Institution

The following pages describe a model based on a
synthesis of the data outlined in earlier chapters of this
218
work combined with information from the published literature.
Several factors must be considered in interpreting the
history of sedimentation in this area: 1) the probable
sedimentary processes before formation of the Puerto Rico
Trench, 2) the effect of formation of the trench on these
processes, 3) the ti me of i ni ti ati on and the effect of
geologically significant deep-current activity in the basin
of the western North Atlantic Ocean, and 4) the subsequent
sedimentary environment. An attempt is made here to resolve
all conflicting interpretations into a single unified evolutionary
sequence. The following discussion will describe the
formation of the Greater Antilles Outer Ridge from middle
Cretaceous time to the present.
MIDDLE CRETACEOUS TO MIDDLE EOCENE
Theoceani c basement under the Greater Anti 11 es Outer
Ridge was probably formed during the early to middle
Cretaceous, and the Puerto Rico Trench had not yet formed
(Fig. 8.1). The distribution of basement peaks which now
penetrate Datum A (Fig. 3.4) suggests that a rugged, ridge-
like elevation occupied the location of the present eastern
Greater Antilles Outer Ridge and possibly also the area of
the pre s en t P u e r toR i co T r en c h . U c hu p i an dot her s (1971)
suggested that the southeastern Bahama Banks, lying on the
same trend as this basement rise, may have formed atop a
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