4.2 Tectonostratigraphy

The stratigraphy of the Suriname-Guyana Basin (Figure 7) reflects the two-phases of geodynamic evolution. The Central Atlantic phase can be subdivided into two megasequences corresponding to a rift-to-drift history. The CA Rift megasequence is equated to the syn-rift sequence of which only the volcanics/volcanoclastics have been penetrated by one well offshore Suriname.   The CA Drift megasequence can be equated with sedimentary section developed along the corresponding Central Atlantic margin of West Africa. Only the upper part of the megasequence (Lower Cretaceous) has been penetrated by wells in the Suriname-Guyana Basin.   The "break-up" unconformity which is Albian-Aptian in age, marks the boundary between the Central Atlantic and Equatorial Atlantic megasequences. The unconformity is enhanced by a preceding phase of compressional deformation related to early opening of the Equatorial Atlantic. Due to the transcurrent nature of the rift phase, no EA Rift Megasequence has been deposited in the Suriname-Guyana Basin.   The EA Drift megasequence developed as monoclinal wedge of sediments which built out over the continental shelf. Several transgressive-regressive cycles can be recognised but the sequence is overall progradational in nature from the Turonian-Coniacian to the present day presenting a general northward advance of the shelf-edge. Several tectonically-enhanced unconformities are recognised representing episodes of basin margin uplift. These include the Base Campanian Unconformity (85 Ma) which was related to a change in the pole of rotation in Atlantic opening, and those of the Base Tertiary (67 Ma) and Mid Miocene (15.5 Ma) which have been used to subdivide the E. A. Drift megasequence. Angular discordance caused by basin uplift and erosion can be seen on seismic data at the Base Tertiary unconformity.