Messinian drawdown and flooding in the offshore Sirt Basin, Libya: A regional facies characterisation

The offshore Sirt Basin is an underexplored basin with considerable hydrocarbon potential, and the Messinian section is poorly understood. It records a significant evaporitic event, and represents a valuable analogue for understanding evaporite deposition in the geological record. Messinian seismic facies in the Gulf of Sirt have been identified, subdivided and analysed to constrain the relative timing of key depositional and erosional episodes in this complex stratigraphic interval. An enigmatic feature of the interval is 'palaeo-Lake Sirt', a marginal evaporitic lacustrine basin containing interbedded evaporite and clastic lithologies subjected to post-Messinian sedimentary deformation. Depositional models have been constructed for the early, mid and late Messinian in the Gulf of Sirt and compared to previous models from other marginal Mediterranean basins. These facies assemblages reflect dramatic changes in climatic, tectonic and sedimentary processes occurring over an extremely short period. It is emphasised that obtaining high quality 3D seismic over a large area is crucial for a sufficient understanding of the depositional systems present in a basin.