Experimental models indicate that sedimentary lobes deposited above mobile evaporites deform gravitationally by spreading outward radially. Radial spreading forms both concentric and radial families of thin-skinned grabens that are then pierced diapi-ically by salt ridges. The overburden blocks located between the ridges become subsiding depocenters. Later, continued spreading after depletion of the salt layer forces salt ridges and diapirs to fall, forming rapidly subsiding bathymetric lows that channel or trap younger sediments. Spreading causes large horizontal overburden movements whose distribution and orientation change when the locus of regional deposition shifts.