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332-6 Integrated stratigraphy and international correlation of the Aptian–Albian forearc basin successions of the Yezo Group, northern Japan

Session: Integrated Stratigraphic, Geochemical, and Paleobiologic Perspectives on Earth System Evolution: A Session in Honor of the Contributions of Bradley B. Sageman (Posters)

Poster Booth No.: 219

Presenting Author:

David Selby

Authors:

Takashima, Reishi¹, Selby, David², Singer, Brad S³, Sageman, Bradley B⁴, Schmitz, Mark D⁵, Li, Youjuan⁶, Matsumoto, Hironao⁷, Kuroda, Junichiro⁸, Hosogaya, Kohei⁹, Yamanaka, Toshiro¹⁰, Nishi, Hiroshi¹¹, Podrecca, Luca G¹²r> (1) Tohoku University Museum, Tohoku University, Sendai, Miyagi, Japan, (2) Department of Earth Science, Durham University, Durham, United Kingdom, (3) Department of Geoscience, University of Wisconsin-Madison, Madison, Wisconsin, USA, (4) Department of Earth and Planetary Sciences, Northwestern University, Evanston, Illinois, USA, (5) Department of Geosciences, Boise State University, Boise, Idaho, USA, (6) Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China, (7) Institute of Life and Environmental Science, University of Tsukuba, Tsukuba, Ibaraki, Japan, (8) Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba, Japan, (9) Tohoku University Museum, Tohoku University, Sendai, Miyagi, Japan, (10) School of Marine Resources and Environment, Tokyo University of Marine Science and Technology, Tokyo, Tokyo, Japan, (11) Institute of Dinosaur Research, Fukui Prefectural University, Katsuyama, Fukui, Japan, (12) Northwestern University, Evanston, IL, USA,

Abstract:

The mid-Cretaceous Aptian–Albian interval was characterized by a peak in igneous activity and frequent Oceanic Anoxic Events (OAEs). To understand the linkages between igneous activity and environmental changes during this period, a goal of our collaborative research over the past 10 years is to provide a precise radioisotopic age model.

The Yezo Group of Hokkaido, Japan is a continuous hemipelagic marine succession spanning from Barremian to Maastrichtian that represents the middle–upper Cretaceous succession in the northwestern Pacific region. Because it contains numerous intercalated silicic tuff beds derived from subduction magmatism of the Asian continental margin, this succession has significantly contributed to refining the Cretaceous timescale; for instance, the radioisotopic age of the Albian/Cenomanian boundary in GTS2020 has relied on the ages of tuffs within this group. Although the Yezo Group yields abundant macro- and microfossils, the occurrence of index fossils common to the Global Boundary Stratotype Section and Points (GSSPs) in the Tethyan region is discontinuous. Consequently, previous international stratigraphic correlations of this sequence with representative Tethyan successions, which relied solely on biostratigraphy, lacked sufficient resolution.

Alongside the compilation of macro- and microfossil biostratigraphy, we have established high-resolution carbon and osmium isotope stratigraphy for the Aptian–Albian interval of the Yezo Group in Hokkaido that is anchored by dozens of U-Pb zircon and ⁴⁰Ar/³⁹Ar sanidine age determinations. Our multi-proxy approach enables precise identification of stratigraphic horizons in the Yezo Group equivalent to OAE 1a, Fallot OAE, OAE 1b (Jacob, Kilian, Paquier, and Leenhardt), OAE 1c, and OAE 1d, as well as the Barremian/Aptian, Aptian/Albian, and Albian/Cenomanian boundaries. Moreover, numerous silicic tuffs intercalated within these OAE horizons and stage boundaries offer potential for this succession to significantly contribute to future improvements in the accuracy and precision of the next generation Cretaceous timescale.

Integrated stratigraphy and international correlation of the Aptian–Albian forearc basin successions of the Yezo Group, northern Japan

Description

Session Format: Poster

Presentation Date: 10/14/2026

Presentation Room: CCC, Hall F

Poster Booth No.: 219

Author Availability: 9:00 to 11:00 a.m.

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