Holocene paleoclimatic fluctuations revealed from dune and interdune strata in Wyoming

An approximately 25-m thick sequence of dune and interdune strata exposed at Clear Creek in south-central Wyoming records arid to semi-arid paleoclimatic fluctuations spanning approximately the last 7500 years. The Clear Creek strata are subdivided into six informal chronostratigraphic intervals that bracket climatically-distinctive episodes of dune and interdune sedimentation and are constrained chronologically by 14C dates. The six intervals are: 7545–7035 (I), 7035–6460 (II), 6460–5940 (III), 5940–4540 (IV), 4540–2155 (V), and 2155 years B.P. to Present (VI). At least four episodes of enhanced eolian activity that reflect increased aridity are recorded in the Clear Creek strata. The most arid climatic episodes occurred during the years 7545–7035 B.P. chronostratigraphic interval I; lesser peaks of aridity occurred during 5940–4540 B.P interval IV. The climate during 7035–6460 B.P. interval II and 4540–2155 B.P. interval V was transitional between arid and semi-arid conditions. Climatic conditions during the years 6460–5940 B.P. interval III and 2155 B.P. to Present interval VI have been relatively moist and semi-arid.