PLEISTOCENE DEPOSITS, GROUND-ICE FORMATION AND GUBIK SAND. 93 



between the Colville and Chipp (Ikpikpuk) River, they are not only far from con- 

 tinuous, but are probably of very limited occurrence. Along the northwest part 

 of the coast, the only locality at which what seems with certainty to be the Kowak 

 clay was observed, is at Wood}- Inlet, about 50 miles southwest of Point Barrow. 

 As this inlet is not far from the seventy-first degree of north latitude it is thought 

 that the deposit may be near that in which Captain Beechey's party obtained elephant 

 remains. 



GUBIK SAND. 



Besides the Tertiary Colville series, which underlies the coastal plain along Col- 

 ville River, the section here also comprises 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 unconf ormably overlies the beds 

 of the Colville series, apparently as a continuous mantle. 



This deposit seems to be distinct from the Colville series and to extend over a 

 large area of country. It not only forms the surficial terrane of the coastal plain 

 along the Colville, but seems to occur at some localities along the coast from the 

 mouth of the Colville westward, in some instances apparently overlying the ground 

 ice and probably the Kowak clay formation, while its inland margin probably over- 

 laps the coastal edge of the Upper Cretaceous of the Nanushuk series along the 

 Anaktuvuk nearly to the mouth of the Tuluga, where, in certain localities, judging 

 from topographic criteria, it also appears to overlie gravels which are very ten- 

 tatively referred to as glacial, but to which its relation is not definitely known. 



The deposit consists of fine sand, with apparently an admixture 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 grass. It is ordinarily 

 free from gravel, but in several instances subangular cherty pebbles ranging from 

 mere sand grains to fragments as large as one-fourth inch in diameter wei'e 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 underlying Tertiary beds, as if representing the basal part of the deposit. 



The deposit 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 materials 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. 



Various hypotheses have suggested themselves to account for the origin of the 

 deposit, of which no one alone seems to be satisfactory. To the writer, the fluviatile 

 delta theory, in conjunction with shallow coastal conditions and intense arctic freezing, 

 seems the most tenable. 



