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CENOZOIC
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STRATIGRAPHY
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Oiselier
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The sections of POR-BBC, POR-OIS, POR-OIC, POR-OIS, POR-ETA and POR-RAV are characterized by conglomeratic deposits belonging to the “Conglomérats de Porrentruy” Formation from Schneider (1960). This latter is included by Picot (2002) in the lithostratigraphic group “Gompholithes & Conglomérats”.
The age of these conglomeratic deposits is difficult to establish because of the lack of biostratigraphic indicators. However, Picot (2002) and Picot et al. (2005) propose the base of Rupelian by correlation with other outcrops in Develier (Jura, Switzerland).
Becker (2003) confirms this datation on the base of rhinocerotid remains (Ronzotherium filholi) discovered in a former site of “Oiselier” (material housed in the Basel Museum).
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Beuchille
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The deposits of “Beuchille” belong to the “Molasse alsacienne” Formation. This latter was revised by Picot (2002) and included in the “Molasse alsacienne” lithostratigraphic group (Fig.1).
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<<--Fig.1 – PDF 96 KB |
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The presence of the anthracotherid Anthracotherium allows a first biostratigraphic approach (Becker et al. 2004). The first known species of this genus appears in Europe only after the “Grande Coupure” (MP21; Brunet & Vianey-Liaud 1987). In other words, Anthracotherium from “Beuchille” represents a typical post-Eocene genus.
The small primitive ruminant Iberomeryx minor is known only in two French localities which have a defined biostratigraphy, Lovagny (Savoie) and Itardies (Quercy), and it seems to be exclusive to the Mammal biozone MP23 (Brunet & Vianey-Liaud 1987; Rémy et al. 1987).
The primitive Theridomyidae Blainvillimys avus also allows a biostratigraphic approach. Vianey-Liaud (1998) dated this species from the Mammal Zone MP24 (Heimersheim).
Thus the “Molasse alsacienne” of “Beuchille” presents two different ages at MP23 and MP24, which is in concordance with the litho- and biostratigraphic revision of the “Molasse alsacienne” Group by Picot (2002).
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Beuchille Est
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The marine deposits of “Beuchille Est” belong to the “Septarienton” lithostratigraphic group of Picot (2002). This later proposed a biostratigraphic interval from MP21 to MP25 for this group (Fig.2). This stratigraphical unit corresponds to the southern extension of Rhinish Sea in the Swiss Jura. |
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Fig.2: Biostratigraphy and lithostratigraphy of Rhinish UMM (modified from Picot, 2002).
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The attempts to obtain dating with calcareous nannofossils show systematically too old Eocene ages, probably because of reworking. Actually, the calcareous nannofossils biostratigraphic interpretations are often derived from disparitions and show older ages than other fossil groups datation methods. New biostratigraphical data, based on dinoflagellate cysts, allow for dating this global Rupelian transgression in the Jura Mountains from the interval top NP22–base NP23. The regression occurs during the top part of NP23.
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Poillat
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As in the “Beuchille” locality, the presence of the small primitive ruminant Iberomeryx minor suggest a dating in the Mammal Biozone MP23.
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Solé
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The association Megacricetodon and Melissiodon is typical for the Mammal Biozone MN4 (Kälin 1997, 1999; Mödden 1999).
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