CHAPTER VI. 



THE LATE PALEOZOIC IN ALASKA. 



While our knowledge of the geology of Alaska is still very imperfect, 

 reconnaissance work has gone so far that we may say with some confidence 

 that no rocks of true Permian age exist in that region and none, with the 

 possible exception of certain series in the southeastern portion, which may 

 represent the interval of time recorded in the "Permian Red Beds" of the 

 southwestern United States. The series reported in the earlier reports as 

 Permian have one after the other been shown by their invertebrate fauna 

 to be lower in the series, as their fossils have very decided affinities with the 

 Gschelian, upper Pennsylvanian, stage of Russia rather than with the true 

 Permian. 



It is, as yet, impossible to delimit the areas of deposition either strati- 

 graphically or geographically with any certainty or to give any thing more 

 than a very approximate account of the conditions of deposition, but a very 

 general idea of the prevailing conditions at the end of the Paleozoic may be 

 offered with some confidence in the accuracy of the broad outlines. 



The following statement from Brooks 1 is an excellent introduction to 

 such a description: 



"The records of the succeeding epoch are obscure, but indicate that lime- 

 stone deposition continued in some places during early Carboniferous times, 

 while in others a considerable land area was exposed to erosion. Deposition was 

 probably almost entirely checked by a crustal movement which took place about 

 the beginning of the Permian, and this was followed by subsidence. On the 

 Yukon there is evidence of an extensive period of erosion which immediately 

 antedated the deposition of the Permian sediments, but this has not been recog- 

 nized elsewhere. 



"The Permian sea seems to have covered much the larger part of the province, 

 for its sediments have been found along the Yukon, in the Panhandle, and in 

 the Copper Basin, where they aggregate 7,000 to 8,000 feet In the two latter 

 districts the deposition apparently continued unbroken into the Triassic and was 

 characterized by a gradual change from limestones to shales. It was ended 

 by a crustal movement which deformed the beds, exposed a considerable land- 

 mass, and thus began another period of erosion. This uplift seems to have begun 

 in Permian times in northern Alaska and progressed gradually southward during 

 Triassic times, for the latter period does not seem to have left any sedimentary 

 record north of the Pacific Mountains. In southeastern Alaska the indications 

 are that the Permian-Triassic cycle of deposition was closed by an extensive 



1 Brooks, Alfred H., The Geography and Geology of Alaska, U. S. Geological Survey, 

 Professional Paper No. 45, p. 265, 1906. 



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