160 ROCHESTER ACADEMY OF SCIENCE. 



Explanation of the Outline Maps (Plates IV to X) 



Illustrating the Later Geographic History 



. OF the 



Lower Irondequoit Valley. 



All the maps cover exactly the same area, identical with that 

 of the preceding Plate III, with which they are meant to be com- 

 pared directly although for convenience reduced in size. Enough 

 only of the geography of each stage is shown to reveal the more 

 important or significant changes that have occurred. In all the maps 

 open stippling means deposits forming under water and close 

 stippling those above water level. 



For description see pages 149 to 158. 



Map A. Lake Dawson stage 



]\Iap B. Hyper-Iroq.uois ("initial Iroquois") stage 



]\Iap C. Lake Iroquois stage at close 



]\Iap D. Lake Emmons stage : Lake Irondequoit 



Map E. Gilbert Gulf stage : Irondequoit Meadows 



Map F. Returning Lake Ontario : early Irondequoit Bay 



JNIap G. Present Lake Ontario and Irondequoit Bay. 



i 



