チュロニアン・コリンニョニケラス類アンモナイトの分布特性について : 特にメガ化石帯の対比の有効性に関連して

概要

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The stratigraphical and geographical distributions of Turonian collignoniceratid ammonites such as Collignoniceras woollgari (Mantell), C. bravaisianum (d'Orbigny), Subprionocyclus neptuni (Geinitz), S. minimus (Hayasaka & Fukada) and Lymaniceras planulatum Matsumoto, which are characteristically found in the Ishikari province, are described in detail. The validity of regional correlations based on their collignoniceratids in various sedimental conditions are also discussed. The differences among the distributions can be explaned by the changes in the sedimentary facies accompanied with transgression or regression. The distribution of Lymaniceras planulatum, which is probably regarded as a member of the "Sobboreal fauna", is characterized by its abundant occurrence in the northern areas of the Ishikari province in the Hokkaido Cretaceous. The limited distribution may be interpreted as a result of the upwelling from the Boreal Region where there is a cold water current.
川村学園女子大学の論文