Copyright by Nysha Chaderton 2009 - The University of Texas at ...
Copyright by Nysha Chaderton 2009 - The University of Texas at ...
Copyright by Nysha Chaderton 2009 - The University of Texas at ...
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Sandy m<strong>at</strong>erial is primarily quartz (75–95%) with minor lithic grains, micas, and<br />
heavy minerals (Faugeres et al., 1993).<br />
<strong>The</strong> largest <strong>of</strong> the prism’s many piggyback basins, the Barbados Basin,<br />
was the focus <strong>of</strong> a 2001 explor<strong>at</strong>ion well, the Sandy Lane #1 (Figure 4.1). A near-<br />
seafloor dredge sample taken from the basin as part <strong>of</strong> this effort recovered fine-<br />
grained quartzose sandstone. <strong>The</strong>se sediments were measured from wh<strong>at</strong> was<br />
interpreted on the basis <strong>of</strong> seismic morphology to be a deposit <strong>of</strong> deep-marine<br />
lob<strong>at</strong>e sediments, internally composed <strong>of</strong> tabular sheet sands (Dolan et al., 2004).<br />
<strong>The</strong>se results suggest th<strong>at</strong> even in this confined, tectonically active basin setting,<br />
reservoir quality sands are deposited as fans and sheet sands in very deep w<strong>at</strong>er.<br />
Barbados Ridge<br />
<strong>The</strong> Barbados Ridge is the topographically highest part <strong>of</strong> the accretionary<br />
prism and the region along which the island <strong>of</strong> Barbados is emergent. <strong>The</strong> island<br />
<strong>of</strong> Barbados is rising <strong>at</strong> a r<strong>at</strong>e <strong>of</strong> approxim<strong>at</strong>ely 0.44 mm/yr (Taylor and Mann<br />
(1991). <strong>The</strong> arcu<strong>at</strong>e ridge, subparallel to the Lesser Antilles Island Arc (Figure<br />
4.1), is formed as accretionary prism m<strong>at</strong>erial moves westward and interacts with<br />
the string basement <strong>of</strong> the Caribbean Pl<strong>at</strong>e, moving up and over the metamorphic<br />
basement. In some cases, this m<strong>at</strong>erial is overriding the lowermost Tobago<br />
Forearc Basin sediments, which are deformed <strong>by</strong> these movements. As a result,<br />
the west side <strong>of</strong> the Barbados Ridge is characterized <strong>by</strong> large, west-facing thrust<br />
faults, while a number <strong>of</strong> northwest-southeast-striking normal faults domin<strong>at</strong>e the<br />
crestal region (Figure 4.6).<br />
<strong>The</strong> east margin <strong>of</strong> the Barbados Ridge is characterized <strong>by</strong> a step-like<br />
succession <strong>of</strong> normal faults. <strong>The</strong> largest <strong>of</strong> these, the Barbados Fault, bounds the<br />
east coast <strong>of</strong> the island <strong>of</strong> Barbados (Figure 4.6). This fault has more than 3 km <strong>of</strong><br />
down-to-the-east vertical displacement. Underpl<strong>at</strong>ing <strong>of</strong> forearc basin and<br />
accretionary prism sediments, as well as the presence <strong>of</strong> basement ridges (Brown<br />
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