Characteristics and evolutionary significance of the Paleocene wood-fall communities

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K05691
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Stratigraphy/Paleontology
• Research Institution: Joetsu University of Education
• Principal Investigator: Amano Kazutaka 上越教育大学, 大学院学校教育研究科, 特任教授 (50159456)
• Co-Investigator(Kenkyū-buntansha): ジェンキンズ ロバート 金沢大学, 地球社会基盤学系, 准教授 (10451824)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 沈木群集 / 暁新世 / 活平層 / Basilika層

Outline of Final Research Achievements

The Paleocene Wood-fall communities consisting of 75 molluscan species have been found from 45 localities of the Katsuhira Formation in eastern Hokkaido, Japan. From three localities of Paleocene Basilica Formation on Spitsbergen Island, the wood-fall communities including 18 molluscan species have been described. As a result of comparison between the Katsuhira and Basilika communities, eight families including thyasirids are shared with each other. However, in the generic level, only two genera are shared. Such difference of the generic composition is due to the difference of living depth.
Limpets and thyasirids are common between two Paleocene and Cretaceous communities.
On the other hand, both Cretaceous and Paleocene communities are different from the younger communities than the late Eocene in having no small bathymodiolins.

Free Research Field

古生物学

Academic Significance and Societal Importance of the Research Achievements

世界で２例しか知られていない新生代初期の暁新世の沈木群集を検討し、種構成を明らかにした。北海道浦幌町の活平層の群集と北極海域のスピッツベルゲン島の暁新統バシリカ層の群集の種構成について検討した結果、化学合成二枚貝であるハナシガイ科を含む8科が共通することが判明し、白亜紀の群集とは類似性が見られるものの、後期始新世以降の群集とは小型のシンカイヒバリガイ類を含まない点で異なることが明らかとなった。この傾向は、メタン湧水や熱水噴出域の化学合成群集の種構成の変遷とも類似する。このことは、化学合成群集の進化を検討する上で、白亜紀末よりも暁新世から始新世にかけての変化が重要であることを示唆している。