Geological researches in China, Mongolia, and Japan, during the years 1862-1865.

104 GEOLOGICAL RESEARCHES IN
cellular rock with amorphous base, containing abundant crystals of n3rnblende and
felspar. The cementing material is a more or less yellowish mineral, with the
lustre of wax, and easily scratched with the knife. This mass also abounds in
crystals of hornblende and felspar, and is cellular in the same manner as the
inclosed fragments. Specimens show a transition from one to the other, and this is
especially observable around the cells in the fragments. The general color of the
rock is dirty yellow. If this be not a true palagonite tufa it must be closely
related to it.
The strata of this formation dip gently, on the western slope, towards the Japan
sea, and on the eastern slope, towards Volcano bay. They consist of two principal
members, the lower, a fine-grained, soft tufa with black mica and fragments of
nearly decomposed pumice; and the palagonite tufa, if I may call it such, as the
upper member.
At about half way between the mines and the sea we came again upon the
argillaceous rock of the mines, containing the same characteristic fossil, but unmetamorphosed, and presenting itself as a soft gray argillaceous shale.
At the village of Yurup, on Volcano bay, we came into the road followed in
going north, and completed the circuit of this itinerary.
Without attempting, in the absence of necessary data, to determine more closely
the ages of the rocks referred to in the preceding pages, they may be generally
classed as follows:I. Older metamorphic.
II. Pluto-neptunian.
III. Recent, including the marine terrace deposits.
IV. Eruptive, of all ages.
The first of these divisions contains all the sedimentary rocks that were observed
to be older than the volcanic tufa-conglomerate formation. They are rocks that
vary widely in character, and perhaps as widely in age. Forming the skeleton, of
at least the southern part of Yesso, they are almost everywhere concealed by the
younger deposits.
The most highly metamorphosed and perhaps the oldest strata observed are the
granulite and conglomerate-breccia beds of Oouta, on the west coast. These last
are made up of older argillaceous and amygdaloidal rocks, but are also older than
three varieties of eruptive rocks-aphanitic trap, syenitic granite, and a greenstone
trap, apparently diorite.
The greatest part of the southeast peninsula, lying between Volcano bay and the
Straits of Tsungara, is formed of fissile clay slates with subordinated beds of sandstone and conglomerates, the uplift trending nearly as the peninsula, about N. W.
by W. These strata are traversed by frequent dykes of the characteristic white
quartziferorls porphyry, and varieties of greenstone, the latter being younger than
the porphyry.
At Wosatzube, on the northern side of the peninsula, there are beds of silicious
schist, having also a northwesterly trend, and strata of a similar character occur
at Kudo, on the west coast, associated with subordinated clay slate and beds of a