This historic book may have numerous typos and missing text.
Purchasers can download a free scanned copy of the original book
(without typos) from the publisher. Not indexed. Not illustrated.
1888. Excerpt: ... CHAPTER III. THE SEDIMENTARY ROCKS. General
character.--The Coast Ranges of California present a truly
remarkable opportunity for the investigation of some of the most
important phenomena embraced under the general term of
metamorphism. To give a clear ideaof the unusual advantages
afforded by this area it is necessary to anticipate some of the
results reached. Field examinations were made for this memoir at
numerous points from above Clear Lake to the region of New Idria,
thus partially covering a belt of the Coast Ranges about 230 miles
in length. Throughout this whole region there is structural and
lithological evidence that granite of very uniform character
underlies the entire country. Excepting the belt of schists along
the coast from Santa Cruz southward, it is estimated that 90 per
cent. of all the rocks of this region are sandstones, altered or
unaltered. These sandstones are also extremely uniform in
character, and wherever they are inconsiderably modified the slides
prepared from them show that they are directly or indirectly
derived from the granite, or, in other words, that they are arcose.
Of this material of known origin a portion has been highly altered.
The alteration processes to which it has been subjected are
identical from one end of the region to the other and innumerable
transitions are presented. It is difficult to estimate the areas
occupied by the metamorphic rocks of the Coast Ranges, because the
occurrences are extremely irregular. A moderate estimate of the
exposures between Clear Lake and New Idria, which consist of
holocrystalline metamorphic rocks, sandstones in which
recrystallization has made considerable progress, phthanites, and
serpentine, is 3,000 square miles. Large areas, covered by late
Cretaceous and Tertiary stra...
General Books LLC
|Country of origin:
||246 x 189 x 10mm (L x W x T)
||Paperback - Trade
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