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

28 GEOLOGICAL RESEARCHES IN
S. E., we enter another valley opening in the S. bW. Frequent fragments of a calcareous deposit strewed over the surface indicate the action of mineral springs.
Gradually ascending this valley, which, as well as that of the Si Ho, is occupied by
a deposit of loam, probably contemporaneous with the terrace loam of the Yang Ho,
we reach a point where this loam deposit, by forming a bar across the valley, causes
a low watershed, on one side of which any drainage there may be flows north to the
Si Ho, and on the other south to the undrained lake Chaganoussu.
We shall see that this remarkable occurrence of alluvial watersheds stretching
across valleys is intimately connected with the formation of the undrained lakes of
this portion of Mongolia, having its origin in a former system of great inland lakes,
and its continuance in the dryness of the climate.
The grassy valley of Chaganoussu has two other openings through the plateau,
one on the east connecting it with the Si Ho valley, and another on the west leading
to the Kir Noor. Both of these are crossed by bars covered by the terrace loam, if
not entirely-formed by it. Our road, after skirting the shallow pond of Chaganoussu
enters the valley leading to the southwest, and passing the dried up bed of the Hoyur Noor descends through a narrow defile till it emerges into the great depression
of the Kir Noor.
From the Si Ho to this point the rocks, both of the adjoining plateau and of the
exposed parts of the valley bottom, belong throughout to the volcanic formation.
From the edge of the plateau, near where the road enters thJ Kir Noor valley, a
view of the whole of this ancient lake-bed is spread out beneath us. It is a large
plain about 15 miles broad, its longer axis trending about N. N. W. On both sides
the lofty and bold plateau edge is seen stretching away to N. N. W. and S. S. E., as
far as the eye can reach, without meeting to inclose the valley.
Away to the southwest of us a distant portion of the plain covered with a dazzling
white efflorescence marks the position of the Kir Noor of a few years since. From
this, the most depressed part of the plain, the surface rises toward every point
of the compass. Far away to the north a bar of the lake deposit seems to stretch
from wall to wall of the valley, while in the south this is certainly the case. Over
this southern alluvial bar the peaks of the Barrier range are seen in the distance.
To the N. N. WT. a distant peak, capped with snow (April 18th), is visible rising
above the level line of the table-land.
The edge of the plateau on both sides of the valley, wherever I visited it, consists
of the volcanic formation, from the summit to under the lake deposits, but the presence on the surface of the latter of granite detritus indicates the presence of the
older rocks at no great distance.
East of the Mongol village of Hoyurbaishin, a gully exposes a section of the
plain deposit near where this abuts against the edge of the plateau. The deposit
is stratified, and its beds have the same dip as the surface of the plain. It consists
of coarse sandstones and fine conglomerates, formed from the detritus of the neighboring volcanic rocks and cemented by a calcareous mineral, the product, perhaps,
of springs, which enveloping each grain or pebble with concentric layers produces a
hard rock. The only trees seen in the valley of the Kirnoor were two old ones