Structure and Stratigraphy of the Tobago-Barbados Ridge and Its Implications for Hydrocarbons in the Barbados Offshore Area

Xiangyun Jiang¹, Paul Mann¹, and Alejandro Escalona^2
1Jackson School of Geosciences, University of Texas at Austin, Austin, TX
²Department of Petroleum Engineering, University of Stavanger, Stavanger, Norway

The recent discovery on Barbados of oil with compositions similar to the Late Cretaceous La Luna Formation of mainland South America 400 km to the south has raised the possibility of a continuous stratigraphic link between the two widely separated and tectonically distinct areas. We have used gravity and seismic data to better map the Tobago-Barbados ridge (TBR), the 300-km-long, 60-km-wide, northeast to north-trending ridge that bathymetrically and structurally connects Barbados to the area of Tobago and northern Trinidad. The TBR exhibits an hour glass shape with a 80-km-wide, twin-ridged southern segment exposing early Cretaceous island arc rocks of Tobago up to 550 m ASL, a 50-km-wide narrow central zone down to 2000 m BSL, and a 60-km-wide northern area exposing Eocene-recent sedimentary rocks on Barbados up to an elevation of 336 m ASL. Structure along TBR ranges from parallel folds forming the twin ridges of the southern area to normal faults forming the twin block-faulted ridges in the northern area. Seismic interpretation shows that the strong basement reflection associated with the Tobago igneous and metamorphic basement complex continues as far north as the central ridge segment. Locally, basement exhibits coherent, gently folded reflectors associated with an older late Cretaceous basin that is distinct from the incoherent sedimentary mélange formed in an accretionary prism setting. We have identified one published well in the Carupano area of the offshore of northeastern Venezuela that contains a Late Cretaceous limestone unit of open marine facies with high TOC overlying Cretaceous arc rocks. We postulate that similar Cretaceous source rock may be incorporated into the northern segment of the TBR and may provide the source for the oils of Barbados.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas