1:06 J.B.TYRRELL — POST-TERTIARY DEPOSITS OF MANITOBA. 



the boundary line the ridges range in altitude from 995 to L,230 feet above 

 the Bea,* while <>n th<- eastern nice of the Duck and Eliding mountains they 

 were found to ascend as high aa 1,460 feel above the Bea, showing a rise in 

 the upper boundary beach, supposing it to continue this far north, of about one 

 fool to the mile from the point of crossing latitude 40° north to the Duck 

 river, where the bighesl lunch was seen, [f the highest beach at the bound- 

 ary does not extend so far north, the rise per mile will be somewhat greater. 



Very few fossils that can be clearly identified have been found in these 

 -ravel ridges; but on Valley river in hit. 51° 13' N.. Long. L00° 20' W\. at 

 a distance of two feet below the surface, some roughly chipped fragments of 

 quartzite have been discovered, lying horizontally among the disk-shaped 

 waterworn pebbles, along with a small bone of a mammal. Precisely simi- 

 lar fragments are now to be found on the shore- of lakes VVinnipegosis and 

 Manitoba in association with well-formed arrow-points, and the traditions 

 of the Indians go back to the time when they were formed and used by their 

 forefathers. A- the gravel had been laid down bv water action and was 

 quite undisturbed, they clearly indicate the existence of man at the time 

 when this lake beach was being thrown up, and it is probable that here, 

 mar the mouth of the former representative of Valley river, was one of his 

 favorite haunts. The summit of the beach in which these "chipped flints" 

 were found is bio feet above lake Winnipeg or 1,135 feet above the sea. 



The positions of the northern and eastern shores of Lake Agassiz have not 

 yet been determined : but from what we know at present we can safely say 

 that there is no land in that direction sufficiently high to form a shore line 

 with an elevation of 1 ,400 or more feet, ami there has been no evidence forth: 

 coming to show that there has been any other disturbance of the country 

 since the lake was at its highest level than the slow uplift towards the 

 north shown by the gradual rise of the ridges in that direction. Tin- theory 

 ha- been suggested that the face of the retreating continental glacier held 

 back the water on these two sides. It is not improbable that a- the glacier 

 retired from the face of the country, which was sloping towards it, a lake 

 would In formed at it- foot. If this be the true explanation of the cause of 



the formation of Pake A.gassiz, it discharged its surplus water through the 

 valhy of Lake Traverse until the glacier had retired far enough or had 

 decreased sufficiently in size to allow id' a discharge for the lake over or 

 around it. The position of this river has not been and may possibly never 



be determined, a- all traces of it may have since been swept away. 



Much ha- yet to I"- learned of the history of all of these post-glacial lake 

 beaches, but a long array of interesting facts is now being gathered together, 

 which it i- hoped will before long solve Bomeofthe mysteries of Quater- 

 nary dynamical geoloj 



rhe Upper Beache* and Oil lal Lake I by Warren Upham: Ball. 301 - 



Or., I. - p 17. 



