Eureka daily sentinel. [volume] (Eureka, Nev.) 1871-1887, 1878-11-07
RI CANYON.
Captain Foley on the Geology of
that Section.

that Section.
EDrroR SENTINEL: Biologists conclude
that the heat of the earth's still molten
nucleus is but o remnant of the heat that
once made molten the entire earth. If we
inquire the origin of those forces which
nave wrought or worked the surface OF our
globe into its present shape, we find them
traceable to changes that are commonly di-
vided into aqueous and igneous heads, under
which we may most conveniently con-
slider them, evidences of the deposits of
an inland sea may be observed by any one
as he rides or travels along the road on his
journey from Eureka to Secret Canyon.
He will see, high above the valley, rem
nants of the old internal sea. While the
geological formation Of Ruby Hill is quite
a simple one, for the reason that the mass
of the hill is formed of an underlying bed
of quartzite, which is capped by transition
strata of silicious limestone, and followed
upward by heavy beds of crystalline met
amorphic limestone, Ruby Hill is evident
ly a spur of Prospect Mountain, and is
tut crouch lIdRIltut VI u lDlu I HtOuiithlu
uplift. The strata Of which it is composed
are submarine in origin, and the testimony
of the fossils indicate that it was an
oceanic deposit. That Of Secret Cam
yon is more complicated and difficult
to understand. The evidence is that floods
Of boiling rocks poured out through beds
of sedimentary rocks, and now lie deeply
buried under a series of eruptive rocks.
This is q fact Of great significance to
prospectors, for the reason that If a primary
ocean had not flowed for ages over this sec
ton, no gold or silver could be found i'll
the rocks. The evidence further shows
that foods of boiling rocks rose high on
the southern TANKS Of the Hoosac and
Prospect mountains, and rolled southwark
into a lake which stood many hundreds Of
feet higher than the present level of the
desert lying a little south Of Secret Canyon.
The evidence Furthermore shows that while
this heated rock cooled under the atmo-
sphere at high elevation and named
~propylite, lower down it became sub
merged and cooled under water and with
the same mineral constituents formed a
tufaceous porphyry. Time passed and the
neither fire sea broke out again. 1t broke
put through the ~propylite and overfiowed
it. This rock contains granules OF quartz:
1t is intermediate between porphyry and
trachyte. This rock has suffered much
decomposition, and the product Of decay
appears as q white, cbalky clay. Another
grea. event in the geologic history Of this
district was the outbreak Of q rock named
dolerise: LIS a greenish color; sometimes
Il is black and takes the name of black jack;
is the matrix of ore bodies Of Secret Canyon.
This dolerite forced its way up between
the diorite and propy.ite, splitting these
rocks asunder. This outbreak seems to
have been the cause Of the formation Of
the fssures in this section. Such an i'm
mense uplift as this, with the consequent
pressure in the axis OF the folds, produces
two great effects, the metamorphism Of the
strata and the assuring OF the strata.
Connected with such deep-seated assuring
is the chemical action which has made
itself evident through these assures, re-
sulting in mineral veins and metallic
lodes. The surface Of the district has
been shaped by glacial action. which has
left its record in characters that are not
easily obiiterated by atmospheric or other
influences. The polished, grooved or
striated rocks and erratic powders, de-
note the existence Of moving ice. The
canyons are cut down into the hard meta
morphic quartzites and porphyries, slowly
worn by the swift currents of streams car
rying large quantities Of water issuing
from the glaciers. The quantities. occu-
plying the summit Of these ridges have I'M
dergone q change by metamorphism. Be-
ing hard and dense, and not subject to
disintegration by the atmosphere, they
retain the polish and striation Of the NOV
ing ice. The metallic field is four miles
wide and six miles long, and contains
within this area many metallic deposits
that will eventually be Of much benefit to
Eureka county. JOHN NJ. Foley.