A New Name for a Slice of the Geological History of the Planet

[Recusant]

The International Union of Geological Sciences has ratified a new name for the period spanning from 770,000 to 126,000 years ago: The Chibanian, formerly known as the Middle Pleistocene.

"Japan Puts Its Mark on Geologic Time with the Chibanian Age" | Eos

Earth's newest geologic time interval has been named after a jurisdiction outside Tokyo, Japan.  The International Union of Geological Sciences (IUGS) recently ratified the name "Chibanian," meaning "Chiba age," for a period of time stretching from 770,000 to 126,000 years ago, during the Pleistocene epoch.

Equating to the Middle Pleistocene subepoch, the Chibanian is named after Chiba, one of Japan's 47 prefectures, and marks the first time a Japanese name has been used in the geological timescale as well as in a Global Boundary Stratotype Section and Point (GSSP). GSSPs are reference points defining the lower boundary of a time interval in the geological timescale. There are dozens of GSSPs around the world, with most in Europe and some in North America and China.

The name was chosen following the discovery of a stratum in Chiba's Ichihara City, about 55 kilometers southeast of central Tokyo. The stratum lies in a cliff along the Yoro River flowing through the Bōsō Peninsula, which separates Tokyo Bay from the Pacific Ocean. The stratum consists of thick layers of late Cenozoic marine strata of silt or clay-bearing marine deposits, minerals, and volcanic ash deposits.

[. . .]

The nomenclature is significant for Japan not only because it puts the country on the geological map but also because of an important event that occurred eons ago. The Chibanian is when the last reversal of Earth's magnetic poles took place, and the section in Chiba has one of the best records of that event. The Brunhes-Matuyama reversal is named for geophysicists Bernard Brunhes of France and Motonori Matuyama of Japan, who was the first to discover that the north and south magnetic poles had changed places in the past. The polarity era that came before the current one is named the Matuyama Chron in his honor.

[Continues . . .]

From LiveScience:

[T]he Brunhes-Matuyama reversal is still the subject of some debate. A 2014 paper published in the Geophysical Journal International used information from a layer of sediment found in Italy to argue that the flip took place in the span of a few decades. A 2019 paper published in the journal Science Advances argued, relying on information from ancient lava flows in Hawaii, that the reversal took closer to 22,000 years. As an excellent geologic record of this flip, the Chiba sediment could eventually help resolve the debate.

[Continues . . .]

[jumbojak]

Just so you know, I may not always comment but I do read these.

[billy rubin]

i read em too. my paleontology work was all much earlier, llandoverian through ludlovian, much farther down in the silurian system



it's historical geology that gives you a sense of the earth, an understanding of place.

[Recusant]

Just so you know, I may not always comment but I do read these.

Cool, I appreciate the comment.   I certainly understand that many of these science stories may not serve as much of a basis for discussion here, but I share them anyway because they may be of interest regardless of discussion.

[Icarus]

I also read them with interest Rec.  Thank you for helping persuade ourselves to pay attention.