Quantitative analysis of aeolian stratigraphic architectures preserved in different tectonic settings

Abstract

Despite a well-documented record of preserved sedimentary architectures of aeolian successions from a variety of different sedimentary basin types, relationships between tectonic setting and aeolian accumulation and preservation remain poorly constrained and largely unquantified. This study uses a database-informed approach to quantitatively document the variability in preserved sedimentary architecture of 56 globally distributed aeolian systems, and to relate these variations to differences in their basin settings. Three different tectonic settings are considered: intracratonic, foreland, and rift basins. Key finding are as follows. (1) Intracratonic basins are characterized by slow accommodation generation. They favour the accumulation and preservation of relatively thin aeolian genetic units; likely generated by dunes and interdunes that climbed at low angles, resulting in the accumulation and preservation of relatively thin dune and interdune elements. Depressed water tables – indicated by abundant dry interdune elements – left accumulated dune successions exposed above the erosional baseline, making them vulnerable to post-depositional reworking. This likely resulted in sporadic episodes of aeolian dune accumulation, between long episodes of sediment bypass or deflation, under conditions of low rates of net accommodation generation. (2) Rapid accommodation generation in the depocentres of foreland basins favours the preservation of thick dune-set and interdune elements, enabled by a rapid rate of rise of the accumulation surface that allowed bedform climb at relatively high angles. High rates of sediment supply associated with erosion of adjacent orogenic belts allowed the construction of large dunes. Elevated water tables – indicated by abundant wet interdune elements – may have allowed aeolian accumulations to be placed beneath the baseline of erosion shortly after deposition, thereby protecting them from potential post-depositional deflation. (3) Despite rift basins experiencing the highest rates of accommodation generation, their fills tend to be associated with the preservation of relatively thin dune and sandsheet elements. Elevated water tables, associated with rapid accommodation generation, create damp substrates and consequently restrict the availability of dry sand for dune construction. In the examples considered here, rapid accommodation generation outpaces sediment supply, favouring the construction and rapid migration of small dunes that consequently accumulate thin dune sets. Aeolian dunes in rift basins are also commonly reworked by fluvial and alluvial processes, in some cases likely related to orographic precipitation, associated with rift shoulder topography. Results of this analysis can be applied to improve predictions of the architecture of ancient aeolian successions at the basin scale, both in outcrop and in subsurface successions.