298 CALIFORNIA ACADEMY OF SCIENCES. 



Its age is therefore not known. From its association 

 with the phthanite it has been thought to be of about the 

 same age, and so is called Jurassic by some. Assuming 

 the existence of a nonconformity between these rocks and 

 the Cretaceous, it may be best for the present simply to 

 consider them as pre-Cretaceous.* 



THE PESCADERO SERIES. 



The San Francisco sandstone was one of the earliest 

 formations recognized and described in this State. Of 

 late, however, as intimated above, it has been thought 

 that the formation originally described under the name 

 San Francisco sandstone, instead of being one formation 

 represents at least two of very differing ages. In most, 

 if not all, the recent papers the California or San Fran- 

 cisco sandstone has been assumed to belong to the pre- 

 Cretaceous series. But the writer has found that a large 

 part of what was originally described as the San Francisco 

 sandstone belongs to a series which certainly is in part 

 Miocene, as at first described by Blake, probably in part 

 Tejon and possibly in part Cretaceous. The best expos- 

 ure of the series was found in the low bluffs near Pesca- 

 dero, extending from Pescadero Point nearly to Pigeon 

 Point. It was the only place found appearing to give 

 anything like a complete section. The beds are practic- 

 ally perpendicular and near one end of the section are 

 fossiliferous. As a matter of convenience, the formation 

 will be distinguished in this paper as the Pescadero series. 



The Pescadero series has a thickness estimated at from 

 200D to over 10,000 (?) feet. Though apparently over- 

 looked by some of the recent writers on California geology, 

 all the earlier workers recognized the existence below the 

 White Miocene Shale of sandstones containing older Mi- 



* American Geologist, vol. ix, 1892, pp. 153 et seq.; also vol. xi, 1893, 

 pp. 69-84. 



