Probable aestivation burrows from the Eocene/Oligocene transition in south-eastern France and their palaeoenvironmental implications

Christian Gaillard (1) , Davide Olivero (1) , Marie Chebance (1)

1 LGL-TPE - Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement

Enigmatic biogenic structures are reported from the Palaeogene of south-eastern France in the Castellane-Blieux area (Alpes de Haute-Provence French Department). They occur at the Eocene/Oligocene transition at the top of the Marnes Bleues Formation, which corresponds to a clearly defined regressive sequence, where thick marls are overlain by lacustrine limestones or sandstones. The marls have abundant shallow marine fauna and the upper part of the Formation corresponds to a rapid transition to non-marine deposits. The studied structures exhibit three main morphologies: vertical shafts, furrows, and tunnels. They can also form dense clusters and cross-cut marginal marine crustacean burrows such as Psilonichnus. By comparison with modern and fossil examples, these trace fossils are interpreted as probably aestivation burrows. The possible trace-makers could be lungfish (in particular for the common vertical burrows) or amphibians (for the furrows and tunnels). The occurrence of these different aestivation burrows defines the border of a basin and probably indicates increasing droughts on the coastal plain. This could reflect the well-known development of arid conditions in south-eastern France at the beginning of the Oligocene.

Mots clés: Aestivation burrows; Lungfish; Amphibian; Palaeoclimatology; Eocene/Oligocene; South-eastern France

Domaines: Sciences de la Terre

Christian Gaillard, Davide Olivero, Marie Chebance. Probable aestivation burrows from the Eocene/Oligocene transition in south-eastern France and their palaeoenvironmental implications. Palaeoworld, 2013, 22 (1-2), pp.52 - 67. ⟨10.1016/j.palwor.2012.12.001⟩. ⟨hal-00832849⟩