lhe sedímentary sequenee from AI1;Jian toSantonian in Sergipe-Alagoas Basin comprises Riachuelo and Cotinguiba fonnations .. It representa the initial development of ao open marine sedimentation in the tectonic-sedimentary evolution of the Braziliancontinental margin basins. lhe Albian/Cenomaniao rocks (Ríachuelo Formation) are eomposed of coarse terrigenous sediments (Angieo Member) at the border of the basin, grading lateral1y to shales interbedded with earbonates (Taquari Member), and are topped by ao essentially carbonatic sequenee with development of large oolitíc bars and algalie biolithites (Maruim Member), deposited in shallow matine conditions. lhe Turonian to Santonian rocks (Cotinguiba Formatíon) are composed mostly of laminated hemipelagic ealeilutites, deposited at the slope of a earbonate platfonn whích was entirely eroded. Shales from the lower part of Taquari Member have good oil-source potential but are thermally ímmature. The best prospeets of the studied sedimentary sequenee are fraetured calcilutites, associated with halokynetic struotures and paleo-highsbasements.