The first submarine test boring for oil in Japan was executed by the late Tokusaburo Iwasa in the sea 1, 970m off Michikawa-mura, Yuai-gun, Akita Prefecture using a springg pole drilling machine (Kazusa-bori) in the summer of 1952. The drilling was cotinued until it reached the depth of 27m from the sea bottom and abandoned after the machine was hit and damaged by a typhoon of August 19, 1952.
As noticed from the geological column accompanied in this note, the sediments consist of the Recent sand at the depth of 0-3m intercalating two thin grabel layers, of dark gray mudstone at 3-10m and of another dark-coloured mudstone at 10-27m intercalating layers of tuffaceous sandstone, and showing a distinct alternation of the dark-colored mudstone and tuffaceous sandstone, while in the upper portion of this part (10-27m) the mudstone is much more dominant.
The fossil foraminifera from the dark-coloured mudstone is characterized by the flood of
Goesella schenchi (Table I).
From the fossil evidence, the sediments except for the uppermost sand and gravel, may be correlated with the Funakawa formation of middle Miocen age typically developed on the adjacent land area.
A fairly large amount of gas and oil of good quality was found in tuffaceous sandstones within the depth of 25-27m.
Other gas and oil seeps in the sea are found off Matsugasaki-mura, 12m south of Michikawa. All the stratigraphical work ever done in the adjacent land area leads us to believe that these two localities of gas and oil seeps just mentioned are related to the similar anticlinal structure to the south of Fakasawa in Matsugasaki-mura, which once produced oil.
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