| Summary: | International audience Stratigraphic correlations are often considered as impossible in thick accumulations of fluvial depositswhere arid conditions are often underestimated. In fact, most of the time, aeolian deposits in arid environmentsdominated by ephemeral alluvial fan or braided river are poorly preserved and particular attention should bepaid to any sedimentological marker of aridity, such as wind-worn stones (ventifacts), sand-drift surfaces andaeolian sheets. Only detailed study of alluvial plain facies and ephemeral streams provide indications ofclimatic conditions within the sedimentary basin, whereas fluvial system only reflects climatic conditions ofthe upstream erosional catchment. Moreover, in such context the deposition of conglomerate of alluvial fansystem could correspond to a peak of aridity without an increase in tectonic activity.Conversely, the sedimentary record of aeolian deposits, often considered as preserved in arid desertbasin, can occur under semi-arid and even humid climates, and from near the Equator to the Arctic Circle.Ventifacts are climate-sensitive sedimentary features that provide evidence for long periods without anyvegetation in terrestrial environment under hot or cold climate. Therefore, they can allow recognizing desertconditions, even where no aeolian dune deposits are preserved. Moreover, the well-preserved widespreadpaleoregs seem to mark major stratigraphic discontinuity above a geomorphic surface remained a long timewithout vegetation as a result of a very dry climate, hot or cold.Detailed sedimentological study and the recognition of bounding surfaces of regional extend (sanddriftsurface, palaeosols, flooding surface.) allow for the identification of stratigraphic cycles, permit correlationwithin time and space and precise the climate conditions. Moreover, these detailed sedimentological andstratigraphic analyses highlight the influence of climate or tectonic change on sediment facies and depositionalenvironments.Applied to various Permian and Triassic ...
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