334 



Subsurface Geologic Methods 



coating of the sample may be significant, particularly, in the case of small 

 samples. However, by using samples weighing about 200 grams, Ref- 

 shauge's work indicates that such errors may be reduced to less than 0.01 

 of apparent specific gravity in the average sample measured. 



Application of Results 



Shale-density determinations may be applied to the estimation of 

 original depth of burial of sediment and the detection of major uncon- 

 formities in the section, as evidence of thrust faulting and as indication of 



-sir 



BULK DENSITY 

 NATURAL - 

 GRAIN - 



-"""^'.S^ 



m • 



4' * • 



iS^_ 



DEPTM OF OVERBUftPgN IN FEET- P 



Figure 137. Relationship of density to depth of burial in Venezuela. 

 (From Hedberg, Am. Jour. Sci) 



the presence of weathered zones. Such data is also of value in geophysical 

 work, particularly in the interpretation of gravity-meter surveys. 



Hedberg has published an excellent summary on gravitational com- 

 paction of clays and shales in which he presents charts showing the re- 



