AGE OF THK MARINE BEDS 137 



l)oul(ler-cl;iy or a striated rock surface, or fortn the U|)[)er beds of kanie- 

 like hills, but have not yet been shown to be covered by boulder-clay or 

 any other well marked <;lacial materials. It is true that scattered 

 boulders, which may be called erratics, sometimes rest on them, ))ut 

 these have probabh^ been transported by floating ice when the sea 

 stood at its hiujher level, just as river ice transports large ])oulders in the 

 Saint Lawrence at the present dny. 



As to the temperature of the time, the plants found in tlie Leda chiy 

 nodules at Ottawa, 28 species in all, as determined by Professor Pen- 

 hallow, are all represented in the same region at present, and include the 

 sugar maj^le, the yellow birch, and the common and balsam poplar, trees 

 of a cool temperate but b}' no means arctic climate. Of the other fossils 

 mu.ch the same may be said. The chipmunk is common in the same 

 region now, the feathers and bone of a ])ird have not been determined, 

 and the four species of insects — Fornax ledensis, Tenebrio calciUensis, Byr- 

 rhus ottawdeasis, and Phryganea ejecta — as determined by Doctor Scudder, 

 are extinct and do not add much to our data. The seals, dolphins, and 

 whales found in our deposits are all still living in the gulf of Saint Law- 

 rence, and the same is true of most of the 26 other marine animals 

 recorded.^ The Arctic species mentioned by Sir William Dawson are 

 apparentl}'' still living in the Gulf and do not indicate a climate greatly 

 different from the present, though perhaps somewhat colder, so that 

 these beds are not interglacial even in the sense of having been formed 

 while glacial ice occupied the shores of the inland sea, though it is pos- 

 sible that the Labradorian ice-sheet had not wholly vanished at the time 

 they were being formed. 



If the usually accepted theory that the Iroquois water was dammed 

 by glacial means is correct, the marine beds of the Ottawa-Saint Law- 

 rence region could not have been formed until the ice-tongue, hundreds 

 or thousands of feet thick, which obstructed the lower end of the Ontario 

 basin, had melted away, and this provides some data for estimating their 

 age. If we suppose the formation of the Iroquois beach to have taken 

 half the time since Niagara began its work, and this is not an unreason- 

 able supposition, there is available for all subsequent events a time 

 variously estimated at from 2,500 to 16,000 years. Within this time the 

 great ice-dam must have melted, implying a retreat of the glacial front 

 for at least 100 miles, and widespread sheets of sand and laminated clay, 

 sometimes more than 140 feet thick, were laid down, and afterwards 

 eroded to the depth of at least 110 feet by the Rideau and other rivers. 



* Can. Ice Age ; also contributions to the paleontology of the post-Pliocene of the Ottawa valley, 

 Dr Ami, Ottawa Naturalist, vol. xi, no. 1, pp. 20-2G. 



XX-BuLL. Geot,. Soc. Am., Vol. 12, 1900 



