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.
1907 Excerpt: ... the river, at the old lock site south of Bohio
and east of Pena Blanca, quite a different phase of this formation
is exposed; it consists of alternating layers of sandstones and
course conglomerates all clearly water transported and deposited.
Many of the bowlders are a foot or more in diameter; they are of
andesites for the most part, but not a few are of a lighter colored
porphyritic rock with abundant hornblende crystals. The finer
layers and the cementing material are very like the rock occurring
at the Bohio quarries. Crossbedding is common and fine material
often occurs in lenses in the grits and conglomerates. The
prevailing strike is N. 25 E., and the dip to the northwest at an
angle of about 14 degrees. The identity of these conglomerates and
the more even-textured breccia-like rock is not at all evident in
the field, but many borings made in the vicinity show a gradual
transition southward from the even-textured breccias of Bohio to
the conglomeratic facies at Pena Blanca. The boring made at
kilometer 24 (hole 24-b) is of interest, since it shows
carbonaceous sandstones in the middle part and fossils in the lower
part of the core. Further study of this formation to the southeast
and by means of borings has shown that it is of variable character,
in some places clearly sedimentary and water sorted, both fine
grained and conglomeratic; in other places the appearance is more
that of a volcanic breccia, possibly water laid but not water
transported. The pyroclastic appearance may be a deceptive one and
due to the alteration of the rock. In general the formation may be
described as a probable fluviatile deposit characterized by sudden
changes and transitions, the composition of the materials being
fairly uniform. It is not improbable that volcanic eru...
|Country of origin:
United States Congress
||246 x 189 x 5mm (L x W x T)
||Paperback - Trade
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