42 ALASKAN MINERAL RESOURCES IN 1906. 
Carboniferous coals of Alaska are of higher grade than those of the 
Jurassic or the Cretaceous, and the Jurassic coals are better than some 
of the Cretaceous coals. The Cretaceous in turn includes some coal 
which is of better quality than much of the Tertiary coal. Thus far 
it would seem as if the theory of the increase in quality of coal with : 
its age were supported by the evidence from Alaska. But when the 
Tertiary coals are considered it is found that they include many beds 
and considerable areas which outrank in quality all the other coals of 
Alaska and which are equaled only at a few areas in other regions. 
The truth of the matter is that the conditions favorable for the forma- ; 
tion of high-grade coal, including character of sedimentation and 
degree of alteration, are dependent on local conditions and are inde- 
pendent of the age of the coal. 
Carboniferous coal is known to exist in commercial quantities at 
Cape Lisburne and smaller amounts are known at other localities.. 
The Carboniferous coal beds at Cape Lisburne are in the lower CarH 
boniferous, which there comprises a lower group consisting of slates,' 
shales, and limestones and containing several coal beds; a middle 
group of black cherts, slates, shales, and cherty limestones; and an] 
upper group of massive limestones of great thickness, which seem to 
shade off into massive white cherts. Coal beds of Permian age have! 
been worked near Nation River on the upper Yukon, but they appear; 
to be of slight extent and of little importance, although the quality ia 
good. Rocks of probable Carboniferous or Permian age are known to 
contain coah shales and thin coal seams at various localities in the 
valley of While River and indicate that workable coal beds may yea 
l>c discovered in them. 
Jurassic locks have a wide distribution in Alaska, and they are 
known to be coal bearing in several places. The largest known area 
of Jurassic coal is at Cape Lisburne, where a horizon of undetermined 
position in the Jurassic is represented. The Wainwright Inlet coal is 
probably of the same horizon. At least part of the coal at Ilercndcen 
Bay may be Jurassic, though other coal-bearing horizons are repre- 
sented. The eastern extension of the Matanuska coal field includes 
large areas of middle and upper Jurassic rocks in which some coal is 
present. 
Cretaceous rocks cover large and widely distributed areas in Alaska 
and are coal bearing at many localities. Cretaceous coal is present on 
Anaktuvuk River, a tributary of the Colville, which flows into the 
Arctic Ocean, in the lower Yukon Valley ,. possibly at the headwaters 
of the Matanuska, and at Chignik Bay and Herendeen Bay, in south- 
western Alaska. All these deposits except that in the Matanuska 
Valley represent the upper Cretaceous. 
Tertiary coal is widely distributed in Alaska, being known fro 
many localities along the Pacific coast, from the interior, and fro 
the Arctic slope. The position of the coal within the Tertiary i 
