanese Upper Cretaceous, some recent studies suggested chronostratigraphic discrepancies between mega-and microfossil biochronologies from the Yezo Group in Hokkaido, Japan. Carbon isotope profiles from organic matters obtained in this study from three sections of Hokkaido resemble to isotope profiles from carbonate in England calibrated by biochronology with Tethyan index fossils. The carbon isotope profiles from the Kotanbetsu and Oyubari areas show negative shift segment through the Inoceramus hobetsensis Zone, stable value segment from the upper part of the Inoceramus hobetsensis Zone through the Inoceramus teshioensis Zone and gradual positive migration segment in the Inoceramus uwajimensis Zone and the Inoceramus amakusensis Zone in an acending order. This stratigraphic pattern of carbon isotope curve corresponds to the pattern characterizing the middle Turonian to lower Santonian for the England section. Short term positive excursions (as large as 0.5～1.0‰) superimposed on the long term fluctuation are observed in the Inoceramus hobetsensis Zone from the three sections. They may be potential stratigraphic markers correlative to the similar positive excursions observed in many European sections.
続きを見る
|
||||||
| 7.
論文 |
論文
|
長谷川, 卓
概要:
金沢大学理工研究域自然システム学系
|
||||||
| 8.
論文 |
論文
|
守屋, 和佳 ; 長谷川, 卓 ; 成瀬, 貴洋 ; 瀬尾, 草平 ; 根本, 俊文 ; 鈴木, 崇章 ; 森本, このみ
概要:
Bulk organic carbon isotope (δ13Corg) analyses across the Cenomanian/Turonian boundary in Hokkaido, Japan, and high-reso
…
lution planktic foramiferal biostratigraphy indicate that the timing of the planktic foraminiferal disappearance in the northwestern Pacific was significantly earlier than that in the Atlantic region. δ13Corg shows a prominent ∼2‰ positive excursion, clear trough interval, steady plateau interval, and recovery interval, which can be used as very precise chemo-stratigraphic markers. Planktic foraminiferal biostratigraphy demonstrates a pair of diversity crisis at a horizon below the initial δ13Corg excursion and at the beginning of the plateau interval. This isolated double diversity crisis of planktic foraminifers has also been identified in the Western Interior region and northern Europe. The timings of this double diversity crisis in the Western Interior and Europe show quite good consistency on the basis of the δ13C chemo-stratigraphy. On the other hand, the double crisis in the northwestern Pacific is significantly earlier than those in the Western Interior and Europe. This offset indicates that expansion of the oxygen-depleted water mass in the northwestern Pacific preceded that in the Atlantic region.
続きを見る
|
||||||
| 9.
論文 |
論文
|
長谷川, 卓 ; 沢田, 健
|
||||||
| 10.
論文 |
論文
|
長谷川, 卓
概要:
The Paleocene-Eocene thermal maximum (PETM) is marked by a large negative carbon isotope excursion (CIE) and massive sea
…
floor carbonate dissolution. Both phenomena are thought to have been caused by a sudden release of a large mass of carbon. The step-like nature of the CIE onset combined with the CIE magnitude has been explained by multiple dissociation of methane clathrate as the primary source of carbon. The natures of onset and the magnitude of CIE, however, are different between marine and terrestrial records implying potential artifacts in either or both records. Recently, the carbon isotope stratigraphy based on various techniques including compound-specific isotope analysis on terrestrial and marine biomarkers, single specimen analysis on surface-dwelling planktonic foraminifera revealed that 'actual' CIE is as large as 4‰ or larger, and the onset of the CIE was geologically instantaneous. These results demonstrated that the CIE magnitude (2-3‰) previously applied to estimate the mass of carbon released during the PETM was considerably underestimated and that abrupt input of ^<13>C-depleted carbon to the ocean-atmosphere system. Forthcoming high-resolution studies on the PETM with precise inter-regional correlation would provide a unique opportunity for comparative research of global warming between PETM period and the present.
続きを見る
|
