THE PLEISTOCENE HISTORY OF THE CHANNEL 

 ISLAND REGION, SOUTHERN CALIFORNIA 



By 



Thomas Clements 

 Hancock Professor of Geology, University of Southern California 



INTRODUCTION 



The Channel Island region of southern California, as the term is 

 used in the present paper, includes the continental shelf area south of 

 the Santa Barbara coast line and west of the Los Angeles-San Diego 

 coast line, and extending offshore approximately 150 land miles. There 

 are two groups of islands in the area: the northern or Santa Barbara 

 channel islands, and the southern group. The first consists of Anacapa, 

 Santa Cruz, Santa Rosa, and San Miguel; the second consists of San 

 Clemente, Santa Catalina, Santa Barbara, and San Nicolas. To the 

 latter group should be added the Palos Verdes Hills, which, although not 

 now an island, have been an island in the recent geologic past. There 

 are also a few shallow submarine banks which likewise have been islands 

 during the time under consideration. Tanner Bank and Cortes Bank, 

 lying approximately 150 land miles west of San Diego and at depths of 

 less than 50 fathoms, are examples of these. 



The sea floor is by no means the conventional gently-sloping, relatively 

 featureless continental shelf of some parts of the world. It consists of 

 high ridges and deep troughs, the latter having depths of 3,000 to 6,000 

 feet below sea level, and in many cases being bounded on one side or 

 another by steep scarps. The islands surmount the crests of the ridges 

 and rise to heights of as much as 8,000 feet above the bottoms of the 



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