Mohave County miner. [volume] (Mineral Park, A.T. [Ariz.]) 1882-1918, 1911-11-11
Great Placer Gold Region.

of the 3OO,OOO,OOOS of California gold
which has been mined from the Ter
tiary placer gravels of the Sierra
Nevada is the subject of an exhaustive
report by Waldemar Lindgren, geolo-
gist, which has been issued by the
United States Geological Survey as
Professional Paper %.
Studies by the Geological Survey on
the Tertiary placer deposits of the
California Sierra began in 1856 and
were concluded about 10 years later
During this period y qnadrangles
were geographically mapped and IA
of these were studied in geologic de-
tail and the results published by the
Survey in geologic follos. Profession
al Paper 70 includes the salient feat
ures of this earlier work, most of
which was accomplished by Mr.. Lind
gren himself. The report, thus COM
prehensive in geographic scope and
the result of careful studies, is belev-
ed to be the most complete and
thorough description of a great placer
gold province ever published.
While in the main the report is a
detailed description of the entire area
covered, including these gold placer
gravels, Mr.. Lindgren's general &C
count of the tremendous earth forces
which built up the Sierra, freed the
gold from its mother rock, and then
brought about its concentration in pre-
historic river channels is most i'm
pressive description of continent build
ing. Looking backward through in
conceivably long vistas of time in
which periods covering millions of
years supplant the centuries by which
we now compute its passage, the geol-
ogist pictures the uplift of the new
born mountain range by the forcing
upward of great bodies of molten gran
tie. This was closely followed by the
introduction of veins and seams of
gold-bearing quartz. The resulting
highland due TO this continental up
lift was then planned down by erosion
in early Cretaceous time-a geologic
period many thousands of years before
the advent of man upon the earth.
After this erosion, and when the
mountains had been reduced to gentle
outlines, deep rock decay took place
and much gold was released. Renew
ed uplift and the formation of sleeper
slopes resulted in greater erosion
which concentrated the loosened gold
along definite stream channels. Dur
ing this period of most active gold con-
centration, faulting and slipping of
the rock masses, with downthrow on
the east side of the Sierra, had trans
formed an approximately symmetrical
mountain range to one with a steep
easterly slope.
Tracing the long pathway of this
early history the geologist now finds
that toward the end of what is known
as Tertiary time-a comparatively re-
cent geologic period long quiescent
volcanic forces vigorously reasserted
themselves. Rhyolite flows pouring
from many craters filled the valley
covered with gold bearing gravels,
deeply burying the gold, and new
stream courses were outlined in the
old valleys. Renewed disturbances
and eruptiOns began along the scarcely
healed eastern breaks of the Sierra,
resulting in a westward fitting of the
main blocks of rock. This encouraged
deeper cutting by the streams, which
repeatedly crossed their old courses,
so that now the concentration of gold
proceeded under less favorable torren-
tial conditions. At this time volcanic
vents were opened along the crest of
The Sierra, many of them sending forth
immense volumes of lavas, ashes, and
mud. These great flows filled many
of the valleys to their rims and con-
verted almost the whole of the north
ern Sierra into a desolate steaming
mass of volcanic mud. Storm waters
now began the canyon-cutting epoch,
amazing in its results as we see them
to-day. In many places the old rivers
of Tertiary time were exposed, and
cross sections of their valleys are now
seen on the steep canyon slopes, many
of them high above the present river
beds; but large stretches of the old
river channels remain blanketed be-
meath Thousand feet or more of vol
canic mud, now hardened into rock
The geologic events thus outlined