24 



SHORTER CONTRIBUTIONS TO GENERAL, GEOLOGY, 1919. 



silts, containing faunal remains. It is tentatively referred 

 to the Pliocene on the basis of fossils collected in place by 

 the writer in the bluff (near its top) on the west side of the 

 Colville about a mile north of the seventieth parallel. 



The section assigned to the Pliocene horizon 

 at Carter Creek, 1 mile from the coast of Cam- 

 den Bay, on the Arctic shore of Alaska, was 

 measured by Leffingwell as follows: 



Section at Carter Creek. 



Top. 



A. Sand with intermixed humus 



B. Sand without fossils, some gravel. 



C. Pale-grav sand with marine fossils . 



Feet. 

 . 30 

 , 80 

 , 100 



The fossils appear from the collections to be 

 most abundant in the lower 100 feet of the 

 section. 



GUBIK SAND. 



Schrader^ describes the supposed Pleistocene 

 deposit of the Colville River region as follows : 



Besides the Tertiary Cohdlle series, which imderlies the 

 coastal plain along CoK-ille River, the section here com- 

 prises deposits supposed to be Pleistocene. Of these, 

 probably the most important and interesting is a surficial 

 deposit of brownish sand or loam about 10 to 15 feet in 

 thickness, which unconformably overlies the beds of the 

 CoKdlle series, apparently as a continuous mantle. * * * 

 The deposit consists of fine sand, with apparently an ad- 

 mixture of considerable silt. In some localities it seems 

 to be more sandy toward the base and more earthy toward 

 the top, where it terminates in from one to several feet of 

 dark-brown or black humus, clothed at the surface with 

 moss and a little gi-ass. It is ordinarily free from gravel, 

 but in several instances subangular cherty pebbles, rang- 

 ing from mere sand grains to fragments as large as one- 

 foiuth inch in diameter, were found. These occur very 

 scatteringly and are sometimes roughened, as if wind worn. 

 In some localities a fine gravel seems to intervene between 

 the base of the deposit and the imderlying Tertiary beds, 

 as if representing the basal part of the deposit. The de- 

 posit as a rule is structureless, or without stratification 

 planes. Owing to this fact, together with its surficial and 

 widespread occurrence and the homogeneity of its mate- 

 rials, for want of a better term in field work it was called 

 loess, but in the fear that this term may be undesirable, it 

 is here named the Gubik sand, after the Eskimo name of 

 Colville River. 



In a low bluif on the coast 15 miles south- 

 west of Point Barrow settlement and in the 

 talus from this bluff Leffingwell found five 

 species of invertebrate fossils, all belonging to 

 recent species. Tliis deposit is probably Pleis- 

 tocene and may be tentatively correlated with 

 the Gubik sand of Schrader, which occupies 

 a similar position in the section farther east. 



1 Op. cit., p. 93. 



NOME ELEVATED BEACHES. 



On the south side of Seward Peninsula (orig- 

 inally given the native name Kaviiak), on the 

 north shore of Norton Sound, the gold prospec- 

 tors have revealed the presence of a series of 

 ancient beaches the gravels of which contain 

 numerous marine fossils, including a consid- 

 erable proportion of extinct species leading 

 to their identification as of Pliocene age. In 

 referring the horizon containing the numerous 

 extinct species to a pre-Pleistocene age my 

 conclusions rest entirely upon the paleontolo- 

 gic evidence. ^ It is proper to state that P. S. 

 Smith and A. H. Brooks, of the Geological 

 Survey, from physiographic observations, are 

 disposed to assign a Pleistocene age to the 

 beaches. In regard to the succession of the 

 strata there is no difference of opinion. 



The present beach near Nome may be consid- 

 ered the "first beach." The "second beach" 

 lies inland, at an irregular distance that varies 

 with the topography but is everj^where less than 

 a mile, and has an elevation above sea level of 

 37 feet. The ''third beach," some 2§ to 3§ 

 miles inland, has been elevated to the height of 

 79 feet above the sea.^ Between the second and 

 third beaches are several less well-defhied inter- 

 mediate beaches, one of which is 22 feet above 

 sea level, thus being lower than the second 

 beach, to the south of it. Between the second 

 beach and the present beach shafts have been 

 sunk to a depth of 65 to 70 feet which reach at 

 about 20 feet below the present sea level the 

 oldest beach of all those now knowTi, which has 

 locally received the name submarine beach or 

 beaches. These beaches have been described 

 in detail by Moffit in the bulletin cited. Doubt- 

 less still others remain to be discovered. 



INDICATIONS OF ELEVATION AND CLIMATE. 



The indications of the Tertiary geology of 

 the northern and northeastern shores of Alaska 

 are therefore, in substance, that from early 

 Pliocene (if not even older) time the land 

 underwent a general elevation, broken by 

 periods of rest sufficient to allow the formation 

 of low scarps with their attendant beaches, 

 and at least one unimportant depression during 

 the earlier portion of the period. The massive 

 granite extrusions, such as form Cape Prince 



" Of 62 species 23, or 37 per cent, are extinct. 



3 Moffit, F, H., U. S. Geol. Survey Bull. 533, p. 41, fig. 9, p. 78, 1913. 



