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University of California. 



[Vol. 2. 



reveals no definite evidence of organic remains, and it is not certain 

 that they are present. The rock has, however, the usual fetid odor 

 of this limestone, and is associated with a hard, black shale that 

 could well belong to the same series. These rocks seem to rest 

 directly upon the granite, and are adjacent to the zone of crushed 

 granite mentioned in another paragraph. This limestone is appar- 

 ently a continuation of the foraminiferal limestone occurring a few 

 miles to the southeast, where it has been quarried for lime. 



This is the only body of this series of rocks that has been 

 found within the boundaries of the field, though they occur abun- 

 dantly just outside of it. The series occupies nearly the whole of 

 the east shore of Tomales Bay, and extends to the southward along 

 both sides of the valley, going toward Baulinas. The series, as a 

 whole, seems not to have been greatly affected by the disturbances 

 which have caused so many oscillations of the adjoining peninsula. 



Miocene Sediments. — The Miocene series consists of three mem- 

 bers, the upper two of which are not distinctly separated. The 

 lower member is a dark, heavy conglomerate, in which the pebbles 

 and stones range from one-half inch to more than one foot in 

 diameter. The second member is a thin-bedded, cream-colored 

 sandstone that passes quite gradually into the upper member, the 

 special features of which will be described later. It is the white 

 Miocene shale of the Monterey series, well known in the Coast 

 Ranges, This series is essentially similar at all the points at which a 

 complete section is to be seen. At the summit of Whittenberg Hill 

 a series of the Miocene sediments, some hundreds of feet in thick- 

 ness, have conglomeratic beds at their base, with a thickness of 

 eight or ten feet, containing pebbles of granite and crystalline lime- 

 stone. 



On Tomales Point, opposite the Skinner Ranch, a similar series 

 overlies the granites. The conglomerates at this point are not more 

 than two or three feet in thickness. By far the most important 

 occurrence of basal conglomerate is at the southwestern extremity 

 of the peninsula, and especially in the immediate vicinity of the 

 Point Reyes Lighthouse. The axis and southern face of the ridge 

 extending east and west, is of granite. This is overlain along the 

 northern slope by heavy beds of conglomerate, dipping steeply north- 



