GEOLOGIC RECONNAISSANCE IN BAJA CALIFORNIA 7737 
fossils. This member is conspicuous in the bed of the arroyo a 
short distance below the village where it is crumpled in a series 
of small but closely appressed flexures: It also outcrops almost 
continously for several miles below this place, mostly in the bed 
of the arroyo. At two localities about y 
4 miles below La Purisima, small arches i 
reveal the top of the underlying Monte- 
rey beds with contact clearly exposed. 
The yellow beds and this basal limestone 
disappear a short distance farther down- : 
stream or near the 1,360-foot boring, as ., ree ae nt ae 
shown in Figure 17. The precise strati- opposite Purisima Vieja, ten 
graphic conditions at this place could ae eee ee 
not be ascertained, but the basal lime- 
stone, at least, appears to abut against the old slope of a mound of 
Monterey beds, probably a local shore line. 
The igneous rocks included in the yellow beds are the products 
of contemporaneous volcanic action, and it is not unlikely that to 
the east they grade into the lower part of the great succession of 
TWO MILES NEAR 
g ABOVE 2ND AT 
TIDEWATER OUTH END NORTH SIDE NORTH OF rd ABOVE DRILL © LA PURISTMA 
BIG BEND BIG BEND BIG BEND _ ee HOLE 
MESA SANDSTONE 
Fic. 17.—Columnar sections along the Arroyo de la Purisima, showing the 
stratigraphical relations of the yellow beds. m, Monterey beds; a, agglomerate; Js, 
fossiliferous limestone at base of yellow beds; s, massive sandstone at La Purisima; 
b, sheet of basalt in mesa sandstone. 
a 
agglomerates, etc., which constitute the base of the high sierra. 
In the valley of the Arroyo San Raimondi (or San Miguel), 40 miles 
northwest of La Purisima, there are many exposures of large 
bodies of agglomerate included in or displacing the upper members 
of the yellow beds (see Fig. 20). One notable outcrop is near the 
Rancho San Antonio, where the rocks have the relations shown in 
