GEOLOGY OF THE SOUTHERN COAST RANGES 565 
most Miocene the rocks of that age in California can no longer 
be looked upon as forming a unit but separated into two divi- 
sions by an extended period of elevation and erosion. This 
point established other and puzzling questions relating to the 
Miocene and Pliocene are in a fair way to be cleared up. 
Paso Robles formation.—The later Neocene in this portion of the 
Coast Ranges consists of a very extensive series of beds having 
apparently a fresh-water origin. They fill the Salinas Valley as 
far up as Atascadero, lapping over unconformably upon the 
upturned and sharply folded San Pablo formation. They are 
characteristically exposed about the town of Paso Robles, hence 
the designation. From Paso Robles the beds extend westward 
toward the Santa Lucia Mountains, and for many miles north 
and east of that place, filling the valley of the Estrella and its 
tributaries, and may reach into the Great Valley. The forma- 
tion consists of conglomerates, sandy and marly clays, as a gen- 
eral thing, but slightly consolidated. The great extent of this 
formation in the drainage area of the upper Salinas River, its 
peculiar character and total absence of marine organisms, or 
organisms of any kind as far as observed, make it appear prob- 
able that it is of fresh-water origin, and for these reasons, though 
it is possibly contemporanous with the marine formation known 
as the Merced beds, it should be given a distinct name. 
The strata are generally almost horizontal, but along the Salinas 
River in particular they are tilted and faulted. Beds of the same 
character overlie the San Pablo formation in the vicinity of 
Arroyo Grande. 
Fresh-water beds of Pliocene age are widely distributed 
through the Coast Ranges. Those in the valleys of the upper 
San Benito and Salinas have been referred to by Lawson as 
Pliocene delta deposits,? and considered the equivalent of the 
Merced beds. While the latter view is probably correct, there is 
no reason to consider them delta deposits; on the contrary, they 
*Monograph No. XIII, U. S.G. S., p. 238; Bull. Dept. of Geol., Univ. of Cal., 
Vol. I, p. 152; Bull. Dept. of Geol., Univ. of Cal., Vol. I, p. 363. 
? Bull. Dept. of Geol., Univ. Cal., Vol. I, p. 153. 
