Abstract

Playas are small, ephemeral wetlands found throughout semiarid and arid regions around the world. Lunettes are dunes that form downwind of some large playas. Two playa-lunette systems on the High Plains were investigated to reconstruct paleoenvironments during playa-lunette system evolution. Both playa-lunette systems are composed of sediment spanning >40 k.y., with earliest deposits accumulating during at least marine isotope stage (MIS) 3, and possibly starting as early as MIS 5. The Gilman Canyon Formation pedocomplex, dating between 42 and 28 ka, dominates this period and is ubiquitous throughout the playa-lunette systems. Climate during MIS 3 was similar to modern, with warm temperatures, low effective moisture, and playa floors exposed long enough to allow pedogenesis. During MIS 2, climate was relatively cool with higher effective precipitation, and playas were inundated for longer periods. The regionally expressed Brady Soil of the Pleistocene-Holocene transition caps these deposits and dates between 11.8 and 9.4 ka. During the Pleistocene-Holocene transition, climate warmed, yet moisture availability remained relatively high. Several distinct shifts in δ13C identify rapid climate changes associated with the Bølling-Allerød–Younger Dryas chronosequence. Warming continued into the Holocene, though moisture availability was highly variable. Holocene soils are common and date between 8.3 and 3.6 ka. Playa-lunette system stratigraphy represents a continuum of the upland loess sequence, though deposits are altered by playa hydrology. Geomorphic processes alternated between dissolution- and fluvial-eolian–driven processes as climate changed and playas developed. Due to the aggradational environment and sensitivity of these systems, high-resolution records of environmental change throughout their evolution are preserved.

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