TY - JOUR

T1 - Early Oxfordian radiolarians from the ammonite-bearing Fludergraben section (Northern Calcareous Alps, Austria)

AU - Suzuki, Hisashi

AU - Gawlick, Hans-Jürgen

PY - 2020/7/17

Y1 - 2020/7/17

N2 - A well-preserved and relatively rich radiolarian fauna is described from red to grey bedded radiolarites of the Fludergraben section in the Northern Calcareous Alps, Austria. These radiolarites were deposited just above the Klaus Formation, dated by ammonites as latest Callovian or the Callovian/ Oxfordian boundary. The radiolarian fauna is therefore of an early Oxfordian age undoubtedly. Among long-lasting radiolarian species coming from the Callovian, we can distinguish some species that appeared in early Oxfordian time: Kilinora spiralis, Fultacapsa sphaerica, Protunuma japonicus, Pseudoeucyrtis reticularis. We discuss these results in the light of existing radiolarian zonations for the middle Callovian to Oxfordian, and redefined the Williriedellum dierschei Zone (lower-middle Oxfordian), which was previously ranked as subzone in the Zhamoidellum ovum Zone, on the basis of the new index species. These new findings fill a gap in the definition of the Oxfordian by radiolarians and result in a better resolution of the radiolarian biostratigraphy. In the chapter of systematic part, we describe 37 genera, 67 species and 2 subspecies including diagnosis emendations of 2 genera (Loopus and Pseudodictyomitra) and 1 species (Protunuma japonicus). The type species of the genus Loopus is examined and redesignated.

AB - A well-preserved and relatively rich radiolarian fauna is described from red to grey bedded radiolarites of the Fludergraben section in the Northern Calcareous Alps, Austria. These radiolarites were deposited just above the Klaus Formation, dated by ammonites as latest Callovian or the Callovian/ Oxfordian boundary. The radiolarian fauna is therefore of an early Oxfordian age undoubtedly. Among long-lasting radiolarian species coming from the Callovian, we can distinguish some species that appeared in early Oxfordian time: Kilinora spiralis, Fultacapsa sphaerica, Protunuma japonicus, Pseudoeucyrtis reticularis. We discuss these results in the light of existing radiolarian zonations for the middle Callovian to Oxfordian, and redefined the Williriedellum dierschei Zone (lower-middle Oxfordian), which was previously ranked as subzone in the Zhamoidellum ovum Zone, on the basis of the new index species. These new findings fill a gap in the definition of the Oxfordian by radiolarians and result in a better resolution of the radiolarian biostratigraphy. In the chapter of systematic part, we describe 37 genera, 67 species and 2 subspecies including diagnosis emendations of 2 genera (Loopus and Pseudodictyomitra) and 1 species (Protunuma japonicus). The type species of the genus Loopus is examined and redesignated.

KW - Tethys

KW - Jurassic

KW - Radiolaria

KW - Biostratigraphy

KW - sedimentology

U2 - 10.9795/bullgsj.71.243

DO - 10.9795/bullgsj.71.243

M3 - Article

VL - 71.2020

SP - 243

EP - 280

JO - Bulletin of the Geological Survey of Japan

JF - Bulletin of the Geological Survey of Japan

IS - 4

ER -