ANALYSIS OF PAIRED LINEAR DUNE STRATIGRAPHY IN THE NEBRASKA SAND HILLS UTILIZING GROUND PENETRATING RADAR

The Nebraska Sandhills were last active approximately 700-1000 years ago when the last major period of drought occurred. Since the formation of the dunes during the latest drought are still obscure in large part because of our limited studies on the internal stratigraphy. Previous studies have suggested bimodal wind regimes formed the paired linear dunes. The bimodal wind theory conveys that two winds oscillate seasonally in two opposite directions creating parallel ridges. With rapid climate change in effect, more evaporation leaves less water for the vegetation which in turn reactivates the dunes. This would cause a destructive outcome to agriculture and animal habitats within the Nebraska sandhills if ill prepared. The goal of this research is to increase our knowledge about the internal layering and stratigraphy of the paired linear dunes in hope for a better understanding on how they formed. The research methodology used was ground penetrating radar (GPR) and topographical data. The GPR antenna frequency was used at 100 MHz and were separated 1 meter apart and the GPR imaging was collected with a Systems and Software PulseEKKO Pro®. Results show several lines of the northern and southern internal stratigraphy of north limbs dipping north while south limbs are dipping south which is similar to Bristow’s GPR profiles of linear sand dunes in the Namib Sand Sea that show strong bimodal dips in stratigraphy with similar north limbs having northern dips and southern limbs having southern dips. Although one line of data is not congruent to the bimodal theory because the northern and southern limbs do not reveal the internal dips. The reason for no dips could have many reasons from the dunes being modified by old blowout features or sand beds being graded vertically. More data will be needed in future to be able to identify why there are and are not any dips in these specific areas.