' LACCOLITHIC STRUCTURES 
117 
Oroche Peak, the high point of the group, lies beyond the belt of 
altered limerock. The cuneiform outlines of the laccolithic mass 
are especially conspicuous. 
Bysmalithic JSlature of Ortiz Mountains. The striking pecu¬ 
liarity of the Ortiz mass is that it occupies the full width of the 
Fig-. 8. Cross-section of Tuertos I.accolith. 
Sierra del Oro mountain-block. It reaches from verge to verge 
of the great horst. Viewed in transverse section the intrusive 
body is in all essential respects a typical bysmalith, as so clearly 
differentiated from the normal laccolith by Iddings.® In longi¬ 
tudinal outline the mass has the shape of Gilbert’s ideal laccolith.® 
The bysmalithic aspect is given in diagram below (figure 9). 
That faults, or lines of crustal fracture, have a controlling in¬ 
fluence in the formation of laccoliths is nowhere better demon- 
8 Journal of Geology, Vol. VI, p. 720, 1898. 
9 Geology of Henry Mountains, p. 20', 1877. 
