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G. C. MARTIN TRIASSIC ROCKS OF ALASKA 



Pseudomonotis-bearing beds have a far wider distribution than the older 

 Halobia-bearing beds, and that the intervening coral-reef limestone is 

 even more restricted, occurring only near the present continental margin, 

 also suggests an Upper Noric transgression following a Lower JSToric re- 

 cession of the sea. The abrupt change in fauna! character from the sup- 

 posedly warm-water Halobia zone to the boreal Pseudomonotis zone also 



• U» Upper Triassic 



• M = Middle Triassic 



ioo o lOOMiles 



Figure 1. — Map of British Columbia and Yukon, showing known Triassic localities 



suggests a withdrawal of the Karnic sea, followed by an Upper Noric 

 transgression, presumably from the Arctic regions. 



The fauna of the McCarthy formation as now known includes Pseudo- 

 monotis subcircularis (Gabb), Halobia sp., Pecten sp., and Arniotites (?) 

 sp. The Pseudomonotis-bearing beds of the other Alaskan districts are 

 correlated with the McCarthy formation on the basis of general lithologic 

 similarity and sequence and also on the basis of the presence of Pseudo- 



