Preservation of Human Tracks in Arid Environments

Abstract

Observations were made on the preservation of modern human tracks in a salina near Cuatro Cienegas, Coahuila, Mexico. Track making potential is relatively high in such arid, ephemeral lake basin settings where salinas or alkali flats typically develop. However, because of the instability of evaporite minerals, long-term preservation potential of such tracks is compromised. The substrate in the study area is composed of a mixture of sand and a high percentage of sulfate crystals (gypsum, bloedite, epsomite). At the sediment-air interface, there is a thin white, crystalline sulfate crust that overlies the original track-bearing surface and prevents water loss. The size and surface growth of sulfate crystals in the crust is affected by the differential pressure caused by the track maker. Such tracks represent a good example of a biogenic process (track formation) affecting a physical sedimentological process.

Keywords:

• Arid
• environments
• human tracks
• Cuatro Ciénegas
• Coahuila
• Mexico

ACKNOWLEDGEMENTS

Travel to Cuatro Cienegas was supported by the co-operative effort of the CU Denver Dinosaur Tracks Museum and the Museo Regional de La Laguna (Museo del Desierto) Coahuila. We also thank Martha Aguillon for helps with access to literature. We particularly thank Arturo Gonzalez, Director of the Museo del Desierto for his initiative in excavating a trench. We also thank Spencer Lucas New Mexico Museum of Natural History and Science, and Karen Houck University of Colorado at Denver for their helpful reviews of this paper.