Vol. i i Osmont.- -Geological Section of Coast Ranges. 87 



as suggested by Anderson, there may have been oscillations along 

 this line in early Tertiary limes. 



After the folding an tiplifl occurred which was no1 contin- 

 uous, bill was marked by periods of rest, and possibly of reversal 

 of motion, since along the const these stoppages are recorded by 

 wide, wave-cut terraces. The coast line of this section is made 

 up almosl entirely of Franciscan rocks, which do nol resist ero- 

 sion well enough to preserve the terraces higher than about 300 

 feet, the elevation of those a1 Point Reyes. The coastal ridge 

 between the writer's two seel ions has a very even crest-line at 

 about 800 feet above sea-level, and on Ibis he lias found pholas- 

 borings a1 two places. To the north, however, I .aw son states thai 

 a well defined wave-cut shelf exists at 1,520 feet, with many 

 others at lower elevations. 



While this gradual elevation was taking place the streams 

 were dissecting and wearing down the rising land, and the im- 

 mense amount of erosion which has taken place since the inaugu- 

 ration of the post-Pliocene uplift is a measure of the vast length 

 of time represented by the Pleistocene. The geomorphic cycle 

 which had its beginning in the post-Pliocene times lias already 

 reached a stage of early maturity. 



Following this elevation, and possibly only one of the retro- 

 grade steps in the general elevation of the coast, came the most 

 recent submergence of the region, as evidenced by the flooding 

 of the lower valleys of the streams and the formation of fiord- 

 like estuaries at Russian River, Drake's Bay, Estero Americano, 

 and San Antonio, Tomales Bay, and the great San Francisco 

 Bay itself, with its estuaries such as Petaluma Slough and Napa 

 River. 



Evidence exists in submerged "Kitchen-middens" to show 

 that this submergence is still going on at a rate which may be 

 measured in terms of inches and hundreds of years. 



*Geomorphogeny of the Coast of Northern California. Bull. Dept. Geol., 

 Univ. (,f Cal., Vol. I, No. 5. 



Berkeley, California, 



December 1, 1904. 



