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Dune fields and loess deposits of the Great Plains of North America contain stratigraphic records of eolian activity that can be used to extend the short observational record of drought. We present a 10,000 yr reconstruction of dune activity and dust production in the central Great Plains region, based on 95 optically stimulated luminescence ages. The integration of data from both eolian sand and loess is an important new aspect of this record. Clusters of ages define episodes of extensive eolian activity, which we interpret as a response to frequent severe drought, at 1.0-0.7 ka and 2.3-4.5 ka (with peaks centered on 2.5 and 3.8 ka); sustained eolian activity occurred from 9.6 to 6.5 ka. Parts of this record may be consistent with hypotheses linking Hobocene drought to sea surface temperature anomalies in the Pacific or Atlantic oceans, or to the El Niño-Southern Oscillation phenomenon, but the record as a whole is difficult to reconcile with any of these hypotheses. [ABSTRACT FROM AUTHOR]

Thick Holocene Bignell Loess sections provide new evidence for the timing of early to middle Holocene aridity in the central Great Plains. The immediate source of loess in these sections was dune fields just upwind, based on thickness trends and grain size data. Thus, periods of rapid loess accumulation indicate episodes of extensive dune activity under drier-than-present climate. In typical Bignell Loess sections, a thick zone of coarse-textured loess with minimal pedogenic alteration is interpreted as a record of the most rapid, sustained Holocene loess accumulation. Optical ages indicate that loess in this zone was deposited beginning about 9000–10000 years ago at five study sites. Accumulation ended shortly after 6500 years ago at three sites, but possibly earlier at the other two. In two well-dated sections, the average rate of loess accumulation between 9000–10 000 and 6500 years ago was about 1.6–3.5 times greater than in the late Holocene. Thus, we infer that the most extensive, sustained Holocene dune field activity, reflecting sustained aridity, occurred from around 9000–10 000 years ago to just after 6500 years ago. Comparison of the Bignell Loess record with other proxy data from the Great Plains indicates general agreement on an early–middle Holocene dry period, but also provides new evidence for spatial variation of early to middle Holocene climatic change, with possible time transgression, both from west to east and from north to south. [ABSTRACT FROM AUTHOR]