SURFICIAL LANDFORM MAP OF EOLIAN ACTIVITY IN SILVER STATE VALLEY AND PARADISE VALLEY PORTIONS OF THE WINNEMUCCA DUNE COMPLEX, HUMBOLDT COUNTY, NEVADA, USA
The Winnemucca Dune Complex (WDC) is the largest dune area (472 km²) in Nevada and the Great Basin Province of western North America. Wind-blown sand deposits extend west to east for 60 km from Desert Valley through Silver State Valley and Paradise Valley and cross the intervening Slumbering Hills and Bloody Run Hills. Mapping of the eolian deposits provides the framework for studies of mineral composition and sources of sand, as well as for future research, including luminescence dating of deposits and landforms and the relationships between climate change and dunefield dynamics. WDC exhibits a range of dune types including areas of active crescentic ridges and barchan-parabolic (barchanbolic) dunes (162 km²) interlaced with stabilized to semi-active sand sheets, parabolic, transverse and linear dunes (310 km²). Measurements from satellite imagery, historical aerial photographs, and topographic maps reveal that between the years 1980 to 2013 the direction and rate of sand dune advancement has fluctuated in space and time. Sand dunes in Silver State Valley and Paradise Valley shown on the surficial landform map have been advancing in the direction of 35-130⁰ at rates varying from 0.2 to 6 myr⁻¹. Laser Granulometer analysis, X-ray Diffractometry, micro-stereoscopic inspection of standard thin sections, and Quartz (mono-polycrystalline)-Feldspar-Rock lithic ternary diagrams indicate that dune sediments physically weather from Very Pale Brown Litharenite medium sand into Pale Brown Feldspathic litharenite fine sand. Quartz-Alkali feldspar-Plagioclase ternary diagrams and X-ray Diffractometry demonstrated that during the processes of dune stabilization and mineralogical maturation of dune sand the relative weight percent of total Quartz will increase 20 to 68% and the percent relative abundance of lithic material will decrease 100 to 45%. Quartz-Alkali feldspar-Plagioclase ternary diagrams and micro-stereoscopic inspection of thin sections also suggests dune sand is supplied by multiple local sources including volcanic, metamorphic, plutonic bedrock and lacustrine deposits.