The response of the water table in coastal aeolian systems to changes in sea level

Abstract

Abstract The water table in some aeolian systems is a control on the type and rate of accumulation, and defines the depth to which deflation will occur in the formation of regional bounding surfaces. At the basinal scale over time, the elevation of the water table may be a function of climate, tectonism, and/or sea level. The latter invokes the hypothesis that the water table underlying an arid coastal sand sea without significant recharge adjusts to changes in sea level for tens to hundreds of kilometers inland. The simplest physical and mathematical model for this hypothesis states that the water table re-equilibrates as an inland-directed diffusion wave to each increment of change in sea level. Model simulations incorporating a range of hydraulic parameters and periods of sea-level cycles demonstrate scenarios ranging from one in which the continental water table is essentially unaffected by sea level, to one in which the water table exactly mimics the sea-level curve. Using a realistic set of mid-range parameters, the model produces a suite of water-table curves that evolve from the coast to inland because of a diminishing amplitude for all cycles, a loss of more minor cycles, and a time lag. The resulting stratigraphic record, from the coast to more inland positions, shows a diminishing number of recorded events, a thinning of the section, removal of previously preserved strata during lowstands, and the appearance of new stratigraphic units far inland. Most of these characteristics are compatible with those of the Jurassic Page Sandstone in regional cross-sections in northern Arizona and southern Utah, but are difficult to distinguish from the effects of tectonism.