180 



ENVIRONMENT OF VERTEBRATE LIFE, ETC. 



dynamic revolution which metamorphosed and deformed the Paleozoic sediments 

 and probably left them very much as they are now." 



On page 224 of the same paper Brooks makes the following statement: 



"A belt of Carboniferous rocks (probably Permian) has been fairly well traced 

 throughout southeastern Alaska; the continuation of the strike of these would 

 carry them into the White, Tanana, and Copper River basins, where there is a 

 very extensive development of Permian beds and also some lower Carboniferous 

 rocks; Permian beds have also been found on the Yukon, near the Arctic Circle, 

 resting unconformably on strata of lower Carboniferous age. In northern Alaska 

 the presence of two Carboniferous horizons is established by fossil evidence, 

 though there is little definite knowledge of their extent or stratigraphic and 

 structural relations. In all except this northern field igneous intrusives are found 

 cutting the Carboniferous rocks, and in southeastern Alaska it is probable that 

 some of the associated greenstone schists are ancient lava flows. In the Copper 

 River basin volcanic rocks are characteristic accompaniments of the sediments 

 referred to the Permian [Upper Pennsylvanian]." 



It will be noted that Brooks speaks freely and with some degree of cer- 

 tainty of the age of the rocks which he regards as Permian, but, as is shown 

 by the quotations given below, it is altogether probable that these rocks 

 are of a lower horizon equivalent to the Gschelian of Russia, and such a 

 correction has been inserted parenthetically in the quotation from his paper. 



Following are given characteristic sections and descriptions of some of 

 the better-known areas which will serve to illustrate the conditions which 

 prevail in the Alaskan Province. 



Rocks originally considered as of Permian age are known from the 

 Panhandle and from all of southeastern Alaska at intervals from the lower 

 end of the Alexander Archipelago to the headwaters of the Copper River. 

 Wright and Wright 1 give the following succession: 



(?) Feet. 



Cherty limestone, breccia, and conglomerate with 



fossils 1,000 



Permian (Upper Carboniferous) 



White, cherty, semi-crystalline limestone with fossils. 800 + 



Conformity. 

 Conglomerate, no fossils; same as above .......... 100 



Probably Permian (Upper Carboniferous) . . . Slate, greywacke and conglomerate; no fossils 3,ooo 



Unconformity. 



Slate, greenstone, lava, agglomerates, tuffs, and 

 breccias, intermixed with argillaceous graphitic 

 slates and schists; metamorphosed and inter- 

 folded in bed-rock complex. No fossils 4,000 + 



Permian to Pennsylvanian (Upper Car- 

 boniferous) 



Slate, amphibole, chlorite, and mica schists, inter- 



stratified with fossiliferous limestone .......... 4,000 + 



(?) 

 Light colored limestones, fossils .................. 600 + 



Conformity. 

 Sandstones, conglomerates, and argillites, containing 



igneous material, with fossils .............. 



1 Wright, F. E., and C. W. Wright, The Ketchikan and Wrangell Mining Districts, Alaska, 

 U. S. Geological Survey Bull. No. 347, p. 34, 1908. 



