BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 10, pp. 165-176 MARCH 24, 1899 



LAKE IROQUOIS AND ITS PREDECESSORS AT TORONTO 



BY ARTHUR P. COLEMAN 



{Read before the Society December SO, 1898) 



CONTENTS 



Page 



Iroquois shore near Toronto and its fossils 165 



Fossils from other raised beaches 167 



Warping of the Iroquois beach 168 



Interglacial water-levels ... 170 



Water-levels during last advance of the ice > 174 



Conclusions 175 



Iroquois Shore near Toronto 



The recent finding of fresh water shells in Iroquois beach gravels close 

 to Toronto appears to settle the long debated question as to whether the 

 Iroquois water was a fresh water lake or an arm of the sea, and is per- 

 haps of sufficient importance to justify a brief redescription of the whole 

 series of lake deposits in the neighborhood. This must be the only ex- 

 cuse for adding to the already voluminous literature on the Iroquois 

 beach and the complicated problems with which it is connected. 



Although Dr Spencer long ago followed and determined the elevation 

 of the Iroquois beach north of lake Ontario, as Dr Gilbert has done on 

 the south, it seemed worth while to make a more careful survey of the 

 old coastline in the neighborhood of Toronto, and the results of this are 

 given in the accompanying map (figure 1), making it unnecessary to give 

 details of the interesting topography revealed. After the survey had 

 been made it was found that the western bay, reaching from Toronto 

 Junction to Weston, had been roughly mapped and briefly described by 

 Sandford Fleming in 1861.* It is worthy of note that the two sand and 

 gravel spits closing the mouths of the Humber and Don bays of lake 

 Iroquois were formed in very much the same way as the present Toronto 

 island, the ma,terials for wbich are now being transported from Scarboro 



* Canadian Journal, new series, vol. vi, 1861, p. 228. 

 XXV— Bull. Geol. Soc. Am., Vol. 10, 1898 (165) 



