312 CLEMENTS 



troughs. Canyons gash the ridges, and the bottoms of some of the troughs 

 appear to have been leveled off by the sediments accumulating in them. 

 The topography and relief of the region have been likened to the topog- 

 raphy and relief of Death Valley and vicinity (Shepard and Emery, 

 1941). 



The deciphering of the Pleistocene history of the Channel Island 

 region involves many problems, and as yet the evidence at hand is too 

 meager to permit the satisfactory solution of many of them. Nevertheless, 

 certain facts have come to light as the result of research carried on in 

 the area by many geologists and oceanographers over a long period of 

 years, and it is possible at this time to suggest, at least for some of the 

 problems, answers that probably are not far from the truth. 



The types of evidence used in the solution of the problems are varied. 

 There is first the direct geologic evidence from the rocks exposed on the 

 islands and on the mainland adjacent to the area. A somewhat less easily 

 obtained type of geologic evidence is that from the sea floor, as brought 

 up in dredge, snapper, and core barrel. The physiographic features of 

 the region tell something of its history in the not too distant past: the 

 wave-cut terraces, the sea cliffs, the submarine valleys, the submarine 

 banks. Fossils tell their part of the story: the dwarfed elephants of the 

 northern islands; the fossil plants; the shells on the uplifted terraces. 



PREVIOUS WORK 



Attention was first called to the contrasting topographies of Santa 

 Catalina and San Clemente islands by Cooper as early as 1863 (in 

 Whitney, 1865, pp. 184-85). Lawson (1893) made a reconnaissance of 

 the islands and the shore of the mainland before the turn of the century, 

 and developed the idea of different histories for the two islands men- 

 tioned. He discussed this again in a later paper (1934). Smith (1897), 

 while first agreeing with Lawson's conclusions, later argued against the 

 idea of Santa Catalina's having differed from the other islands in its 

 history (1933). 



The geology of the various islands has been discussed by a number 

 of writers: San Nicolas by Bowers (1890) and later by Kemnitzer 

 (1936) ; Santa Catalina by Smith (1897), with a later paper on the 

 metamorphic rocks by Woodford (1924); San Clemente by Smith 

 (1898) ; Santa Rosa by Kew (1927), by Moody (1935), and by Sey- 

 mour (unpublished); Santa Cruz by Bremner (1932), and Rand 

 (1931) ; San Miguel by Bremner (1933) ; Santa Barbara by Kemnitzer 

 (unpublished) ; and Anacapa by Yates (1890), The Palos Verdes Hills 



