7i6 



JAMES H. GARDNER 



form hog-backs. At some places the slopes are extensively covered 

 by bowlders and wash, principally granite and granite porphyry 

 from the mountain mass. The broad plateau country, stretching 

 westward to San Juan River, is a dry, barren expanse of highly 

 colored mesas and badlands, known as the Nacimiento Desert. 



The following generalized section presents the stratigraphic 



Fig. 3. — Silicified stump in Puerco formation, near Encina Spring, New Mexico 



relationship of the Nacimiento group in the region of the Puerco 

 River: 



GENERALIZED SECTION OF ROCKS IN THE PUERCO REGION 



System 



Quaternary 

 Tertiary 



Cretaceous 



Series 



Pleistocene 



Eocene 



Upper 

 Cretaceous 



Group or Formation 



Recent terraces, etc . 



Wasatch formation (Unconformity) 



Nacimiento group ( Torrejon formation 



(Unconformity) < (Unconformity ?) 



( Puerco formation . . 



"Laramie" formation 



Lewis shale 



Mesaverde formation . 



Mancos shale 



Dakota sandstone 



Thickness 

 in Feet 



0-50 



1,000 

 275 



560 



900 

 500 

 400 

 1,000 

 300 



