Agate.—Agate
in bowlders from a few inches to a foot across, of rich red, brown, and
mottled tints, is found in the vicinity of Austin Bluffs, near Colorado
Springs and Colorado City, Colorado.
Agatized wood.—In
the eighth annual report of the U. S. Geological Survey for 1886-87,
Prof. Lester P. Ward, has contributed the most exhaustive treatise on
the geological distribution of fossil plants throughout the world,
including silicitied and agatized wood, that has appeared up to the
present time. He says:
"
These remarkable petrifactions are believed to occur in the Shina-rump
group of Powell, and their mode of occurrence is described by him in
his ' Geology of the Uintah mountains,' 1876, p. 69. These great trees
of stone are believed by the Indians to be the shafts of their
thunder-god, Shinauav, and from this Major Powell named the group,
which he regards as of Cretaceous age."
On
visiting Chalcedony Park, the nearest of the three so-called forests
in this formation on the Atlantic and Pacific railroad, the writer
found it to be about a mile square and inclosed by table lands from 50
to 100 feet in height. Nearly all the agatized wood is found on the
flat plain below these table lands, and rests on layers of sandstone.
The lower layer is chocolate-red, another white, another black, and
another a compact sandstone, gray, and on these rests a layer of white
sandstone in which all the wood at this locality originally belonged.
By the washing and weathering away of this formation, the tree trunks
have rolled down to the level plain below, and none of them were ever
in place there. In the upper layer, where they belong, no trunks occur
in the upright position, nor were any roots visible; and since none of
the trees retain any of the original bark, it seems very probable that
all this deposit was once the bed of an inland sea or lake.
There
exist two more deposits of jasperized wood, distant respectively 8 and
16 miles from Chalcedony Park; and also a number of outcrops of this
material are seen along the line of the Atlantic and Pacific railroad,
although the quality is not as fine as that of the three original
deposits.
Within
3 miles of Los Cerrillos, New Mexico, there is a small fossil forest of
agatized and jasperized wood, closely resembliug that of the Chalcedony
Park in Arizona. Two sections from this locality, weighing about a ton
each, are to be seen in the collection of the Historical Society of New
Mexico, at Santa Fe.
Dr.
Alexis A. Julien, who has made a careful microscopic, study of the
jasperized wood, made the following communication to the New York
Microscopical Society at the January meeting, 1892: " In the jasperized
wood from Arizona, many of the wood cells are traversed by the
well-preserved mycelium of a fungus, secreting iron oxide, of which the
still living species has already been described.—[Jour, of the N. Y.
Microscopical Society.] The fine threads are silicified and heavily
coated with yellowish to reddish brown ferric oxide, and, by their
minute and
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