THE LATE PALEOZOIC IN ALASKA 185 



fossils." Keele refers to it as a "mass of white, bedded, crystalline lime- 

 stone forming the greater part of a mountain group." 



Dawson found a siliceous crystalline limestone on Tagish Lake which 

 he considered as Carboniferous and correlated with the Cache Creek series. 

 (Canadian Geological Survey, 1887, part b, p. 170B-171B.) This limestone 

 has been shown by later work of Dawson, Gwillen, and Kindle to be very 

 doubtful in position and unsafe for use as any basis of conclusion. 



The following summary statements are given by Mendenhall, and by 

 Brooks and Kindle. MendenhalF says: 



"We have seen that the earlier and middle Paleozoic history seems to have 

 been largely continental — that of a land-mass, or its shore-lines, with coarse 

 sediments and volcanic materials; but with the end of the Paleozoic the sea 

 invaded the province through a general subsidence following the outflows of the 

 Nikolai greenstone, and although no doubt varying in depth and shifting its 

 outlines, practically maintained control until the middle of the Mesozoic. 



" In the northern part of the province the sea seems to have only gradually 

 invaded the land areas. The earliest Permian sediments there are shore deposits 

 in part, and include sands, tufaceous beds, and flows, which denote the dying out 

 of the earlier eruptive epoch, perhaps the last feeble activity of the Tetelna stage. 

 But toward the middle of the period represented by the Permian rocks truly 

 marine conditions prevailed and abundant marine life existed, while heavy 

 limestones and fossiliferous black shales were being laid down in what is now 

 the upper Copper River Valley. It is probable that this Permian sea was wide- 

 spread in eastern Alaska. Its records are preserved on the middle Yukon, in the 

 Copper Valley, in the valley of the upper White, and east of there toward Pyramid 

 Harbor. It extended also to southeastern Alaska, where, however, the recognized 

 beds belonging to it are marine sandstones instead of limestone. The even, 

 exclusively marine phase of the upper part of the deposits makes it wholly im- 

 probable that there existed at this time any marked relief where the present great 

 ranges stand. They may have been mountains before the Permian and after, 

 but probably not during this era. 



"In the Chitina Valley a shallow sea held possession through the Permian 

 epoch and well into the Triassic, the deposition of thin, dark limestones and black 

 shales continuing uninterruptedly." 



Brooks and Kindle say:^ 



"The Carboniferous of Alaska is represented by three stages, the first of 

 heavy limestone partly Devonian and partly lower Carboniferous. This stage is 

 succeeded by a series of rocks in the Yukon area which 'are made up of littoral 

 and in part at least of fresh-water deposits, embracing some very coarse material 

 and aggregating nearly 3,000 feet in thickness. This same epoch of deposition is 

 probably represented in the White-Copper River region and in the Alaskan Range, 

 where, however, it appears to form the base of the Carboniferous, indicating that, 

 if the older limestone had ever been present in this area, it was removed by 



^ Mendenhall, W. C, Geology of the Central Copper River Region, Alaska, U. S. Geological 



Survey, Professional Paper No. 41, p. 76, 1905. 

 ^ Brooks, A. H., and E. M. Kindle, Paleozoic and Associated Rocks of the Upper Yukon, 



Alaska, Bull. Geol. Soc. Amer., vol. 19, p. 304, 1908. 



