74 RECONNAISSANCE IN NORTHERN ALASKA IN 1001. 



other trends nearly northwest, approximately parallel with the strike of the rocks, 

 and dips northeastward at an angle of 60 to 70 . These jointings, however, do not 

 cut up the rock greatly, not nearly so much as do those in the Lower Cretaceous 

 rocks of the Anaktuvuk series iu the interior. 



Age. — Remains of fossil plants found in the Cape Beaufort region, and more 

 particularly in the shale near the Thetis mine at Cape Sabine, by Mr. Dumars, Mr. 

 Wbolfe, and others, have been identified" by Professor Fontaine and Doctor Ward as 

 not older than the Oolitic of the Jurassic, nor younger than the Lower Cretaceous, 

 and as probably transitional between the two. Similar evidence is afforded by 

 fossil plants collected by the writer on the coast about 7 miles southwest of Wain- 

 wright Inlet, which have been identified by the same authorities as — 



Nageiopsis longifolia Font. 



Older Potomac of Virginia (Lower Cretaceous). 

 Podozamites distantinervis Font. 



Older Potomac of Virginia (Lower Cretaceous). 

 Baiera gracilis (Bean) Bunbury. 



Oolite of Yorkshire, England (Jurassic). 



On the above evidence, therefore, the Corwin series is provisionally assigned to 

 the Jura-Cretaceous. 



Correlation. — Except the Kennicott* formation in the Copper River district, no 

 Jura-Cretaceous rocks with which the Corwin series can be correlated have thus 

 far been found in Alaska. 



ANAKTUVUK SERIES (LOWER CRETACEOUS). 



Character^ and occurrence. — The Anaktuvuk series takes its name from the native 

 name of the river along which it was observed by the writer. It underlies the 

 southern or principal part of the very gently rolling Anaktuvuk Plateau, along 

 the north side of the Endicott Range, whence, with surface sloping gently northward, 

 it continues to form the country rock for a distance of about 50 miles, where it is 

 succeeded by younger rocks. 



Along the base of the mountains the series, judging from the topograph j t (see 

 PI. IV), is believed to rest unconformably on the Devonian, or Lisburne formation. 

 Of this, however, we have no conclusive evidence, as the actual relation between the 

 two rocks was not seen, because of the covering of glacial drift. The first exposure 

 of the series visited by the writer is about 8 miles from the mountains. 



To the east the Anaktuvuk series is probably soon limited by the Paleozoic front 

 of the range, while to the west and northwest it probably constitutes in part the 



a A full description of these collections, including the forms collected by the writer, will appear in Doctor Ward's second 

 paper on the Older Mesozoic floras, to be published by the U. S. Geological Survey. 



bSchrader, F. C, and Spencer, A. C, Geology and Mineral Resources of a Portion of the Copper River District, Alaska 

 (a special publication of the U. S. Geol. Survey), 1901, p. 48. 



