The Pre-(Jretaceous of California. — Fairhankx.. 71 
Cisco granite outcrops first near Pt. San Pedro, and appears at 
intervals, above the Tertiary wliicli covers the western slope of 
the mountains, as far as Santa Cruz. Ten miles away in a south- 
east direction, in line with the former outcrops, rises the Gavilan 
range, called by Prof. Blake •' a might}- mass of primitive rock." 
The range proper has a length of fifty miles and a width of ten. 
It is composed almost wholly of granitoid rock. Near the 
northern end are bodies of limestone and crystalline schists. 
Southeast of the Chelone peaks the range blends with the Monte 
Diablo range, and the granites are largely replaced by rocks of 
the Metamorphic series. These rocks form a long high ridge 
which sinks beneath the Tertiar}- before reaching Polonio pass. 
The granite of the Gavilan range does not terminate in the Che- 
lone peaks, but outcrops in places along the western base of the 
Metamorphic ridge for a distance of forty miles more. Its 
width cannot be determined for it is covered by the Tertiary on 
the west. 
In the canyon of Nelson creek the granite is seen to be brec- 
ciated, and to include broken strata of limestone. In a small 
gulch which enters the canon of Nelson creek from the high ridge 
of Metamorphic rocks on the northeast, there is exposed one of 
the most important contacts seen in the whole Coast range, and 
one which should settle the disputed question of the relation of 
the granites to the Metamorphic series. The gulch cuts squarely 
across the formation exposing the succession of strata very finely. 
Beginning at the mouth of the caiion we find outcropping first a 
fine grained granite so crushed that a hand specimen could not 
be obtained; next a stratum of limestone also brecciated and 
wholly inclosed in the granite. Following the granite, another 
irregular stratum of limestone. These dip to the southwest at 
an angle of 80 degrees, the granite overlying. They are followed 
by several hundred feet of mica schist, often presenting a pearly 
and hydrous appearance. Another stratum of limestone adjoins 
the schist, and that is succeeded })y a width of twenty feet of 
banded green jasper. Then there is a great body of semi- 
crystalline limestone thirty feet thick; above that, green jasper 
again; the whole .series dipping 80 degrees southwest. Farther 
up the hill the jasper gives place to crushed sand.stone and ser- 
pentine. It does not seem that there can be any doubt about the 
granite having Ijcen intruded into these rocks which are an in- 
