26 



SCIENCE 



[N. S. Vol. XXXII. No. 809 



practically the entire submarine bank. The 

 sanda extend beneath the limestone formations 

 as far south as Miami, and perhaps to the 

 southern keys. Along the more northerly 

 portions of the bank coquina aeeumulated ; 

 along a curve, first southward and then bend- 

 ing westward, from Biseayne Bay, a coral reef 

 flourished, separated by a channel of deeper 

 water from the main bank, on which the 

 Miami oolite was forming or had formed in 

 shoal water, strongly agitated by currents. 

 Along the southwestern portion of this bank, 

 also in shoal water, the Lostmans River lime- ■ 

 stone accumulated. West of the coral reef, 

 on an extensive flat in shoal water, the Key 

 West oolite was formed. Toward the close of 

 the Pleistocene the previously formed sands, 

 marls and limestones southward beyond 

 Miami received a thin coating of siliceous 

 sand. Contemporaneous with this purely 

 marine work, the terracing of rivers to the 

 north was taking place. 



Pleistocene time was closed by an uplift, 

 which may have been intermittent, or may 

 have been accompanied by oscillations. There 

 is some evidence of slight depression since the 

 principal uplift. After this uplift the living 

 coral reefs developed, the Everglades were 

 formed, and the Florida of to-day was the 

 result. 



Deformation. — The Ploridian Plateau owes 

 its origin to a fold of the sea-floor in pre- 

 Oligocene, probably Eocene, time, producing a 

 platform on which sediments during the later 

 geologic periods were laid down. The whole 

 earth mass, since the origin of the platform, 

 has been subjected to a succession of deforma- 

 tions due to compression between forces act- 

 ing from the east and west, resulting in the 

 axes of the gentle folds coinciding in direc- 

 tion with the longitudinal axis of the plateau. 

 An uplift with deformation took place, as 

 nearly as can be determined, toward the close 

 of the Vicksburgian deposition period. The 

 Vicksburgian nucleus lay nearer to the eastern 

 than the western margin of the plateau, and 

 was roughly dome-like in form, but with a 

 longer north and south than an east and west 

 axis. The subsequent growth of the peninsula 



was by filling the channel between the island 

 of older Oligocene (Vicksburgian) rocks and 

 the mainland, and by growth eastward and 

 southward from it. There was little or no 

 westward growth. There was additional 

 deformation in later Oligocene (Apalachi- 

 colan) time, between the Apalachicolan and 

 Miocene deposition periods, between the Mio- 

 cene and Pliocene, between Pliocene and 

 Pleistocene, and succeeding the Pleistocene 

 deposition. The result of each of the series 

 of deformations was to add, beginning with 

 the Miocene-Pliocene number of the series, 

 one or more anticlinal swells with interme- 

 diate synclinal depressions to those that pre- 

 ceded, the additions above sea-level always 

 taking place toward the east, and at each 

 elevation the uplifting was propagated south- 

 ward. The continued effect of all the uplifts 

 was to elevate the eastern portion of the pla- 

 teau above the western, or there has been 

 elevation on the eastern side of the plateau 

 coincident with stability or even slight depres- 

 sion on the western side. 



Currents. — The ocean currents, combined 

 with winds and tides, have been important in 

 shaping the land area of Florida. Before the 

 history of the currents of the region can be 

 thoroughly understood it is necessary to know 

 the history of the Hatteras Axis of North 

 Carolina. The present Florida counter-cur- 

 rent seems to be due to the impingement of 

 the Gulf Stream against the Hatteras projec- 

 tion, resulting in a portion of the waters being 

 deflected southward along the coast, instead 

 of continuing their northward journey. The 

 Hatteras Axis has existed as a dividing line 

 between depositional areas apparently since 

 middle Cretaceous time, and it has been either 

 a region of shoal water, or occasionally a land 

 area, since later Eocene time. The Vicks- 

 burgian and Apalachicolan seas were both 

 warm, tropical or subtropical in temperature. 

 It is not definitely determinable at present 

 whether the warmth of these waters was due 

 to currents directly from the tropics or to a 

 warm return current produced by the north- 

 ward flowing Gulf Stream having a portion 

 of its waters diverted southward by impinging 



