SILUKIC SECTION/ KOCHESTER TO LAKE HURON 317 



Disconformity. No Medina sandstone here. Contact sharp between adjacent 



beds. 

 Gntaract formation. Thickness exposed 18 feet. 



Cabots Head shale memher. Upper green shales with very thin bands 



of magnesian limestone abounding in Helopora to within 18 inches 



of top ; 7 feet thick. 

 Red shales dominated by ferruginous (almost an iron-ore), more or 



less magnesian limestones, 6 feet thick. Replete with many species 



of bifoliate and Trepostomata Bryozoa typical of upper Cataract. 



Also here Leptwna rhomb oidalis, Camarotwchia neglecta, and small 



hemispheric masses of Favosites. 

 Red shales, with some thin bands of green shales down to railway ; 



5 feet seen. Helopora are also common, but the bryozoans of the 



higher beds are practically absent. 

 The remainder of the Cataract is not exposed here. At Kelso, 13 miles 



southwest, the formation has a thickness, according to Williams, of 



92 feet. 



Glenwilliani, Ontario, section (5 utiles north of Liviekouse). — On the 

 lower part of cuesta. 



Cataract formation. Lowest part only exposed. 



ManitouUn member. Magnesian thin-bedded limestones, more sandy and 



shaly than usual. Fossils are also less abundant. Glathrodictyon 



vesiculosum, Favosites venustus, Heliolites interMinctus, Halysites 



- microporus, Zaphrentis bilateralis, Rliinop or a verrucosa, Rhipidomella 



circulus, Leptwna rhomboidalis, Atrypa rugosa,Gdlymene, Encrinurus. 



Whirlpool member. Basal gray sandstone, 12 feet thick. The lowest 2 



to 4 inches abound in pyrite, and the sands fit into the Sun^crackings 



of the Queenston below. The lower 9 feet regularly bedded and 



making a good building stone much used in Toronto. In color it 



is usually gray, but in places is blotched with red or passes entirely 



into a light red color. The upper 3 feet are much cross-bedded and 



>; contain many Modiolopsis (?) orthonota and an abundance of "fu- 



coid" markings and vertical "worm burrows" (the shape of cup 



corals). 



Disconformity. Base of Siluric. 



Queenston brick-red shales, much used here for pottery, drain pipes, and 

 brick. Top of Ordovicic (Richmondian). 



Cataract, Ontario, section (IS miles north of Limehouse and 48 miles 

 nofthivest of Toronto). — Cuesta along Forks of Credit. Type section of 

 Cataract formation along the valley of the Credit and about the cataract. 

 See Parks, (jruide Book No. 5, Twelfth International Geological Con- 

 gress, 1913, pages 8-13. 



Lockport dolomite. Heavy-bedded, cavernous, light gray dolomite seen on the 

 railway to Elora at the spring near Cataract Junction. ThickiiesS 

 present 30 feet. 



Disconformity. No Rochester or Clinton here. 

 XXIII — Bull. Geol. Soc. Am., Vol. 25, 1913 



