238 F. C. SCHKADER — GEOLOGICAL SECTION IN NORTHERN ALASKA 



tocene till, which is soon found resting on Lower Cretaceous, a belt of 

 several miles has been left blank. It is thought possible that Carbonif- 

 erous and Lower Mesozoic strata may occur in this region between the 

 Devonian and the Lower Cretaceous. 



The rocks encountered comprise representatives of most of the geo- 

 logic formations from Silurian to Kecent. In point of distribution, as 

 shown in the section, they consist primarily of a belt of Paleozoics 80 to 

 100 or more miles in width, constituting the Endicott mountains, against 

 whose slopes, unconformably on either side, rest the edges of the plateaus 

 or uplands, composed of Mesozoics, which in turn are succeeded by Ter- 

 tiary. Beginning with the oldest, these several formations or rock series 

 will be briefly noted. As the field is new, the names here employed to 

 designate the various formations or series are proposed provisionally. 

 To afford a more comprehensive view of the relations of the several 

 series and avoid repetition in referring to them individually, it may be 

 well to note at the outset some features of structure which are common 

 to nearly all the Paleozoic series and apply to the range as a whole, 

 namely, that the series all strike or trend approximately east and west, 

 parallel with the trend of the range. They are nearly all traversed by 

 the dominant jointing or major structure of the range, cutting the rocks 

 in a northeast and southwest direction, with dip nearly vertical or 

 steeply northwest, at an angle of 75 to 80 degrees. This dip may be 

 considered normal, since the uplift of the land mass of the range to the 

 east exceeds that on the west. The series also nearly always exhibit 

 one or more sets of secondary jointing or minor structure, trending in a 

 general northwest or southeast direction, approximately at right angles 

 to the major structure. The above statements of structure pertaining 

 to the Paleozoics in the range apply also in a limited way to the adja- 

 cent Mesozoics on either side. 



We may also note that, with the exception of the greenstone schists 

 occurring iii the Totsen series, the Paleozoics of the range, as well as the 

 younger formations of the Arctic slope, are all sedimentary and, so far 

 as observed, free from igneous intrusions of any kind. 



The Endicott range consists of two somewhat distinct geologic axes, 

 of which the southern seems to be composed of the oldest rocks, namely, 

 the Skajit formation, and the Totsen series, of which the former is the 

 most prominent. 



Paleozoics 



skajit formation ( upper silurian) 



Character and occurrence. — The rocks of the Skajit formation consist of 

 heavy-bedded limestone and mica-schist. The limestone is highly al- 



