| Marnes Rouges Inférieures Formation | |
|---|---|
| Stratigraphic range: Late Campanian - Maastrichtian ~ | |
The Marnes rouges inférieures Formation at Campagne-sur-Aude, left bank of the Aude River. | |
| Type | Geological formation |
| Sub-units | Marnes rouges de Campagne Member, Grès des Estous Member, Marnes rouges de la Maurine Member, Fleuri Gonglomerate Member |
| Underlies | Calcaires de Vignevieille Formation |
| Overlies | Grès d'Alet Formation |
| Thickness | 130 m (430 ft) |
| Lithology | |
| Primary | Mudstone |
| Other | Sandstone, conglomerates, siltstones |
| Location | |
| Coordinates | 42°91′N 2°20′E |
| Region | Occitania |
| Country | |
| Type section | |
| Named for | French: "Lower Red Marls" |
The Marnes rouges inférieures Formation (lower red marls Formation) is a geological formation located in the south of France and dating from the upper Cretaceous (upper Campanian to lower Maastrichtian) between 72.5 and 70 million years ago approximately.
This formation consists of marls, sandstones, conglomerates, and siltstones, corresponding to fluvial deposits (river channels and floodplains) deposited in what was then the Ibero-Armorican island, a landmass made up of large part of France and Iberian Peninsula.
The Marnes rouges inférieures Formation contains abundant remains of terrestrial vertebrates, mainly titanosaurians sauropod dinosaurs.
The Marnes rouges inférieures Formation is located in the department of Aude and Ariège in Occitania region. The formation crops out mainly in the Rennes-les-Bains syncline, located in the Upper Aude Valley, whose rocks can be seen particularly near the villages of Campagne-sur-Aude, Espéraza, Fa, Granès, Rennes-le-Château, Brenac, Saint-Ferriol.
The Marnes rouges inférieures Formation conformably overlies the Grès d'Alet Formation (Alet Sandtones Formation) and conformably underlies the Calcaires de Vignevieille Formation (Vignevieille limestones Formation).
The Marnes rouges inférieures Formation is also present in Ariège department in the Benaix, Dreuilhe, Péreille, and Le Mas d'Azil anticlines, where it lies unconformably on several Upper Cretaceous formations Coniacian to late Campanian in age.
The Marnes rouges inférieures Formation reaches about 130 metres (430 ft) in thickness and is subdivided into four members including from bottom to top:
In 1985, Bilotte reported in the marnes rouges de Campagne Member the presence of a palynological association suggesting a late Campanian age, and consequently attributed a Maastrichtian age to the three overlying members..
In 2016, a magnetostratigraphic study revealed that the upper part of the Marnes rouges de Campagne, the Grès des Estous, and the first twenty meters of the Marnes rouges de la Maurine belong to the normal chron C32n corresponding to the beginning of the lower Maastrichtian. More specifically, the vertebrate localities in the basal part of the Marnes rouges de la Maurine are located at the top of subchron C32n.1n, corresponding to an age of 71.5 million years. The rest of the Marnes de la Maurine, as well as the Poudingue Fleuri, are located in the reverse chron C31r, corresponding to the upper part of the lower Maastrichtian. Thus, the age of the Poudingue Fleuri, at the top of the Marnes rouges inférieures Formation, is estimated to be between 70 and 69.5 million years old. Above, the upper Maastrichtian could be limited to a few meters in the Vignevieille limestones or is totally absent. Regarding the lower part of the Marnes rouges inférieures Formation, the Campanian-Maastrichtian boundary (set at 72.2 million years) would be located below the section sampled by Fondevila et al., probably in the middle or lower part of the Marnes rouges de Campagne Member, or even lower in the Grès d'Alet Formation. These results indicate that in the Upper Aude Valley, the Marnes rouges inférieures Formation dates almost exclusively from the lower Maastrichtian, with only the lower half of the Marnes rouges de Campagne Member possibly dating from the top of the Campanian.
In the Plantaurel massif in Ariège, the Marnes rouges inférieures Formation becomes younger due to the progressive and diachronic migration of continental facies towards the west in a context of marine regression. In this region, the Marnes rouges inférieures Formation grade laterally into the Marnes d'Auzas Formation, which has a lagoonal and continental origin and dates back to the late Maastrichtian.

The Bellevue quarry in Campagne-sur-Aude is the main vertebrate site of the Marnes rouges inférieures Formation and is one of the richest Upper Cretaceous sites in Europe. It is located at the base of the Marnes rouges de la Maurine Member just a few meters above the Grès des Estous Member, and corresponds to a former river meander where many disarticulated bones and entire corpses have accumulated. Vertebrate remains are concentrated in conglomerate and siltstone levels 4 to 6 m (13.1 to 19.7 ft) thick intercalated in the mudstones. The different fossiliferous levels (six recorded in 1999, then seven in 2002) are all located at the top of the conglomeratic levels. The variable state of preservation of the bones (from very eroded to well preserved), most often disarticulated, as well as the faunal composition, which varies from one level to another, testify to more or less significant transport and suggest considerable taphonomic biases in the composition of the fauna, which cannot be considered representative of an ecosystem.
The Bellevue quarry has yielded several thousand fossils including at least 1400 dinosaur bones belonging mainly to titanosaurian sauropod. This locality was long considered a monotaxic titanosaur bonebed represented by Ampelosaurus atacis. Since the 2010s, however, several studies have suggested the presence of a multispecific titanosaur assemblage at the Bellevue site. En 2012, Bernat Vila et al. distinguished three morphotypes based on femur morphology and tentatively assigned one of them to the genus Lirainosaurus. A generic attribution contested by Veronica Díez Díaz et al. in 2013. In 2021, Veronica Díez Díaz et al. also admitted the existence of a second titanosaur at Bellevue but found more similarities with the genus Garrigatitan from the Upper Campanian of southeastern France. In 2023 and 2024, Bernat Vila et al. presented at several scientific conferences the preliminary results of an in-depth study of the titanosaur remains of Bellevue confirming the presence of several titanosaur species (possibly up to four) at this site. The results of this study imply a future modification of the diagnosis of Ampelosaurus and the material attributed to it, and the description of at least one new species.
The Marnes Rouges Inférieures Formation contains many fossils of continental vertebrates. They are especially abundant at the base of the Marnes rouges de la Maurine Member but are also present in the Grès des Estous Member. These vertebrate remains are represented by teeth and bones as well as more or less complete eggs and shell fragments. Some invertebrates (freshwater gastropods and bivalves) and plant remains are also known. The macroflora, found particularly in Bellevue, is represented by palm and cycad leaves, as well as fragments of angiosperm wood from trees 10 to 15 m high.
Color key
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Notes
Uncertain or tentative taxa are in small text
crossed out taxa are discredited.
| Fish of the Marnes Rouges Inférieures Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Fossils | Notes | Images |
| Axelrodichthys | A. megadromos | Bellevue | Marnes rouges de la Maurine Member (lower part) | MDE-C3-02-57, a small fragment of a tooth plate | A freshwater mawsoniid coelacanth. | |
| Lepisosteus | Indeterminate | Bellevue | Marnes rouges de la Maurine Member (lower part) | Ganoid scales and teeth. | A gar | |
| Crocodyliformes of the Marnes Rouges Inférieures Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Fossils | Notes | Images |
| Allodaposuchidae indet. | Undescribed form | Bellevue | Marnes rouges de la Maurine Member (lower part) | A rear skull (specimen MDE C3-276) published in 2017 was assigned to an undetermined allodaposuchid. Other unpublished allodaposuchid remains are represented by a complete skull (MDE-C3-1402), vertebrae, limb and pelvic bones, and isolated teeth. | An allodaposuchid eusuchian. The complete skull, although not yet described, was initially attributed to Allodaposuchus precedens, a species later found to be endemic to Eastern Europe. The complete skull from Bellevue shows more similarities with the Spanish taxa Musturzabalsuchus buffetauti and Allodaposuchus subjuniperus with which it shares a marked lateral festooned profile of the snout. | |
| Turtles of the Marnes Rouges Inférieures Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Fossils | Notes | Images |
| Compsemydidae indet. | New taxon | Bellevue | Marnes rouges de la Maurine Member (lower part) | One skull and an isolated costal plate | An unpublished taxon close to Calissounemys matheroni from the Late Campanian of Provence. | |
| Foxemys | F. mechinorum | Bellevue | Marnes de la Maurine Member (lower part) | MDE-C3-774, a skull and shell fragments | A foxemydine bothremydin | |
| Pterosauria of the Marnes Rouges Inférieures Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Fossils | Notes | Images |
| Pterosauria indet. | Indeterminate | Bellevue | Marnes rouges de la Maurine Member (lower part) | Several hollow bone fragments and possibly a last phalanx of the fourth digit. | Possibly an azhdarchid. The material is too fragmentary, and the identification of the recovered elements (a rib or a terminal phalanx of the wing finger) is too uncertain to allow for a clear and definitive assignment to this clade. | |
| Dinosaurs of the Marnes Rouges Inférieures Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Fossils | Notes | Images |
| Ampelosaurus | A. atacis | Bellevue | Marnes rouges de la Maurine Member (lower part) | A braincase; a right dentary; one tooth; cervical, dorsal, and caudal vertebrae; numerous limbs bones, scapulocoracoids, pelvis bones; and four osteoderms. | A lirainosaurine lithostrotian. The fossils attributed to Ampelosaurus are currently being restudied because some of this material belongs to at least one new titanosaur species. An unpublished partial skeleton (nicknamed Eva) including an almost complete disarticulated skull, was also referred to A. atacis. However, a preliminary study based on lower jaw morphology suggests that the Eva specimen may belong to a distinct taxon as the jaws of both species are adapted for browsing in different height of the vegetation. | |
| Cairanoolithus | C. dughii | Bellevue; Gourg de l'Encantado; Rennes-le-Château/Founbit; La Valdieu; Les Boudous | Marnes rouges de la Maurine Member (lower part) | Eggs and shell fragments | Eggs tentatively attributed to a nodosaurid ankylosaur | |
| C. roussetensis | Bellevue; Rennes-le-Château; La Valdieu | Marnes rouges de la Maurine Member (lower part) | Eggs and shell fragments | |||
| Dromaeosauridae indet. | Indeterminate | Bellevue | Marnes rouges de la Maurine Member (lower part) | Teeth. | An indeterminate dromaeosaurid | |
| Fusioolithus | F. baghensis | F5; Véraza | Top of the Marnes rouges de la Maurine Member (above the Poudingue Fleuri) | Shell fragments | Initially described under the name Megaloolithus pseudomamillare this oospecies was reinterpreted as a junior synonym of Megaloolithus baghensis, then finally assigned to the new oogenus Fusioolithus in 2015. This oospecies is present in France, Spain, India, Argentina, Peru and Bolivia. The presence of embryonic remains in such eggs in Argentina (Auca Mahuevo site) proves that this oospecies was laid by titanosaurs. | |
| Gargantuavis | G. philoinos | Bellevue | Marnes rouges de la Maurine Member (lower part) | MDE-C3-525 (holotype), an incomplete pelvis. | A giant flightless bird | |
| Megaloolithus | M. mamillare | Roque Fumade 4 | Marnes rouges de la Maurine Member (upper part, but below the Poudingue Fleuri) | Shell fragments | Eggs attributed to titanosaurian sauropods | |
| M. siruguei | Les Labadous; Rennes-le-Château; Roque Fumade 1,2,3 and 5 | Marnes rouges de la Maurine Member (lower, middle and upper levels (but below the Poudingue Fleuri)) | Eggs and shell fragments | |||
| Montanoolithus | M. labadousensis | Les Labadous | Marnes rouges de la Maurine Member (middle part) | Shell fragments | Eggs attributed to a dromaeosaurid theropod. | |
| Struthiosaurini indet. | Indeterminate | Bellevue; Espéraza | Marnes rouges de la Maurine Member (lower part), Grès des Estous Member | Isolated dermal plates, a right scapula | Represented in the Marnes rouges de la Maurine by isolated dermal plates. An incomplete right scapula from the Grès des Estous could belong to a struthiosaurin nodosaurine distinct from Struthiosaurus. | |
| Rhabdodon | R. priscus | Bellevue, Espéraza, Gourg de l'Encantado | Marnes rouges de la Maurine Member (lower part), Grès des Estous Member | Two dentaries, one maxilla, two maxillary teeth, two dentary teeth, dorsal vertebrae, sacrum elements, numerous caudal vertebrae, many bones of the forelimbs, pelvic bones, many femora and tibiae, and some foot bones. | A rhabdodontid ornithopod | |
| Titanosauria indet. | Indeterminate | Gourg de l'Encantado | Marnes rouges de la Maurine Member (lower part) | MDE-RC10-20, an osteoderm | The spine shaped osteoderm MDE-RC10-20 was first referred to a nodosaurine ankylosaur. It was then reinterpreted as belonging to a titanosaurian sauropod. | |