Middle Jurassic to Lower Cretaceous Radiolarian Biostratigraphy of Shikoku with Reference to Selected Sections in Lombardy Basin and Sicily
スポンサーリンク
概要
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The biostratigraphic distribution of Middle Jurassic to Early Cretaceous radiolarians from nine sections in Shikoku, Japan is investigated with reference to four sections in the Lombardy Basin and Sicily. Documentation of the stratigraphic ranges of diagnostic radiolarian species permits the recognition of datum levels as the first order criteria for correlation. Thirteen radiolarian zones are proposed on the basis of 12 datum levels for a Middle Jurassic to Lower Cretaceous interval. These zones are, in ascending order : the Eucyrtidiellum unumaense Zone, Obesacapsula magniglobosa Interval-zone, Tricolocapsa tetragona Interval-zone, Guexella nudata Interval-zone, Archaeodictyomitra(?) mirabilis Interval-zone, Amphipyndax tsunoensis Interval-zone, Stylocapsa(?) spiralis Interval-zone, Gongylothorax sakawaensis Zone, Foremanella hipposidericus Zone, Zhamoidellum mikamense Zone (Podocapsa amphitreptera Interval-zone applied in Tethyan region), Sethocapsa cetia Interval-zone, Ditrabs sansalvadorensis Interval-zone and Sphaerostylus septemporatus Zone. A direct correlation of the Shikoku sequences with the Tethyan sequences is attempted mainly by means of these datum levels and zonation herein proposed. In addition, correlation of the proposed zones with those of previous authors is discussed. A detailed comparison of the proposed zonation with nannofossil data from both the Shikoku and Tethyan sections provides important clues to the age assignment of the radiolarian zones. A total of 152 radiolarian species are discriminated by using both a transmitted light and scanning electron microscopy in this study, and 17 of them are described as new species.RadiolariaJurassic-CretaceousShikokuLombardy BasinSicilybiostratigraphyzonation
- 東北大学の論文
- 1987-09-30