GEOLOGY OF THE SOUTHERN COAST RANGES 555 
above the sea, and separated from Los Osos valley by a divide 
not 50 feet high, and then pass directly into the San Luis range, 
cutting across it in narrow canyons at right angles to its course 
for a distance of over three miles. The most westerly of these 
streams, the San Luis Creek, has cut through where the range is 
1000 feet high ; and the other, Pismo Creek, traverses it where 
it is but little lower. The watershed between these streams has 
almost disappeared, and but little change in the topography 
would cause the whole drainage to pass westward along the 
northern slope of the San Luis range to Morro Bay. When the 
courses of these streams were originally outlined the San Luis 
range probably did not exist, and the general slope of the 
country was southwesterly. With the beginning of the upward 
movement along the axis of the range erosion continued to be 
rapid enough so that the original drainage was maintained. 
SEDIMENTARY TERRANES. 
An almost continuous series of sediments from the Middle 
Mesozoic down to the present is represented in different por- 
tions of the central and southern Coast Ranges, but owing to 
the oft repeated mountain-making disturbances the series is 
not complete at any one spot. Except for the absence of 
the Horsetown beds, the Eocene, and possibly the marine 
Pliocene, the ‘series is practically complete in the region under 
discussion. 
In the northern portion of the Santa Lucia range and other 
portions of the Coast Ranges there is still an older series of 
sedimentary rocks which are of unknown age, but were involved 
in the granite magma at the time of its formation and now 
appear as marbles, schists, etc. All that is known about these 
rocks is that they are older than the granite, and that the gran- 
ite itself is much older than the Golden Gate series (Jurassic) 
which rests upon it with a basal conglomerate. None of these 
metamorphic rocks appear associated with the granite north of 
the upper Salinas River, although farther northwest along the 
same crystalline axis they are extensively developed. 
