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Charophytes from the Upper Jurassic-Lower Cretaceous of the northern Aquitaine Basin (SW France)

Abstract : Upper Jurassic and Lower Cretaceous charophyte assemblages of three sites from the northern part of the Aquitaine Basin (SW France) are studied. It allows to understand paleoecological, paleobiogeographical and biostratigraphic features of this area during this time, where Early Cretaceous deposits are scarce in comparison to others European basins. The presence of Latochara latitruncata (PECK, 1937) MÄDLER, 1955 in Chassiron represents the most southern occurrence of this genus during Upper Jurassic. The presence of Nodosoclavator bradleyi (HARRIS, 1939) GRAMBAST, 1969 is noticed for the first time in the assemblage of Chassiron, and allowed the observation of the structured layer features. The presence of Porocharacean, in association with Clavatoracean and scarce Characean, in Cherves-de-Cognac and Angeac-Charente is relevant concerning the hypothesis of brackish environments. The association of charophytes with abraded specimens of marine taxa (i.e. bryozoans) in Angeac-Charente An2-SA and An1-SA is similar to assemblages found in deltaic-estuarine facies from Iberian basins (Spain). The presence in the same populations of Clavator grovesii var. grovesii (HARRIS, 1939) MARTÍN-CLOSAS, 1996 along with C. grovesii var. discordis (SHAÏKIN, 1976) MARTÍN-CLOSAS, 1996 and intermediate in Cherves-de-Cognac and Angeac-Charente strata is of stratigraphic relevance, since they have been recognised in the Maillardii, Incrassatus and Nurrensis charophytes biozones which represent the Berriasian. In the case of Angeac-Charente, this result differs from the previous study of this site, which gave a Hauterivian- Barremian age to this site, considering the charophyte as reworked material. This result is relevant for the study of the sedimentary history of the northern part of the Aquitaine Basin, while there is no Latest Berriasian to Latest Albian deposits discovered in this area. Grambast, L. 1969. La symétrie de l’utricule chez les Clavatoracées et sa signification phylogénétique. Comptes Rendus de l’Académie des Sciences [Paris], vol. 269, pp. 878-881. Harris, T. M. 1939. British Purbeck Charophyta. Londres: British Museum (N. H.). 119 p. Mädler, K. 1955. Zur Taxinomie der tertiären Charophyten. Geologisches Jahrbuch, vol. 70, pp. 265-328. Martín-Closas, C. 1996. A phylogenetic system of Clavatoraceae (Charophyta). Review of Palaeobotany and Palynology, vol. 94, pp. 259-293. Peck, R. E. 1937. Morrison Charophyta from Wyoming. Journal of Paleontolgy, vol. 11, part 2, pp. 83-90. Shaïkin, I. M. 1976. New data on biostratigraphy of the Jurassic and Cretaceous of the Fore-Dobrogean Trough. Geol. Zh., vol. 36, T2, pp. 77-86.
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Submitted on : Wednesday, October 26, 2016 - 10:26:57 AM
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Roch-Alexandre Benoit, Carles Martin-Closas, Didier Néraudeau. Charophytes from the Upper Jurassic-Lower Cretaceous of the northern Aquitaine Basin (SW France). 25 ème Réunion des sciences de la Terre (RST 2016), Société Géologique de France, Oct 2016, Caen, France. pp.41. ⟨insu-01387790⟩

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