730 N. H. DARTON 
Smaller exposures are revealed by the Arroyo Salado and its 
branches near Rancho Sauce, 35 miles west-northwest of San 
Hilario, and by arroyos Conejo and Datilari, 20 miles south- 
southeast of San Hilario (or about 40 miles due west of La Paz). 
The rocks are light-gray sandstone, mostly soft, but with 
harder layers and hard concretions. Some argillaceous members 
are included and some 
of the sandstone layers 
have a greenish tint. 
In the extensive expo- 
sures on the Arroyo 
Colorado about Rancho 
Tepetate where dips are 
from 3° to 5°, the thick- 
ness is not less than 
3,000 feet unless the 
strata are duplicated by 
faulting. The dips are 
somewhat steeper near 
Rancho Sauce where 
more than 2,000 feet of 
beds are exposed. One 
of the largest outcrops 
in this vicinity is just 
south of Rancho Santa 
Rosa where sandstone 
Fic. 8.—Sandstone (Eocene?) on the Arroyo ledges extend along the 
Colorado one mile below Rancho Tepetate, ten panks of the arroyo 
miles west of San Hilario, Baja California. 
for several miles. It 
is capped by late Tertiary or Quarternary conglomerate and lime- 
stone. In the valley of the Arroyo de los Liebres, ledges of sand- 
stone and sandy clays are exposed in a wide area of low ledges and 
buttes which extend to, or nearly to, the mouth of the arroyo. All 
the dips are at low angles to the north. 
The exposures in the valley of the Arroyo Colorado extend 
from the junction with the Arroyo de los Liebres nearly to the mouth 
of the Arroyo Caracol. Prominent cliffs of the sandstone occur at 
2. ae 
