Old Mines of Southern California: Desert-Mountain-Coastal Areas Including the Calico-Salton Sea Colorado River Districts and Southern CountiesFairbanks, Harold W. (Harold Wellman)
History
Old Mines of Southern California: Desert-Mountain-Coastal Areas Including the Calico-Salton Sea Colorado River Districts and Southern Counties
Fairbanks, Harold W. (Harold Wellman)
Geology -- California, Southern; Mines and mineral resources -- California, Southern
extend to the summit, and undoubtedly further examination would reveal
more fossils. Several specimens were sent to the National Museum and
pronounced Carboniferous in age. We have here, then, the first
announcement of the age of the Santa Ana range. This range stands in
such intimate relation to the granite and crystalline schists farther
south, that an approximate determination of the latter is made possible.
Professor Whitney and others following him have classified this range as
Cretaceous. Their grounds are utterly untenable stratigraphically, but
this discovery of Carboniferous fossils makes the evidence of greater
age certain.
On the eastern side of the range, near its northern end, the sandstones
were observed to be silicified, being filled with a network of quartz
veinlets, exactly similar to the silicification of the metamorphic rocks
of the Coast Range proper.
The lowest Cretaceous beds are between Silverado and Williams Cañons,
but the fossils are very similar to those generally found through the
Cretaceous of this region. The lowest beds are a duplicate of those seen
at the mouth of the Silverado Cañon, though apparently a thousand feet
lower in the series. Between the two beds there is another conglomerate
stratum, carrying bowlders different from any seen in the Santa Ana
Mountains. Many of the porphyry bowlders in the basal Cretaceous
conglomerates resemble the porphyry about Temescal. The Santa Clara Coal
Mine, at the mouth of Silverado Cañon, is undoubtedly in strata of
Cretaceous age, though no fossils are found in the strata above till the
Miocene is reached. Up the Santiago Cañon as far as Madame Modjeska’s
place, the fossils are chiefly confined to the eastern side of the
cañon, but the character, dip, and strike of the strata on both sides
are the same. The Cretaceous is separated from the metamorphics by a
line of cross cañons. The highest portions of the Cretaceous terminate
in a line of hills with sharp eastern escarpments.
Shrewsbury Cañon comes in just below Modjeska’s. After passing the
Cretaceous, through which the cañon has cut, the Metamorphic Series was
seen to consist of slates and sandstones, followed by light-colored
granitic rocks, chiefly hornblende and triclinic feldspar. The
metamorphic rocks generally dip to the east.
A mile above Modjeska’s the Santiago Cañon cuts through bold cliffs of
Cretaceous sandstones and conglomerates, and higher up still has eroded
a cañon in the Metamorphic Series. The cliffs, a little back from the
stream, rise probably 1,000 feet. Sandstone belonging to the Metamorphic
Series outcrops in the cañon for some distance, and is followed by
conglomeritic porphyries, containing purple and red bowlders. In some
places the inclusions are angular. These rocks are extensively developed
about the Santiago Mines and higher up in the mountains.
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