A Central Atlantic Petroleum System has been delimited through seismic interpretation of the Jurassic rift basin (Central Atlantic Rift Sequence); though definition has been limited by lack of well penetrations. The Takutu graben (Guyana) is a failed rift arm, where Jurassic lacustrine source rocks charged a non-economic light oil accumulation. Being part of the same system as the Jurassic grabens offshore, it can be used to estimate the early basin fill.
Lacustrine source rocks, alluvial fans and fluviatile deposits, together with volcano-clastics, comprise the lower stratigraphy, whilst salts form the base of the overlying marine clastics and carbonates. The regional unconformity of Albian/Aptian age (marking he break-up of Africa and South America) is overlain by a prograding sequence of clastic sediments, with only short periods of carbonate deposition. The sedimentary environment ranges from terrestrial to deep marine, roughly paralleling the modern day situation.
Numerous onshore and 22 offshore wells provide a reasonable data set to evaluate the stratigraphy younger than the Jurassic. An excellent Cenomanian-Turonian marine source rock, deposited over large parts of the basin, overlies the Aptian/Albian unconformity. This extensive Canje Source Rock has a documented gross thickness of 50-500m and total organic carbon content of up to 16%.
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