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Journal of Geography (Chigaku Zasshi), 2022 Vol.131 No.4

2022 Vol.131 No.4

“Herd-like Landforms (Gyugun Tikei)” in Tokyo

In 1961, an Eschrichtius akishimaensis fossil was discovered at Akishima City, Tokyo, in the Tama Riverbed beneath a railway bridge on the JR Hachiko Line. The fossil was excavated from the Komiya Formation (equivalent to the Hirayama Formation) of the Kazusa Group, suggesting that at least two lineages of the genus Eschrichtius survived in the Early Pleistocene. Downstream from the excavated site, many island-like landforms of about 2 m in height developed parallel to the river flow. The grooves between the islands are long and narrow downstream. When the water level rises, the islands look like a swimming herd of cattle, which is why Koizumi (1996) called them “herd-like landforms (gyugun tikei).” Gravel was actively extracted from the bed of the Tama River from around the Meiji era until 1968. There were as many as 104 gravel pits (as of the end of fiscal year 1963) between Ome City and Komae City. Gravel extraction triggered exposure of the Komiya Formation, which consists mainly of semi-consolidated sand, and the water flow gradually carved longitudinal channels, forming the landforms shown in the photo, which are rarely seen elsewhere in the world. Unlike fossils, the herd-like landforms do not remain and are gradually lost, showing the framework of the Anthropocene.


(Photography & Explanation: Tetsuya WARAGAI)


Reference

[Koizumi, T. (1996): “Herd-like topography” under the Tama River railway bridge of the Hachiko Line. Tama No Ayumi, 83, 56-57. (in Japanese)*]

*Title etc. translated by T.W.



Original Articles

Monitoring Mountain Weather Variabilities Based on Decadal Observations
 of the Present Weather Sensor in the Highland of Central Japan

Yihui YANG and Kenichi UENO

Journal of Geography (Chigaku Zasshi), 2022, 131(4), 393.

DOI:10.5026/jgeography.131.393

Western End of Late Cretaceous Fore-arc Basin and Provenance in SW Japan:
 Detrital Zircon U–Pb Dating of Upper Cretaceous–Paleogene Sandstones
 in Nagasaki-Nishisonogi Peninsula, Western Kyushu

Satoshi YOSHIDA, Yukio ISOZAKI,
Tomohito NAKANO and Yukiyasu TSUTSUMI

Journal of Geography (Chigaku Zasshi), 2022, 131(4), 407.

DOI:10.5026/jgeography.131.407

Multi-decadal Landform Evolution in the Sittaung River Estuary, Myanmar

Naoko NAGUMO and Shinji EGASHIRA

Journal of Geography (Chigaku Zasshi), 2022, 131(4), 427.

DOI:10.5026/jgeography.131.427

Short Articles

Blockslopes Caused by Large to Meso-scale Rock Slope Failures
 in the Upper Okumatajirodani Valley
 on the Eastern Side of Mount Maehotaka-dake North Ridge,
 Northern Japanese Alps

Yoshihiko KARIYA, Satoru HARAYAMA, Yuki MATSUSHI,
Yusuke SHIMIZU and Hiroyuki MATSUZAKI

Journal of Geography (Chigaku Zasshi), 2022, 131(4), 447.

DOI:10.5026/jgeography.131.447

Developing Teaching Materials on the Geology of the Kamisugi Area in Sendai City
 Using the Computer Game Minecraft

Junko IWAHASHI, Akinobu ANDO, Yoshiharu NISHIOKA,
Daisaku KAWABATA and Takahisa SHIRAISHI

Journal of Geography (Chigaku Zasshi), 2022, 131(4), 463.

DOI:10.5026/jgeography.131.463

Letter

Radiocarbon Measurements of Samples Collected
 from Conglomeratic Beachrock Developing
 at Higashihama-cho, Sasebo, Nagasaki Prefecture

Kunio OMOTO, Akiko IKEDA and Yoriko YOKOO

Journal of Geography (Chigaku Zasshi), 2022, 131(4), 473.

DOI:10.5026/jgeography.131.473

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