A giant Late Triassic–Early Jurassic evaporitic basin on the Saharan Platform, North Africa

Abstract: This paper describes the Late Triassic and Early Jurassic evaporites of the Berkine/ Ghadames Basin in eastern Algeria and western Libya, which is important because it forms the regional seal to a number of hydrocarbon reservoirs in the Triassic Argilo-Gréseux Inférieur. This evaporitic succession spans the time interval Norian to Late Liassic and is divided into three contrasting units (S1, S2 and S3). S1 consists of five evaporitic cycles dominated by mud-stone and halite, which represent the main salt deposits of the Berkine Basin. At this time the Berkine/Ghadames basin was a restricted evaporitic basin with a barrier to the north (Medenine High) separating the basin from the developing peri-Tethys and North Atlantic. The succession thickens to the west, thins around the Hass Messouad Ridge and continues across the Maghreb into the western High Atlas of Morocco, a distance of some 1500 km. S2 is represented by the basin-wide development of a carbonate platform in Pliensbachian times. This is the product of a relative sealevel rise concomitant with the developing extension of the region and may reflect the opening of an Atlantic gateway. S3 comprises five cycles that are predominantly mudstones, fine-grained carbonates and anhydrites. Mounded structures, evident on seismic sections, may rep-resent the development of patch reefs and the whole succession is interpreted as a shallow-marin