go DONALD C. BARTON 
amplitude of 250 gammas. Part, approximately half, of the steep 
north gradient and steep southerly decrease of Ag is regional and has 
no relation to the Ingolstadt structure. The gravity maximum is not as 
sharp or as flat topped as the magnetic maximum. Their respective 
shapes indicate that the extra dense mass is not co-extensive with the 
magnetically extra-permeable mass, but is somewhat larger and ex- 



roe 
INGOLSTADTE 
\ 
— ~~ Ne 
\ \ 
PFAFFENHOFEN 
“ 

Fic. 8.—Observed variation of Az, Ingolstadt area. 
tends somewhat deeper. The form of the magnetic anomaly indicates 
that the extra-permeable mass has a crudely disc-like form. Crude 
calculations in which the magnetic profile was treated as if it were a 
gravity profile indicate a depth to its top of approximately 3,000 feet 
and a thickness of approximately 800 feet for the disc. The high mag- 
netic permeability of the rock of the disc suggests a basaltic character. 
The Vohburg (C-10, Fig. 8), Weichering (D-9), and Strass (D-8) 
magnetic maxima are similar anomalies and presumably likewise rep- 
resent basaltic, probably laccolithic, intrusions (Figs. 3 and 10). 
612 
