as the migration of deformation continued southward along the fault zone, during the early mississippian time, the final collision occurred with the alabama promontory . ettensohn later refers to the fourth tectophase as the mississippian tectophase of the acadian orogeny, since it demonstrated an unusually long duration (mississippian-early pennsylvanian). subsequently, the pocono & equivalent clastic wedges essentially filled the epicontinental sea. the deposition of middle mississippian carbonates marks the end of the acadian orogeny and catskill delta complex.