abundantly and, when found, are on an arid stretch of country several miles from water.
The
geology of Arizona and Utah in the Navajo Reservation has been little
studied, and in the limited time given for the trip to the garnet
region but few notes were obtained to add to the general knowledge. The
route followed led over the mesa country north from Ganado and down the
valley of Nasklini Creek to Chin Lee at the mouth of Canyon de Chelly.
From Chin Lee, through a mistake of the Indian guide, a northwesterly
course was followed to a point within a few miles of Agathla Needle,
some 25 miles S. 60° W. of the garnet fields. From this point the route
led down Gypsum Valley, which drains into the Chin Lee Valley near its
mouth. The garnet field is several miles northwest of this canyon. The
return trip was made over the elevated country south of the garnet
fields, across the Chin Lee Valley nearly opposite the mouth of Carriso
Creek, up Car-riso Creek to Bradley's store, and then south to Chin Lee.
Descending
from the mesa several miles north of Ganado one passes over several
miles of petrified forests in which the trees are not so numerous as in
the famous localities near Adamana. The formation in which the trees
are embedded, however, appears to be identical with that near Adamana.
The rock exposures in Canyon de Chelly and along the Chin Lee Valley
north to the garnet locality appear to be similar and consist
principally of red beds, largely cross-bedded sandstone and
conglomerate. This sandstone forms great blocky vertical cliffs from
one hundred to several hundred feet high along the Chin Lee Valley and
the canyons entering it. This formation extends west from the Chin Lee
Valley and northwest from Gypsum Valley, forming the semimesa country
on which the garnet deposits occur. These red beds may correspond to
those described by L. F. Warda in the Little Colorado region to the south, referred to the Tri-assic age and provisionally thus accepted by N. H. Darton.6
The red sandstones extend over 30 miles west of the Chin Lee Valley to
the region around Agathla Needle. In the latter region basic rocks
outcrop at numerous places and in several instances have formed sharp
needle-like masses hundreds of feet high with small bases. Agathla
Needle is evidently composed of such a rock and stands several hundred
feet high. One of these hills or outcrops about 4 miles south of
Agathla Needle was composed of two types of rock—one a dark, hard,
dense basaltic rock with visible olivine phenocrysts and the other a
dark-gray, somewhat porous olivine-mica rock. A few small pieces of
peridot were found weathered out of this rock. Between Agathla Is
eedle and the garnet locality basaltic and other basic rocks outcrop at
several places both as needles and as dikes, cutting the sandstone
formations.
The
extent of the area over which gem garnets are found was not determined.
Actual examination was limited to a stretch of country about 2\ miles
long in a northwesterly direction and half a mile wide. From the
apparent similarity of the formations around this strip it was judged
that garnets should be found over an area of several square miles,
probably 4 miles north and south and 5 or 6 miles east and west, while
the field might extend several miles beyond a line of hills to the
north.
• Mon. U. S. Geol. Survey, vol. 48,1905, p. 45.
& Reconnaissance of part of western New Mexico and northern Arizona: Bull. U.S. Geol. Survey. (In preparation.)
