GEOLOGY OF THE COASTAL REGION 461 



ent beds as they occur at the eastern end of Crescent bay, while figure 2, 

 plate 56, shows a characteristic exposure of the formation at tide level 

 in the same region. In the region of Crescent bay the lower basalt has 

 an exposed thickness of 200 feet, while the tuffs and upper basalt sheet 

 each show approximately the same. The Freshwater Bay section gives 

 basalt and coarse massive basalt tuff 600 feet, thin bedded green tuff 375 

 feet, and black vesicular basalt 200 feet. The base of the Crescent forma- 

 tion is not exposed, so that the subjacent rocks are unknown. The over- 

 lying sediments consist of coarse conglomerates separated from the basalt 

 by an erosion interval. Faults define the contact between the Crescent 

 formation and the Clallam formation (Oligocene-Miocene) adjacent. 



These basalts and tuffs are the only rocks of igneous origin found along 

 the whole length of the northern shore of the peninsula. Taking into 

 consideration the volcanic activity which prevailed during the Eocene in 

 the Cascade range, only a comparatively short distance away, this single 

 and rather limited occurrence of eruptives seems rather remarkable. The 

 paucity of igneous rocks, however, may possibly be accounted for, at 

 least along the northern coastal border of the Olympics, by the fact that 

 formations younger than the basalt are the only ones exposed, and it is 

 possible that some of these newer rocks are underlain by the Eocene basalt 

 series. 



Oligocene-Miocene : Clallam formation. — Besting unconformably upon 

 the Eocene and older rock of the Olympic peninsula is a series of con- 

 glomerates, sandstones, and shales rich in fossils and extensive in occur- 

 rence. The formation is well exposed in the region between Clallam bay 

 and Pillar point, to the east, and for that reason is here named the 

 Clallam formation. According to Doctor Dall, the fossils of the forma- 

 tion indicate that the basal portion of the series is Oligocene in age, while 

 the upper part is certainly Miocene. Since the separation of the two 

 members will necessarily have to be made on paleontologic grounds and 

 will require a more detailed study of the material in hand than time has 

 yet permitted, the term "Oligocene-Miocene series'' will be used tem- 

 porarily to designate the age of the beds. A portion of the formation is 

 unquestionably the equivalent of the Astoria sandstones and shales occur- 

 ring at the mouth of the Columbia river, 130 miles farther south. 



All of the pre-Pleistocene deposits along Fuca strait from Freshwater 

 bay to cape Flattery, with the exception of the Eocene basalts and tuffs 

 of Crescent bay and the Pliocene conglomerate and sandstone of the 

 Clallam Bay-Hoko Eiver region, belong to the Oligocene-Miocene series, 

 and at least the greater part and possibly the whole of the thick series of 



