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Identification of Permian palaeowind direction from wave-dominated lacustrine sediments (Lodève Basin, France)

Authors


Present address: Stéphane Pochat, Laboratoire de Planétologie et Géodynamique, UMR-CNRS 6112, Université de Nantes, 2 rue de la Houssinière, BP 92208, 44322 Nantes cedex 3, France.

Abstract

Lacustrine environments are an excellent indicator of continental palaeoclimate. In particular, the sedimentary record of waves in lakes may be used to constrain atmospheric palaeocirculation. Wave ripples have been identified in a Permian lacustrine basin (the Salagou Formation, 260–250 Ma, Lodève Basin) located in the southern French Massif Central, part of the western European Hercynian mountain chain. Wave ripple patterns are interpreted with regards to hydrodynamics and water palaeodepth. It is shown that, in the case of the Salagou Formation, wave ripple orientations were controlled by the direction of the prevailing palaeowind. The Late Permian wind blew from between north and 20° east of north, possibly over several millions of years and certainly throughout the period of deposition of about 2000 m of strata in the Lodève Basin. Permian lacustrine sedimentation is widespread and well preserved on the Earth's surface and so wave ripple data may help constrain numerical modelling of the Earth's past climates, especially with regards to Permian times outside of desert regions.

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