Aeolian Dune Height Controls on the Internal Architecture of Cross Sets: White Sands Dune Field, New Mexico
Abstract
The internal architecture of an aeolian cross set is defined by the arrangement and geometry of the deposits defining its cross strata: grainflow deposits, grainfall laminae, and wind ripple laminae. These deposits are a record of the sedimentation on a dune's lee slope that drove the dune's migration. Most often, the thickness of a cross set is used to reconstruct an ancient dune field from the rock record, but cross-set thickness can be controlled by several processes. We hypothesize that relationships between the internal architecture of an aeolian cross set and its formative dune would be useful in further constraining ancient dune-field reconstructions from preserved cross sets. Here, we present field results from White Sands Dune Field, New Mexico, USA, in order to understand how dune height controls the arrangement, abundance, and geometry of the cross strata contained within cross sets. At White Sands, the internal cross strata of dunes are commonly exposed across their erosional stoss slopes. Grainflow thicknesses and widths were measured on several of these stoss exposures at different elevations for each of eight crescentic dunes. Measurements were limited to cross strata aligned normal to the mean migration direction of White Sands dunes. Dune heights ranged from 1 m to 11 m. Grainflow thickness averaged between 1 cm to 4 cm, with no overall increasing trend between dune height and grainflow thickness. Smaller dunes were characterized by simple, lens-shaped grainflows separated by planar grainfall laminae. The tallest dune (11 m) produced many thick grainflow packages of 10 cm to 30 cm in which individual grainflows were indistinguishable and amalgamated. Additionally, larger dunes typically produced wind ripple reworked bounding surfaces and stacked grainflows near the top of the dune and amalgamated contacts at the bottommost section where multiple grainflows merge in order to reach the base of a longer slipface. Thus, the amalgamation of bounding surfaces is characteristic of larger dunes due to the lack of grainfall separating the grainflows.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMEP23C2268Z
- Keywords:
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- 3322 Land/atmosphere interactions;
- ATMOSPHERIC PROCESSES;
- 1625 Geomorphology and weathering;
- GLOBAL CHANGE;
- 5210 Planetary atmospheres;
- clouds;
- and hazes;
- PLANETARY SCIENCES: ASTROBIOLOGY;
- 5415 Erosion and weathering;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS