8 IN LOWER FLORIDA WILDS 



this Pleistocene submergence this depression of 

 "yesterday." 



It was probably at this time that the great coral 

 reef along the Floridian border of the Gulf Stream 

 was started, and grew until it finally appeared at 

 the surface of the sea. After being worked over by 

 wave and storm action and with slight further 

 elevation it formed and then became the present 

 Upper Keys. This reef lay on a bank at some 

 distance from what was later to become the main- 

 land and was nourished by the warm, food-laden 

 waters of the great ocean river that swept along it. 

 When it had been built up to near its present 

 height another coral reef or fringe began to grow 

 up outside it and this is the present outer reef, 

 which we shall visit in a later chapter. 



During this same period of subsidence extensive 

 beds of shallow water limestone were deposited 

 over much of what was later to become our present 

 Lower Florida. One of these limestone beds, an 

 oolitic, covered the area which has since become 

 the present region of the Lower Keys, and it is 

 quite possible that this same formation extends to 

 and includes all the present southeast coast where 

 the rock is called by geologists the "Miami lime- 



