250 F. C. SCHRADER — GEOLOGICAL SECTION IN NORTHERN ALASKA 



a wide area of country. It not only forms the surficial terrane of the 

 coastal plain along the Colville, but seems to be persistent along the coast 

 from the mouth of the Colville westward, while its inland margin seems 

 to overlap onto the Upper Cretaceous of the Nanushuk series. In char- 

 acter, the material composing the deposit is fine-grained and, on the 

 whole, uniform or homogeneous. Its description as fine sand, with an 

 admixture of considerable silts or earthy material, perhaps best conveys 

 an idea of the texture of the deposit. In some localities it seems to be 

 more distinctly sandy toward the base and earthy toward the top, where 

 it sometimes grades into from one to several feet of dark-brown or black 

 humus or muck, clothed at the surface with moss and a little grass. 

 The deposit is ordinarily free from gravel, but in several instances peb- 

 bles ranging from mere grains to as large as one-fourth of an inch in 

 diameter were found. These consist essentially of dark flint and may 

 be characterized as subangular. They are sometimes roughened or 

 grooved, as if wind-worn. They occur very scatteringly indeed. It 

 should be noted, however, that in some instances a very fine gravel or 

 grit occasionally intervenes between the base of the deposit and the. 

 underlying Tertiary beds. 



The deposit, as a rule, is structureless or devoid of stratification. In 

 only a few instances were indications of stratification observed, and this, 

 though it was faint and indefinite, seemed to dip at a considerable angle 

 and was accompanied by indistinct crossbedding. Weathered faces of 

 the deposit frequently present the appearance of unpronounced stratifi- 

 cation ; but on careful removal or cutting away of this weathered part, 

 in search of more conclusive evidence, the material is found to be struc- 

 tureless. Owing to its surficial and widespread occurrence, the homo- 

 geneity of its materials and its structureless character, and the difficulty 

 of explaining its origin, for want of a better term in field-work the de- 

 posit was called loess. After further consideration, however, it is feared 

 that the retention of the term would be undesirable, for which reason 

 the deposit is here given the name of Goobic sands. 



To account for the origin of the Goobic sands, the following causes 

 have suggested themselves, namely, glacial, fluviatile, delta, eolian, 

 marine or beach, none of which alone seems to afford a satisfactory ex- 

 planation. It is probable, however, that the fluviatile delta theory, in 

 conjunction with shallow coastal conditions and intense Arctic freezing, 

 may prove the most tenable. 



GLACIAL MATERIAL 



While there is no evidence of truly regional glaciation in northern 

 Alaska, it is now known that ice action has been far more extensive than 



