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

106 GEOLOGICAL RESEARCHES IN
breccia, altered in great part to a wacke and strongly resembling palagonite-tufa.
Bordering the eastern end of the southeastern peninsula, we have seen the representative beds of this formation, but differing from those of the west coast in that
the inclosed fragments have more the character of quartziferous trachytic porphyry,
thus approaching closely in character to the wall rock of the Esan crater and its
recent ejecta, as also to the rock of Hakodade peak.
The only traces of fossils observed in this formation, were some fragments of the
spines of an Echinoderm found near Washinoki.
The presence of these deposits over so large an area, and the fact that they
always contain beds of coarse material, points to a corresponding range of volcanic
activity. The same is indicated in the numerous lava flows and dykes that are
intimately associated with these beds.
They are probably of submarine origin, and since their formation the island has
undergone many changes of level. A large part of Southern Yesso was under
water during the deposition of these deposits; it seems to have been gradually
elevated and submitted to littoral erosion, forming the different terraces, and then
to have been partially submerged to receive the recent terrace clay deposits.
This recent terrace deposit exists as beds of clay, almost exclusively, along the
southern slope of the southeastern peninsula, and bordering the western shore of
Volcano bay, and in depressions inland from this, as in the valley of the Toshibetz.
Along the west coast where the depth of water is great, and the coast precipitous,
this deposit rarely exists as clay, and then only bordering deep indentations like
the Bay of Odaszu; but it is perhaps partially represented by the gravelly covering
of the volcanic conglomerate terraces As has been already stated, this terraceclay deposit abounds in the remains of recent Mollusks
After the elevation of these recent terraces, and after the action of an extensive
erosion, there were formed the auriferous gravels of Kunnui, and finally, more
recent and still progressing, subaerial deposits, as the volcanic-ash beds around
Comangadake.
Very little is known of the physical character of the rest of Yesso. Volcanic
cones, extinct and active, seem to exist throughout the island. Coal occurs at
several points on the east coast, and several ammonites and a piece of obsidian were
shown to me by the Governor of Yesso, as coming from the Monbetz creek, on the
northern coast.
The island receives an additional interest from being a point of intersection of
three lines of upheaval, and evidently owes its remarkable shape to this fact.
The first of these lines is represented by the northwesterly trend, of that portion
of the island extending from Esan volcano to the mouth of the Toshibetz, and this
is also the trend of the uplifted metamorphic strata; indeed the southeastern
peninsula seems to be an anticlinal axis, the dip of the beds being on both sides,
along the coast, toward the sea. This is also the trend of the peninsula south of
Strogonoff bay, and of the northern coast line,
The second line is that extending from the headland of Matzmai, northeast
through the longer axis of the island and of the KIurile chain to Kamschatka. This
determines also the northeasterly course of the eastern coast line.