DAVIS: THE PLATEAU PROVINCE OF UTAH AND ARIZONA. 17 
The fifty miles of fault line between Upper Kanab and Pipe spring 
have not yet been closely described in any geological] report or article. 
The effect of the fault and of subsequent erosion on the White cliffs 
of the Jurassic sandstones may be commended as offering excellent 
subjects for a thesis in structural geology in a region of great scenic 
attraction. 
CoNNECTION OF SEVIER AND ToroweEap Fau.ts. — It is on account of 
the second one of the above-mentioned effects of erosion that the south- 
ward extension of the Sevier fault to the Toroweap is not easily traced. 
South of the Shinarump escarpment by Yellowstone spring, the throw 
of the fault seems to decrease somewhat from its measure further north : 
for in Antelope valley (see sheet XXII, Dutton’s Atlas) the middle 
Permian clays on the west seem to stand against the lower Permian 
clays and the yellowish super-Aubrey beds on the east. But in this 
district of weak strata there is little or no cause for the fault to express 
itself in the topography. It is probable, however, that a general view of 
the district, such as might be obtained from the southermost Shinarump 
bluff, would disclose a dislocation of.the color belts by which the gray 
and reddish clays and the yellowish calcareous beds are often revealed 
on the surface. 
Still further south on the eastern side of Wonsits plain, a low bluff of 
super-Aubrey beds overlooks what I took to be Permian beds on the 
west, as mentioned in my previous essay : the fault’ probably passes near 
the base of this bluff, which lies near the final letter N of ‘ Wonsits 
plain” on sheet VII of Dutton’s Atlas.) The geological coloring of this 
sheet gives a different interpretation from the one just suggested. 
Still further south, about twenty miles beyond Yellowstone spring, 
the existence of the fault and a not-recent date for it are indicated by 
the attitude of the extensive lava beds that are there spread over the 
uplands on both sides of the inferred fault line. On the southeast, the 
lavas appear to lie for the most part with low edges on an upland of 
super-Aubrey or Aubrey limestone, in which relatively narrow valleys 
are opened where the lavas are absent. On the southwest, the lava 
beds, apparently at the same altitude as those on the southeast, form 
mesas with well-scarped edges that surmount slopes of lower Permian 
or super-Aubrey beds. The difference of horizon is not many hundred 
feet, but it seems to show that the lavas were spread out on a broad 
peneplain formed late in the plateau cycle by the far advanced erosion 
of the dislocated plateau blocks, asin Figure 6. To-day the peneplain is 
preserved only where it consists of resistant Aubrey beds, or where it is 
VOL. XLII. — No. 1 2 
