Pattern formation and preservation in aeolian systems
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Aeolian sediment transport forms natural patterns common on Earth and other planetary bodies. The self-organization of sand in transport results in dune fields with dune morphologies determined by wind regime. Patterning in dune fields is known to arise from the autogenic process of dune interactions, but the evolution of dune patterns over time remains poorly constrained. In this work dune fields were parameterized in terms of dune interactions to quantify dune-field pattern stability. Interactions are fundamental to dune-field development, but studies of interactions have focused on their surface expression, and how interactions are expressed in the ancient record has yet to be documented. This problem is addressed with five examples of interaction-generated stratigraphy identified in well-known Jurassic aeolian sandstones using criteria based on recent near-surface interpretations of interaction stratigraphy form White Sands Dune Field, New Mexico. Interactions control the autogenic development of dune fields, but allogenic factors including basin subsidence, water table rise, and sediment supply largely control the accumulation and preservation of aeolian strata. In a case study of a section of the Jurassic Entrada Sandstone, this work addresses the interplay between allogenic and autogenic controls on what is actually preserved in the rock record, and demonstrates how long stretches of time can be collapsed into surfaces between geologic units that represent relatively short-lived events. The competition between allogenic and autogenic influences on aeolian pattern formation is not unique to Earth, and Mars also hosts patterned landscapes thought to be generated by aeolian sediment transport. Such landscapes include intra-crater layered mounds such as Aeolis Mons in Gale crater, the landing site of the Mars Science Laboratory rover. Competing hypotheses about whether these mounds formed by aeolian erosion of crater-filling deposits, or by aeolian deposition were addressed with wind tunnel and large eddy simulation experiments. The results are compatible with an erosional origin of the mounds. Additional analyses of wind-formed landscapes within and around Gale crater further supported the wind-erosion hypothesis of the central mound.