244 F. C. SOHRADER GEOLOGICAL SECTION IN NORTHERN ALASKA 



foreign coast visited by Doctor Dall he reports the rock to be essentially 

 crystalline or igneous. 



Mesozoics 



corwin series (jura-cretaceovs)* 



Character and occurrence. — The Corwin series is not represented in the 

 section, nor is it known to extend so far eastward as the Anaktoovuk. 

 It was encountered several hundred miles northwest of this on the 

 coast near Wainright inlet, whence it extends south westward a dis- 

 tance of 180 miles to near cape Lisburne, where it plays a very impor- 

 tant part in the geological section of that locality, and since the topog- 

 raphy and the open, uniform character of the intervening country sug- 

 gests a probable great extension of the series to the eastward, and its 

 geological horizon is known on fossil evidence to be above the Fickett 

 and below the Anaktoovuk, to be next described, it seems not unlikely 

 that the Corwin series occupying this horizon may extend far inland 

 along the north slope of the range to near, if not beyond, the meridian 

 of the section. The series consists of medium to heavy bedded impure 

 gray and brown sandstone and arkose, with shale, shaly slate, and coal. 

 The coal includes the Wainright, Beaufort, Thetis, and Corwin coals, to 

 which the names Cape Lisburne coals and Cape Beaufort Coal Measures 

 have also been collectively applied, and which are likely to prove of 

 economic value. While the northwestern edge of the series forms the 

 coast line, the southern edge seems to rest unconformably on the Paleo- 

 zoics on the south. 



Structure. — The beds lie nearly horizontal or dip southwest at an angle 

 of 30 to 40 degrees, are slightly folded and faulted, and are traversed by 

 two sets of jointings, one approximate^ 7 parallel with the strike and the 

 other approximately at right angles to it, agreeing in a general way with 

 the major and minor structures in the inland portion of the range, as 

 has been noted. 



Age. — Fossil plants found in the Cape Beaufort region, and more par- 

 ticularly in the shale near the Thetis mine, at cape Sabine, by Mr Dumars 

 and Mr Woolfe and others, have been identified by Professor Fontaine 

 and Doctor Ward as not older than the Oolitic nor younger than the 

 Lower Cretaceous, but as probably on a line between the two.f 



On this evidence, together with forms collected by the writer from 



*It is possiblo that the rocks at cape Beaufort may on further research prove to be older than 

 Jura-Cretaceous, but for the present it seems best to include them in the Corwin series. 



t A full description of these collections will appear in Doctor Ward's second paper on the Older 

 Mesozoic floras to be published by the U : S, Geological Survey. 



