On the origin and age of the Great Sand Dunes, Colorado

Variable wind ripple migration at Great Sand Dunes National Park and Preserve, observed by timelapse imaging

“…Mineralogical surveys of the dune sand lead to conclusions that the majority of the sand is sourced by volcanic rocks of the San Juan Mountains (Hutchinson, 1968;Wiegand, 1977). The age distribution of zircon in the sand suggests that 70% of the dunefield sand originates in the San Juan Mountains and 30% in the Sangre de Cristos (Madole, 2008). The granules and very coarse sand fraction have a granitic composition.…”

The rate of granule ripple movement on Earth and Mars

“…The GSDNPP dune field experiences a bimodal wind regime where the dominant flow is westerly, but with occasional reverse flow from off the Sangre de Cristo Mountains immediately east of the dunes (Merk, 1960;Johnson, 1967;Janke, 2002;Marin et al, 2005;Madole et al, 2008). The sand at GSDNPP has a bimodal particle size distribution, particularly along the southern margin where Medano Creek supplies fresh material (including the granule size fraction) from the nearby mountains (Ahlbrandt, 1979).…”

Luminescence dating of anthropogenic features of the San Luis Valley, Colorado: From stone huts to stone walls

“…The PlioceneePleistocene Alamosa Formation is not officially designated into different members (or beds) but comprises thin bands of gravels, alternating with sands, as well as beds of silty clay and sands (Madole et al, 2008) to a thickness of approximately 1165 ft (355 m). The Alamosa Formation is overlain by Quaternary age dune sands, alluvial fan deposits, stream channels, floodplain alluvium and lake sediments (McCalpin, 1982) that vary in thickness and volume due to interfingering of the deposits.…”

“…The Alamosa Formation is overlain by Quaternary age dune sands, alluvial fan deposits, stream channels, floodplain alluvium and lake sediments (McCalpin, 1982) that vary in thickness and volume due to interfingering of the deposits. The Quaternary stratigraphy is generally thought to be 100e130 ft (30e45 m) with thicknesses increasing toward the Sangre de Cristo Mountains (Madole et al, 2008).…”