Initiation of diapirs is one of the least understood aspects of salt tectonics. Sedimentary differential loading and erosion are both effective, but not universal, causes of diapir initiation. A survey of 18 major salt-diapir provinces shows that salt upwelling is closely linked in time and space to regional extension. Extended salt basins typically develop salt structures, whereas nonextended basins do not.

Discovery of volcanic glass detritus in fluvial deposits of the middle Frio Formation (Seeligson and Stratton fields) of South Texas has resulted in a new classification of reservoir types (type I and type II) within this formation. Type I reservoirs consist of sandstones that do not contain volcanic glass and have an average permeability of 36 md (geometric mean).