Page 10 - maxson1928

7,

shown by Figure 3.

Overlying this series u.nconformably is the Modelo? formation
1
{upper Miocene?). The bu.ff and brown colored sandstones and shales of

this series are marine in origin. Figure 4. includes ,some beds assigned

to this formation. The few invertebrate fossils found in some of the

beds point to an upper Miocene age. Mr. Clements has recently obtained

a varied fau.nal assemblage from localities in the Tejon Quadrangle and

is at present engaged in studying it. This study may lead to a closer

determination of age. Correlation on the basis of invertebrate material

with other California marine horizons will have considerable importance

in assisting in the determination of the upper age limit of the Mint

Ca.eyon series.

Along the contact with the basement complex and apparently in

the lower strata of the Mint Canyon formation, the coloration is

dominantly red. :rhe fossiliferous horizons occur in fine grained, silty

members. They are ferruginous a.nd contain numerous rounded ½uartz

pebbles. Exposures of these beds in Mint Canyon and near San Francisquito

Ce.nyon have yielded teeth of Pe.rahippus sp. and Merychippus californicus.

Toward the south and ascending in the series gray beds become

predominant. They vary from coarse sandstones and conglomerates to

lenticular silt layers with intercalated fine grained, colored beds of

distinctly sub-aerial origin. 'l'he gray beds are extensive and apparently

are lacustrine deposits. Some of the interbedded silts contain abundant

tests of fresh water gastropods belonging to the species Paludestrina

imitator Pilsbry ( identification by Dr. G. D, Hanna). Occasionally

mammalian remains are associated with them.

Figure 5. shows a section of these gray beds truncated by a

Quaternary level of the Santa Clara Valley. Figure 4. indicates the

l Kew, W. S. 11,, U.S.G.S. Bull. 753, p, 68, 1924