570 HEALD AND MATHER— RECONNAISSANCE OF EASTERN ANDES 



This same direction of stress seems to hold in the more intensely de- 

 formed areas. On the east front of the mountains the Bermejo sand- 

 stones form well-defined hogbacks, or cuestas, whose back slopes dip 

 eastward with angles of 20 degrees or less until they disappear beneath 

 the Quaternary deposits of the Santa Cruz plains. 



