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

Abstract

International audienceEnigmatic 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

Ambergris cololites of Pleistocene sperm whales from central Italy and description of the new ichnogenus and ichnospecies Ambergrisichnus alleronae

“…The converging striae of A. alleronae are typical and never found in other fossil marine or freshwater cololites, although spiral bromalites are known and have been associated with primitive fish, for example freshwater sharks Orthacanthus (Shelton, 2013). Striae are reported in other trace fossils such as the aestivation burrows of lungfish from the Eocene to Oligocene of southeastern France (Gaillard et al, 2013). Nevertheless, these striae are short and parallel, of the same width and regularly spaced, while striae of A. alleronae are convergent towards the apex and of irregular length (Figure 3.3).…”

“…The Allerona specimens differ from other similar large structures induced by diagenetic processes, because of the external shape and internal structures both of complex and simpler cololites. Although externally it may resemble vertebrate and invertebrate burrows (Gaillard et al, 2013, Figures 6 and 8), or shafts of Tisoa siphonalis from the Early Jurassic (Pliensbachian) (van de Schootbrugge et al, 2010), A. alleronae differs significantly in important aspects. The internal arrangement of A. alleronae is helicoidal or concentric around a central nucleus (usually a dark grey clay core, Figure 3.6); this feature is lacking in most invertebrate burrows, as well as in the simple or columnar, abiotic carbonate concretion of Tisoa siphonalis.…”

A revised listing of fossil mammals from the Haasgat cave system ex situ deposits (HGD), South Africa

“…The Allerona specimens differ from other similar large structures induced by diagenetic processes, because of the external shape and internal structures both of complex and simpler cololites. Although externally it may resemble vertebrate and invertebrate burrows (Gaillard et al, 2013, Figures 6 and 8), or shafts of Tisoa siphonalis from the Early Jurassic (Pliensbachian) (van de Schootbrugge et al, 2010), A. alleronae differs significantly in important aspects. The internal arrangement of A. alleronae is helicoidal or concentric around a central nucleus (usually a dark grey clay core, Figure 3.6); this feature is lacking in most invertebrate burrows, as well as in the simple or columnar, abiotic carbonate concretion of Tisoa siphonalis.…”

Hettangian tetrapod burrows from the continental Steierdorf Formation at Anina, western Romania

“…Among fishes, lungfish bur row deeply to avoid des ic ca tion dur ing dry pe ri ods, pro ducing ver ti cal bur rows about 10 cm in di am e ter (Romer and Olson, 1954) and with en larged basal cham bers (Johnels and Svensson, 1954), a mor phol ogy strik ingly dif fer ent from those described herein. Fur ther more, fos sil ex am ples of lungfish burrows are com monly re ported to be tied to lac us trine to re gressive mar ginal ma rine depositional en vi ron ments (e.g., Surlyk et al, 2008;Gaillard et al, 2013), un like the sed i men tary set ting re ported here for the Anina bur rows.…”