Copyright by Nysha Chaderton 2009 - The University of Texas at ...

Oligocene-age sediments are deposited over a broadening, deep, Tobago
Basin. Sediments of the Barbados Accretionary Prism (BAP) continue to be
accreted beneath the Tobago Basin and sediments deposited on the Atlantic
Abyssal Plain are thrust beneath older BAP sediments. This latter action causes
the prism to broaden and thicken, particularly at the thrust front. During this time,
sedimentation within the Tobago Basin keeps pace with the increasing height of
the prism, eventually surpassing the prism growth and depositing sediments over
the prism (Figure 4.10b). During the Early to middle Miocene, sediments
accumulate across the entire area of the very broad Tobago Basin. The most
regionally extensive stratigraphic surface, the Mid-Miocene Unconformity,
developed in the basin at this time (Figure 4.10c).
Following the extensive erosional event of the Middle Miocene, the BAP
continued to thicken through the processes of accretion and underplating. The
Barbados Ridge became emergent, uplifted through ongoing accretion of
sediments due to increased thrusting and underplating (Figure 4.10d). The
Caribbean Plate continued to inhibit the westward movements of the Atlantic
Plate prism sediments causing increased offscraping and accretion of sediments,
which caused the broad pre-Middle Miocene Tobago Basin to become segmented
into several sub-basins.
The Tobago Basin continued to diminish in size to the present, and since
the Late Miocene, Tobago Basin sediments have accumulated in a much narrower
area than the pre-late Miocene sediments (Figure 4.10e). Today, subduction of the
Atlantic plate is ongoing and the Barbados Ridge continues to rise as a result of
ongoing underplating. This process has led to extensive crestal faulting along the
Barbados Ridge creating steep slopes and resulting instability along the ridge.
The largest of these extensional normal faults is the Barbados Fault. This fault,
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