LATER TERTIARY (MIOCENE AND PLIOCENE). 835 



N 10. UPPER PEACE AND FBASEB RIVEBS, BRITISH COLUMBIA. 



Under the title Lignite group Dawson ^^"^ described the occurrences of sandstone 

 and shale which carry lignite beds and commonly underlie the basalt flows of the 

 upper Fraser Valley, British Columbia. At Quesnel they have yielded a flora of 

 Miocene or earlier age associated with insects. 



N-O 4. ALASKA PENINSULA. 



Atwood *^° thus describes the Miocene of the Alaskan Peninsula : 



Miocene sediments appear in Unga and Popof islands and at several places on the north 

 and south sides of Alaska Peninsula. ' They consist of sandstones, shales, and conglomerates 

 that represent off-shore, shallow-water deposition. An abundance of fossil material was pro- 

 cured and has been identified by Mr. Dall. At Coal Harbor, Unga Island, the Miocene strata 

 conformiably overlie the Kenai formation (upper Eocene), but at other localities the Miocene 

 sediments appear to rest unconformably upon different formations and to have been restricted 

 to local basins. They are but little disturbed. 



One collection of fossil plants, from the Herendeen Bay district but from a lithologic unit 

 that occupies a very small area, seems to indicate post-Miocene age. The most extensive post- 

 Miocene formations consist of volcanic tuffs and basic lava flows. They are widespread on the 

 mainland in the vicinity of the Balboa-Herendeen Bay district and cover many square miles in 

 the islands to the south and in the region about Chignik Bay. 



For Kodiak Island and Katmai Bay, see Chapter XVI (p. 784). 



O 4. BRISTOL BAY. 



On the east shore of Nushagak Bay, which enters Bristol Bay from the north, 

 Spurr^^'^ observed strata to which he gave the name Nushagak. He says: 



The high bluffs which form the east shore of Nushagak Bay are composed of stratified 

 gravels, coarse sands, arkoses, and clays, which in places are slightly consolidated, apparently 

 being cemented by iron which has leached out of the arkoses. These beds, in general horizontal , 

 are frequently distinctly flexed, sometimes dipping as much as 20°, and in places there is even: 

 considerable folding and distortion. The strata are often heavily cross-bedded and contain 

 pebbles derived from a great variety of rock, some of which are striated, apparently from ice. 

 This formation is exposed for a number of miles along the shore of Nushagak Bay and aroimd 

 Cape Etolin to Bristol Bay. 



-Overlying the folded clays and gravels which have been called the Nushagak beds are 

 imconformable horizontally stratified clays and gravels which contain many pebbles and 

 frequently large bowlders, often being striated by ice. Near Nushagak these upper beds occupy 

 the tops of the bluffs, which are in places as much as 150 feet high, but where the bluffs become 

 lower and the beds themselves become thicker they often come down to the beach line, so that 

 the underl3dng unconformable series is not exposed. These upper beds must be referred to the 

 Pleistocene, so that those which underlie are probably Tertiary. In this connection a note 

 made by Dr. Dall'' concerning fossils collected at Nushagak by C. W. McKay is of interest. 

 According to this, fossils were collected in an "indurated clayey matrix," which evidently refers 

 to the Nushagak beds just described. They include Modiola multiradiata Gabb, Pectunculus 

 jmtulus Conrad, Nucula tenuis Lamarck, and Serripes gronlandicus Beck and determine the age 

 of the clays and gravels in which they occur as Miocene. 



Regarding the above Atwood states in a personal communication: "I have not 

 been at this locality. The pebbles and bowlders striated by ice, which are reported 



<» Report on coal and lignite of Alaska: Seventeenth Ann. Kept. U. S. Geol. Survey, pt. 1, 1896, p. 847. 



