Vol. XI] DICKERSON—PT. REYES AND SANTA ROSA QUADRANGLES ^79 



Kenwood Valley- 

 One of the highest points in this Kenwood valley region 

 is Sonoma Mountain, elevation 2465 feet. This mountain 

 mass is separated from the Mayacamas Mountains by a long 

 narrow valley which we will refer to as Kenwood valley. 

 The highest point in this area is Mt. Hood, one of the peaks 

 of the Mayacamas Range with an elevation of 2715 feet. 

 Sonoma Mountain is separated from the northern extension 

 of the Mt. Tamalpais Mountain mass by Petaluma and Santa 

 Rosa valleys. These physiographic units are, in part due to 

 geologic structure, and in part, due to erosion. Only recon- 

 naissance work was done in the Mayacamas Mountains, but 

 the anomalous drainage of this mass is at once apparent from 

 a brief study of the Santa Rosa Quadrangle. A part of the 

 drainage on the southwest side of this range goes into Santa 

 Rosa Creek, a tributary of the Russian River, while the other 

 half reaches the ocean indirectly by way of Sonoma Creek, 

 which empties into San Pablo Bay. The course of Sonoma 

 Creek is particularly anomalous. Sonoma Canyon and its 

 tributary stream, Bear Creek, drain the rugged eastern side 

 of Mt. Hood Ridge, and a northwestern tributary which 

 drains the northwestern side of Mt. Hood Ridge meets the 

 main Sonoma Creek one-half mile northwest of Kenwood 

 village. The main stream, which has been crowded to the 

 southwestern side of Kenwood valley by the alluvial fans of the 

 short, sharp streams descending from the southwestern slope 

 of the Mayacamas Mountain scarp, suddenly abandons what 

 appears to be a perfectly direct course out of the valley, to 

 cut across the hills on the southwest side of Kenwood val- 

 ley. After flowing in a canyon for two miles due south, the 

 stream then turns and maintains a general southeastern course 

 for two miles until it is joined at the village of Glen Ellen 

 by Calabazas Creek and then proceeds through a narrow 

 valley for a mile to Eldridge. A brief study of the topo- 

 graphic map near Los Guilicos quickly shows that the un- 

 named western tributary of Sonoma Creek has sometimes 

 swung upon its fan so that the drainage from this slope has 

 been out by way of the small stream draining through An- 

 nadel, which for the lack of a better name will be used to 

 designate this odd but significant wet-weather stream. Anna- 



