Le site paléontologique de Mauvières (Indre-et-Loire, France) se situe dans le Sud-Ouest du Bassin parisien, à 55 kilomètres au Nord-Ouest de la ville de Tours. Ce site est une carrière périodiquement exploitée pour ses sables et ses faluns miocènes. En 2000, L. Ginsburg et son équipe signalent une riche faune de vertébrés continentaux de l'Orléanien inférieur (= Burdigalien inférieur-moyen, biozone MN3). Dans cette première étude, les contextes géologique et taphonomique ne sont pas détaillés. En 2020, suite à de nouveaux travaux d'aménagement du site, une étude complémentaire axée sur les données contextuelles manquantes a été réalisée. La série géologique comporte plusieurs ensembles distincts comprenant des marnes du Paléogène, des sables continentaux du Miocène inférieur, des formations carbonatées marines du Miocène inférieur à moyen et des formations superficielles de la fin du Néogène. Leur description faciologique met en évidence une relation directe entre la sédimentation néogène et le canevas structural local polyphasé. En parallèle, de nouvelles données paléontologiques ont été recueillies dans les différents niveaux fossilifères dont: des dents de Chondrichthyes et d'Osteichthyes (Rupélien ou Miocène inférieur) remaniées dans les sables continentaux de l'Orléanien inférieur, vingt-et-un taxons supplémentaires dans l'assemblage de vertébrés de l'Orléanien inférieur (biozone mammalienne européenne du Néogène du MN3) et un assemblage de mammifères terrestres de l'Orléanien moyen-supérieur (MN4 à MN5) remanié dans le conglomérat marin langhien. De plus, les positions biostratigraphiques de vertébrés terrestres du Miocène inférieur ont pu être précisées (Ligerosaurus pouiti (Augé, Bailon & Malfay, 2003)) ou confirmées (Ballusia hareni (Ginsburg, 1989), Ursavus isori Ginsburg & Morales, 1998 et Hemicyon gargan Ginsburg & Morales, 1998). Toutes ces nouvelles données (géologiques, paléontologiques et taphonomiques) confirment que le site paléontologique de Mauvières devrait rentrer dans la liste nationale des sites géologiques patrimoniaux à conserver.

New geological and biostratigraphic data from the vertebrate paleontological site of Mauvières, near Marcilly-sur-Maulne (Early and Middle Miocene; Indre-et-Loire, France).

The paleontological locality of Mauvières (Indre-et-Loire, France) is located in the South-West part of the Paris Basin, 55 kilometers North-West of the city of Tours. This site is a quarry that is periodically exploited for Miocene sands and shelly sands. In 2000, L. Ginsburg and his collaborators identified a rich fauna of continental vertebrates from the early Orleanian (=early-middle Burdigalian, Orleanian European Land Mammal Age [ELMA] MN3 biozone). In this first study, the geological and taphonomic contexts were not precised. In 2020, following new excavation work in the quarry, a new study focusing on the missing contextual data started has been launched. The geological succession includes several distinct formations: Paleogene marls, Lower Miocene continental sands, Lower to Middle Miocene marine carbonates and Upper Neogene superficial deposits. Their faciological analysis highlights a direct relationship between the Neogene sedimentation and local tectonic controls. In parallel, new paleontological data from the different fossiliferous levels were collected, including: Chondrichthyes and Osteichthyes teeth (Rupelian or Early Miocene) reworked in the lower Orleanian continental sands, twenty-one additional taxa in the early Orleanian vertebrate assemblages (MN3) and a terrestrial mammal assemblage from the middle-late Orleanian (=Langhian standard age, biozone MN4 à MN5) reworked in the marine Langhian conglomerate. In addition, the biostratigraphic position of Early Miocene terrestrial vertebrates have been clarified (Ligerosaurus pouiti (Augé, Bailon & Malfay, 2003)) and confirmed (Ballusia hareni (Ginsburg, 1989), Ursavus isori Ginsburg & Morales, 1998 and Hemicyon gargan Ginsburg & Morales, 1998). All these new data (geological, paleontological and taphonomic) confirm that the paleontological site of Mauvières should be included in the national list of French geological heritage sites to be preserved.

The paleontological site of Mauvières is located in the South-West part of the Paris Basin, on the northern border of the Ligerian Basin, 55 kilometers to the North-West of the city of Tours (Fig. 1). It is a small quarry, occasionally exploited by the Poirier family (the owner of the site and of the farm of La Brosse). In 2000, a first paleontological study reported the presence of a rich fauna of continental vertebrates from the Early Miocene (Orleanian European Land Mammal [ELMA], biozone MN3) (Ginsburg et al. 2000). Between 2020 and 2022, new excavations have been performed in these fossiliferous strata.

Our study complements previous works (Ginsburg et al. 2000) by adding detail concerning the geological and taphonomic contexts, as well by actualizing the faunal content. The sedimentary succession is divided into six formations: Eocene-Oligocene lacustrine marl, lower Miocene continental sand, upper Burdigalian-lower Langhian marine limestone, Langhian marine conglomerate, upper Miocene-Pliocene fluvial sand, and Quaternary superficial formations. The faciological analyses show a relation between Cenozoic tectonics (Pyreneo-Alpine orogenic phases) and the development of sedimentary architectural elements. During the Paleogene, the activation of normal faults - with a South Armorican Hercynian heritage direction – generated many small lacustrine basins. A shortening begins during the Early Miocene with a significant folding of the area and subsequent erosion of the “Château-la-Vallière anticline” (Fig. 2) as well as the channeling of a fluvial system in the “Esvres syncline” valley (Gagnaison et al. 2020). At the end of the Burdigalian, the farfield westward progradation of alpine deformation is responsible for tectonic subsidence and the first transgressive pulse to the East of the Ligerian Basin. The marine sediments are channeled into pre-existing structures (Bouchet 2009). This tectonic activity occurres throughout the Middle Miocene (Temey 1996) forming submarine reliefs. At that time, the “Château-la-Vallière anticline” is still a structural high and blocks the marine transgression to the North-East (Fig. 2). This tectonic influence slows down at the end of the Neogene (Bouchet 2009).

The new paleontological and taphonomic data bring out two coherent Miocene vertebrate assemblages. The assemblage 1 consists of 53 taxa, including the 32 taxa of Ginsburg et al. (2000; Tableau 1) found in situ in the Lower Miocene fluvial deposits (*synonymy, **new attribution, ***new for the locality): Tinca sp., ***?Lates sp., ***Amphibia indet., Chelydropsis sp., Ptychogaster sp., Testudo promarginata Reinach, 1900, Trionyx sp., ***Ligerosaurus pouiti (Augé, Bailon & Malfay, 2003), ***Lacertidae indet., Diplocynodon styriacus (Hofmann, 1885), Diplocynodon sp., Tomistoma cf. lusitanica (Vianna & Morales, 1945), ***Aquilavus sp., Rallidae indet., ***Talpidae indet., ***Erinadeidae indet., ***Soricidae indet., Lagopsis cadeoti (Viret, 1930), Prolagus vascociensis (Viret, 1930), Amphilagus ulmensis (Tobien, 1963), ***Ochotonidae indet., Eucricetodon infralactorensis (Viret, 1930), Steneofiber depereti Mayet, 1908, *Megamphicyon carnutense (Antunes & Ginsburg, 1977) (synonym of Amphicyon lathanicus (Ginsburg, Cheneval, Janvier, Pouit & Sen, 2000) in Ginsburg et al. (2000), ***Amphicyon sp., Cynelos helbingi (Dehm, 1950), ***Ballusia hareni (Ginsburg, 1989), ***Phoberocyon aurelianensis (Mayet, 1908), ***Phoberocyon dehmi (Ginsburg, 1955), ***Plithocyon bruneti Ginsburg, 1980, ***Hemicyon gargan Ginsburg & Morales, 1998, ***Ursavus isori Ginsburg & Morales, 1998, ***Plesiogale angustifrons Pomel, 1854, Martes laevidens Dehm, 1950, ***Viverridae indet., ***Broiliana nobilis Dehm, 1950, ***Semigenetta elegans Dehm, 1950, ***Stromeriella franconica Dehm, 1950, *Styriofelis turnauensis Hoernes, 1882 (synonym of Pseudaelurus turnauensis in Ginsburg et al. 2000), ***Paratapirus intermedius (Filhol, 1885), ***Protaceratherium minutum (Cuvier, 1822), Diaceratherium aurelianense (Nouel, 1866), ***Plesiaceratherium sp., Aureliachoerus aurelianensis (Stehlin, 1899), ***Xenohyus venitor Ginsburg, 1980, Brachyodus intermedius Mayet, 1908, Cainotherium lintillae Baudelot & Grouzel, 1974, **Palaeomeryx kaupi Meyer, 1834 (synonym of Oriomeryx willii Ginsburg, 1985 in Ginsburg et al. 2000), **?Heterocemas sp. (synonym of Procervulus praelucidus (Obergfell, 1957) in Ginsburg et al. 2000), Ligeromeryx praestans (Stehlin, 1937), Andegameryx andegaviensis Ginsburg, 1971, ***Andegameryx serum (Ginsburg, 1999), ***Amphimoschus cf. ponteleviensis Bourgeois, 1873.

Similar assemblages are already known in other paleontological localities of the region: Chitenay (Ginsburg et al. 2000), Les Beilleaux (Ginsburg 1989b), La Guimardière (Gagnaison 2013), and Pont-Boutard (Gagnaison 2017). It is a typical fauna of the MN3 biozone (early Orleanian = early-middle Burdigalian). The confirmation of the presence of five taxa (Ligerosaurus pouiti, Ballusia hareni, Hemicyon gargan, Ursavus isori and Paratapirus intermedius) in the Ligerian Basin during the biozone MN3 is to be noted.

The assemblage 2 includes three terrestrial mammal taxa (Prodeinotherium bavaricum Meyer, 1831, Plesiaceratherium sp., and Palaeomeryx kaupi) whose fossils have been found reworked at the base of the Langhian marine conglomerate. This fauna may come from an indeterminate continental interval of the Middle-Late Orleanian (biozone MN4-5; Steininger 1999) or has been transported from a nearby shore. This assemblage is already known in Anjou-Touraine (Ginsburg 2001) but is described here for the first time.

The Mauvières quarry presents a remarkable natural heritage combining geological, paleontological and taphonomic data that are key for the period and regional context. In our opinion, it deserves to be included in the French national inventory of the important geological sites to be preserved (project launched by the Paris Museum).