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Welcome to the Chibanian Age! The First Geological Age with a Japanese Name

An outcrop of the Chiba section along the Yoro River in Tabuchi, Ichihara City, Chiba Prefecture.

The International Union of Geological Sciences (IUGS) have approved a Japanese research team’s application to register the “Chiba section”—a geological layer in Ichihara City, Chiba Prefecture— as a Global Boundary Stratotype Section and Point (GSSP).

By this formal decision of the Chiba section GSSP, the Middle Pleistocene, which is a geological time period ranging between about 774,000 and 129,000 years ago, was newly named as “Chibanian”.

Strict criteria for approval

The IUGS approves a geological layer as a GSSP only if the layer is found to be the most representative boundary in the world within a specified geological time.
The research team was required to satisfy several conditions to gain approval for the Chiba section to be recognized as the most representative section marking the beginning of the Middle Pleistocene (770,000 years ago) when the latest geomagnetic field reversal on earth occurred. To qualify for approval, a candidate geological layer should also be a layer resulting from continuous accumulation of sediments on the seabed and comparable from a range of perspectives with other layers in a target geological time.

How the Japanese team won approval

For the application, the research team used high-resolution data of the Chiba section for the period when the geomagnetic field was reversed and also identified it in the geological layer records showing the occurrence of global-wide environmental changes as a result of the accumulation of sediments in the Pacific Ocean. This research helped differentiate the Chiba section from other candidate geological layers. The IUGS appraised the submission and officially ratified it as “Chibanian,” a new geological time. The Chiba section joins only 74 sites worldwide officially approved as a GSSP.

Using Chibanian to raise interest in the education of geology

The “Chibanian” site is easily accessible making it an ideal location for student field trips and for raising overall public interest and awareness of the fascinating world beneath our feet.

Source: The Geological Society of Japan, “The Quaternary part of the International Chronostratigraphic Chart” (Website)

Last updated:2020-05-14