Complexities in eolian and marine interactions: Processes and eustatic controls on erg development

Abstract

The interplay between eolian and marine realms includes process interactions, cycles of transgression and regression, and possible inland effects of marine-coastal events. Process interactions are geologically common and most obvious where eolian and marine environments are adjacent. These interactions include sediment exchange between the two environments, the supply of marine ions to the erg for surface and near-surface cementation, and the control (directly or indirectly) of marine events on the sediment budget of an erg. Regression accompanied by erg progradation over marine deposits occurs with both onshore and offshore winds. Marine transgression of ergs varies from producing a planar, marine-scoured surface, to a planar deflation surface that precedes the transgression, to varying degrees of paleotopographic dune preservation, and a variety of transitional facies. The extent of paleotopographic dune preservation is largely a function of the energy level of the transgressing marine realm, the rate of the transgression, and potential for early dune cementation. General correlations between ergs and global eustatic sea level and coastal onlap curves occur for coastal and near-coastal cyclic erg sequences. Eustatic control of inland ergs exists to the extent that sea level controls, in large measure, the extent of the basin exposed to subaerial processes (i.e., regional base level), and, probably to a lesser extent, the sediment supply to the erg. Direct correlation of inland erg events to coastal onlap curves is dubious at present, but an indirect relationship may exist.