Miisozoic 305 



Professor Alplieus Hyatt made the following statement regarding tliis 

 find: 



"Tlie fossils in the shale are clearly the remains of a Monotls of a Triassic 

 type allied to Monotls suhcircularis Gabb — a characteristic Triassic form in 

 California. This one seems to be distinct specifically, but is evidently of the 

 same age." 



These Triassic rocks appear to rest conformably on Upper Carbon- 

 iferous limestones. A number of later investigations in this and adja- 

 cent areas have found extensive developments of Triassic rocks, consisting 

 chiefly of argillites and limestones. ^^^ 



Another locality of Triassic beds in the Yukon region is one reported 

 by Keele^^^ in the Stewart River basin. The fossils from these beds 

 occur in a dark limestone associated with gray and green argillites. On 

 the basis of these fossils Keele has provisionally assigned to the Triassic 

 a considerable area of argillites, sandstones, grits, quartzites, and lime- 

 stones. Further work will probably show that a considerable part of the 

 area indicated as Triassic by Keele in the Stewart Eiver region^-* is of 

 Carboniferous or Devonian age. Whatever detailed studies may show 

 regarding the extent of Triassic beds iii this field, it is certainly impor- 

 tant to know definitely that the Triassic sea covered portions of the Yukon 

 basin. 



The fauna obtained by Mr Keele in the Stewart River basin and re- 

 ferred provisionally to the Triassic by Doctor Whiteaves contains two 

 species "having the general appearance of Manotis suhcircularis and 

 HaJobia lomelle."'^^^ 



The only member of the Mesozoic extensively developed along the 

 Yukon are the so-called Aucella beds, which may be either Jurassic or 

 Lower Cretaceous, but may here for convenience be assigned to the latter 

 system. These Lower Cretaceous beds form a practically continuous belt 

 along the Yukon from about the mouth of Foiirth of July creek to Coal 

 creek (see map, figure 2). There may be, however, some of the younger 



>22 It is not proposed here to summarize the knowledge regarding the occurrence of 

 Triassic roclss in Alasl<a, except in so far as it bears niore or less directly on the stra- 

 tigraphy of the Yukon basin. A summary statement will be found in the Geography and 

 Geology of Alaska, Professional paper no. 45, XJ. S. Geological Survey, pp. 226-231. It 

 is perhaps well to call attention to the fact here that since the summary was prepared 

 V. H. Moffit and A. G. Maddren have found Triassic fossils in the Chitistone limestone 

 in the Wrangell mountains, and C. W. Wright and W. W. Atwood have found Triassic 

 fossils in southeastern Alaska. 



^-^3. Keele: Report on the Upper Stewart River region, Yukon. Geological Survey of 

 Canada, no. 943, 1906, pp. 14-15C. 



"* Ibid., map. 



i» Ibid., p. 17C. 



