THE BANNOCK OVERTHRUST 7O1 
tion of the thrust fault surface here described. Southward deposits 
of travertine occur at intervals along the base of the range to a 
point opposite the mouth of Three Mile Creek, about 3 miles south 
of Georgetown. It seems probable therefore that the Swan Lake 
fault is closely related to the Georgetown fault and may represent 
a part of the same thrust plane so deformed as to constitute the 
west limb of a gentle syncline. This interpretation is shown on 
the map and stereogram (Figs. 1 and 2). 
WEST BEAR LAKE FAULT 
In 1910 the writers encountered a great thrust fault on the west 
side of Bear Lake near Paris. This fault was followed southward 
beyond St. Charles, and northward beyond Soda Springs, a distance 
of over 45 miles (Fig. 1). The fault surface or plane appears to 
dip gently west. The upper block comprises rocks of Cambrian 
to Devonian age, while the underlying rocks are Pennsylvanian 
Lower Triassic (Upper Wells to Thaynes). Hence the structural 
relations here are similar to those of the Georgetown-Swan Lake 
fault except that the range of the formations involved and the 
magnitude of the throw are somewhat greater. The presence of 
two such great and similar overthrusts upon opposite sides of Bear 
River Valley, together with the known fact of deformation in the 
eastern fault, leads to the interpretation that the West Bear Lake 
fault and the Georgetown-Swan Lake fault are parts of the same 
great thrust fault, and that they have been separated by the 
partial erosion of an anticlinal fold in the thrust plane (see map 
and stereogram, Figs. 1 and 2). 
FAULTS NEAR LAKETOWN AND WOODRUFF, UTAH 
In 1909 Gale and Richards reported the existence of thrust 
faults at Laketown (1of) and near Woodruff (10g), Utah. These 
faults also represent movements from the west and bring rocks of 
Mississippian or greater age over younger formations. It is not 
possible to follow these faults and to trace their connection with 
each other and with the West Bear Lake fault to the north because 
of the extensive development of Tertiary beds (Eocene) in the 
intervening area. Their position and structural relations lend 
support to the view that they represent the southern continuation 
