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

BENICIA SANDSTONE —LITHOLOGICAL CHARACTERS-FOSSILS.
SECTION OF rHE STRATA AT NAVY POINT, BENICIA.
Feet.
10
15
1. Sandstone, fine-grained and soft, with spherical masses of great hardness inclosed-only about 10
feet exposed.. —-------------------------------------------------------------------
2. Sandstone, harder than No. 1, and highly charged with peroxide of iron.. —----------------
3. Sandstone, with layers of small pebbles and coarse grains of quartz. Some hard masses also
seen. Ferruginous. Fossils and a shark's tooth —--------------------------------------
4. Slaty sandstone in thin layers, hardened by the presence of a considerable portion of oxide of iron.
ITrendS. 75~ E.; N. 750W —--------------------------------------------------------
5. Slaty sandstone, similar to No. 4 -------------------------------------------------------
6. Sandstone, fine-grained, soft, regularly bedded —------------------------------------------
7. Sandstone, soft, in beds separated by thin partings of shale, and traversed by thin seams of gyp sum, generally in horizontal layers. The shales and the beds of soft sandstone are much
stained by oxide of iron.. —-------------------------------
8. Sandstones and shales, all soft and decomposing; some of the beds consist of fine-grained white
sand. The general characters are the same as the previous beds. Thickness of this series, from
No. 7 to the point of conglomerate, estimated to be 6C0 feet —--------------------------— 6
9, h. Conglomerate of gravel and pebbles forming the end of the point10, g. Decomposed silicious sandstone traversed by nearly horizontal seams of gypsum, and divided
in the centre by a thin parting of shale.. -------------------------------------------
11, f. Thin layers of sand or sand and clay, forming a kind of shale. —---------------------------
12, e. Decomposed sandstone, containing some hard masses, and traversed by seams of gypsum,
partly fibrous ----------------------------------------------------------------
13, d. Thin layers, finely stratified, like No. 11. —---------------------------------------------
14, c. Soft decomposed sandstone —--------------------------------------------------------
15, b. Soft decomposed sandstone stained by waving lines of peroxide of iron, looking like the grain
of wood ------------------------------------------------------------------------
1g, a. A succession of beds of sandstone and thin partings of shale, all more or less discolored by
oxide,of iron, and traversed by seams of gysum in nearly horizontal lines. Thickness about
150 feet. —----------------------------------------------------------------------
These strata are all conformable, and the combined thickness is a little over one
thousand feet. The section commences at the low ground on the western side of
the point near a quarry, and extends along the beach, under the face of the bluff,
to a little cove, where the rocks are no longer exposed. The dip and general
appearance of the strata are shown in the appended section; an enlarged view of a
portion of the series is presented on the sheet of sections, Chapter XIII. This
portion is that lying east of the conglomerate, and it is indicated in the descrip tive section by letters which refer to the plate. It includes a thickness of about
175 feet.
The quarry was opened in the thickly-bedded sandstone, containing hard, rounded
masses, which, when broken open, revealed a bluish nucleus similar in color to
that of the rock at Yerba Buena and other localities near San Francisco. These
hard masses seemed, at first, like concretions, but they probably originate in the
same manner as the spheriods at Yerba Buena-by decomposition of angular blocks.
When these nuclei are broken up, they are found to contain small dark-colored
plates and fragments of an earthy character, but apparently the remains of lignites.
In some of them, the carbonaceous material is quite apparent; and in the softer
and more decayed parts of the rock, I found several specimens in which the organic
structure of plants was well exhibited. The small black films in the sandstones
of the bay of San Francisco, that have already been described, all lie in planes
parallel with the stratification, and are similar to those in the hard masses of this
and I consider them, in part, as of vegetable origin. The thickness of this stratum,
151
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l._
20
I,.... )-..
I
I:
A.,
locality;.
6
15
63
30
600
25
30
1 14
~4'
.
oN
15
1i
16
6
150