ADVANCES IN OIL PROSPECTING 143 
SecTIONS SHOWING VaRIATION OF 
Evectrica Conouctivity ano DertH or Cover 
— ——————"_ UPPER SURFACE OF ROCK fats 
erm —— CONDUCTIVITY AT 120 FT INTERVAL Lists vom 
eae eee res, --" 7 ” 40 7 oo 
i Oe nomronraL SCALE eee ieas Cole 
(conc. owrinate ) 
° » 6o a eorscr 
—— VERTICAL SCALE 
~~ ro 2 
CONOUCTivITY SCALE 
ah 
oo] 
RY 0 30 
S 20 60 
x 
2 
“} 30 90 
q 40 120 
§ 
Dh 50 180 
a .18D0 

Fic. 26.—Resistivity mapping with two electrode separations to determine depth 
of cover (after Lancaster-Jones). 





a rs 
z g 
z MOLE N12 * Cle as 2 
N ; 
3 
2000 secs) 3 
Ez 
3 
: 
3 
1900 sve © 
*) 
q 
09. 500 
OVER BURDE | PRECAMORUAM ROCK PRECAMBRIAN 
CCR 
OVER BUROEN 
50 700 50 490 158 
CLICIAL OKT ROGK GLACIAL CAAT: Roch 
Fic. 27.—Results of electrical vertical drilling to determine thickness of cover 
(after Leonardon). 
A: Diagram in case of fairly homogeneous overburden. Accuracy fairly satisfactory. 
B: Form of results when overburden is composed of different layers. 

473 
