By RYUTARO ITO/ Staff Writer
February 16, 2023 at 07:10 JST
Researchers collect soil samples from Beppu Bay’s seabed in June 2021. (Provided by Michinobu Kuwae)
Japanese researchers hope that a new geologic epoch covering the present time will be named after Beppu Bay in western Japan, a second such example following the Chibanian Age.
Work is under way at the International Union of Geological Sciences (IUGS) to define the Anthropocene, the period from 1950 that is marked by the human impact on the Earth’s environment, and choose a reference site that retains its evidence.
Researchers from Ehime University, the University of Tokyo and other institutions proposed Beppu Bay, called “Beppu-wan” in Japanese, as a Global Stratotype Section and Point (GSSP) for the Anthropocene, hoping that the epoch will be known as a Beppuwanian age.
“Beppu Bay is a silent witness to how significantly human activity has disturbed the environment,” said Michinobu Kuwae, an associate professor of paleoenvironmental studies with Ehime University.
Geologists have assigned the present time to the Holocene Epoch of the Quaternary Period, part of the Cenozoic Era, on the time scale of the 4.6-billion-year history of the Earth.
However, Paul Crutzen (1933-2021), a Nobel Prize in Chemistry laureate, said humanity has already moved into a new epoch that should be called the Anthropocene.
The Earth’s history is divided into time units primarily marked by environmental changes caused by events such as large-scale volcanic eruptions and gigantic meteorites crashing down.
But Crutzen said human activity is having an impact on the environment on par with those events. The Greek root word “anthrop” means “human.”
There is consensus among most geologists that the Anthropocene began in 1950, although there are different views on what time period it covers, experts said.
Beppu Bay, off Oita Prefecture, is located in the western part of the Seto Inland Sea.
Japanese researchers said the bay’s unique seabed topography has allowed the human impact on the Earth’s environment to be preserved, particularly in its innermost part.
The water is deepest on the landward side and becomes shallower toward the outer sea. Marine currents remain in shallow bodies of water, meaning the seafloor in the bay’s innermost part is seldom exposed to currents.
The ocean bed is covered by a body of seawater containing no oxygen, allowing it to be inhabited by few organisms. Sedimentary layers are preserved there undisturbed.
Kuwae’s team collected core samples of sediments from a depth of 70 meters in the bay’s innermost part in 2020 and 2021.
Analysis has found plutonium fallout from U.S. and Soviet nuclear tests conducted during the 1950s; changes in phytoplankton that point to shifts in ecosystems, including the emergence of red tides; and the accumulation of microplastics and polychlorinated biphenyls.
“The Anthropocene is not just the name of an age,” Kuwae said. “It is also a warning about the serious crisis being brought about by humankind to the Earth.”
An IUGS working group is expected to whittle down candidate GSSPs for the Anthropocene in the coming months and take a full year to determine a single site. Only one site can qualify to be a GSSP for a single geologic age.
A geological formation in Ichihara, Chiba Prefecture, where records of the last geomagnetic reversal event is preserved, was chosen as a GSSP in January 2020.
The designation of a period lasting from 774,000 years through 129,000 years before the present as the Chibanian Age made headlines in Japan.
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