296 BROOKS AND KINDLE PALEOZOIC ROCKS OF UPPER YUKON 



It has not seemed desirable to give this limestone horizon a formation 

 name, because on the Yukon its limits were not definitely determined and, 

 moreover, its type locality is probably to be sought in southeastern 

 Alaska. The Upper Carboniferous liinestone is typically exposed in 

 some large open folds, accompanied by more or less faulting, along the 

 north side of the Yukon for some 3 or 4 miles above Nation river. The 

 same horizon was identified aboiit 30 miles below, on the south side of 

 the river and just west of the mouth of Coal creek. Here it is exposed 

 in a small area closely associated with some pyroclastic material similar 

 in every way to that occurring with the Devonian rock. Were not the 

 paleontologic evidence in regard to this occurrence conclusive, this lime- 

 stone would have been placed with the Devonian. The occurrence, how- 

 ever, goes to prove that there was some igneous activity during late Car- 

 boniferous time. It also suggests the possibility that some of the igneous 

 rocks which have been mapped as Devonian may eventually prove to be- 

 long to the Carboniferous. 



The fauna characterizing this highest Carboniferous limestone is shown 

 in the following list of fossils determined by Doctor Girty : 



"Lot 14: Fossils from tvest Bank of Yukon, J% miles al)ove Nation River 



Aulosteges sp. 



Marginifera aff . splendens Norwood 

 and Pratten. 



Spirifer aff. marcoui Waagen. 

 Squamularia aff. perplexa McChesney. 

 Spiriferella arctica Hougbton. 

 Cleiotliyrodina n. sp. 

 Rhyncliopora aff. nikitini Tschern. 

 Scliizodus sp. 

 Aviculipecten sp. 

 Omphalotrochus sp. 



Zaphrentis sp. 



Stenopora sp. 



Streptorhynchus aff. S. pelargonatus 



Schlot. 

 Chonetes aff. morahensis Waagen. 

 Productus aff. horridus Sowerby. 

 Productus aft', aagardi Toula. 

 Productus aff. P. porrectus Kut. ? 

 Productus aff. mammatus Keys. 

 Productus aff. irginw Kut. 

 Productus aff. koninckianus Vern. 

 Productus sp. 



"Lot 15: Fossils from Limestone i% miles southeast of Mouth of Nation River 



Streptorhynchus aff. S. pelargonatus Aulosteges sp. 



Schlotheim. Marginifera ? aff. splendens Norwood 

 Productus aff. aagardi Toula. and Pratten. 



Productus aff. koninckianus Vern. Spiriferella arctica Hougbton. 



"Lot 22: Fossils from south Bank of the Yukon helow Glenn Creek 



Spirifer aff. cameratus Tscberny. non 



Morton. 

 Spiriferella aff. artiensis Stuckenberg. 

 Spiriferella arctica Hougbton. 

 Squamularia aff. perplexa McCbes- 



ney. 



aff. pelargonatus 



Polypora sp. 

 Rhomhopora sp. 

 Streptorhynch us 



Scblotbeim. 

 Productus aff. transversalis Tscberny 

 Productus aff. aagardi Toula. 



