General Geology, Vol. 4 No. 1, October 20, 2020

- Article -

Investigation of the Paleo-Lake Kutchan: Diatom and pollen analyses of the late Pleistocene sediments in the Kutchan, Hokkaido, Japan [PDF link]
Tsumoru Sagayama,Tatsuo Sekine and Fusa Hoshino
General Geology, Vol. 4, Page 1–7.


It has been suggested that the Paleo-Lake Kutchan spread in the Kutchan area at the late Pleistocene. In order to investigate the detail geologic time and areas of lake deposits, diatom and pollen analyses of geologic samples picked from the late Pleistocene sediments, which outcrops to the south of the Kutchan downtown, were carried out. Diatom analysis yielded a lot of planktonic freshwater species reconfirmed the existence of the Paleo-Lake Kutchan. Results of pollen analysis show some lower temperature compared with present day. The lake deposits may be assigned to the Makkaribetsu Formation, although further dating studies are necessary to confirm the surmise.

- Article -

Stratigraphy of the upper Pleistocene to Holocene boring in the Kita Ward, Sapporo, Japan; Geologic time of the Sapporo fan deposits, and sea level of the MIS 5a [PDF link]
Tsumoru Sagayama, Yukio Izima, Satoshi Okamura and Yoshitaka Sakata
General Geology, Vol. 4, Page 9–18.


In order to elucidate stratigraphy and sedimentary environments of the Pleistocene and Holocene in the Ishikari Lowland, we carried out analyses of volcanic ash and diatom for a boring core (N8・1) of 44 meters long obtained from the Kita Ward, Sapporo, central Hokkaido. Results of volcanic ash analysis show the geologic horizons of following two late Pleistocene ash layers: the Shikotsu Pumice Flow deposits (Spfl) of ca 41 ka in ca 19.42 m depth and the Toya volcanic ash (Toya) of ca 106 ka in ca 43.58 m depth. Diatom analysis indicates that silt bed in ca 24.35 m depth of the core deposited in fresh water environments. Meanwhile the analysis of clay beds, being correlated with the silt bed in neighboring two cores, HU and GSH, shows sedimentary environments brackish. It is inferred that geologic age of those muddy beds is MIS 5a by two ash layers, Spfl and Toya, and maximum sea level of MIS 5a stage was ca 13 m below the present sea level.

- Report -

Visiting Deccan Trap -Report of travelling in India in March, 2020 [PDF link]
Hiromitsu Yamagishi
General Geology, Vol. 4, Page 19–26.

(no English Abstract)

- Report -

Visiting Geoparks on Jeju Island, Korea-Participating the 12th Asian Regional Conference of IAEG, 2019 [PDF link]
Hiromitsu Yamagishi and Dou Ji
General Geology, Vol. 4, Page 19–26.

(no English Abstract)

- Note -

People who saw the 1874 eruption of Mt. Tarumae [PDF link]
Seigo Miyasaka
General Geology, Vol. 4, Page 35–42.

(no English Abstract)

- Review Paper -

Kazuo Kiminami

General Geology, Vol. 4, Page 43–49. [PDF link]

England, P.C. and Katz, R.F., 2010, Melting above the anhydrous solidus controls the location of volcanic arcs. Nature, 467, doi:10.1038/nature 09417.

Ribeiro, J.M., Ishizuka, O., Lee, C.-T.A. and Girard, G., 2020, Evolution and maturation of the nascent Mariana arc. Earth Planet. Sci. Lett., 530, doi. org/10.1016/j.epsl.2019.115912.

Liu, J., Sun, H., Wang, Z., Xia, Q. and Li, W., 2020, Continuous water supply from the subducted pacific plate to the Eastern Asian big mantle wedge: New insights from the water content of late Cretaceous OIB-like basalts. Lithos, 352-353,

Lin, Y., Zhang, C., Li, C. and Deng, H., 2020, CFrom dextral contraction to sinistral extension of intracontinental transform structures in the Yanshan and northern Taihang Mountain belts during Early Cretaceous: Implications to the destruction of the North China Craton. Jour. Asian Earth Sci., 189, doi. org/10.1016/j.jseaes.2019.104139.

Koulakov, I., Kukarina, E., Fathi, I.H., Khrepy, S.E. and Al-Arifi, N., 2015, Anisotropic tomography of Hokkaido reveals delamination-induced flow above a subducting slab. Jour. Geophys. Res.: Solid Earth, 120, 3219−3239.

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