The Middle Miocene marked the emergence of the Appalachian uplands as a significant sediment source to the Gulf of Mexico. As a result, the Tennessee River joined the Mississippi in creating the dominant fluvial–deltaic depocenter. At the same time, supply from Western Interior uplands decreased. Two Miocene deposodes and multiple eustatically modulated high-frequency Pliocene–Pleistocene deposodes are recorded in northern Gulf stratigraphy. The continental slope wedge prograded onto the shallow Sigsbee salt, initiating canopy deformation and rapid basinward canopy advance. Salt-encased minibasins created rugose slope topography with multiple, efficient sediment traps. Nonetheless, large volumes of sediment bypassed the continental slope and constructed a series of large, long-lived abyssal plain fans. A narrow coastal plain and shelf prograded along the western Gulf margin. Extensional growth faulting was compensated basinward by compressional faulting and folding above Paleogene detachments. In the Sureste, the river-fed, prograding continental margin and ongoing basement deformation mobilized salt of the Campeche salt basin.