| Abstract | The Upper Red River of the South has largely gone understudied by the scientific community. Tributaries and neighboring regions have been observed in some detail, but very little has been done on the Red River itself. In the course of this investigation, 13 discrete fluvial terraces were discovered within and above the Upper Red River Valley, providing a record that potentially spans to the Late Pliocene. Definitive dates spanning between the MIS 5c, some 0.1 Ma, and the Medieval Climatic Anomaly (MCA), 1 ka BP provide an avenue in which formational and degradational events can be assigned to specific climatic cycles, such as the Wisconsinan Glaciations, Last Glacial Maximum (LGM), and their interstadials, the Younger Dryas and its subsequent Collapse (CYD), and the MCA. Utilizing Optically Stimulated Luminescence (OSL) dating in conjunction with a hand auguring campaign, the terraces were drilled, logged, dated, and analyzed to determine architecture and characteristics of the fluvial deposits while pedogenic analysis allowed for the determination of the length of subaerial exposure to which these terraces were subject to prior to later burial. The dates for the terraces allowed for the further correlation of terrace construction, abandonment, and valley incision since the middle Sangamon Interglacial. These deposits record an ancient Red River vastly different to the stream seen today.
Thick assemblages of deposits and broad terraces reflecting a massive aggradational system suggest that this paleo-Red River was significantly larger. Relict deposits of the Lower Red River Valley confirm that the ancient River was similar in discharge and yield to the coeval Mississippi River, indicating that this ancestral Red River was a continent-scale river, thus suggesting a montane source to the west. In reconstructing a distribution model that connects the present Red River drainage basin to the Rocky Mountains, it is apparent that an additional fluvial axis would be required to nourish the ancient Red River. The Canadian River was identified through this study as being the ideal candidate for such a vector. However, this likewise suggests that the eventual pirating of the Canadian River by the Arkansas River became the Red’s downfall, as the Red River became both starved of sediment and discharge, relegating the former continent-scale River to the desert stream that rises atop the Llano Estacado today. |
