CLASSIFICATION 341 



of sedimentary strata. Hence the plan of work was to follow up a river 

 with canoes, portage across the divide into the adjacent river basin, follow 

 that down to the bay, proceed along the coast of the bay to the next im- 

 portant river, ascend this, cross the divide, and follow down the next, 

 etcetera. In this manner the sequence and detailed sections of the strata 

 and a careful collection of their fossils were made of the Ordovician rocks 

 exposed along Nelson and Shammattawa rivers; of the Silurian strata 

 along the Severn, Winisk, and Ekwan rivers, and of the Devonian beds 

 at the south end of the bay, along the Moose and its tributary, the Abitibi 

 Eiver. 



The general succession and classification of the Paleozoic rocks recog- 

 nized in the Hudson Bay region is shown in the following table : 



Classification of Paleozoic Eocks of Hudson and James Bay 



Eegion 



Devonian system 

 Upper Devonian 



Long Rapids shale "^Yn feef 



Correlated with the Sweetland Creek shale of Illinois 

 and Iowa and with the corresponding shale horizon in 



other parts of North America 55 



Abitibi River limestone 



Correlated with the lower strata of the Upper Devonian 

 in Iowa and northwest Illinois; upper rocks of Devo- 

 nian age in the Lake Winnipeg region and farther west 



and northwest in North America About 110 



Middle Devonian? 



Sextant sandstone and shale 



Contains no fossils ; presumably Middle Devonian, but in 



the absence of fossils no correlation has been attempted 75 



Silurian system 



Niagaran series 



Attawapiskat coral reef 



Correlated in time with the late Niagaran rocks contain- 

 ing numerous corals in Ontario and the upper Missis- 

 sippi Valley About 85 



Ekwan River limestone 



Correlated with the rocks of early to middle Niagaran 

 age in Ontario, and about equivalent in time to the 

 lower and middle parts of the Niagaran of the upper 



Mississippi Valley About 100 



Alexandrian series 



Severn River limestone 



Correlated with the lower part of the Silurian rocks in 

 the Lake Timiskaming region, the lower part (Hen- 

 dricks dolomite and Fiborn limestone) of the Silurian 



