GEOLOGY 195 



These dark gneisses are inclosed and penetrated by the granite- 

 gneisses, and probably represent portions of the ancient bedded 

 series. 



Beyond Cape Wolstenholme, gneisses occupy the eastern coast 

 of Hudson bay to within a short distance of Cape Smith, where 

 a high ridge of trap runs inland in a northeast direction and 

 has a width of several miles. Further south the gneisses again 

 predominate along the coast to the Portland promontory in 

 latitude 58 N. 



GEOLOGY OF THE NORTHWEST SHORES OF HUDSON BAY. 



The following account of the geology of the northwest shores 

 of Hudson bay has been compiled from observations made dur- 

 ing the trip of the launch from Winchester inlet to Chesterfield 

 inlet in September, 1903. These are supplemented by the notes 

 made in May, 1904, while making a track survey from Cape 

 Fullerton to the entrance of Chesterfield inlet. The observations 

 to the north of Fullerton were made by Mr. Caldwell, in April 

 and May, 1904, while on his surveying trip to the head of 

 Wager inlet ; to these are added observations by the writer made 

 on a boat trip along the coast later in that spring, on the way 

 to and from Southampton island, when the rocks of the main- 

 land were examined as far north as Yellow bluff. 



The rocks seen along the shore between Chesterfield and Win- 

 chester inlets are largely a flesh-red to pink mica-hornblende 

 granite-gneiss, often only slightly foliated, and varying in tex- 

 ture from medium to coarse-grained. These are associated with 

 broken bands of dark-gray or red gneisses, usually very quartz- 

 ose, and containing a considerable quantity of mica and horn- 

 blende, the latter often partly decomposed to chlorite. These 

 gneisses have evidently been cut and broken by the intrusion of 

 the granite-gneisses. Many veins of pegmatite cut all these 

 rocks; it consists chiefly of red or violet feldspar with much 

 quartz, and in some places large crystals of black hornblende. 



