Anderson.] 



Point Reyes Peninsula. 



137 



nature, forming the cliffs that are so conspicuous from the mouth 

 of Bear Valley. They are of a light yellow color and are thin- 

 bedded, dipping gently away from the granites and overlying the 

 conglomerates along the northern slope of the ridge. To the 

 northward they pass by insensible gradations into whiter and more 

 shaly material as they ascend the series. 



On the peninsula the shales cover the larger part of its area, 

 underlying the lower portions surrounding Drake's Bay and Estero, 

 and composing the lower hills west of the main granitic ridge. In 

 the lower portion of the peninsula they dip at a low angle and are 

 very little disturbed, but along their western margin their inclina- 

 tion is very much greater. They have here been faulted and 

 thrown into a series of short monoclines in which the dip sometimes 

 amounts to as much as 45 °. 



At the summit of Whittenberg Hill the shales have a somewhat 

 darker color than ordinarily, though in other respects they retain 

 their characteristic features. The minute casts of foraminifera are 

 abundant in them and they are composed of essentially the same 

 material as the whiter beds are elsewhere. On account of the 

 peculiarities of their stratification the section at the summit of this 

 hill deserves more than a passing notice. It consists mostly of the 

 finer-grained material composing the main body of the formation, 

 in which are interstratified several layers of a coarse sandy char- 

 acter. These sandy layers, which are usually less than a foot in 

 thickness, form a striking contrast to the strata of finer grain in 

 which they are intercalated. An explanation of this peculiar phe- 

 nomenon is not very easily made. Possibly they have only a 

 limited extent and are records rather of fluctuating currents than of 

 any considerable disturbances. 



Figure 2. — Section drawn east and west just south of White Gulch. 



It is seen from the above description that the Miocene sediments, 

 lying between the main granite ridge and smaller area at the south- 

 western angle of the peninsula, have been gently folded into a broad 



