Paleoenvironmental Change and Dune Movement in Response to Prehistoric Droughts in the Nebraska Sand Hills, USA

Séminaire (en salle Pyrénées) du Professeur Paul HANSON Géologue /Quaternaire

The Nebraska Sand Hills are the largest dune field in the western Hemisphere, covering approximately 50,000 km². Historically the dunes have been grass-covered and inactive but in the Holocene they were activated four times, with the last period corresponding to the Medieval Warm Period ~ 800 years ago. Recent research is geared at deciphering the paleoenvironmental conditions that resulted in reduction in grass cover and dune movement, as well as determining the conditions that favored dune re-vegetation following the drought. This work involved determining paleo-wind directions by imagining the dunes with ground-penetrating radar and dating dune sediments with optically-stimulated luminescence dating methods.