REVIEWS 



The Copper Deposits of Ray and Miami, Arizona. By Frederick 

 Leslie Ransome. U.S. Geological Survey, Professional 

 Paper 115. Washington: Government Printing Office, 19 19. 

 Pp. 186, pi. 54, index. 



The region described is about 70 miles southeast of the center of 

 Arizona, in the mountainous district separating the plateaus of north- 

 eastern Arizona from the desert plains of the south. The Ray district 

 lies in Pinal County; Miami is 18 miles north-northeast of Ray in Gila 

 County, and 4 miles west of Globe, the geology of which was described 

 by Ransome in Professional Paper 12. 



A brief description of the earlier mining operations is followed by a 

 bibliography and commentary. The stratigraphy of the region is then 

 considered. The area is crossed by four ranges of hills and mountains, 

 trending roughly northwest and southeast and separated by broad 

 valleys which are partly structural in origin. The rock sequence com- 

 prises limestone and clastic sediments of pre-Cambrian, Cambrian, 

 Devonian, and Carboniferous age, followed by intrusives of Mesozoic 

 and Tertiary time, above which lie Tertiary and Quaternary elastics 

 and lava flows. The succession does not differ markedly from that of 

 the Globe district as presented in the work already referred to. The 

 pre-Cambrian rocks are partly sedimentary, partly meta-igneous, as 

 shown by chemical analysis and petrographic study. New formations 

 are distinguished in the Cambrian, thanks to the better exposures in 

 this area. These and the succeeding rocks are described in chronologic 

 order, without separating the igneous rocks, as is the common custom. 



Notable igneous intrusions occurred during Mesozoic times, the 

 magmas ranging from basaltic to granitic. Andesitic extrusions of 

 Cretaceous age are noted; no definite progressive differentiation is 

 observed. The early Tertiary, too, was marked by acid and inter- 

 mediate extrusions, and these were succeeded in turn by the deposition 

 of conglomerates, sandstones, and flows of which the Gila conglomerate 

 (provisionally assigned to the Pleistocene) is especially noteworthy; this 

 formation is thought to be of alluvial origin and has a thickness of 2,500 

 feet; it offers attractive problems to the student of sedimentation. 



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