SANTA CLARA VALLEY: VAQUEROS FORMATION. 
15 
fig. 3. The lithologic features of this section indicate the correlation 
of the red and white sandstones with the Sespe red beds and of the 
overlying fossiliferous rusty beds with the Yaqueros formation, the 
heavy body of rusty sandstones occurring at the base of the Vaqueros 
in the Tar Creek _ locality being possibly a variable factor from one 
point to another. 
VAQUEROS FORMATION SOUTH OF THE SANTA CLARA. 
South of the Santa Clara, along South Mountain, Oak Ridge, and 
the Santa Susana Mountains, is a body of shale, sandstone, con¬ 
glomerate, and limestone, identified by their fossils with the yaqueros, 
but at variance with that formation north of the Santa Clara in 
the accession of conglomerate and in the relative proportions of the 
other sediments. Sandstone, for instance, is far more abundant in 
the formation south of the Santa Clara than north of it. Moreover, 
the thickness of the beds is greatly reduced south of the river, a mini¬ 
mum of 400 or 500 feet appearing in Oak Ridge and South Mountain, 
increasing to about 1,000 feet in the Santa Susana Mountains. 
The formation south of the Santa Clara, in its simplest form, con¬ 
sists of 300 or 400 feet of banded chocolate and gray argillaceous and 
arenaceous shales, sandstones, scattered limestone concretions, and 
more or less persistent mollusca-bearing calcareous grits, similar to 
the fossiliferous Vaqueros formation of the Tar Creek amphitheater. 
As a rule 50 to 100 feet of massive, coarse gray to yellow sand¬ 
stone, also yielding lower Miocene remains, separate the formation 
from the red and gray banded beds below, and another very similar 
bed, 40 or 50 feet thick, carrying fossils of the same age, marks the 
summit of the terrane. This upper sandstone divides the underlying 
shale from 200 or 300 feet of other shale that is more siliceous and 
chalky and nearer the Monterey type. 
Locally the shale of the Vaqueros formation south of the Santa 
Clara, in addition to its chocolate and gray colors, assumes faint green, 
blue, and red hues. Thin layers of white limestone appear here and 
there, some of which is highly crystalline, with almost the aspect of 
marble. The sandstone, ^particularly in the eastern half of the field, 
where it is better developed, carries spherical concretions resembling 
those of the lower Modelo stratum north of the Santa Clara. Besides 
the molluscan remains, casts and imprints of forammifera are common 
in the calcareous and siliceous members from base to summit of the 
formation. Toward its top a yellow color is to be observed at many 
places, pervading alike both shale and sandstone. 
The foregoing description of the Vaqueros south of Santa Clara 
River is more particularly applicable to that portion of the forma¬ 
tion which lies west of Garberson Canyon. East of this region con¬ 
siderable modification occurs. In Wiley Canyon, for instance, the 
