218 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



similar to the St. Peter sandstone of Minnesota, can not be regarded as definitely of the same 

 age, since no evidence of Chazy fossils has been found in it. 



The thickness of pure sandstone in the Lake Winnipeg basin is apparently much less than 

 to the south. The several sections give varying thicknesses [40-100 feet], owing to the uneven 

 nature of the floor on which it was deposited. * * * 



The Lower Mottled limestone is the lowest naember of the limestone series and rests directly 

 on the basal sandstones and shales. These limestones form the principal part of the sections at 

 Grindstone Point, Bull Head, and Dog Head, and on the islands north to Berens Island. The 

 combined section given by these several exposures amounts to a thickness of about 70 feet. 

 The lowest beds are those seen at Deer Island and Grindstone Point capping the sandstone. 

 Immediately above are the beds occurring at Dog Head, followed by the upper part of the Black 

 Bear Island exposure. Those on Tamarack and Jack Head islands are evidently higher but 

 belong to the same series and form, together with those mentioned above, the following descend- 

 ing section: 



Feet. 



1. Hard mottled limestone, dark yellow, ■witK bro-vcnisli-yellow spots, breaking up into lumpy 



fragments not wearing discoidal on the beach but irregular. A few pieces from top beds are 



not so mottled and break smoothly (probably base of Cat Head limestone) 15 



Exposure on west side of Jack Head Island. 



2. Thin-bedded, mottled buff and grayish-white limestone, weathering ashy-white, in which are 



many large cephalopods: Orthoceras, Sactoceras, Poterioceras, Oncoceras and Cyrtoceras, 



while specimens of Maclurea manitobensis and ReceptacuKtes oweni are abundant 15 



Eleven feet of these beds are exposed on Little Tamarack Island and similar beds are exposed 

 on Little Black Island near Berens Island. 



3. Mottled limestone, buff-colored but weathering lighter, in rather thicker beds than above 



and not so rich in fossils 10 



These form the upper part of cliff on Black Bear Island. 



4. Thin beds of similar rock, rich in fossil remains 20 



This band occupies the lower portion of the exposures on Black Bear Island, on Snake Island, 



and Dog Head or Whiteway Point and the upper part of the cliffs of Bull Head and inter- 

 vening exposures. 



5. Darker mottled impure limestone, where not weathered, almost blue on fracture; fractures 



into thin flags with surfaces covered with fucoidal markings. The lower beds are of very 

 earthy limestone resting on the sandstone of the basal series -. 10 



70 

 ******** * 



The Cat Head limestone, the central portion of the limestone series, is best developed at 

 the prominent point on the west side of Kinwow Bay, called Cat Head. The beds are of a fine- 

 grained, evenly colored yellow dolomitic limestone, with numerous concretions of dark-colored 

 chert, filling cavities apparently left by the decay of corals. These beds are seen in the high 

 cliff at Cat Head and along the shore to Lynx Bay. At the western end of the section, 3 miles 

 west of Cat Head, the cherty concretions attain large dimensions. Several are over a foot in 

 length, and one measured 2 feet by 10 inches. The lower beds are fine grained, resembling 

 lithographic stone, and are very rich in fossil remains. The total thickness as observed on the 

 lake is 68 feet. This includes the top beds of Cat Head and Outer Sturgeon Island, which are 

 similar in color but coarser in texture, becoming finally crystalline. The section is made up 

 as follows : 



Feet. 



1. llard, flinty, coarse-grained limestone (Sturgeon Island) 10 



2. Yellow granular limestone, weathering roughly and slightly honeycombed (Cat Head) 8 



3. Similar coarse-grained, weathering dark-yellow, with fucoid-like markings, and very much 



honeycombed (Cat Head) 3 



4. Yellow limestone with fucoidal markings similar to No. 2 (Cat Head) 10 



5. Fine-grained yellow rock with numerous ashy-colored spots scattered over the whole face of 



the exposure, from the weathering of small impure flinty concretions (Cat Head) 27 



6. Fine-grained yellow limestone, rich in foissil remains, with numerous large concretions of dark 



cherty material (Cat Head, McBeth Point, and Inmost Island) 10 



