i80 STRUCTURAL AND FIELD GEOLOGY 
the inlier represents a higher crustal level—the Horst owes 
its existence as such to the faults or dislocations by which it 
is bounded. An old plateau-land has been fractured—the 
tracts surrounding the inlier having broken away from it, 
and dropped to a lower position. 
Conformity and Unconformity.—When one series of 
strata has been laid down upon the undisturbed and un- 
denuded surface of another series, so as to form a continuous 
succession, the beds are said to be conformable—the structure 
being known as conformability or conformity. In a true 

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Fic. 58.—MARKED UNCONFORMITY IN HORIZONTAL STRATA. 
conformity, therefore, each successive bed rests regularly 
upon its predecessor. When, on the other hand, one set of 
beds has been deposited upon the worn or denuded surface 
of another and older series, we have what is termed an 
unconformity or unconformability, and the two sets of beds 
are said to be unconformable with each other. Unconformity 


Fic. $9.—INCIDENTAL EVIDENCE OF UNCONFORMITY IN HORIZONTAL 
STRATA. 
2, z, unconformable junction ; d, d, dykes; f, fault. 
sometimes occurs without any change in the relative position 
of the younger and older strata. Both may be horizontal, or 
may dip at the same angle and in one and the same direction 
(Figs. 58, 59). In such cases the lower series will usually 
afford evidence of having been more or less denuded before 
the deposition of the overlying series had commenced. 
Occasionally, however, such evidence of a physical break or 

