318 



MINERALS AND GEOLOGY 



and Credit ; also at Point Boucher on Nottawasaga Bay, and at Cape 

 Rich, Point William, Cape Crocker, and Point Montresor, farther 

 west. 



The Medina Formation is regarded as forming the base of the 

 Upper Silurian series It is chiefly made up of red marls and soft 

 red sandstones, interstratified with red and green arenaceous shales, 

 and capped by a bed of fine-grained sandstone commonly known as 

 the "grey-band" averaging about ten or twelve feet in thicknes?, 

 but presenting in places a thickness of over thirty feet. This grey 

 sandstone is largely quarried for building purposes in the township 

 of Nottawasaga, and at Dundas, Hamilton, and other places along 

 the great Niagara escarpment. The Medina formation, presenting 

 collectively a thickness of about 600 feet, extends along the shore 

 of Lake Ontario westward from the vicinity of the River Credit to 

 the escarpment (or so called " mountain ") at Hamilton ; and it 

 occupies the strip of land lying between the escarpment and the lake 

 as far as the Dominion boundary on the Niagara River. Northwards, 

 it extends through the^townships of East and West Flamborougb, 

 Nelson, Caledon, Mono, Mulmur, and Nottawasaga : from- whence, 

 turning westward, it continues along the course of the escarpment, 

 but with greatly diminished thickness, and loss of the " grey-band," 

 to the base of the bold promontory known as Cabot's Head on 

 Georgian Bay. Fossils are of comparatively rare occurrence in this 

 formation. The principal comprise : the fucoid Arthrophycus Harlani 

 (fig. 113) and a small lingula, L. oblonga (fig. 127). The best ex- 

 posures occur about Wellington Square, Hamilton, Dundas, Queen- 

 ston, and Georgetown, and at the Dennis quarries in Nottawasaga. 



The Clinton Formation which immediately succeeds the Medina, 

 consists at its lower part essentially of green, red, and greyish shales, 

 in places more or less ferruginous ; and at its upper part mostly of 

 dolomitic limestones. The lower portion should properly be referred 

 to the Medina Formation, and the upper part to the Niagara. The 

 lower shales hold casts, often in great abundance, of Arthrophycus 

 Harlani (fig. 113), and remains of a small coral (or bryozoon) Hdi- 

 pora fragilis. The formation, generally, follows the course of the 

 Niagara escarpment between the Niagara River and Georgian Bay 

 gradually increasing in thickness, from a few feet to about 100 feet, 

 between these points. Conventionally, all the beds lying above the 



