Late Quaternary evolution of a lunette in the central Great Plains: Wilson Ridge, Kansas

Lunettes are aeolian dunes that form on the downwind margins of playas. Although common on the Southern High Plains and elsewhere, they are poorly understood. Geomorphic and stratigraphic investigations at Wilson Ridge in the central Great Plains of Kansas reveal a complex late Quaternary history, with episodic deflation of the playa and sedimentation on the lake's southern margin. Ten stratigraphic units are present, five of late Wisconsinan age and five related to Holocene events. Woodfordian deposits consist of silt and fine sand containing crushed gastropods. Late Wisconsinan sedimentation was interrupted when a well-developed soil formed around 17,000 yr B.P., a period of high water in the playa. Pleistocene and Holocene deposits are separated by another well-developed paleosol on the south side of the dune and by an unconformity on the north slope. Although Holocene sediments are texturally similar to older deposits, they lack gastropods, suggesting arid conditions in the playa. Early Holocene instability probably was confined to the north slope, because prevailing winds remained northwesterly. Holocene sedimentation has been episodic on the dune, with pedogenesis occurring around 5700 yr B.P. in the playa, two periods of stability are indicated by paleosols that dated to around 7500 and 3000 yr B.P. To the south of the dune, stability prevailed throughout the early Holocene, resulting in an extremely well developed soil. Over the past 5000 years, prevailing winds have shifted to the southwest.