Abstract With the lifting of economic sanctions, western companies have come back to explore for hydrocarbons in Libya, onshore and offshore. However, virtually no modern marine seismic data has been acquired over the past twenty-five years to assist in this renewed exploration effort. During the past year, new 2D pre-stack time migrated seismic data has been acquired and used to examine the large-scale structural and depositional features of the Libyan shelf and slope. The data cover approximately 38,000 line kilometers in water depths ranging between 15 to 2200 meters. The present day Libyan shelf margin has a demonstrably progradational character. Thick, laterally extensive deltaic deposits dominate the shallow shelf and upper slope. These deposits display classical clinoform geometries that suggest multiple phases of progradation during the past 3-5 Ma. Seismic resolution within the clinoform packages is high, as growth faulting, distributary channels, slump scars, and rotated blocks within the delta front are readily visible. Clinoform geometries visible below, but truncated by, the Messinian unconformity indicate that the early to middle Miocene margin of Libya was also progradational at certain times. Recent deltaic deposits sit upon and within a deeply eroded and scarred paleotopography, suggesting large-scale retrogradation of the shelf margin. The erosional surface extends for nearly 500 km along strike in the Sirt Embayment. A 65 km long portion of this erosional surface displays high relief truncated strata, healed fault scarps, and related deep-seated faults. In this area it is likely that a very large volume of shelf margin strata is missing. The Libyan margin is tectonically active today and has been through most of the Cenozoic. Many faults penetrate from deeply underlying Mesozoic strata to the ocean bottom. The close association of active faults scarps, truncated strata, a potentially large missing section, and a laterally extensive erosional unconformity combine to suggest the possibility of catastrophic margin failure. The exact timing of margin retrogradation is uncertain at present but erosional relationships hint that margin failure occurred either coincident with or following the Messinian salinity crisis.

Abstract A combination of 3D pre stack and post-stack time-migrated seismic data was used to examine salt structures, stratigraphy, and hydrocarbon potential in the BES 2, 100, 200 and BMES 1, 2, and 9 blocks of the Espirito Santo Basin, Brazil. Salt structures display a proximal to distal basinward transition from salt rollers, to vertical diapirs, to diapirs with overhangs and alloch-thonous tongues, and finally to salt canopies. The original autochthonous salt thickness increases following a similar proximal to distal basinward gradient. Deformation, driven by a combination of gravity gliding and gravity spreading, has been a relatively continuous process in the Espirito Santo Basin. Contraction began early in the Albian and continued unabated up to the present-day. However, individual structures ceased movement at different times depending on geometry, salt supply, and overburden thickness. A major thermal pulse affected the basin in the early to middle Eocene, associated with emplacement of the volcanic Abrolhos Plateau. Both intrusive magmas and extrusive flows are interpreted to exist. Intrusive dikes and sills display characteristic saucer shapes in cross section, elliptical to circular shapes on time slices, and cone shapes in 3D. Magmas appear to have used existing salt structures and associated fault planes as preferred pathways to reach shallower levels. Extrusive flows were identified only where seismic character, clear stratal relationships, and direct ties to intrusive geometries allowed. All the elements for excellent hydrocarbon potential exist in the Espirito Santo Basin. The main Syn-rift II source bed found in the Campos Basin exists across the basin. Several other less documented source intervals also exist. Numerous contractional folds, turtle structures, and diapir-flank traps are present. Reservoir intervals exist in Albian carbonates, Upper Cretaceous transgressive sands, and Cenozoic regressive sands. At least one deepwater hydrocarbon system is operating, as evidenced by numerous shallow bright spots, gas chimneys, and a recent major deep-water discovery. The presence of intrusive magmas may adversely affect deeper source intervals in some places, but could locally bring immature source rocks into the oil window.