東京湾の地質と地質構造  [in Japanese] The geology and geologic structure of Tokyo Bay  [in Japanese]

The data of multi-channel seismic reflection in Tokyo Bay carried out by the Hydrographic Department in 1982 (KATO, 1984a,b) are reexamined. The geology of the bay is divided into the basement, Tf, Te, Td, Tc, Tb and Ta formations in ascending order. Tf, Te and Td formations are correlated to the upper part of the Miura Group of Pliocene in age. Tc and Tb formations are correlated to the lower and middle parts of the Kazusa Group of lower and middle Pleistosene in age respectively. Ta is correlated to the upper part of the Kazusa Group and Shimosa-Sagami Group of upper Pleistocene in age. The Miura Group overlies unconformably on the basement and the lower formation is distributed in the south, the middle formation in the south and central part and the upper formationin south, central and north. The Kazusa Group is distributed in the whole area of Tokyo Bay and thickest part is in the south in the lower formation, and in the north in the middle formation of the Kazusa Group and the Shimosa-Sagami Group and the upper formation of the Kazusa Group. Three depressed and two upheaved parts near the base, and one upheaved and one depressed parts near the surface are observed in the A-2 multi-channel section. The depressed part in the central part of the section was formed in the course of formation of the Miura Group, accompanying the formation of the south wing of the north upheaved part. The north wing is formed during the deposition of the middle part of the Kazusa Group. The simulation experiment by virtual basement displacement method shows that the basement might be split into blocks as strain becomes large in the nearly same places at different stages.