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CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



certain Pleistocene beds which are exposed along- the Straits 

 of Carquinez at Rodeo with his warm water facies of the 

 Pleistocene, the Upper San Pedro. Concerning this Arnold 

 states : 



The Pleistocene deposits on the shore of San Pablo Bay between the 

 Union Oil Refinery and Point Pinole have been visited by Dr. Merriam 

 and the writer. The deposits, which rest on the upturned edges of the 

 San Pablo strata, consist of horizontally bedded layers of sand, gravel, 

 and clay. Teeth of the mammoth, and bones of the giant sloth and ex- 

 tinct bison have been found in these Pleistocene layers by Dr. Merriam. 

 In certain places the Pleistocene layers consist almost entirely of oyster 

 and mussel shells. Fossils from the Pleistocene deposits on San Pablo 

 Bay between the Union Oil Refinery and Point Pinole are, Ostrea hirida, 

 Ostrea conchaphila, Mytilus cdulis, and Tagelus californianus. The 

 character of these Pleistocene strata and of the fauna leads the writer 

 to correlate them with the upper San Pedro series. 



Arnold further states concerning his upper San Pedro as 

 follows : 



The upper San Pedro beds do not represent the top of the Pleistocene. 

 The fauna of these upper beds, although having many species in com- 

 mon with the living fauna of the same locality, is still quite distinct. 

 This would suggest a period of considerable length since the deposition 

 of the strata. The number of distinctly southern forms living at San 

 Pedro during the period of deposition of the upper beds also shows 

 that there has probably been a change in climatic conditions since that 

 time. A raised beach unconformable with the upper San Pedro strata 

 at Deadman Island shows that there have been orographic movements 

 since the upper San Pedro beds were deposited. All of this evidence, 

 then, leads to the conclusion that there has been a sufficient lapse of time 

 since the deposition of the upper San Pedro strata, to admit of marked 

 faunal and orographic changes. 



Lawson" in his "Geomorphogeny of the Coast of Northern 

 California," states in the concluding paragraph concerning 

 the Rodeo beds that, "Seemingly the last event is a slight up- 

 lift in the vicinity of the Straits of Carquinez." 



Arnold's tentative correlation was probably based upon the 

 occurrence of Tagelus californianus (Conrad) whose present 

 range is from Santa Barbara to the Gulf of Tehuantepec, 

 and indicates that it is restricted to warmer waters than those 

 of the San Francisco Bay of today. As noted above, Arnold 

 clearly recognizes that the Upper San Pedro fauna is not 



13 Lawson, A. C, Univ. of Calif. Publ., Bull. Dept. Geol., Vol. 1, p. 271. 1894. 



