458 GEORGE ROGERS MANSFIELD 
the Rex chert member of the Phosphoria formation (Permian) 
form the east limb of the anticline and indicate the occurrence of a 
syncline farther east. In the middle of the view is a sharp anti- 
clinal fold inclined eastward. Near the base of the slope at the 
right (west) is another drag fold, very sharp and inclined eastward. 
These drag folds are composed of upper beds of the Wells formation 
and of the overlying phosphatic shales of the Phosphoria formation, 
which are relatively less competent than the Rex chert above or 
the bulk of the Wells formation below. The effect of the drag 
folds is to duplicate the outcropping beds of phosphatic shales, 
which appear as separate bands on the hillside. The anticline, of 
which the drag folds form a part, is largely eroded, but its west limb 
is exposed in a branch canyon to the north. Figure 7B is a view 
north from a somewhat different viewpoint. It shows the westerly 
dipping beds of the west flank of the anticline and the same two 
drag folds illustrated in the previous view. 
Fan folds —Folds of this type have been recognized at several 
places in the region. Usually they are so deeply eroded that only 
their stumps remain, or they are broken by faults. In the vicinity 
of Sugarloaf Mountain, however, in the Cranes Flat quadrangle, 
see Figure 8, there is a fine example of an inverted fan fold. The 
rocks immediately involved belong to the Homer limestone member 
of the Wayan formation (Lower Cretaceous ?). 
Sugarloaf Mountain was selected by St. John" of the Hayden 
Survey years ago as a station, and he drew a geologic structure 
section through it, in which he shows a southwesterly dipping series 
of strata, overlapped on the west by basalt at Sheep Mountain 
just west of the area shown in the figure, and arched into a promi- 
nent anticline at Sugarloaf Mountain by anigneousintrusion. The 
structure of the area near Sugarloaf Mountain is not so simple as 
figured by St. John. The limestone, which he did not differentiate 
from the other strata, is there thrown into a series of relatively 
sharp folds, among which narrow folds of the underlying sandstone 
rise to the level of erosion here and there. Southwest of Sugarloaf 
Mountain the dips of the limestone and the related strata are 
Orestes St. John, “‘ Report of the Geological Field Work of the Teton Division,” 
U.S. Geol. and Geog. Survey Terr. (1877), 1879, pp. 351-60. 
