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case, they believe it to be inconceivable that the Santa Monica 

 shelf and canyons were eroded during the Miocene period. How- 

 ever, both the shelf and the walls of the canyons contain 

 Foraminif era of Miocene age enclosed in nodules, and Miocene 

 age rocks are on the shelf and probably in the canyons. The 

 second hypothesis - residual concentration of Miocene age 

 phosphorite nodules =• perhaps is a better explanation, since 

 it would account for the abundance of phosphorite on the 

 Santa Monica shelf and in the walls of the canyons even though 

 each may have been cut in relatively recent time. Neither 

 hypothesis adequately explained the existing conditions; there- 

 fore, the authors presented two alternative possibilities to 

 account for the Miocene age Foraminifera in nodules of Quater- 

 nary ages (1) phosphorite deposits formed by infiltration of 

 phosphatic solutions into porous Miocene age formations with 

 the replacement of some of the Miocene age material, (2) the 

 phosphorite deposits may have been formed by enclosure of 

 reworked Miocene age Foraminifera in nodules formed during 

 the Quaternaryo Thus, they tentatively conclude that possibly 

 the nodules dredged off southern California were deposited on 

 the present shelves, banks, and in the canyons during the 

 Quaternary and that previously an abundance of Miocene age 

 Foraminifera had been eroded or weathered out of the Miocene 

 age formations and concentrated on the sea floor surface 

 where phosphorite deposition took place. 



No additional age determinations of the phosphorite 

 dredged from Santa Monica Bay have been made so that the 

 determinations by Dietz, Emery, and Shepard are the only 



