Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean: Vol. 5, Pt. 2

METAMORPHIC SANDSTONE AND LIMESTONE.
At a point near 212, quartz rock again makes its appearance in a bed about one hundredfeet
thick; then follows a fine-grained syenite two hundred feet thick; and a second bed of quartz
and one of limestone, (at 212,) in which there are numerous imperfectly formed crystals of a
brown garnet.
This is the last outcrop of limestone in the Pass, and is succeeded, five hundred feet eastward,
by a fine mica and hornblende slate, with a trend N. 37~ E., dip S. E. about 45~. This rock
is remarkably homogeneous, and its trend and dip is unusually distinct. It has planes of
cleavage other than those in the direction of the beds, giving to the broken masses a sharp,
angular outline, which, with the dark color, makes them resemble a trap or basaltic rock.
This series of beds of granite, quartz rock, limestone, and hornblendic rock presents a slightly
different appearance when examined at the outcrops along the wagon trail about threequarters of a mile further north. There, the last described syenitic rock is more highly crystalline, and contains transverse veins of white limestone and quartz several inches in width.
These rocks are the last that are exposed in the natural section, and hardly rise above the
surface of the broad slope of the Great Basin, which is composed of sedimentary accumulations
of modern age.
We have thus considered in succession all the outcrops of the rocks from the Tulare Plains
to the summit of the mountains, and then downwards along the course of a creek on the east
slope to the Great Basin.
It is evident that the rocks east of the summit are chiefly metamorphosed sedimentary formations, and it is probable that a great part of those on the western flank are also metamorphic.
The predominance of the rocks, with the composing minerals arranged in parallel planes, is one
of the most striking features of the section; and west of the summit it becomes difficult, if not
impossible, to distinguish between the metamorphic rocks and those which are decidedly eruptive in their character. If the structural condition of the rock was regarded as conclusive
evidence of its metamorphic character, we would be obliged to consider the whole series as
metamorphosed. There is, however, little reason to doubt that the gray and compact granite,
with its included lenticular masses of minerals, is eruptive. The beds of white limestone, with
the adjoining beds of quartz rock, are exceedingly interesting. The limestone varies from a
coarsely crystalline structure to a fine-grained,, granular or sacharoidal marble. It is very white,
and some of the beds contain disseminated crystals of graphite. The metamorphism is so complete that if the rock originally contained fossils, they are now completely destroyed. A part
of the rock very closely resembles the coarsely crystalline white limestone of Sussex county,
New Jersey.
The quartz rock may be regarded as metamorphosed beds of sandstone. The color is light
buff, or yellowish, and not unlike that of the Potsdam sandstone along Lake Champlain.
Several of the specimens exhibit a sub-granular structure, and prove to be calcareous.-(See
No. 4, Catalogue and descriptions.) The recurrence of similar beds at regular intervals along
the section leaves little doubt that they were formerly continuous, and that they have been
uplifted and thrown into flexures, or plicated. This is also shown by the dips or inclinations
of the beds, those nearest the summit being nearly vertical, while those lower down the slope
incline at a considerable angle from the vertical. The flexure has possibly taken place as
indicated upon the section by a dotted line. If such a plication exists, the upper parts of the
curves have been removed by denudations. This view of the relations of the beds is presented
with some hesitation, as the probable plication was not recognized in the field, and only became
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