NOTES ON SOME IGNEOUS ROCKS OF JAPAN 
to the beginning of the Diluvium. Besides these 
extrusive rocks, there are intruded masses of 
granites, quartz-syenites and their allied por- 
phyries, occurring in a limited area. It is highly 
probable that all these igneous rocks are younger 
than the bottom beds of the Tertiary, which 
make up the base of the islands. 
At Dogo, the Tertiary formation is met with 
in the southwestern and northeastern sea-cliffs 
overlaid by lava flows, and in the middle of the 
island, where the elevation is about 300 meters 
above the sea-level. It consists of tuffs, con- 
glomerates, sandstones, and shales, in which 
deposit plant fossils are preserved. The forma- 
tion is intruded by andesite sills and by schistose 
granites and their allied porphyries. It is folded 
and faulted, and its strikes and dips are variable 
in places, but the general dip is gentle. 
At Dozen, the Tertiary formation occurs in 
a small area and is free from andesite sills, so 
far as the writer’s observation goes. But it is in- 
truded by quartz-syenite and its apophyses, and 
at the place of contact, metamorphosed sand- 
stone with abundant brown mica is exposed. 
The age of the formation is considered to 
be Miocene, corresponding to that of the forma- 
tion along the northwestern coast of Honsht. 
The Diluvium is exposed near T6g6, a small 
village in Dogo. It consists of gravels and 
blocks of trachydolerites and trachytic rhyolites, 
and is overlaid by the younger trachydolerite 
flow. The outcrop is clearly seen at a new 
cutting, a little south of Togé. The formation 
seems to have been locally deposited in a lake, 
which now forms the bay of Saigo. 
The Alluvium is river deposit, seen in a 
limited area along valleys. The description of 
659 
Fic. 2.—Dé6zen as seen from the southeast 
