Neogene upland gravels of the Mississippi River valley have been interpreted to be terraces of the ancestral Mississippi and Tennessee River systems. The gravels are called the Citronelle Formation in Louisiana, Pre-loess gravels in Mississippi, Upland Complex in Tennessee and Arkansas, the Mounds and Grover in Illinois, and possibly the Windrow in Wisconsin, Iowa, and Minnesota. Large arcuate topographic lows in the upland gravels of northwestern Mississippi have been interpreted by previous investigators to be paleo-meanders of a large Pliocene Arc (Mississippi) River estimate to have had seven times the discharge of the modern Mississippi River and have had its headwaters in Canada. The present study explores that possibility by mapping gravel data from 97 wells in Illinois and gravel distributions of previous studies. The distribution of these Pliocene uplands gravels allows a partial reconstruction of the course of the Pliocene Arc River system and its elevation from central Minnesota to Memphis, Tennessee along the modern course of the Mississippi River. A longitudinal profile of the contoured surface of the base of the upland gravels was constructed and projected into southern Canada. This profile shows that the base of the Pliocene Arc River floodplain would be ~30 m above the modern ground surface and that the Arc River in Canada used to flow across Paleozoic strata that have been removed by glaciation. Within the northern Mississippi embayment 557 well logs reveal that the Pliocene Upland Complex of western Kentucky and Tennessee and Crowley\u27s Ridge in Arkansas has been displaced by east-striking normal faults. The normal faults extend east and west of the margins of the Reelfoot rift thus suggesting that right-lateral simple shear has extended from the Commerce geophysical lineament/fault to the Big Creek/Ellendale fault. Within this strain model north-striking stepover structures are interpreted to have experienced local east-west compression and the east-striking normal faults are a consequence of local north-south extension. The north-trending stepover structures have Quaternary uplift with uplift rates of 1-3 mm/yr
