[M-IS28] Global Boundary Stratotype Section and Points

[MIS28-P01] Promising radiolarian bio-events for the primary marker of the Jurassic-Cretaceous boundary

*Atsushi Matsuoka¹ (1.Department of Geology, Faculty of Science, Niigata University)

Keywords:Jurassic-Cretaceous boundary, radiolaria, bio-events, primary marker, GSSP

The decision of the Global Boundary Stratotype Section and Point (GSSP) of the Jurassic–Cretaceous boundary (JKB) is one of urgent tasks because the JKB is the last system boundary without stratotype in the Phanerozoic. The previous Berriasian Working Group (BWG) in the International Subcommission on Cretaceous Stratigraphy (ISCS) decided to use the base of the Calpionella alpina Subzone as the primary marker and proposed the Tre Maroua section in south France as the candidate for the GSSP of the Berriasian Stage in 2019. However, the ISCS did not support this proposal as the result of ballot by the voting members. Upon this situation, a new working group was organized in January 2021. The author is one of the BWG members (17 in total) and is expected to review radiolarian biostratigraphy and to provide JKB related data from the Pacific and Asian regions. As a result of extensive review of radiolarian fossil records, several promising radiolarian bio-events as a primary marker are identified. They include the evolutionary first appearance biohorizons of Bistarcum irazuense (Aita), Cinguloturris cylindra Kemkin & Rudenko, Eucyrtidiellum pyramis (Aita), Hsuum feliformis Jud, Pantanellium berriasianum Baumgartner, Pseudoeucyrtis acus Jud and Vallupus japonicus Kawabata. Their qualification as primary marker will be discussed. This presentation introduces ongoing activities of the BWG.