CAKBONIFEROUS UNDIVIDED. 393 



Exposures on the north side of the bay and just west of the peninsula, which are lower 

 but not continuous with this section, would add, if included in it, several hundred feet to its 

 thickness. The total thickness of the Lower Carboniferous section is probably not less than 

 1,500 feet. 



The Lower Carboniferous in southeast Alaska, whUe representing a different facies from 

 that of the Mississippi Valley, is stUl much more closely allied to the interior continental faunas 

 than is the Upper Carboniferous fauna of this region. The Lower Carboniferous fauna is 

 widely distributed in Alaska. It has been recognized as far north as Cape Lisburne, on the 

 Arctic coast, and it occurs at numerous points on the Yukon and Porcupine rivers in eastern 

 Alaska. 



Concerning the interval between the Upper and Lower Carboniferous faunas in this region 

 we have but few data. No fauna representing it has been found. 



The younger of the two Carboniferous faunas of southeastern Alaska is well represented in 

 the limestones about Pybus Bay, on the southeast side of Admiralty Island, where they outcrop 

 extensively along both arms of the bay. The limestones characterized by this Upper Car- 

 boniferous fauna have a thickness of about 600 feet at Pybus Bay. These Upper Carboniferous 

 hmestones are generally heavy-bedded or massive. * * * "phe Lower Carboniferous 

 limestones where observed have thinner . bedding and are darker colored than those of the 

 higher horizon. 



The following section, taken along the west shore of the east arm of the bay, indicates 

 the character of the Carboniferous limestone (c of the section) and the associated beds : 



[Mesozoic:] Feet. 



(g) Black to dark-gray argillaceous slates 300 



(/) Covered interval 100 



(e) Massive or heavy-bedded gray limestone with conchoidal fracture 40 



[Carboniferous:] 



(d) Light-gray limestone full of small angular cherty masses 80 



(c) Light-gray cherty limestone in 10 to 30 inch bands, fossils abim.dant 600 



[Age undetermined:] 



(6) Red chert in 6 to 20 inch bands 300 



(a) Black chert in 4 to 10 inch bands, with rarely a brown or red band 550 



1,970 

 The Mesozoic beds are represented by the two divisions e and g of the section. 



The faunal relations of this limestone are considered by Girty to be rather 

 with the Gschelstufe of Russia, which underhes the Russian Permian, than with 

 that Permian itself. The horizon is, however, the same as that of those formations 

 of Alaska which have been assigned to the Permian. The fauna is unlike any of 

 the faunas of the Mississippi Valley but resembles that of the McCloud limestone of 

 California. (See K 10, p. 376.) Kindle says: 



The fauna of the Pybus limestone is the same which has been previously referred to the 

 Permian in Alaska. Dr. George H. Girty, to whom the writer is indebted for the determination 

 of the horizons represented by the Carboniferous collections, states, however, that he finds 

 "that a greater resemblance exists with the Gschelian stage of the Russian section than with 

 the Russian Permian. Provisionally, therefore, I will correlate this horizon with the Gschel- 

 stufe, in which occur a great number of equivalent or identical species. This fauna is entirely 

 unlike anything in the Mississippian province of the United States, but some of our western 

 faunas resemble it." 



Fossils are usually abundant and well preserved wherever the Upper Carboniferous 

 limestone is found. The character of this fauna is shown by the list of the species collected 

 at Pybus Bay, which has been furnished by Dr. Girty. 



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