The Lower Cambrian deposits of the Le Rozel Formation (Normandy, NW France): Insight into a newly described ichnofossil assemblage - INSU - Institut national des sciences de l'Univers Accéder directement au contenu
Article Dans Une Revue (Article De Synthèse) Palaeogeography, Palaeoclimatology, Palaeoecology Année : 2024

The Lower Cambrian deposits of the Le Rozel Formation (Normandy, NW France): Insight into a newly described ichnofossil assemblage

Marc Poujol

Résumé

The rise of morphological complexity and taxonomic diversity of trace fossils during the Cambrian Period has been a prominent focus to track the evolution and diversification of early animals. Here, we present a newly described trace fossil assemblage from the lower Cambrian Le Rozel Formation in Normandy (Northwestern France) composed of the following ichnogenera: Archaeonassa, Bergaueria, Helminthoidichnites, Helminthopsis, Nereites, Psammichnites, and Treptichnus. Trace fossils are exquisitely preserved on top of strata (i.e., epirelief), and are distributed through the entire thickness of the siliciclastic succession of about 200 m. This thick sedi- mentary succession shows sedimentary environments with ripples generated by unidirectional current processes or by oscillatory processes, such as hummocky cross-stratification (HCS) storm facies, tidal facies with flaser stratification, and unidirectional current ripples. In addition, syneresis cracks and microbially induced sedi- mentary structures (MISS) suggest that the Le Rozel Formation was deposited in a shallow marine shelf envi- ronment. New U-Pb dating of detrital zircon grains suggests a late Ediacaran maximum deposition age of 549 ± 3 Ma. This dating is supplemented by the substantial preservation of the three-dimensional burrow systems (Treptichnus pedum) and the large sediment bulldozers (Nereites, Psammichnites). Collectively, our findings suggest that the trace fossils assemblage was deposited during the Terreneuvian Epoch, beneath the first archaeocyaths and the first trilobite-bearing facies from both other lower Cambrian Carteret and Saint-Jean-de-la-Rivi`ere Formation. The ichnofauna described from the Le Rozel Formation complements the worldwide trace fossil re- cord around this critical time of life history.
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insu-04502188 , version 1 (13-03-2024)

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Baptiste Coutret, Didier Néraudeau, Damien Gendry, Alfredo Loi, Marc Poujol. The Lower Cambrian deposits of the Le Rozel Formation (Normandy, NW France): Insight into a newly described ichnofossil assemblage. Palaeogeography, Palaeoclimatology, Palaeoecology, 2024, 641, pp.112126. ⟨10.1016/j.palaeo.2024.112126⟩. ⟨insu-04502188⟩
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