Date of this Version
Bruihler, Jacob C., 2016. Dating Late Quaternary Alluvial Fills in the Platte River Valley using Optically Stimulated Luminescence Dating. University of Nebraska - Lincoln. Masters Thesis
Alluvial fills underlying the Platte River Valley in Nebraska record the geologic history of the Platte River in the late Quaternary. This study investigated the alluvium underlying the valley near the cities of North Platte and Kearney, Nebraska. Data obtained from sediment cores drilled in the alluvial deposits was used to investigate the changes in Platte River dynamics on a glacial – interglacial timescale. Optically Stimulated Luminescence (OSL) dating was used to determine burial ages of recovered sediments and to quantify the thicknesses of the late Pleistocene and Holocene alluvial fills at each study area. Our geochronology depicts considerable differences in age with depth at the two study sites. Results from OSL dating indicate that the Platte River was aggrading during the late Pleistocene and into the early Holocene. Approximately 8 to 10 meters of sediment was deposited near North Platte, and 15 + meters of sediment was deposited near Kearney. Aggradation ended sometime in the early Holocene, most likely between 10 to 11.9 ka, and during the Holocene the Platte re-worked these older alluvial deposits. The total thickness of the Holocene fill ranged from 3 to 8 meters near North Platte, and 10 to 12 meters near Kearney. Locally, the Holocene alluvial fill is entrenched 3 to 4 meters into the underlying late Pleistocene alluvium. This fundamental change in river dynamics is attributed to long-term changes in the ratio of discharge to sediment supply in the basin.
Advisor: Paul R. Hanson