The silver state. [volume] (Winnemucca, Nev.) 1909-1925, 1913-09-27
THE Wise man
DEFINES ROCK

oCOfOkltdf survey, Ou tnc HifncS VI
Humboldt county is of particular in
terest, even though his survey was
made prior to the discovery of Roch-
ester. He has this to say, in part, Of
the Humboldt range:
"The Humboldt range has a total
length of about rs miles, and attains
maximum altitude, in Sar Peak, of
nearly 10000 feet. AS all who have
written about the range have recog-
nized, it is divisible into two distinct
parts, separated by a fault, the posi-
tion of which is marked by a low
transverse pass known as Cole canyon.
The northern division, called by Lou
derback the Star Range Peak. trends
north and south, an is about 32 miles
long. The southern part is called by
the same writer the Humboldt Lake
Range, and trends northwest by south
west and is over forty miles long. The
course Of Cole canyon is north-north-
west.
According to Hague the Hum
boldt range consists of an Archean
nucleus upon which rest Triassic
strata of great aggregate thickness.
These are overlain by Jurassic beds.
There are also, on the lower slope, con-
siderable masses of Tertiary rhyolite
and basalt and a few rather small ex-
posures of Miocene beds belonging to
the Truckee formation.
When it is remembered that the
geologists of the fortieth parallel
survey mapped an enormous area, that
tions necessarily depended upon the
III r
seen from some commanding point of
view, that their geologic field work
was done before the Topographic maps
were available, and that the science of
microscopieal petrography was then in
its infancy, no surprise need be felt
that many and important changes
must be made in their mapping by
those who follow in their footsteps.
Louderback has shown that the So
called Archean nucleus, exposed in
Rocky canyon, southwest of Ryepatch,
consists of mass of post Triassis in
trusive granite with associated con-
tact metamorphic rocks. The intrus-
ions as Luderback observes, probably
took place during the period of post
Juriassic reformation, that affected
the great basin region and the Sierra
Nevada.
':The total thickness is roughly es-
timated by Hague at 1000 feet.
"The Star Peak formation is noted
for its abundant middle Triassic ver-
tebrate and intervettrebrate fossils,
which have been described by others.
The stratigraphic section, however,
is much in need of detailed study.
Less hurried work will, / believe,
make considerable changes in the Sc
quence and lithology as interpreted by
Hague, and is likely to show some
duplication of units in this section.
Hyatt and Smith state that the upper
Triassic is also represented in the
Humboldt range and lists half a doz-
; en- fossils. The beds containing them
are said to be uncomfortably overlain
by limestone containing Jurassic
forms.
"The lower division of the Triassic
was called by Hague the Kiopato for
nation, from the Indian name of the
Humboldt range. 1t is described as a
ceries of quartzite and "porphyroids,
with total thickness roughly estimat-
ed at 5000 feet The "porphyroids, I"
although recognized as closely resem-
bling eruptive rocks, were regarded by
Hague as metamorphic products of
the mixed quartz and feldspar rocks
of the serles of beds underlying the
limestone of the Star Peak Triassic. -
90 In the light of modern petropraph-
ic knowledge, Hague's descriptions
and the accompanying chemical analy-
ses of the "porphyroids strongly
suggest that they are not metomor-
phosed sediments, but are for the most
part eruptive rocks. The exigencies
of hasty reconnaissance did not per-
init thorough examination of the
Kiopato formation in 1908. Enough of
it was seen, aowever, to leave no
doubt of its dominantlv ingenious
character. 1t consists of volcanic
flows, mostly rhyolitic, but including
also andestIc lavas, associated with
tufts, conglomerates, grits and lime
stones. The porphyroids are for
the most part true igenius porphy-
ries, although some ofthe tufts may al
so have been included under this des-
ignation. AS is to be expected in the
pre-tertiary lavas that have been sub
iected to considerable reformation,
the originally more or less CLASSY rocks
are devirified and altered. in some
places even to being rendered rudely
sehistose. The extrusive and tuff-
aceous rocks are cut by rhyolitic and
diortie dikes that are also of early
Mesozoie age, and the Kiopato forma-
tion as whole is a volcanic complex
of which volcanic sediments, in
eluding limestones, form a subordi-
nate part. No true quartzite was OBJ
served in the Kiopato in the course of
reconnaissance.
Hague calls attention to the fact
that the division of the Sar Peak
formation is very similar to the Kio-
patio formation. An examination of
these rocks near the Sheba mine, in
Star canyon, shows that they com
prise andesitic and rhyolitic flows
tufts with some beds of tuffaeious grit
and of limestone. All are altered and
are slightly schistose parallel with the
ha1 II