Chap. 7] 



GRAVITATIONAL METHODS 



267 



better suited for determining the vertical boundaries of mass elements in 

 a horizontal bed this may be written 



(2,2 2 I 2\ 



Xi +22 X2 -\- Zi 

 Xi -\- Zi Xi -\- Z2t 



Ua' = 2k8 I tan"' - + tan"' - 



Xi Xi 



tan ' - — tan' 



X\ 



-\Z<\ 



Xi)' i 



(7-95c) 



t' 1 I lllllllll I I ,. 



7 6 4 2 2 4 6 7 

 1, 1 .1,1)1 - 111.1.1,1. 1 



r 



I 'l 'l'l'll i ll lM 



I I Mil nil I I 



6 4 2 .. 2 4 6 

 6 4 2 2 4 6 



,1 ,l.l.l))MI,l.l, i. I, 



T I I I I II Mill I \1 



7 6 4 2-246 7 



-4 — I'l'i 'i ' i ' i -h ' i ' i'i'i — V 



/ 6 4.2.246 7 



II I 1 

 4 6 



III I 



(b) 



I 



- f \ t 

 I I I — rti — IT 



12 3>.i ' 



5\5 





J 'i i 



3 ; 3 



■ '/ ■ ' 



J / 3 



II ;', ; — \ — r~r 



2 3\J 2/0 





II 



I 



3 \3 



(d) 



f _ 



T^ 



I r 



1 I 



/ 2 

 I . I 



(f) 



Fig. 7-101. Interpretation diagram for two-dimensional features (after Barton). 



Diagrams based on these equations are shown in Figs. 7-lOla and 7-1016.'" 

 In the calculation the vertical sequence of formation boundaries is deter- 

 mined by the assumption that 2n+i = (10/9)2n • Therefore in semilog- 

 arithmic representation, as in the figure, the vertical formation interval is 



D. C. Barton, A.I.M.E. Geophysical Prospecting, 489 (1929). 



