Abstract: As an extreme structural form of thin-skined extension under gravitational gliding, salt rafts are widely developed in the salt-bearing basins on a passive margin, which exerts important impacts on the evolution of the basin after the rifting period. Based on physical modelling, the combined effects of basement angle and syn-kinematic deposition rate are studied. In this study, the initial model setting and actual geological conditions are emphasized in addition to considering the single factor effects of salt layer thickness, base angle, and thickness of pre-kinematic sedimentary layer, making the results more meaningful. The results show
that the Cretaceous salt raft activity in the Congo Basin was caused by gravity gliding rather than differential loading; the most critical controlling factors of the salt raft structures are the basement angle and the syn-kinematic deposition rate; the basal angle controls the fracture distribution and rafts gliding rates; while the syn-kinematic deposition rate controls the pattern of deposition between the rafts during the formation process. The relative speed of the two controls the structural styles of the salt rafts. The Cretaceous salt rafts in the Lower Congo Basin was a result of the relatively fast depositional conditions.

Key words: salt rafts, gravity gliding, physical modelling, basement angle, syn-kinematic deposition rate