THE DON BEDS 



245 



away, and not from the Keewatin center, 1,400 miles away, as suggested 

 by Professor Wright. 



The lowest boulder-clay in most parts of the Don A'alley rests on the 

 Lorraine shale, with a thickness of 3 or i feet ; but at one point, near the 

 bend of the Don, both the boulder-clay and the shale beneath were cut 

 away by a small intergiacial river to the depth of 16 feet, over a breadth 

 of 400 feet. The cutting into the shale, with its resistant layers of thin 

 limestone, was as deep as that made by the Don in post-Glacial times, 

 and probably required as long a time to accomplish. 



In this old river valley a fairly swift current deposited shingly gravel 

 made from the underlying shale mixed with leaves, Avood, bark, and other 

 vegetable material, including wood of the red cedar and pawpaw, showing 

 that the climate was no longer glacial, but had already become warmer 



30\ 



rr^TTuw ;i ■■■'■fPecgh'?-} \ '-. ■{•■.'■.•.•.'•.■;.• 



Do n BedsJUnios, etc.) 



L orraine 



Level o/" Don ff/ver 



fiorizon/a/ ySc^e. of feet 

 <2 £o /j^o 



Section at bend of Don 

 Figure 1. — -Cross-section of the Don Beds 



Lorraine 



than lliat of Toronto at present, 'i'hei'e are many iiiibrolscn niiios. a.no- 

 tions, and gastropod shells in the Finer beds above. 



At the Don Valley brickyard wood, sometimes as tree trunks 1'^ (u* 15 

 feet long and still retaining branches, is found flattened into the surface 

 of the boulder-clay, and many unios arc embedded in a few inches of 

 clay resting on the till. These shells are often in pairs and are still cov- 

 ered \vith the greenish epidermis found on living unios in the Don near 

 by. It is evident that they lived and died on the spot where they are 

 Pound. 



Above the blue clay resting on the till there are well stratified beds of 

 sand and clay, rising for about 17 feet, laid down in the shallow water of 

 a lake. They contain many shells, especially unios, sphiBriums, and pleuro- 

 (teras, seldom broken, thougli many are worn by ihe sand and flue gravel 

 willi wliich they were deposited. In a few of the thin beds of clay be- 



