GEOLOGIC RECONNAISSANCE IN BAJA CALIFORNIA 747 
covered by a deposit of sand of Quaternary age which to the south 
extends to the Arroyo Salado and beyond, and some distance up 
the slopes to the east. At Aqua Verde near Rancho Salado 
(latitude 24° 31’, longitude rrr° 31’), underlying yellow sands 
with hard, limy ledges appear in a cliff 40 feet high. The section 
at this place is as follows: 
: Feet 
Gray conglomerate sandstone, which floors the adjoining low 
Slope pmaesawh fateie:.. icc planer Leen Can ee oiake I5 
Yellow, fine-grained sandstone somewhat harder beds above, 
and at base a wedge-shaped, hard, limy ledge with fossils’ 25 
The fossils collected here were determined by Dr. Julia A. 
Gardner-as follows: Turritella sp.; Arca aff. A. microdonta Conrad; 
Mytilus sp.; Modiolus sp.; Periploma (Halistrepta) sulcata, Dall?; 
Tivela n.sp.; Chione latilamenosa, A and M? C. sp.; Metis aff. M. 
alta Conrad and Balanus,sp. ‘‘ Age post-Miocene.”’ 
These yellowish beds extend for 3 or 4 miles up the Arroyo 
Salado and lie on the Eocene (?) sandstone. Probably -their 
yellow*color is due to material from the Monterey formation or 
yellow beds underlying them. They extend up the adjoining 
plateaus to an altitude of 500 feet or higher. Limestones of this 
formation are conspicuous in the Cerrito Flor de Melba, 60 miles 
west of La Paz, and on the walls of various arroyos from Datilar 
to Cuafio, as well as in cliffs along the ocean (60-40 miles west of 
La Paz). These limestones occur at several horizons, and they are 
highly fossiliferous at most places, but the fossils of the upper 
beds at least appear to be post-Pliocene. The dip is to the south- 
‘west at a low angle, and the beds extend far up the west slope of 
the sierra where they overlie the mesa sandstone. 
THE GREAT UPLIFT 
‘It has been found that much of the peninsula of Baja Califor- 
nia has been uplifted out of the sea in very recent geologic times. 
Deposits of modern sea shells occur at many places in regions up 
to altitudes of 1,000 feet and they are reported as high as 3,300 feet. 
Old belts of sand dunes and shore lines are conspicuous far above 
