WINISK RIVER SECTION 361 



strata which probabl}' were originally present having been removed dur- 

 ing the post-Ordovician erosion interval before the Silurian rocks were 

 deposited. This fold resulted in such an elevation of the rocks of the 

 region farther west that the sedimentary rocks have been eroded from the 

 larger part of the area. In the banks of the Winisk River limestones are 

 exposed at intervals for a distance of about 16 miles above this fold and 

 for 6 or 8 miles below it. Ledges of limestone 15 to 25 feet high in many 

 places border one or both sides of the Shammattawa River for a distance 

 of 10 or 12 miles above its junction with the Winisk. 



All the limestones exposed in the Winisk River basin are of Silurian 

 age, and the greater part of them correspond to the Severn River lime- 

 stone, as that formation is developed along Severn River. The Ekwan 

 limestone and the Attawapiskat coral reef, the youngest and most con- 

 spicuous Silurian formation present along the Severn and Ekwan rivers, 

 are not exposed in the banks of the Winisk, the outcrop being pushed 

 eastward and northward by the elevation of the arch above mentioned. 

 The coral reef horizon outcrops in a few places farther north along the 

 shore of Hudson Bay near Wabuk Point and in places for several miles 

 farther north. 



A detailed section of the Silurian rocks outcropping along Winisk 

 River and its tributary, the Shammattawa, is given below. 



SECTION OF ROCKS EXPOSED ALONC WINISK AND SHAMMATTAWA RIVERS 



Silurian system 



Alexandrian series 



Severn River limestone Thickness 



o -r • ^^ feet 



d. Limestone, rather fine grained, gray, with occasional 



layers of buff, dolomitic limestone containing few 

 . fossils; exposed in the banks of Winisk River below 

 the mouth of the Shammattawa and in the upper 

 part of the bluffs bordering the Shammattawa ; con- 

 taining the fossils named below : 25 



Streptelasma pygmceum var. occidentale. 



Zaphrentis stokesi ? 



Favosites favosus. 



Cf. Alveolites niagarensis. 



Trimerella ekwanensis. 



Stropheodonta acanthoptera. 



Stropheodonta cf. philomela. 



Schuchertella sp. 



Dalmanella elegantula. 



Camarotcechia ekwanensis. 



Camarofcechia ? winiskensis. 



Atrypa cf. reticularis. 



Rhynchospira loivi. 



