58 C. H. Gordon — Mississippian Formations 



Akt. VI. — Mississijppian (Lower Carboniferous ) Formations 

 in the Rio Grande Valley, New Mexico ; * by C. H. 

 Gordon. 



Introduction. 



The observations upon which the following notes are based 

 were made during the summer of 1905 in connection with an 

 investigation by the U. S. Geological Survey of the mines and 

 mining districts of New Mexico under the direction of Mr. 

 Waldemar Lindgren, the results of which are to appear in a 

 forthcoming report by the Survey. For the identification of 

 the fossils collected, the writer is indebted to Mr. George H. 



Girty.f 



Exposures of rocks belonging to the Mississippian series 

 occur at a number of places in New Mexico. They have long 

 been known to occur at Lake Valley, from which circumstance 

 they early received the name of the Lake Yalley Limestone.:}; 

 The observations of the writer show that exposures of the Lake 

 Yalley limestone occur in many places in the region about the 

 southern extension of the Black and Mimbres ranges, and rocks 

 apparently identical were observed in the Caballos Mountains 

 but fossil evidence of the age of these beds is not at hand. In 

 Socorro County there are but two small areas in which outcrops 

 of Lower Carboniferous rocks are known to occur, one in the 

 Magdalena Mountains, where they constitute the principal ore- 

 bearing formation of the lead and zinc mines at Kelly, and 

 another on the Arroyo Salado at the base of the Sierra La- 

 drones, discovered in 1905 by "W. T. Lee,§ of the U. S. Geo- 

 logical Survey. 



The limestones at Kelly are seemingly unfossiliferous, though 

 Lower Carboniferous crinoids are reported || to have been found 

 in them. The evidence on which this announcement is based, 

 however, is lacking, and in the absence of satisfactory data these 

 beds can not well be correlated with the Lake Yalley lime- 

 stone. Herrick^f gave to these beds the name Graphic-Kelly 

 limestone. A hyphenated name of this kind is objectionable 

 and they will be here referred to as the Kelly limestone, from 

 the town in the vicinity of which they occur. 



* Published by permission of the Director of the U. S. Geological Survey. 



f A bulletin of the U. S. Geological Survey treating of the fauna of the 

 Lake Valley formations is now in preparation by Dr. Girty. 



% Cope, E. D., Eng. and Mining Jour., vol. xxxiv, p. 214, 1882. 



§ Personal communication. 



|| Herrick, C. L., Am. Geol., vol. xxviii, p. 310, 1904 ; Jour. Geol., vol. 

 xii, p. 138, 1904. Keyes, C. E., Proc. Iowa Acad. Sci., vol. xii, p. 169, 1904. 



^[Loc. cit. 



