Guyana

Potential Source-Rocks

Transgressive Phase of the Continental Encroachment Cycle

In this area, the generating petroleum sub-system is associated with the transgressive sediments of the post-Pangea continental encroachment stratigraphic cycle and in particular with the Albian and Cenomanian-Turonian maximum flooding surfaces (MFS 91.5 Ma). These transgressive intervals, induced by marine ingressions, are characterized by the retrogradational geometry of the associated sedimentary regressions, i.e., by increasingly important marine ingressions and increasingly smaller sedimentary regressions. The transgressive phase is fossilized by the progradational wedges of the sediments of the regressive phase (increasingly smaller marine ingressions and increasingly important sedimentary regressions). The reflection induced by the post breakup volcanic flows (SDRs) were, for long time, considered, erroneously, as sediments of rift-type basins. The breakup unconformity (BUU) is here limited between the basement and the bottom of the sub-aerial lava flows, which are bounded by the breakup unconformity (BUU) and the top SDRs unconformity (SU). On the other hand, the SDRs are fossilized by onlapping of the sediments of the transgressive phase in which potential source- rocks are deposited (they will become source-rocks if they are buried enough for their organic matter reach maturation).

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