Geomorphology of the Samalayuca Dunes Northern Chihuahua, Mexico

The Samalayuca Dunes are one of the largest and least studied sand seas of North America. They are located in northern Chihuahua, Mexico approximately 45 km south of the USA-Mexico border. The Samalayuca Dunes sands are derived from the sandy shoreline deposits of Pleistocene Pluvial Lake Palomas and its successor playas in the Bolson de los Muertos. These sands are transported northeastward across an aeolian corridor and accumulate on the upwind sides of two ranges, the Sierra del Presidio and Sierra de Samalayuca. Unlike other dune fields in the region (e.g. White Sands, NM) which are influenced by a unidirectional wind regime (mainly from the SW), the morphology of the Samalayuca Dunes is influenced by bi-directional effective winds, one from the West-southwest and another from the north. This variation from the regional wind patterns may be due to the local topographic effects of the nearby mountains. The morphology of the active dunes is dominated by straight crested groups of dunes oriented almost perpendicular to each other with general NS and EW crest orientations. These dunes are 4-5 m high with crests spaced at approximately 60 m. They were previously described as an “Akle” pattern, but are in fact a nearly perpendicular interference pattern. These younger dunes are superimposed on the remnants of much larger Northwest trending mega dunes with crests trending Northeast to Southwest and fanning out from South to North within the dune field. These features are spaced at 1 km and are approximately 50 m high. The westernmost ridge is an active set of reversing and star dunes up to 120 m tall increasing in size and complexity from South to North. Northwest trending along axis flow is evident from the eroded topographic lows flanking this active ridge and is a major factor shaping these ridges.