238 The American Geologist. October, 1897 
lowing quite closely the post-Miocene folding of this region 
and we have no direct evidence yet as to the relative import- 
ance played by structure or erosion in its formation. 
The Santa Maria has a very irregular course, much of its 
channel having been cut across the structural features of the 
mountains. The broad bottom of this valley extends back from 
the ocean for a distance of 20 miles with a grade of about 20 
feet to the mile. At Fulger's point it issues from the Cuya- 
nias canon, uniting at the same time with the Sisquoc. Both 
streams are baseleveled still many miles above the Junction. 
This feature is particularly noticeable in the Santa Maria 
which has cut directly across the mountains through the Ju- 
rassic, Cretaceous and Miocene strata. The baseleveled con- 
dition extends into the canon for about 15 miles, the bed of 
the stream being quite broad but bordered by steep mountains, 
and the waters everywhere flowing over a sand bed. There can 
be no doubt that to stream erosion is due the broad low^er por- 
tion of the Santa Maria valley as well as the upper portion. It 
has clearly been cut out of Miocene rocks at its upper end, as 
well as near its mouth, where, on the south side the Miocene 
rocks forming a part of Point Sal rise very abruptly and dip 
away. Through the most of the first 20 miles of its course the 
river is bordered by low hills which are in part of Pliocene 
age or even younger. The numerous wells 200 to 300 feet 
deep sunk in various parts of the broad valley have pierced 
layers of gravel, sand and clay which are apparently entirely 
undisturbed having a dip corresponding to the alluvial sur- 
face. These deposits are in all probability very deep and resem- 
ble in every character those of known Pleistocene age in the 
other large valleys of the state. We can thus distinguish here 
two periods of elevation, one following the Miocene, the other 
the Pliocene. 
From Santa Maria north to Carmelo numerous streams have 
cut transverse valleys in the Coast Ranges but none of these 
have a very large watershed. San Luis Obispo, Morro, San 
Simeon and numerous other small creeks, as well as the ar- 
royos La Cruz and Corpo Joro and the Sur river all clearly 
show at the points at which they enter the ocean indisputable 
evidences of a former elevation. The lower portions of all 
ohese streams flow over gravelly beds in alluvial bottoms 
