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~<br />

PREVIOUS THEORIES<br />

CHAPTER VI I I<br />

THE GEOLOGICAL EVOLUTION OF THE<br />

GREATER ANTILLES OUTER RIDGE<br />

Earlier concepts concerning the formation of the<br />

transparent layer which comprises most of the Greater<br />

Antilles Outer Ridge have relied on interpretations of<br />

seismic profiles. Ewing and others (1968) felt that the<br />

transparent layer must predate the deposition of Nares<br />

Abyssal Plain sediments because portions of the layer dip<br />

beneath the stratified sediments of the Nares Abyssal Plain,<br />

and they offered two possible explanations: 1) filling of<br />

a long depression with lutites, followed by later elevation<br />

of the sediment body, or 2) formation of the transparent<br />

1 ayer as the extreme outer end of the Bl ake-Bahama ri dge<br />

system, with later separation by erosion at the southern end<br />

of the Hatteras Abyssal Plain. Bunce and Hersey (1966)<br />

observed a thin layer of transparent sediments dipping<br />

beneath the Puerto Rico Trench Abyssal Plain and suggested<br />

that the layer was the remnant of a Puerto Rico continental<br />

rise predating formation of the trench. Savit and others<br />

217<br />

(1964) speculated that sediment erosion and/or transportation<br />

processes might be active in regulating the configuration of<br />

the transparent layer, but they made no comment on the timing<br />

or methods of formati on.

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