1922] Vaughan: Geology of San Bernardino Mountains 363 



quartzite, 430 feet in thickness. Above this is the Abrigo limestone, 

 which is 770 feet thick and contains middle Cambrian fossils. Across 

 the Mexican border at Cananea 15 are the Capote quartzite and the 

 Puertecitos limestone, which are believed to be correlatives of the 

 Bolsa and Abrigo respectively. Again in the Clifton-Morenci 10 dis- 

 trict we find a similar sequence. The loweraiost sedimentary forma- 

 tion is the Coronado quartzite of Cambrian age and above it lies the 

 Longfellow limestone, which is Ordovician. Quartzite is also found 

 at the base of the section at Globe, 17 but, as the oldest fossils above it 

 are of Devonian age, its correlation is less certain. 



The upper age limit of the limestone and the age of the Saragossa 

 quartzite is only conjectural. No Ordovician, Silurian, or Devonian 

 rocks are found in the Iron Mountains, and yet the structural break 

 between the Cambrian and Carboniferous is not marked. This may 

 have been due to a slight uplift which prevented deposition during 

 that time. A similar uplift in the San Bernardino Mountain region 

 may have merely brought about a change to near-shore conditions 

 which would permit the deposition of the Saragossa quartzite. If the 

 Furnace limestone is partly Ordovician as suggested, however, this 

 uplift must have been later in the San Bernardino Mountain region 

 than in the Iron Mountain region. This would mean that the Sara- 

 gossa is Silurian or Devonian. 



Conclusion. — Prom the evidence available at present it seems prob- 

 able that the Arrastre quartzite was deposited in lower Cambrian time. 

 During upper Cambrian and Ordovician time the Furnace limestone 

 was laid down. The Saragossa quartzite is probably Silurian or 

 Devonian. 



Granites 



Granites are the most widespread rocks in the region. Nearly all 

 the rocks outcropping in the portion of the Mohave Desert included in 

 this area are granites. The largest area in the mountains extends from 

 Cienaga Seca Creek and Rattlesnake Canon eastward beyond the limits 

 of the San Gorgonio Quadrangle. Another large area extends from 

 Bear Lake southward to Little San Gorgonio Creek and southeast- 

 ward beyond San Gorgonio Mountain. Besides these masses there are 



i° Emmons, S. F., Cananea Mining District of Sonora, Mexico, Economic 

 Geology, vol. 5 (1910), pp. 312-356. 



is Lindgren, Waldemar, Copper deposits of the Clifton-Morenci district, Ari- 

 zona, U. S. G. S., Professional paper no. 43. 



17 Kansome, F. L., Geology of the Globe Copper district, Arizona, U. S. G. S., 

 Professional paper no. 12. 



