Formal ratification of the Global Boundary Stratotype Section and Point (GSSP) for the Chibanian Stage and Middle Pleistocene Subseries of the Quaternary System: the Chiba Section, Japan†

Yusuke Suganuma; Makoto Okada; Martin J. Head; Koji Kameo; Yuki Haneda; Hiroki Hayashi; Toshiaki Irizuki; Takuya Itaki; Kentaro Izumi; Yoshimi Kubota; Hiroomi Nakazato; Naohisa Nishida; Masaaki Okuda; Yasufumi Satoguchi; Quentin Simon; Yoshihiro Takeshita

doi:10.18814/epiiugs/2020/020080

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Communication of IUGS Geological Standards

Episodes 2021; 44(3): 317-347

Published online September 1, 2021

https://doi.org/10.18814/epiiugs/2020/020080

Formal ratification of the Global Boundary Stratotype Section and Point (GSSP) for the Chibanian Stage and Middle Pleistocene Subseries of the Quaternary System: the Chiba Section, Japan^†

Yusuke Suganuma^1,2*, Makoto Okada³, Martin J. Head⁴, Koji Kameo⁵, Yuki Haneda^1,3,6, Hiroki Hayashi⁷, Toshiaki Irizuki⁷, Takuya Itaki⁶, Kentaro Izumi⁸, Yoshimi Kubota⁹, Hiroomi Nakazato¹⁰, Naohisa Nishida¹¹, Masaaki Okuda¹², Yasufumi Satoguchi¹³, Quentin Simon¹⁴, Yoshihiro Takeshita¹⁵

^†This paper is dedicated to the memory of the late Prof. Hisao Kumai in appreciation of his crucial work in promoting the Chiba section as a candidate for the Middle Pleistocene GSSP
¹National Institute of Polar Research, 10-3 Midori-cho, Tachikawa, Tokyo 190-8518, Japan
²Department of Polar Science, The Graduate University for Advanced Studies (SOKENDAI), Midori-cho 10-3, Tachikawa, Tokyo 190-8518, Japan
³Department of Earth Sciences, Ibaraki University, 2-2-1 Bunkyo, Mito, Ibaraki 310-8512, Japan
⁴Department of Earth Sciences, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, Ontario L2S 3A1, Canada
⁵Department of Earth Sciences, Chiba University, 1-33 Yayoi, Inage, Chiba, Chiba 263-8522, Japan
⁶Geological Survey of Japan, AIST, Tsukuba Central 7, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8567, Japan
⁷Interdisciplinary Graduate School of Science and Engineering, Shimane University, Nishikawatsucho 1060, Matsue, Shimane 690-8504, Japan
⁸Faculty and Graduate School of Education, Chiba University, 1-33 Yayoi-cho, Inage, Chiba, Chiba 263-8522, Japan
⁹Department of Geology and Paleontology, National Museum of Nature and Science, 4-1-1 Amakubo, Tsukuba, Ibaraki 305-0005, Japan
¹⁰Institute for Rural Engineering, NARO, 2-1-6 Kannondai, Tsukuba, Ibaraki 305-8609, Japan
¹¹Department of Environmental Sciences, Tokyo Gakugei University, 4-1-1 Nukuikita, Koganei, Tokyo 184-8501, Japan
¹²Natural History Museum and Institute, Chiba, 955-2 Aoba-cho, Chuo, Chiba 260-8682, Japan
¹³Lake Biwa Museum, 1019 Oroshimo-cho, Kusatsu 525-0001, Japan
¹⁴CEREGE UM34, Aix Marseille Univ, CNRS, IRD, INRAE, Coll France, 13545 Aix en Provence, France
¹⁵Institute of Education, Shinshu University, 6-ro Nishinagano, Nagano 380-8544, Japan

Correspondence to:^*E-mail: suganuma.yusuke@nipr.ac.jp

Received: May 19, 2020; Revised: August 21, 2020; Accepted: August 21, 2020

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The Executive Committee of the International Union of Geological Sciences on January 17, 2020 ratified the Global Boundary Stratotype Section and Point (GSSP) defining the base of the Chibanian Stage/Age and Middle Pleistocene Subseries/Subepoch at the Chiba section of the Chiba composite section, Japan. The Chiba composite section is a continuous and expanded marine sedimentary succession in the east-central Japanese archipelago facing the Pacific Ocean. It contains well-preserved pollen, marine micro- and macrofossils, a tightly-defined Matuyama–Brunhes (M–B) paleomagnetic polarity boundary, two geomagnetic field paleointensity proxies, and numerous tephra beds, allowing the establishment of a robust and precise chronostratigraphic framework. Its open-ocean continental slope setting has captured both terrestrial and marine environmental signals from upper Marine Isotope Stage (MIS) 20 to lower MIS 18. The M–B reversal serves as the primary guide for the Lower–Middle Pleistocene boundary, yielding an astronomical age of 772.9 ka. The GSSP is positioned 1.1 m below the directional midpoint of the reversal, at the base of a regional lithostratigraphic marker, the Ontake- Byakubi-E (Byk-E) tephra bed, in the Chiba section. The GSSP has an astronomical age of 774.1 ka and occurs immediately below the top of Marine Isotope Substage 19c.