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

LITHOLOGICAL CHARACTERS OF THE STRATA.
ance, being sometimes comparatively quiet, and at others, thrown into currents. The thick
beds of sand also present evidences of variations of current, both in direction and velocity. The
inclined stratification, called diagonal stratifcation, is very common, and in many cases is beautifiully shown by multitudes of the finest layers of sand, inclined in different directions, as shown
in the sectional representation of the strata at e, Geological Sections, Sheet I.
The distinctness of these lines is caused by the difference in the sizes of the grains of'sand,
and by slight differences of the materials, which have become stained yellow and brown since
they were deposited by the infiltration of ferruginous water from the superincumbent strata.
These examples of diagonal stratification were found in the lower portions of the strata, in the
hill-sides near the level of the creek. They were thus probably about eight hundred feet below
the higher beds of the formation. The diagonal stratification of the lower beds, and other
facts about to be mentioned, indicate that their deposition took place in comparatively shallow
water.
The mineral constitution and alternation of the strata will be better understood by the examination of the section which has been referred to. This represents the succession of the strata
in a vertical height of one hundred and sixty-two feet, and it is drawn on a scale of twenty feet
to an inch.
The hill in which this order of the strata occurs is near the spot which was occupied as the
Depot camp, and is on the south side of the creek. The upper parts of the series were not exposed to view, and are not included in the section. It is, of course, impossible to represent,
within the limits of this section, the numerous lines of the strata; they are innumerable, and
very regular; most of the layers, among the finer materials, being as thin as paper.
The following is a brief description of the principal beds in the series, in their order of succession, from the level of the creek upwards. The letters refer to corresponding divisions of the
section.
SECTION OF THE STRATA AT OCOYA CREEK.
Feet.
a. Fine, friable, gray sand, stained with lines of oxide of iron, and enclosing nodules of various sizes encased in
oxide of iron. ---------------------------------------------------------------------------—.
b. Sand, in thin layers, stained with oxide of iron —------------------------------------------------.
Gravel and sand, enclosing casts of fossils, obliquely stratified, and all strongly cemented with sesquioxide of
iron ------------------------------------------------------------------------------------------
iron
c. Sand, stained by iron; includes a thin layer of pebbles ---------------------------------------------
d. Casts and moulds of fossil shells in sesquioxide of iron, gravel and sand; layers oblique —-----------------
e. Fine gray sand, cross stratification distinct, contains nodules of clay -2
f. Fine gray sand, with an occasional layer of pebbles. -(This stratum is partly hid) —---------------------
g. Argillaceous sand, filled with small nodular masses of clay, from one-quarter of an inch to three inches in diameter
h. Fine sand, with curved layers of oxide of iron —------------------------------------------------—.
Fine sand, with small, spherical and ellipsoidal masses of white pumice-stone. Thin layers of charcoal, in
fragments ------------------------------- ------------------ ----------------------------— 0 —i. Fine white sand, derived from pumice-stone, with intercalated layers of pumice in nodules and in powder-.
j. Pumice-sand, or volcanic ashes, very fine and white, in thin strata --------------------------------—.
k. White clay and fine sand —-----------------------------------------------------------------—.
1. Sand, with clay nodules —-------------------------------------------------------------------
m. Gravel and pebbles, with sand. ----.
. Gravl sand, withblayers wifh pebbl --------------------------------------------------------------
n. Gray sand, with layers of pebbles ------------------------------------------------------------------
Sandstone and layers -of pebbles crop out at intervals on the side of the hill for fifty or sixty
feet above the last stratum described. Higher than this, a harder sandstone and a layer of conglomerate is found. Still above, to the tops of the hills, the strata are completely obscured by
167
2.0
0.6
0.7
2.0
1.4
24.0
41.0
1.0
4.0
0.6
25.0
15.0
2.0
20.0
1.0
20.0