MIDDLE AND UPPEE ORDOVICIAN. 221 



The rock is a coarse yellowish-white dolomitic limestone, closely resembling that of Lake 

 Winnipeg. It lies almost flat, being broken only by long, low anticlines and syncliaes. At 

 the Limestone Rapids of the Severn, where it is more contorted than usual, it rises in a number 

 of low domes, closely resembling a sheet of letter paper when dampened. The total thickness 

 of the beds exposed does not exceed 100 feet. 



References to these limestones occur in subsequent reports, but on account of 

 the isolation and small areas of the outcrops there is no complete section nor any- 

 definite knowledge of the area of strata bf Trenton age or of higher strata. Brock " 

 states : 



With reference to the southwestern coast of Hudson Bay our information is not definite. 

 There are very few exposures and only isolated fossils have been brought down, some possibly 

 from loose bowlders. From Tyrrell's fossils and Bell's it is evident that there is at least a band 

 of Trenton, and from other fossils it is certain that Silurian is present, but where the boundary 

 lies between them we do not know. 



P-a 3-7. ALASKA. 



Ordovician strata in Alaska are in general not distinguished on the map of 

 North America, the areas in which they occur being classed as Paleozoic undivided. 

 Their presence is known, however, through the discovery by Brooks and Prindle ^"^ 

 of Ordovician graptolites on the western slope of the Alaska Range, in carbonaceous 

 strata which are intimately associated with phyllites, limestones, and cherts and 

 which have been called the Terra Gotta "series." These strata are probably repre- 

 sented in the metamorphic rocks of the upper Tanana region, formerly known as 

 the "Tanana" schist ^"^'^ but recently correlated with the Birch Creek schist."^ 

 Ordovician fossils have also been found on the Porcupine in bluish-gray nonmag- 

 nesian limestone 600 feet thick. "^ 



Thus the presence of the Ordovician is shown on fossil evidence in the central 

 eastern portion of the Alaska Peninsula. Similar fossiliferous beds are known at 

 several points in British Columbia. Strata which have as yet yielded no fossils, 

 tho' Wales "series," lie beneath and are older than upper Silurian in southeastern 

 Alaska. On the other hand, toward the north and northwest from the Yukon 

 region the more or less metamorphic schists of the Endicott Mountains and Seward 

 Peninsula include early Paleozoic sediments, possibly Ordovician, and there are 

 similar schists in southern Alaska about Prince William Sound and the'Wrangell 

 Range."^ 



P-Q 17-19. SOTJTHAMPTON ISLAND, FOX LAXD, AND UNGAVA BAY. 



The central portion of Fox or Baffin Land is mapped as Silurian, as are also the 

 islands in the north of Hudson Bay. The presence of Ordovician strata is established 

 in Frobisher Bay, and is probable throughout the areas in this region shown with 

 the 'Silurian color. (See pages immediately preceding.) 



Akpatok Island, in the ^orthern part of Ungava Bay, is described by Bell ®^ 

 as presenting a wall of gray limestone 400 to 500 feet high all along the coast from 

 the north end to the middle of the east side. The strata are horizontal and the 

 total thickness exposed in the heights of the island is estimated at 900 feet, to which 



a Brock, R. W., Acting Director Geol. Survey Canada, letter May 27, 1908. 



