The effect of allochthonous salt evolution and overpressure development onsource rock thermal maturation: a two-dimensional transient study in the northern Gulf of Mexico Basin

Sequential two-dimensional forward modelling of source rock maturation alon g a north-south 600 km megaregional profile across the northern Gulf of Mex ico Basin illustrates the coupled influence of allochthonous salt evolution and overpressure development on source rock maturation. Model results indi cate that allochthonous salt evolution strongly affected local and regional source rock maturation, while overpressure development had a minor impact. Within the lower slope portion of the profile (south of the Sigsbee escarp ment to the Tabular Salt/Minibasin province), localized thermal lows associ ated with salt stock development locally retarded the maturation of source rocks, while the slow development of overpressures effected little influenc e on the maturation. Within the centre of the profile (offshore Louisiana s helf, however, the evolution of allochthonous salt sheets and shallow salt structures locally and regionally lowered the oil generation window. The ti ming of overpressures in this region, related to the progradation of the Ce nozoic marine depocentre, may have accelerated the maturation of middle Eoc ene source rocks, although the deeper Turonian source rocks had reached mat uration at the time of greatest overpressure development. In the northern p ortion of the profile (southern Louisiana), the Terrebonne salt sheet lower ed the oil generation window and retarded the maturation of the middle Eoce ne source rocks.