THE COASTAL TERRACES 229 



The effect has been not only the general aggradation of the 

 valley floor, but also the development of a combined delta and 

 superimposed alluvial fan at the valley mouth. The seaward ex- 

 tension of the delta has been hastened by the gradation of the 

 shore between the bounding headlands, thus giving rise to marine 

 marshes in which every particle of contributed waste is firmly 

 held. The plain of Camana, therefore, includes parts of each of 

 the following: a delta, a superposed alluvial fan, a salt-water 

 marsh, a fresh-water marsh, a series of beaches, small amounts 

 of piedmont fringe at the foot of Pliocene deposits once trimmed 

 by the river and by waves, and extensive tracts of indefinite fill. 

 (See the Camana Quadrangle for details.) 



With the coastal conditions now before us it will be possible 

 to attempt a correlation between the erosion features and the de- 

 posits of the coast and those of the interior. An understanding 

 of the comparisons will be facilitated by the use of diagrams, 

 Figs. 151-154, and by a series of concise summary statements. 

 From the relations of the figure it appears that : 



1. The Tertiary deposits bordering the Majes Valley east of 

 the Coast Eange were in process of deposition when the sea 

 planed the coastal terrace (Fig. 151). 



2. A broad mature marine terrace without stacks or sharply 

 alternating spurs and reentrants (though the rock is a very re- 

 sistant granite) is correlated with the mature grades of the Coast 

 Eange, with which they are integrated and with the mature pro- 

 files of the main Cordillera. 



3. Such a high degree of topographic organization requires 

 the dissection in the late stages of the erosion cycle of at least 

 the inner or eastern border of the piedmont deposits of the des- 

 ert, largely accumulated during the early stages of the cycle. 



4. Since the graded slopes of the Coast Eange on the one side 

 descend to a former shore whose elevation is now but 1,500 feet 

 above sea level, and since only ten to twenty miles inland on the 

 other side of the range, the same kind of slope extends beneath 

 Tertiary deposits 4,000 feet above sea level, it appears that ag- 

 gradation of the outer (or western) part of the Tertiary deposits 



