Anderson.] 



Point Reyes Peninsula. 



downward movement of the other, which resulted in an accumula- 

 tion of the Merced deposits of considerable thickness, in its typical 

 locality south of the Golden Gate. 



Following the Merced subsidence, there was probably a wide- 

 spread orogenic movement, which quite singularly seems to have 

 disturbed and tilted the lately-formed Pliocene strata, without 

 greatly increasing their elevation. The nature of these movements 

 is not very clear, but evidently the land both east and west, that is 

 to say, both orographic blocks, were simultaneously left at a level, 

 considerably below the present one, from which they slowly 

 emerged, forming the terraces previously described, and the corre- 

 sponding deposits of Pleistocene gravels, which have been called by 

 Professor Lawson the "terrace formations." These deposits, how- 

 ever, appear to have been formed only during the earlier stages of 

 the uplift, or rather only the earlier deposits are at present observ- 

 able, the latter being now submerged by a subsequent inundation. 



The Miocene beds of the peninsula have been deeply scarred by 

 the long-continued atmospheric action, probably in part effected 

 during the period of terracing and elevation, but mainly as it seems 

 at a prior epoch, since the detritus of the terraces is mostly con- 

 fined to the valleys previously excavated. Three quite distinct 

 terraces are recognizable, marking the principal pauses in the 

 process of this elevation. These have already been described, two 

 of which are to be seen along the hills, while the third is entirely 

 submarine. It appears, therefore, that the gradual rise of land 

 which is marked by these benches continued until the shore-line 

 was thrown westward, nearly to the verge of the continental bench, 

 at which time the land must have stood at a level of more than 200 

 feet above its present position. This is shown by the broad sub- 

 marine terraces just alluded to. From this altitude there has been 

 a sinking, more or less general, which is probably yet in action. 



This subsidence has resulted in two well-marked effects: (1) 

 The beveling of the submarine terrace, which is in part, at least, 

 due to such causes ; and (2) the inundation of the stream valleys, 

 which is illustrated in Drake's Estero. 



3 



