ransome: the ray quadr.\ngle 387 



characteristic Devonian fossils. These Hnk the formation so 

 closely with the Martin limestone of the Bisbee region as to 

 warrant the extension of the name Martin limestone into the 

 Ray-Globe region. 



In the Ray quadrangle the formation is comparatively thin- 

 bedded and is divisible into two nearly equal parts, recogniz- 

 able in natural sections by a difference in color. The prevailing 

 hue of the lower division is hght yellowish gray, while the upper 

 division, less uniform in tint, displays alternations of deeper 

 yellow and darker gray. No identifiable fossils have been found 

 in the lower division which consequently can not be regarded as 

 unequivocably Devonian. The top bed of the formation is a 

 yellow calcareous shale, which breaks up on exposure into minute 

 thin flakes and which consequentlj^ has no prominent outcrops. 

 The yellow color is characteristic of all natural exposures, al- 

 though before weathering the shale is gray. Being overlain by 

 thick-bedded chff-making Carboniferous limestone, the bed of 

 shale is in many places concealed by talus and^its thickness has 

 not been exactly determined. It may be from 15 to 20 feet. 



The average thickness of the Martin hmestone in the Ray quad- 

 rangle is 325 feet, which compares closely with the 340 feet found 

 at Bisbee. 



Devonian, presumably the Martin limestone, has been found 

 by Prof. C. F. Tolman Jr.,^ in the Santa Catalina Range. The 

 presence of the Martin limestone has been fully established also 

 in the Roosevelt section by the finding, in 1914, of sufficient 

 fossils to confirm a lithologic and indecisive paleontologic identi- 

 fication made a year earUer, A list of the fossils, as determined 

 by Dr. Edwin Kirk, and a fuller discussion of the extent and 

 correlation of the Devonian will be published later. 



Tornado limestone. The Devonian Martin limestone is con- 

 formably overlain by thick-bedded light gray limestone that is 

 nearly everywhere a prominent cliff -maker in the Ray-Globe 

 region. The name here used is derived from Tornado Peak, in 

 the Dripping Spring Range. The Tornado hmestone as exposed 



^ Unpublished manuscript of Tucson folio. 



