LATE QUATERNARY CLIMATE CHANGES ON THE CENTRAL HIGH PLAINS RECORDED IN PLAYA-LUNETTE SYSTEMS

Playa-lunette systems (PLS) are common features of semi-arid and arid regions. Playas are relatively small depressional wetlands; lunettes are dunes that form along downwind playa margins and consist of material deflated from playas and regional uplands. Thus, PLS provide a record of local- to meso-scale climate changes. Research focuses on the Central High Plains of western Kansas, where 135 playa-lunette systems have been identified.

Soil cores were collected from playa centers and along the windward side of lunettes using a Giddings coring machine, and were then described in detail and analyzed at the National Lacustrine Core Facility. Bulk density was measured for whole cores using a Geotek gamma density sensor. Cores were then split in half length-wise and magnetic susceptibility and spectral color were measured simultaneously using a Geotek-mounted Bartington MS2E point sensor and Konica-Minolta color spectrophotometer. Stable carbon isotope samples were collected from cores in 1 – 8 cm intervals. Isotope data collected from playas indicate the frequency and duration of water storage, while data collected from the lunettes provide information about regional climate and episodes of landscape disturbance. Age control was provided by AMS radiocarbon dating of buried soils preserved within cores.

Radiocarbon dating indicates that paleoclimatic records within playas precede the Pleistocene-Holocene (P-H) transition, while lunette records precede the Last Glacial Maximum (LGM). Preliminary stable carbon isotope and core geochemistry data indicate that playas were inundated for prolonged periods prior to the P-H transition and then experienced highly variable and decreased inundation from the P-H transition through the Holocene. Multiple well-developed Holocene-aged buried soils are common within playas. Data from lunettes indicate that prior to the LGM the regional climate was similar to today, with warm temperatures and low effective moisture. During and immediately following the LGM, the climate cooled and effective moisture increased; loess deposited on lunettes during this period consists of several meter thick sequences of thin laminations interpreted as A-C profile soils. From the P-H transition through the Holocene, the climate warmed while effective moisture was highly variable.