JOHNSON: GRAND CANON DISTRICT. 157 
recent ])arts of the small gorges a short distance back from their 
mouths (pi. 20). 
The facts set forth above require certain modifications of the excel- 
lent report by Huntington and Goldthwait. Their geological map 
(|)late 7 of their report) correctly represents the distribution of the 
lava-capped mesas at the crest of the cliff, the lava strip adhering to 
the face of the cliff, and the lava at the base of the cliff. But the cross- 
section E-F on plate G of their report, incorrectly represents the strip 
of lava adhering to the face of the cliff as a fault splinter. Their 
cross section of this same lava strip where it crosses the Virgin River 
is correctly shown to lie in its original position against the face of the 
cliff (fig. 5, p. 225). But they erroneously interpret the strip at this 
point as being the same as the lava cap of Sugar Loaf Mesa. This 
accounts for their statement that the recent displacement was but 300 
feet at this point, although a displacement of 1,400 feet was noted 
just south. Xo attempt is made to explain the manner in which the 
lava capping the Permian shales at an elevation 1,000 feet higher 
could have its continuation on the face of the cliff of Carboniferous 
limestone below. It should be appreciated that figures 4 and 5, 
placed on opposite pages of their report as illustrating two examples 
of the same feature ("The first faulting"), really represent different 
features, separated by a long interval of erosion. The lava caps in 
the two cases are of different ages, as well as the faults which they 
cover. The features shown in their figure 4 did formerly exist in the 
region represented by figure 5, but erosion completely destroyed tho.se 
features in the latter region ; and the close resemblance of the present 
relations to those which formerly existed should not prevent a full 
recognition of the significant difference between the two. In figure 
5, the lava covering the eastern branch of the fault should be slightly 
displaced if the conditions are to be accurately represented, as the last 
faulting movement affected the main fault plane to that extent, al- 
though the principal displacement was along a plane just west, iii the 
region of this particular cross section. The 300-feet displacement 
recorded by Huntington and Goldthwait at the Virgin River represents 
the movement due to the third faulting only; while the 1,400-feet 
displacement noted a little farther south represents the movements of 
both the second and the third faulting periods. The total recent 
displacement at the two localities is probably about the same. 
The baselevelling which followed the first faulting was probably 
more nearly complete than supposed by Huntington and Goldthwait. 
