Vol. XI] niCKERSON—PT. REYES AND SANTA ROSA QUADRANGLES 531 



the faunas in both formations are sub-tropical and indicate 

 warm interglacial epochs. Just what time interval is repre- 

 sented by the unconformity which separates these two forma- 

 tions is very difficult to evaluate as these beds are in the im- 

 mediate line of faulting along the San Andreas Rift where 

 great changes are possible within a very limited space of 

 geologic time, but the writer believes that this was an im- 

 portant break. In both beds, well preserved cones of the 

 Monterey pine (Pinus radiata) were found. This species 

 does not at present range north of San Mateo County, it 

 being replaced in the present day flora of this region by 

 Pinus muricata, Thus it is evident that both the faunas and 

 the floras of these beds indicate warmer climates during the 

 Pleistocene interglacial epochs than at the present time in 

 these latitudes. 



Review of the Literature 



This region was cursorily examined by Whitney 4 who 

 noted that marine sandstones rested upon the metamorphics 

 (Franciscan) and he referred these sandstones to the Mio- 

 cene. We now know that they are Pliocene, the Merced for- 

 mation. Gabb" described Mctula rcmondii from the sand- 

 stones of this Pliocene formation at San Antonio Estero near 

 the town of Tomales, and several other fossils from the vicinity 

 of Mark West Creek from beds of the same age. Lawson," 

 in the Geomorphogeny of the Coast of California, gives the 

 first detailed information about this area. He recognized that 

 the terraces of Point Reyes Peninsula were due to wave 

 erosion, described briefly the great fault which conditions 

 Tomales and Bolinas bays, and perceived that the last move- 

 ment, recognized in this vicinity, the subsidence which gave rise 

 to San Francisco Bay, had also affected Point Reyes Peninsula. 

 "Even more significant of the recency of the depression are the 

 flooded streams which end at the sand beach of Drakes Bay. 

 These are called Drakes Estero on the Coast Survey Chart. 

 They are finger-like inlets which are very clearly flooded stream 

 canyons, representing a drainage convergent towards the south. 



4 Whitnev, J. D., Geology of California, vol. 1, pp. 81-85 1865. 



5 Gabb, Wm., Geological Survey of California; Paleontology, vol. 2, pp. 3, 72, pi. 



' ^Lawson^ A. C, Univ. of Calif., Publ. Dept. Geol., vol. 1, No. 8, pp. 245-246, 

 264-265, and 268-269, 1894. 



