Investigation of a Parna (Silt) Dune Formation in the Panhandle of Oklahoma.

Significant, large dune-like features located in southwestern Beaver County in the Panhandle of Oklahoma offer intrigue and insight into past environmental conditions. Yet, what make these dunes especially intriguing is the inclusion of parna (sand-sized carbonate cemented silt/clay aggregates) sediment unlike the commonly recognized sand dunes of the region (adjacent to playas and rivers).  Eight currently identified mounds range from 10 to 150 ha in area, with relief ranging from 4.5 to 14 m. Deep-core observation was performed on the summit of two mounds, Blue and Gray, for stratigraphical interpretation and chemical and physical analysis.  Resulting 10-13 m cores showed pedologic and stratigraphical features along with physical and chemical data that suggest a period of landscape stability with soil formation followed by a significant period of soil landscape instability for the region. Radiocarbon dating of a well-developed soil sequence below the parna sediment has yielded AMS ¹⁴C ages of 19.0 k RC yrs BP (directly below) and ages of 19.8 k and 20.8 k RC yrs BP (150-200 cm below). Optically stimulated luminescence dating from within the parna sediment will aid in determining actual time of dune formation. Thin-section analysis of individual grains will also aide in determining if the parna (carbonate cemented aggregates) is pedogenic or detrital in origin. Another key distinction between the parna dunes in this study and other river and playa associated dunes in the region is the apparent lack of source material for parna dune formation. Detailed analysis and interpretation of parna dunes of the Panhandle of Oklahoma is yielding significant insight into environmental conditions that dominated landscape formation of the past and may hold clues to possible future climate change.