The Mesozoic basins of Yemen have a multiphase history of rift development. Sediments of the ‘Furt Formation’ were deposited as a result of a second, discrete phase of rift activity during the Hauterivian to Barremian and unconformably overlie older deposits (A. C. Ellis, H. M. Kerr, C. P. Cornwell and D. O. Williams, 1996, Petroleum Geoscience2, 29–42). The name is taken from the suggested type well, AI Furt-1, where the unit reached its maximum drilled thickness to date, in the Jeza-Howarime Basin. The lithology in the type well predominantly comprises calcareous mudstones with subordinate carbonates. In western Yemen and more marginal settings, the ‘Furt Formation' is dominated by arenaceous facies. Biostratigraphic analysis suggests that the upper and lower limits of the 'Furt Formation' are bounded by stratigraphic breaks. Regional seismic lines suggest and biostratigraphy confirms the extension of the 'Furt Formation' into basin margin areas and other rift basins, supporting the case for regarding the Furt section as a formation in its own right. The Qishn Formation has been divided on a tripartite basis. The oldest units are the ‘Clastic’ and ‘Lower Carbonate Members’ which are lateral facies and age equivalents. The ‘Clastic Member’ is found in the west of Yemen while the ‘Lower Carbonate Member’ is best developed in the east. The transition between the two is seen in the Jeza-Howarime Basin. The middle unit, the ‘Shale Member’, is a regionally extensive mudstone facies thought to relate to a maximum flooding event. The youngest unit, the 'Carbonate Member', comprises a limestone sequence. The Qishn Formation is unconformably overlain bythe clastics of the Harshiyat Formation and in the extreme east of the Yemen by the carbonates of the Fartaq Formation. The Qishn Formation represents a transition from a rift to a post rift-phase (Ellis et al., 1996).