426 



MAGNETIC METHOD 



^Chap. 8 



magnetic Cretaceous sediments and low values to the southwest cor- 

 responding to less magnetic Eocene strata. In the Pettus area (Bee 





-4990 Contour, top of the Coitroe Sand 

 Fig. 8-70. Magnetic survey of Conroe area (after Williams). 



Fig. 8-71. Magnetic survey of San Andreas fault, California (peg model) (ifter 



Lynton). 



County, Texas) Barret*^ observed a definite minimum on the principal 

 fault whose throw is some 500 feet in the Pettus sand (Eocene, about 

 4000 feet deep). Magnetic anomalies of faults are often greater than 



1" Loc. cit. 



