THE NARIN TERTIARY BASIN. 
93 
were taken as evidence of a fluviatile origin of the deposits as a whole, while the salt 
and gypsum deposits, with tlieir associated clays in the lower central beds, were taken 
to mark a shallow central depression without outlet, sometimes holding a bitter 
lake, sometimes sheeted over with playa muds. The thickness of the whole 
fonnation must amount to thousands of feet. As in many other basins of hea\'y 
deposition, the basin floor, originally a land surface, must have been depressed 
thousands of feet, so that it in all probability lay below the sea-level. Hence, as 
far as crustal movements are concerned, the Narin basin is perhaps as noteworthy 
as the Dsungarian basin, at the east of the Tian Shan, in which the land surface 
to-day is below sea-level. The unusual feature of the latter basin may not be so 
much the depth of its depression, but the absence of sufficient waste or water-filling 
with which to fill it to a more ordinary level for a mid-continental area. The Narin 
basin was more normal in this respect, for while its area was slowly warped into 
basin form, centripetal streams carried abundant waste from the ele\-ated margins 
toward the depressed center, and the latter was aggraded at the expense of the former. 
The lenses or channel fillings in the mar- 
ginal conglomerates on the upper Maknial were 
from 30 to 70 feet wide and up to 10 feet thick. 
They usually showed cross-bedding, and were 
commonly of different texture from that of the 
bed in which the channel had been eroded. 
The lenses in the gray clays, well exposed on 
the south side of the Alabuga for several miles 
below the new road bridge, are ver}- numerous. They are from 20 to 100 feet 
wide and from i foot to 10 feet deep. They frequently exhibited a gentle cross-bed- 
ding. All the lenses were convex downward and plane upward. There can be 
little doubt that they represent cross-sections of the shifting channels of the streams 
by which the basin was aggraded. 
THE PERIOD OF DEFORM.^TION AND EROSION. 
The Narin strata have been much deformed on certain lines, but as a whole 
they have not been greatly disturbed. A generalized cross-section of the basin is 
given in fig. 57, representing a breadth of 20 or 30 miles. The dip of the basal 
g^^^^^^^^^ 
■\\\\\\\\\\\\\v^^^ 
Fig. 58. — A small Monocline in the Narin 
Formation, looking east. 
Fig. 59. — Three-mile section through Ulu-tuz Gorge, looking east. 
conglomerate along the border of the Chaar Tash is sometimes as much as 50° or 
60°, but this measure decreases rapidly as one enters the basin. A well-defined 
monoclinal flexure, trending about east and west, was crossed as we followed down 
the Makmal. A small monocline of diagrammatic pattern, with a displacement of 
about 300 feet, was seen a few miles farther south ; it is sketched in fig. 58. The 
strong and complex anticline, by which the lower beds are brought to light near 
