THE COASTAL TERRACES 



227 



ride south of Camana, where locally they 

 attain a thickness of several hundred feet. 

 Their upper surface was well graded and 

 they show a prolonged period of deposi- 

 tion in which the former coastal terrace 

 was all but concealed. 



The uplift of the coast terrace and its 

 subsequent dissection bring the physical 

 history down to the present. The uplift 

 was not uniform ; three notches in the ter- 

 race show more faintly upon the granite- 

 gneiss where the buried rock terrace has 

 been swept clean again, more strongly 

 upon the softer superimposed sands. They 

 lie below the 700-foot contour and are in- 

 significant in appearance beside the slopes 

 of the Coast Eange or the ragged bluff of 

 the present coast. 



The effect of the last uplift of the coast 

 was to impel the Majes River again to cut 

 down its lower course nearly to sea level. 

 The Pliocene terrace deposits are here en- 

 tirely removed over an area several 

 leagues wide. In their place an extensive 

 delta and alluvial fan have been formed. 

 At first the river undoubtedly cut down to 

 base level at its mouth and deposited the 

 cut material on the sea floor, now shoal, 

 for a considerable distance from shore. 

 We should still find the river in that posi- 

 tion had other agents not intervened. But 

 in the Pleistocene a great quantity of 

 waste was swept into the Majes Valley, 

 whereupon aggradation began; and in the 

 middle and lower valley it has continued 

 down to the present. 



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