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

CHINA, MONGOLIA, AND JAPAN 71
be the remnants of a deposit the horizontal beds of which were continuous over the
area in question. I examined one of these hillocks, about 50 feet high, near lake
Bilika Noor, and found it made up of the following beds, from younger to older:
Compact, yellowish-gray limestone, with a tendency to oolitic structure.
Thin bed of dark clay, or earth, with concretions of manganese.
Bed of finely crystalline, white, saccharoid gypsum.
Gypsum in massive, transparent crystals associated with more or less red clay.
The stratification is horizontal throughout, and the same structure seemed to be
continuous as far as the Mingan hills. What the character of the plateau is I could
not determine; as seen in the distance it limits the depression with a cliff and long
talus.
An alluvial deposit of red loam is present in many of the valleys, and is, perhaps,
nearly contemporaneous with the erosion of the water-courses.
Nov. 27. In the morning we found ourselves in the Mingan hills, apparently an
isolated protuberance rising only a few hundred feet above the plateau. The rocks
of these hills, where first observed near the southern edge, were chiefly quartzite,
compact sandstone, and a talco-argillaceous schist, in highly inclined strata trending
N. W. and dipping to N. E. Several miles further to the northwest we came to
ridges of limestone, in beds also highly inclined, with a strike W. N. W. and dip to
S. S. W. This rock resembles the limestone of the hills west of Peking. It is traversed by dykes of greenstone. In the Mingan hills I found a few rolled fragments
of basaltic lava similar to that of the southern edge of the plateau.
To the west of these hills lies the broad deep valley of Olannoor, which seems to
connect the depression south of these hills with the great plain of Tamchintala,
to which we now descend. As we enter upon this steppe we see before us nothing
but an unbroken sandy and gravelly plain with a little scattered grass. A considerable percentage of the pebbles on the surface consists of agate, cornelian, and
chalcedony.
Nov. 28. The morning found us still travelling on the Tamchintala, but we
soon descended into a large valley-like depression. The plateau is here cut into
to the depth of perhaps 150 feet, the vertical wall giving an insight into its local
structure. The whole exposed thickness consists of horizontal strata of white calcareous sandstone with thin beds of arenaceous limestone interstratified. At the
bottom of the section a bed of red arenaceous clay crops out. The sandstone varies
in grain from a fine grit to a fine conglomerate, the ingredients of both being apparently identical with those of the gravel on the surface, between which and the
underlying rock there is no line of demarcation. If the pebbles of agate, cornelian
and chalcedony are derived from the amygdaloidal lava, so common farther south,
their occurrence in this deposit throws light on the relative. ages of the two formations.
After crossing this valley depression, which is several miles broad, we ascended
to the plain at about the same level, apparently, as on the other side.
Nov. 29. During the previous night we left the plain and entered a rough and
very undulating country. Here a belt of older rocks, about seventy miles broad,