age; the latter consittuting about half of the entire sequence. Newell (1955) stated 

 that the coarse, open cavernous texture found at many horizons in the above boring 

 indicated leaching near sea level; thus, making the unavoidable conclusion that this 

 part of the shelf had quietly subsided more than 2^ miles since early Cretaceous, and 

 that it is still sinking while the Platforms are being built up near the surface by accu- 

 mulation of calcium carbonate. He calculated an average rate of accumulation of 

 consolidated sediment on the Great Bahama Bank of about 3.6 cm per 1,000 years. 



Gravity data, interpreted by Worzel et al (1953), show a small seaward increase 

 of gravity across the Platform, with negatrve~Free air anomalies of about 110 milligals 

 along the eastern boundaries of the Bahamas and southern part of the Blake Plateau. 



Evaluating all existing data, Newell (1955) concluded that the region has long 

 been isolated from sources of terrigenous sediments, that no compelling evidence 

 exists of folding or faulting in later geologic times, and that little data have been 

 presented to show that frequent interruptions in the general subsidence (probably the 

 result of isostatic adjustment to the steady accumulation of carbonates) have occurred 

 during the past 130 million years or so. 



The Tongue of the Ocean 



The majority of reports on the TOTO have been primarily concerned with the 

 method of channel formation and are based on gravity, bathymetric, and seismic data. 

 However, recently a number of sediment samples have been collected from the floor 

 of the TOTO which give a somewhat general picture of the material covering the 

 bottom and the mode of deposition. 



Origin: Hess (1933) attributed initial formation of the deep Bahamian channels 

 to the action of running water under subaerial conditions; the drainage patterns being 

 structurally controlled by some unknown factors. Subsequent to formation of the ero- 

 sional valleys, subsidence and rapid deposition of calcareous material on the higher 

 prominances formed the present Bahamian platforms and channels. Hess (Ibid.) further 

 stated that the continuous slope of the valley floors from the upper reaches ot the 

 channels to the edge of the continental slope excluded a graben and synclinal -trough 

 hypothesis, and noted that marine erosion is not likely to produce a valley with an 

 inner gorge or channel running down the middle and a continuous slope in one direction, 



Schuchert (1935) advanced the hypothesis that Andros Island once faced the open 

 Atlantic, and later the suspected volcanic eastern portion of the Great Bahama Bank 

 grew up in front of Andros leaving the Tongue of the Ocean between. 



Ericson et al (1952), on the basis of lithological and paleontological evidence 

 from sedlmenTcores collected in the TOTO, concluded that turbidity current erosion 

 may be largely responsible for excavation of the TOTO and Providence Channels. 



Worzel et al (1953) re-examined gravity observations collected from the Banks, 

 and, in refer'ence to the origin of the TOTO, concluded that most of the anomalies 

 can be explained by simple erosion of the deep-water portions without compensation, 

 or, alternately, construction of the shallow -water portions without regional compen- 

 sation. Newell (1955) combined both of these alternatives and theorized that the 



