G. F. Becker—Mineral Belts of the Pacific Slope. 211 
The Arizona deposits lie in a zone stretching entirely across 
the territory from southeast to northwest. This zone includes 
or lies close to the dividing line between Paleozoic strata to the 
northeast and the Archzean area of Southwest Arizona, depos- 
its occurring both in the granites or crystalline schists and in the 
Paleozoic limestones. The main contact between the Paleo- 
zoic and the underlying strata is laid down, in the geological 
maps of the Surveys West of the 100th Meridian, continuously 
from Virgin Cafion to Camp Verde, a distance of 170 miles, 
Farther south the most westerly occurrences of Paleozoic shown 
are in the Pinal mining district near Florence and in latitude 
32° 20’, longitude 109° 40’. These are probably near the edge 
of the area, though there is some evidence of detached patches 
still farther to the south, and to the west of the general course 
of the contact so far as traced. The Chiricahui range has been 
shown by Mr. Gilbert to be largely made up of Paleozoic strata, 
and the mines of the Tombstone district are many of them sun 
on deposjts in limestone. In this region limestones can hardly 
be ne than Paleozoic, and they are reported as containing 
Carboniferous fossils. 
he rocks adjoining the Paleozoic to the southwest are un- 
questionably Archean, for their relations to the Silurian are 
Clear at a great number of points, and their lithological charac- 
ter in this region is very characteristic and persistent. The 
edge of the Paleozoic has also been followed by Mr. Gilbert in 
a westerly direction into California, near Owens Lake, whence 
'ts course is deflected to the north (Mesozoic strata, in part over- 
lie close to the contact. Scarcely anything is known of the 
geology of the region north of Battle Mountain, but Mr. Meek 
determined fossils cdllected on the northern boundary of the 
nited States at the 114th Meridian by Mr. Geo. Gibbs as Car- 
boniferous,* and it is probable that the contact passes through 
the mining region of Idaho. 
The western edge of the Paleozoic in the belt of country 
surveyed by the Exploration of the Fortieth Parallel represents 
the structural line along which the Paleozoic area of Eastern 
Nevada and Western Utah was uplifted at the close of the Car- 
boniferous. In Arizona faults practically parallel to the trend 
of the contact are known to have had an important influence 
on the orography of the belt of country in which the contact 
between: Archsan and Paleozoic occurs, but how far if at all 
the present exposure of Archzean is due to the erosion of Pale- 
* Bull. U. S. Geog. and Geol. Surveys, vol. ii, p. 351. 
AM. Jour. Sc1.—Turrp Serres, Vou. XXVIII. No. 165.—Sepr., 1884. 
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