VALLEY-FILL ARCHITECTURE AND ALLUVIAL LANDFORMS WITHIN THE UPPER KANSAS RIVER: AN UNDERGRADUATE USGS EDMAP EXPERIENCE

Kansas River is unique amongst other Great Plains fluvial systems because it lies entirely within the Great Plains. This presentation, a continuation of research presented on the lower Kansas River drainage basin (LKR) last year, investigates the upper Kansas River drainage basin (UKR) to map the alluvial architecture and to document the chronological development of the river valley. Remotely-sensed data (e.g., LiDAR, NAIP), other databases (e.g., SSURGO, well logs), and field investigations were used to map river terraces within a 40-km reach of the UKR. Four terraces previously mapped in the LKR were also mapped in this reach: the Menoken, Buck Creek, Newman, and Holliday. Sample sites were established on each terrace, and stratigraphy was ascertained through exposures, hand auguring and hydraulic coring. Numerical age data were derived from OSL and ¹⁴C samples collected at select sites.

As in the LKR, the Menoken contains glaciofluvial sediments that thicken in proximity to the river—this deposit has been ascribed to the Kansan Glaciation (600-700 ka). In the LKR, the Menoken is overlain by Pleistocene dunes (31-36 ka), however, due to the limited expression of the Menoken in the UKR, these same dune deposits are found mantling bedrock. Eolian dunes were also mapped at the headwaters of the UKR, but these are believed to be much younger. The most widely mapped terrace in the UKR is the Buck Creek, a thick, fine-grain deposit that has been previously dated at ~15 ka. Investigations into the Buck Creek in tributaries indicate that the terrace fill may have a lower sandy unit thus far undocumented within the main river valley. The Newman is extensive on the south side of the river valley and consists of a variably thick basal soil that formed between 10-14 ka and overlying Holocene alluvium with intercalated paleosols. The Holliday is late Holocene in age (<4 ka), and consists of primarily abandoned meander scrolls and active channels.

Data from this project, combined with the results collected from the LKR, were integrated into GIS and used to produce various databases and maps including a 3D river valley bedrock map extrapolated from LiDAR and water and oil well logs. These data provide a perspective on the recent geologic history of the region, which enhances our understanding of river response to climate change in the Great Plains.