Soudan2

Liberia Offshore

Harper Geographic Basin

On this tentative interpretation of a manual autotrace of a Liberia offshore seismic line crossing the St. Paul fracture zone, over pre-rifting strata, a Lower Cretaceous rift-type basin formed and infilling during the lengthened of the Gondwana continental crust is clearly recognized. Th breakup unconformity (BUU), that highlights the onset of the Atlantic-type divergent margin is , also, recognized without major difficulty. On the right part of the autotrace, it corresponds to the top of the rift-type basin, while on the left part it underlines the southern border of the St. Paul fracture zone, which is fossilized by the onlapping of the SDRs (lava-flows) that form the volcanic sector of the Atlantic-type divergent margin. The clastic sector of the margin, on the left part of the autotrace, is formed by the strata overlying the SDRs and on the right part, by the strata overlying the rift-type basins, which are, rarely, covered lava flows (SDRs).