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University of California. 



I Vol. i. 



to the brink of a gently undulating plateau, the significance of the 

 topography of which has not been investigated. In studying these 

 terraces the ground has been visited several times; but in determin- 

 ing their altitude a single favorable line was followed, and it is not 

 supposed that the list of altitudes here given represents all of the 

 terraces which score the coastal slope. In several instances it is 

 very apparent that the terraces are discontinuous, owing to their 

 having been locally obliterated by the excessive recession of the sea- 

 cliff of a later stage of the uplift. For this reason parallel profiles 

 do not always show the same number of terraces with the same inter- 

 vals; and other strand lines may exist than those here recorded. It 

 is even possible that the highest observed strand, at 1,201 feet, may 

 not be the highest discoverable on this part of the coast, although 

 locally there is no suggestion of any higher strand line. 



It is probable that the topography of the valleys of the antece-' 

 dent streams which come down from the Santa Cruz Mountains may 

 be definitely correlated with the terraces, i. e., with the different 

 stages of the uplift. This is certainly possible as regards some of 

 the features of the San Lorenzo, which has a sharp V-shaped gorge 

 for about five miles back from Santa Cruz, cutting through the shale 

 and the underlying granite. At this point, above the breast of the 

 gorge, the valley opens out and clearly represents the topography 

 established when the stream was at base-level and had time for cor- 

 rasion. This broader valley bottom is over three hundred feet above 

 sea level ; and the five-mile gorge, largely through granite, is the 

 measure of the time, since the initiation of its uplift. 



THE MERCED SERIES. 



General Note. — The most remarkable development of Pliocene 

 rocks in North America is on the Peninsula of San Francisco, a few 

 miles south of the Golden Gate. The remarkable features are; (1) 

 The great thickness of continuous sedimentation which it represents, 

 and (2) the local disturbance to which it has been subjected. Both 

 of these features are observable and quantitatively determinable in 

 the magnificent line of sea-cliff which extends from Lake Merced, 

 near San Francisco, to Mussel Rock, about eight miles south of 

 Point Lobos, at the entrance to the gate. For convenience the Pli- 



