7i8 



JAMES H. GARDNER 



The Puerco and Torrejon formations are not sufficiently contrasted 

 lithologically to permit of their being readily separated at all points 

 without fossil evidence. Along the Puerco River, where erosion 

 has removed the greatest amount of material the stratigraphic suc- 

 cession is more clearly exposed than at any other point within the 

 area. Here the entire group, with a total thickness of about 835 

 feet, forms prominent escarpments, mesas, and badlands along a 

 wide belt between the outcrops of the "Laramie" and the Wasatch. 



Fig. 4. — Torrejon formation, eight miles northeast of Encina Spring, New Mexico; 

 showing one of the natural monuments from which the Arroyo Torrejon takes its 

 name. 



In this vicinity, the Puerco formation is characterized to some degree 

 by the presence of dark to black layers of carbonaceous shale. At 

 a point about three miles north of east of Nacimiento and at about 

 the same horizon, near the base of the formation eleven miles west of 

 south of the same town, there are local thin lenses of coal in the Puerco 

 formation. In the Torrejon formation northeast of Encina Spring, 

 where fossil mammals were found, thus enabling positive identifica- 

 tion of those beds, there are occasional, lenticular layers of dark 



