GEOLOGY AND PALEONTOLOGY OP THE CANAL ZONE. 



269 



The accompanying map (fig. 7) shows the location of the Oligocene 

 reefs with reference to the Plateau surface. 



That Pliocene deposition was followed by uplift, erosion, and de- 

 pression, is shown by the fact that the Pleistocene shell marls along 

 Caloosahatchee River rest on the eroded surface of the Pliocene. The 

 Pleistocene reefs, the location of which is shown on the map (fig. 8) , 

 were formed during subsidence which followed uplift at the close of 

 Pliocene deposition. At the base of the reef, which is 105 feet thick, 



Fig. 7. — Florida, Ocala limestone plateau with superposed Oligocene and Miocene coral reefs 



AND REEF CORALS. Oc. Zs.=OCALA LIMESTONE; THE FIGURES ARE FOR THE DEPTHS OF ITS UPPER SURFACE 



below sea level. cti=chattahoochee and tampa oligocene formations. al. -s.=alum bluff 

 Miocene formation. 



is a calcareous deposit, 55 feet thick, of undetermined age. Beneath 

 it are 450 feet of sand, mostly quartz, of Miocene age, below which 

 follow in descending order, limestones of Chattahoochee and Ocala 

 age, but without any development of reef -corals. Planimeter meas- 

 urements indicate an area of 66 square miles for the Pleistocene reef 

 against an area of 1,670 for the chemically precipitated calcium car- 

 bonate of the Miami and Key West oolites. I have already published 



