128 



GENERAL DESCRIPTION OF FORMATIONS. 



The Queenston formation consists essentially of 

 red shales with an occasional green band. This formation 

 is unfossiliferous in the Niagara and Hamilton sections, 

 but in the Collingwood section, a distinct Richmond 

 (Ordovician) fauna is revealed. It has therefore become 

 necessary to separate the Queenston shale from the Medina 

 formation in which it has been long included. The over- 

 lying grey sandstone (Whirlpool sandstone of Grabau) 

 has hitherto been regarded as Medina, but it is now pro- 

 posed to consider it as the basal member of a new formation- 

 the Cataract — which represents an invasion from the north 

 and west at the commencement of Silurian time. The 

 upper limestones and shales of this formation are highly 

 fossiliferous and present a fauna comparable with that 

 of the Brassfield formation of Ohio and Kentucky. 



In the Credit region, this basal sandstone has been 

 confused with the upper or true Medina sandstone of the 

 Niagara gorge; in consequence, the shales and limestones 

 overlying it have been erroneously ascribed to the Clinton. 



All the strata exposed in the Niagara gorge continue 

 as far as Grimsby and even to Hamilton, but at the latter 

 place, the Rochester shale, the Clinton and the Medina 

 have become greatly reduced in thickness. At the Forks 

 of the Credit, these formations have disappeared entirely 

 and the Cataract formation has increased correspondingly. 

 At Collingwood the Cataract formation is again decidedly 

 thinner and presents a different petrographic aspect, 

 consisting of limestone with some shale at the top. 



The gradual decrease of thickness in the Rochester, 

 Clinton and Medina strata, and the increase in the Cataract 

 in passing northward is indicated in the following table : — 





u 

 bo 



5? 



JO 

 en 



,fi 

 'C 







O 4) 

 C/)(J 



c 

 



1 

 a 



X 



u 



1> 



-i-t 



nj 

 u 



c 

 < 



-a m 



<u U 

 u 

 Ufa 



■li 

 6°* 



Niagara. Lockport dolomite, 



cherts, etc 



Rochester shale 



Clinton. Limestones and shales. 

 Medina. Grey band sandstone. . 



Red sandstones, etc . . . 

 Cataract. Shales and limestones. 



Sandstone 



ft. 



68 

 32 



1\ 

 50 

 26 

 25 



ft. 



12 



45 



(25 



74 

 6 



ft. 

 13 

 25 

 13 

 14 



79 

 6 



ft. 

 22 



15 

 12 

 12 



80 

 10 



ft. 



12 

 12 

 II 



?? 

 ?? 



ft. 

 30 



00 

 00 



00 



95 

 i6§ 



ft. 



75 

 00 

 00 

 00 



55 

 00 



Richmond. Red shales of great thickness, extending far below the 

 section, except at Collingwood. 



