DIASTROPHICS OF NORTHERN MEXICO 



77 



older rocks were incidentally noted very early. These outcrops 

 were so widely disconnected as to give rise in some quarters to not 

 a little doubt concerning the actual presence of some of the terranes. 



,1' 



NEW MEXICO 



Fig. I. — Areal distribution of Paleozoic periodic formations 



Pioneer observations now seem to be fully verified. As early 

 as 1874 Dr. W. P. Jenney' called attention to the presence of Cam- 

 brian rocks in the FrankUn Range north of El Paso. In the same 

 locality Dr. A. Wislizenus,^ thirty years before, collected charac- 

 teristic Ordovician fossils. Numerous organic remains of Silurian age 



' Proc. New York Lye. Nat. Hist., Vol. II (1874), p. 69. 



* Memoir of Tour through Northern Mexico in 1846-47 (1848), 141 pages. 



