Anderson.] 



Point Reyes Peninsula. 



149 



semimarsh portion through which the current is ordinarily sluggish. 

 The drainage of the eastern margin is directly into Tomales Bay 

 by short and tolerably rapid streams. That of the western portion 

 is by longer streams, most of which find their way into Drake's 

 Bay either directly or indirectly. Many of them converge into 

 Drake's Estero, the outline of which beautifully illustrates the 

 effect of a drowned valley. 



DYNAMIC HISTORY. 



Granitic Intrusion. — Evidences of the earlier disturbances of the 

 coast, either epeirogenic or orogenic, are not well shown upon the 

 peninsula. The earliest of which there is any clear record to be 

 found is that of the granitic intrusion into the older crust of sedi- 

 mentary rocks which has resulted in the distortion and metamor- 

 phism of the latter. There is no evidence yet recognized that fixes 

 with any certainty the date of this event. In the absence, therefore, 

 of contradictory facts it may be supposed to be contemporaneous 

 with some of the granites of the Sierra Nevada. At the same time 

 the relatively slight metamorphism of much of the Franciscan 

 (Golden Gate) series, even in actual contact with the granites, makes 

 it evident that the intusion took place prior to the deposition of 

 these rocks, which mark the next epoch of which there is any 

 record here. 



Subsequent Movements. — After the erosion, which followed the 

 granitic up-thrust, there was a prolonged period of subsidence, 

 during which the strata of the Franciscan rocks were laid down. 

 This event is recorded not only by the small body of limestone and 

 slate found west of Olema, but also by the whole Franciscan ter- 

 rane lying to the eastward of the peninsula. 



From our knowledge of oscillations that have affected other and 

 neighboring portions of the coast, it would seem that there must 

 have been movements here during the Cretaceous and early 

 Tertiary which have not left legible records. 



From the beginning of the Miocene, however, our knowledge is 

 more perfect. The character and order of the Miocene deposits 

 show that at the beginning and throughout the Miocene the move- 

 ment of the land was downward. 



