CORRELATIOX OF DEYOXIAX STRATA 375 



CORRELATION OF THE DEVONIAN STRATA EXPOSED ALONG ABITIBI RIVER 



Sextant sandstone and shale. — On account of the absence of fossils and 

 the indecisive evidence furnished by their stratigraphic relations, the age 

 and correlation of the Sextant sandstone and shale outcropping in tlie 

 vicinity of Sextant Portage along Abitibi Eiver can only be provisionally 

 determined. From their stratigraphic position, it is known that they are 

 older than the Devonian strata included in the Abitibi Eiver limestone. 

 The generally red color of these rocks and the arkosic character of some 

 of the sands indicate that they were deposited under arid climatal con- 

 ditions, and suggest that they may possibly correspond in age with some 

 of the salt-bearing Devonian rocks which furnish the salt in the salt 

 springs of western Manitoba. However, it is recognized that gypsum 

 deposits, indicating similar conditions of aridity, also occur in Devonian 

 strata along Moose Eiver, but the latter are thought to correspond in age 

 to a higher horizon in the Abitibi Eiver limestone. In the absence of 

 definite evidence regarding the age of these sandstones and shales, they 

 are tentatively referred to the Middle Devonian. 



Al)itil)i River limestone. — The fauna of the Abitibi Eiver limestone 

 appears to be more closely related to that of the Upper Devonian of the 

 Manitoba and Iowa regions — the Interior Continental province of AVil- 

 liam's — than to that of any Devonian horizon in the Eastern, or ^ew 

 York, section. This fauna contains a relatively larger proportion of 

 compound corals and fewer simple cup corals than usually occur in the 

 New York Hamilton. 



Furthermore, the characters of the fossil called Stropheodonta demissa 

 are those of species found in the Interior Continental province. Favo- 

 sites aJpenensis. Schizophoria iowensis, Athyris fidtonensis, and Atrypa 

 m-issouriensis are characteristic species of the Devonian of this Western 

 region. From these considerations it is thought that the Abitibi Eiver 

 limestone is to be correlated with some part of the late Devonian of the 

 Interior Continental province, as developed in Iowa and western Mani- 

 toba, rather than to any part of the late Devonian section of the Eastern, 

 or New York, province, with some part of which these strata doubtless 

 correspond in age. 



Compared with the Devonian fauna of Manitoba, the absence of 

 Strinqoceplialus hurtoni and several of its associates is conspicuous, and 

 the Abitibi Eiver limestone fauna corresponds more closely with that of 

 the youngest formation (Manitoban of Tyrrell) than to that of either of 

 the older Devonian formations of western Manitoba, as does also the late 

 Middle Devonian fauna of Iowa. After the Winnipegosan dolomite which 

 contains the String oceplialus hurtoni fauna had been deposited in this 



