Vol. 5] 



Weaver. — San Pablo Formation, 



247 



In 1899, Mr. F. M. Anderson 8 in his paper on the Geology of 

 Point Reyes Peninsula states that there are beds near the town 

 of Tomales which are supposed to be of San Pablo age. 



In 1904, Professor J. C. Merriam, in his paper on the Fauna 

 of the Lower Miocene in California, states that the Contra Costa 

 County Miocene contains two faunal zones and that the upper 

 division has its nearest affinities with the San Pablo but is dis- 

 tinguished from it by the presence of Clypeaster brewerianus, 

 Trocliita costellata, and several other forms. 



In the same year in a paper by Mr. H. L. Haehl 1 " and Dr. 

 Ralph Arnold on the Miocene Diabase of the Santa Cruz Moun- 

 tains in San Mateo County, California, the Purisima formation 

 is described. It is described as an extensive series of conglom- 

 erates, fine-grained sandstones and shales. They lie unconform- 

 ably upon the Vaqueros sandstone and Monterey shale. The 

 upper limit was considered to be the base of the Merced. Its 

 age was considered to represent the lower or perhaps the middle 

 Pliocene. 



In 1905, Dr. H. W. Fairbanks, 11 in his description of the San 

 Luis Folio, states that "overlying the Monterey shale uncon- 

 formably is a series of soft white sandstone, conglomerate, diato- 

 maceous beds and flinty shales which represent the San Pablo 

 group. The names Pismo and Santa Margarita were given to 

 these strata. Fossils showed them to be of Neocene age, but 

 whether Miocene or Pliocene was not certain. 



In the same year Mr. V. C. Osmont 12 published a paper on a 

 Geological Section of the Coast Ranges north of San Francisco 

 Bay. In this he gives a description of several areas in which 

 San Pablo strata are found. Strata of undoubted San Pablo age 

 occur in the core of the hills on the west side of Carneros Creek. 

 It is considered as San Pablo by reason of its physical appearance 

 and its fossil fauna. Prevolcanic beds made up of four hun- 

 dred feet of a very coarse hard sandstone and yellow to buff 

 colored sandy shales are found between Freestone and the mouth 



s Bull. Dept. Geol. Univ. Calif., vol.. 2, no. 5. 



a Bull. Dept. Geol. Univ. Calif., vol. 3, no. 1(5, pp. 377-381. 



10 Proc. Am. Phil. Soc, vol. 43, pp. 15-53. 



11 San Luis Folio: Geologic Atlas U. S., folio 101, U. S. Geological 

 Survey, Washington. 



12 Bull. Dept. Geol. Univ. Calif., vol. 4, no. 3, pp. 39-87. 



