DETAILS OF VALLEYS. 
35 
TEMPLE BAR. 
Virgin Canyon widens westward as the river emerges from the 
crystalline rocks and enters the detrital beds. At Temple Bar the 
sand and gravel filling the Detrital Valley is exposed in vertical cliffs 
several hundred feet high. At the base of the cliffs is a coarse breccia 
exposed through a thickness of about 300 feet and composed princi- 
pally of fragments of a rhyolite flow breccia cemented into a resistant 
mass. The cementing material is mainly carbonate of lime, but in 
some places it is silica and in other places oxide of iron. Springs 
issuing from this 
breccia are strongly 
charged with com- 
mon salt and alkali, 
which gather as 
white incrustations 
about the springs. 
Resting un con- 
formably upon this 
breccia and abut- 
ting against it, as 
illustrated in sec- 
tion F, fig. 5, occurs 
the characteristic 
Temple Bar con- 
glomerate. The 
conglomerate con- 
sists of well-strati- 
fied sand and gravel 
(see PL VIII, A), 
and, although 
poorly consolid at e< I , 
forms perpendicu- 
lar cliffs hundreds of feet in height. PL II shows this conglomerate 
in one of its most characteristic exposures, where the cliffs rise 
abruptly from the water's edge to a height of 815 feet. A large 
number of equally conspicuous sand and gravel cliffs and monuments 
occur in the vicinity of Temple Bar, extending from the river level to 
altitudes of 2,000 to 2,500 feet. 
Sheets of basalt occur at several horizons of the conglomerate. A 
shelf about 200 feet from the base (see PL II) is formed by one of 
these sheets of basalt, and other sheets occur at higher horizons 
(section F, fig. 5). South of the river a basalt sheet resting on top 
of the gravel beds may be younger than those included in them, or 
may be one of the included sheets exposed by erosion. 
•&&S 
TTj-yz 
— 
./i^7I^>~-"^\ ' V 
Vn-^7n- n 7^' 
/V v /~' 
;;;4 
7 7 
^V:4_ 
/ n > 
88^ 
Fig. 5.— Diagrammatic sections across Colorado River. F, At Temple 
Bar; G, at Virgin River; //, in Boulder Canyon. 1, Temple Bar 
conglomerate; 2, basalt; 3, Greggs breccia; 4, granite; 5, salt and 
gypsum beds. 
