Geology of Mdffawa and Otfairn TaUeys. — Taylor. 119 
Wherever the hills were ascended in the region east and 
northeast of Georgian bay it became at once apparent that 
their even tops were the remains of an ancient peneplain. 
From the hills south of Callender (C. P. R.) Mt. Talon, 15 or 
20 miles to the north and beyond the Mattawa valley, was 
seen rising high above the general plain as a fine monadnock. 
No other so prominent was noticed in this region. In the 
highlands south of the Mattawa the Algonquin beach marks 
a water level that entered the deep valleys between the hills 
and extended far into the interior. On the north side of the 
Mattawa not only is the beach depressed, but the peneplain 
seems to show a corresponding depression also. In short, the 
descent of the Algonquin beach northwai'd from Trout creek 
appears to be due to deformation since the beach was made, 
and it seems probable, therefore, as previously stated,* that 
there are post-Algonquin faults between Trout creek, or 
rather between South river, orSundridge and Nelson's. And 
this deformation appears to have been finished before the be- 
ginning of the Nipissing beach. 
The upheavals which tilted and warped the plane of the 
Algonquin beach before the formation of the Nipissing beach 
have bee^ called the Algonquin uplifts. f Whether these occur- 
red after, or part of them during the making of the Algonquin 
beach is a very complex question, which is full of importance 
in its bearing on the lake history and the history of the Nia- 
gara gorge. There is much reason to believe that the Simcoe 
region, including the Trent vallej^ outlet, was raised during 
the life of lake Algonquin and before the breaking of the ice 
dam in the Ottawa valley. Sharp warping occurs in the region 
east and northeast of Georgian bay, but it apparently dies 
out towards the southwest so that the St. Clair river and the 
south end of lake Huron were onlj'- slightly affected. If the 
Mattawa-Ottawa region was uplifted before the ice-dam broke 
it would follow that the surface of the lake in the region near 
the dam was not up to the level of the highest beaches at the 
time of the break, and hence that the whole lake was not 
lowered over 500 feet when the dam broke, as it must have 
been the case if that event occurred before all the uplifts. In 
*Aq). Jour. Sci. vol. xlix, April 189.5, footnote on page 258. 
tThe Inland Educator, Terre Houte, Ind,, vol. 2, No. 4, p. 222, May 
18'.)6. 
