738 N. H. DARTON 
Figure 15. Another similar mass is exposed in the Arroyo Valle, 
8 miles west of Rancho San Antonio, and on the Arroyo Vaca, 50 
miles west by north of La Purisima, there is an exposure high in the 
canyon walls showing the relations indicated in Figure 21. This 
section shows that the agglomerate was erupted during the time of 
deposition of the yellow beds and prior to the lava flow which now 
caps the mesas. A small amount of agglomerate lies on the Mon- 
terey beds in the Arroyo San Gregorio, 11 miles W. 10° S. of La 
Purisima, and also near the 1,360-foot bore hole on the Arroyo de — 
la Purisima. 
Fic. 18.—Yellow beds and overlying Mesa sandstone on the Arroyo de la Purisima, 
ten miles below La Purisima, Baja California. Massive fossiliferous bed near center. 
Thin sheets of basalt are included in the yellow beds in the 
lower part of the canyons of the Arroyo San Raimondi and the 
Arroyo Caije. The relations of the old lava flows are well exposed 
just south of Caije and along the west side of San Juanico Bay, 
7 miles due west of La Purisima. ‘The exposure near Caije is due 
to a low dome, and here the lava is overlain by a 30-foot, soft, 
gray sandstone, a Jocal member of the yellow beds. A thin sheet 
of basalt caps the yellow beds at Purisima Vieja, as shown in 
Figure 16, and halfway between that place and Poza Honda an 
igneous Mass occupying the bottom of the valley was probably 
a vent from which this sheet was erupted. 
