Evidence of Regional Holocene Climate Change Based from Four Different Diatom Records Across the Nebraska Sand Hills

Jens Schmieder and Sherilyn Fritz
Geosciences, University of Nebraska-Lincoln, Lincoln, NE

The Nebraska Sand Hills consist of roughly 58,000 km² of dunes stretching 425 km across the state. With dunes as high as 130 m and as long as 35 km, the Sand Hills represent the largest dune formation in the Western Hemisphere. The sand is currently held in place and stabilized by a thin cover of vegetation. However, previous studies have shown that the dunes experienced significant periods of dune reactivation during the Holocene (e.g. Nicholson & Swinehart, 2005; Miao et al., 2006).

Here I present an 8,000-year multi-proxy reconstruction of Holocene regional moisture fluctuations and dune activity based on 4 different lake records scattered across the central and eastern parts of the Sand Hills. Optically stimulated luminescence (OSL) ages from adjacent dune sands aid in further constraining the timing of major sand mobility.

Diatom analyses, as well as weight percent sand and carbon to nitrogen ratios from two nearby lakes (East Twin and West Twin) suggest a high climate variability during the last 4,200 cal. yr BP with generally wet conditions for the central part of the Sand Hills. This finding is further supported by diatom data and pollen analysis from Beaver Lake. Both, the diatom record as well as bulk sediment chemistry data indicate a major climatic shift occurring at around this time of the Mid-Holocene switching from drier to generally wetter conditions.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas