Reelfoot Rift: Reactivated Precursor to the Mississippi Embayment

Abstract

Tectonic elements involved in the formation of the Mississippi embayment, as inferred from geophysical and geological information, originated in late Precambrian time with continental rifting (the Reelfoot rift) and intrusion of high-density magma into the crust. Isostatic subsidence in early Paleozoic time formed the Reelfoot basin, approximately coincident with the modern embayment, in which several kilometers of sediment were deposited. Closing of the proto—Atlantic Ocean and subduction in the southern Appalachian Mountains in middle to late Paleozoic time were accompanied by uplift and widespread erosion in the midcontinent. A period of rift reactivation and intrusion in late Mesozoic time, in association with rapid subsidence in the Gulf of Mexico, prompted renewed isostatic subsidence within the embayment, forming the elongate depositional trough observed today. Continued seismicity and positive free-air gravity anomalies indicate that isostatic adjustment continues to the present time.