The role of dune morphogenetic history in the interpretation of linear dune luminescence chronologies: a review of linear dune dynamics

Contemporary knowledge on aeolian dune dynamics is reviewed to enable an appraisal of evolutionary mechanisms involved in linear dune stratigraphic sequence development. The degrees of depositional record retention in the dune structures are evaluated and the corollary applied to methods used in the interpretation of luminescence dating chronologies acquired from such sedimentary accumulations. It is demonstrated that morphogenetic aspects of dune development are an imperative element to invoke when carrying out palaeoenvironmental reconstruction using luminescence dating ages acquired from linear dune sequences. To help depict the role of dune morphogenesis, hypothetical scenarios that simulate the preservation of stratigraphical records in linear dune sequences are presented using two different theories that have been advanced to explain origin and development of linear dunes: bidirectional wind regime and helical roll vortices. It is illustrated that linear dune systems that evolve under bidirectional wind influence are intrinsically inefficient at preserving complete records of their depositional history and this places major constraints for palaeoenvironmental reconstruction using luminescence chronologies. When linear dunes develop under the influence of helical roll vortices, on the other hand, it is shown that the degree of sequence preservation would be higher. The possibility of lateral migration of linear dune structures is indicated to be an additional limitation that may encumber the interpretation of luminescence ages.