THE MECHANICAL INTERPRETATION OF JOINTS ait 
quite obviously owe their origin to this 
process, are of common occurrence in 
the bottoms of ravines cut into clays 
or shales, and are often directly asso- 
ciated with landslip terraces. Identical 
surficial anticlinal buckles? which have 
been observed under a cover of glacial | 
drift without any connection with steep 
slopes or landslides, probably owe their 
origin to similar stress relations resulting 
from the cracking or other deformation 
of the Pleistocene ice cover. 
In the vicinity of Cincinnati, wherever 
the most recent rejuvenation has cut 
into the bottom of ravines within the 
Eden shales, similar bucklings are quite 
common. Frequently, however, these 
anticlines are not only overturned, but 
faulted, generally in the form of a minia- 
ture overthrust, such as shown in the 
Figures 16 and 17. 
In the light of the preceding discus- 
sion, it appears highly probable that 
these miniature ‘“‘reversed faults’? have 
nothing to do with horizontal compres- 
sive stresses. The shales are distinctly 
ductile, as is implied by the very exist- 
ence of the anticlines due to flowage. 
They are, however, ductile only to a 
limited degree. After the strain has 
reached a certain limit, they rupture 
FIG. 19.—Sec. 1 shows the 
structure exposed on the south 
side of the stream channel 
shown in Fig. 18. Secs. 2 and 
3 are drawn parallel to and 5 
and to feet, respectively, south 
of, sec. 1. Sec. A shows the 
result of squeezing out the 
shale layers from underneath 
the joint plane in such a way 
that the lower portion of sec. 2 
is pushed out so as to rest 
under the upper portion of sec.t. 
In sec. B this process is carried 
farther, the lower portion of 3 
pushed out so as to rest under- 
neath the upper portion of 1. 
along planes of shearing. Here the obtuse angle formed by two 
tE.g., T. C. Hopkins and W. M. Smallwood, “Discussion of the Origin of Some 
Anticlinal Folds near Meadville, Pennsylvania,” 
IV, No. 1, 18 (quoted from Van Horn, Joc. cit.). 
Bull. Syracuse University, Ser. 
2 For instance, G. K. Gilbert, ‘Dislocation at Thirtymile Point, New York,’ 
Bull. Geol. Soc. Amer., Vol. X (1899), pp. 131-34; F. R. Van Horn, “Local Anticlines 
in the Chagrin Shales at Cleveland, Ohio,” ibid., Vol. XXI (1910), pp. 771-73. 
3E. L. Braun, “The Cincinnatian Series and Its Brachiopods in the Vicinity of 
Cincinnati,” Jour. Cinc. Soc. Nat. Hist., Vol. XXII (1916), No. 1. 
