E. Bose — Permian of CoaJmila, N. Mex. 187 



Art. XII. — On the Permian of CoaJmila, Northern Mex- 

 ico; by Emil Bose. 



In 1913, Doctor Erich Haarmann published his dis- 

 covery of marine Permian beds in northern Mexico.^ 

 This discovery was rather surprising, as everysvhere in 

 northern central Mexico the lowest exposed rocks had 

 seemed to be of the Upper Jurassic. Furthermore, there 

 did not appear to be any indications of large dislocations, 

 which alone could apparently be the explanation of an 

 exposure of lower beds, as the Jura-Cretaceous series 

 seemed to be uninterrupted at every point of this region 

 where the geology was known. Haarmann on a very 

 rapid journey found the Permian beds on the Hacienda 

 de las Delicias, 68 kilometers north of San Pedro de las 

 Colonias, at the foot of the high Sierra del Sobaco, in the 

 southern part of the state of Coahuila. The geographic 

 position of these Paleozoic beds made the occurrence still 

 more surprising, since a little south of San Pedro the 

 Upper Jurassic is exposed in many places (Concepcion 

 del Oro, Mazapil, Sierra de Ramirez, San Juan de Guada- 

 lupe, etc.). Moreover, w^est of San Pedro de las Colonias, 

 the same conditions had been observed at San Pedro del 

 Gallo, Durango, and as it is well known that the Jura- 

 Cretaceous series exists in many parts of eastern Chi- 

 huahua, it therefore seemed very improbable that any 

 Paleozoic rocks were exposed in this region. On the 

 other hand, the discovery could scarcely be doubted, 

 especially since Haack published^ an account of the little- 

 fauna of Permian age collected by Haarmann. 



Haarmann distinguished two different Paleozoic for- 

 mations at Las Delicias. He considered as the older one 

 a series of at least 2000 meters thickness, the lower por- 

 tion of which is largely volcanic in nature and consists 

 mainly of pebbles and cemented sands ; upward the 

 pebbles grow smaller and decrease in quantity; thick 

 beds of sands derived from volcanic rocks predominate 

 and might at first view be taken for weathered volcanics : 

 still higher follow dark to black marly shales and marls, 

 which contain geodes and beds of dark limestone. Haar- 



"■ Erich Haarmann, Geologische.Streifziige in Coahuila. Zs. deutsch. geol. 

 Ges., 65, 1913, Monatsberichte. 



^Wilhelm Haack, Ueber eine marine Permfauna aus Nordmexico nebst 

 Bemerkungen ueber Devon daselbst. Zs. deutsch. geol. Ges., 66, 1914. 



