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

42 GEOLOGICAL RESEARCHES IN
Although the disturbance, which was to produce the N. E. S. W. system of folds,
appears to have been in operation before the deposition of the limestone, it was not
until after the completion of the coal-bearing series, that this action cumulated in
the great revolution by which the eastern portion of the continent received its outline, and the coal-bearing strata and oler rocks were folded and lprepared for the
almost universal metamorphism that has affected them.'
An immense hiatus now occurs, for filling which there are no observed facts.
This extends over the whole time that passed between the deposition of the coalbearing rocks and the period of volcanic action in Southern Mongolia.
During this period occurred the eruption of the Kalgan trachytic porphyry and
the deposition of its pluto-neptunian beds, and the outflowing on a gigantic scale,
along the 41st parallel, of trachydoleritic and basaltic lavas.
The next phenomenon, of which the effects are visible, was the great dislocation
by which at least the southern edge of the Mongolian plateau was raised. Near
Fungching we have seen the high escarpment of the table-land, caused by this
fault, trending away in a E. N. E. W. S. W. direction. If we produce this line
toward the E. N. E. we shall find that it cuts the highest known point of the
southern edge of the plateau-that near Ha Noor. The action of springs, that
seem to rise along this fault line, is visible in the calcareous deposits seen near
Maanmiau, and on the lower plateau near Fungching.
This great zone of volcanic action seems, as such, to mark the coast line of an
extensive sea or ocean lying to the north, and it is an interesting fact that it lies
nearly in a line with the axis of the Tienshan, in which we have every reason to
believe that volcanoes still exist, though perhaps only as solfataras.
The dislocation by which the great escarpment of the plateau was formed, determined the depression between the table-land and the mountains south of it, which
was to be occupied by the lakes already mentioned.
Before the e the deposition of the terrace deposit, the edge of the plateau had already
been subjected to extensive erosion, by which great bays and channels were cut into
it, and the valleys of the Te Hai and Kir Noor formed.
We come now to an interesting question-the origin of the chain of lakes so
often referred to in the preceding pages, and of the deposit of loam by which they
have recorded their former existence.2
That this deposit was formed in fresh water is shown by the presence of the
shells found in the terrace of the Te Hai. The uniform character of the loam in
the different basins, and in all parts of the same basin, its great extent, and the
fineness of the material of which it consists, are conditions which prove that it is
not of local origin, or derived from the detritus of the neighboring shores, but that
it was brought into the lakes by one or more large rivers which must have drained
an area of great extent. Now throughout the region in question, the only rivers
are those of the Yang Ho and Sankang Ho basin, and, independently of the fact
that these streams drain a very small area, the valley systems of these were almost
entirely occupied by the lakes.
1 See Chap. VII. 2 See Map XI, on P1. 5.