The Sables du Castrais Formation, also known as the Molasses du Castrais, is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

(

Ypresian In the geologic timescale the Ypresian is the oldest age or lowest stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by the Eocene Lutetian Age. The Ypresian i ...

Bartonian The Bartonian is, in the ICS's geologic time scale, a stage or age in the middle Eocene Epoch or Series. The Bartonian Age spans the time between . It is preceded by the Lutetian and is followed by the Priabonian Age. Stratigraphic defin ...

) age,

outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. Features Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficia ...

ping in the Montagne-Noire region of

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan ar ...

.Noulet, J.-B. (1858) – Du terrain éocène supérieur considéré comme l’un des étages constitutifs des Pyrénées. ''Bulletin de la Société géologique de France'', 1858, p. 277-284

History

Petrified In geology, petrifaction or petrification () is the process by which organic material becomes a fossil through the replacement of the original material and the filling of the original pore spaces with minerals. Petrified wood typifies this proce ...

fossil remains" were known from the Sables du Castrais Formation since at least the 18th century,Fauré, Philippe. (2011). UN PATRIMOINE GEOLOGIQUE PEU CONNU : LES GISEMENTS DE VERTEBRES FOSSILES DE L’EOCENE MOYEN DU CASTRAIS (TARN, LUTETIEN SUPERIEUR A BARTONIEN SUPERIEUR). and several of these fossils were described by

Cuvier Jean Léopold Nicolas Frédéric, Baron Cuvier (; 23 August 1769 – 13 May 1832), known as Georges Cuvier, was a French naturalist and zoologist, sometimes referred to as the "founding father of paleontology". Cuvier was a major figure in nat ...

(1804) and Cuvier (1822) as belonging to ''

Palaeotherium ''Palaeotherium'' (Ancient Greek for 'old beast') is an extinct genus of perissodactyl ungulate known from the Mid Eocene to earliest Oligocene of Europe. First described by French naturalist Georges Cuvier in 1804, ''Palaeotherium'' was among ...

'' and ''

Lophiodon ''Lophiodon'' (from el, λόφος , 'crest' and el, ὀδούς 'tooth') is an extinct genus of mammal related to chalicotheres. It lived in Eocene Europe Europe is a large peninsula conventionally considered a continent in its own ...

''.Cuvier, G. (1822) – Recherche sur les ossements fossiles où l’on rétablit les caractères de plusieurs animaux dont les révolutions du globe ont détruit les espèces. Nouvelle édition.. Tome second, 1er partie. In 1845, a jaw assigned to '' Lophiodon lautricensis'' was discovered in the formation and was described by Noulet (1851); Noulet also mentioned that he had himself collected fossils from the formation alongside

pharmacist A pharmacist, also known as a chemist (Commonwealth English) or a druggist (North American and, archaically, Commonwealth English), is a healthcare professional who prepares, controls and distributes medicines and provides advice and instructi ...

J. Parayre as early as . Léonce Roux du Carla discovered several more fossils from the Grès d'Issel Member of the Sables du Castrais formation from February 1855 until his death in 1859, and this helped Noulet (1858) to confirm the

age of the deposit. Despite this, all that remains today of du Carla's collection is a single jaw of '' Palaeotherium castrense'' from the Sables du Castrais Formation. Between 1850 and 1868, during the construction of the

Castres Castres (; ''Castras'' in the Languedocian dialect of Occitan) is the sole subprefecture of the Tarn department in the Occitanie region in Southern France. It lies in the former province of Languedoc, although not in the former region of Lang ...

Albi Albi (; oc, Albi ) is a commune in France, commune in southern France. It is the prefecture of the Tarn (department), Tarn Departments of France, department, on the river Tarn (river), Tarn, 85 km northeast of Toulouse. Its inhabitants ar ...

railroad, several more fossils were recovered from the Sables du Castrais Formation, including M. Zebrowsky's 1868 discovery of fossils within the area. The Grès d'Issel Member was identified by Henri de Sévérac in 1873, and the Sables du Castrais Formation was first described by M. Richard in 1946.M. Richard. (1946). Contribution a l'étude du basin d'Aquitaine, Les Gisements de Mammiferes Tertiares. ''Memoires de la Societe Geologique de France, Nouvelle Serie'' 24(52):1-380 The Grès d'Issel Member is located in a quarry which closed around 1966 and is now inaccessible due to it currently being located underneath a private garden.

Age of the formation

The age of the Sables du Castrais Formation was listed as

by Noulet (1858) and in 1867,

Gervais Gervais may refer to: People * Gervais (name), list of people with the given name or surname Places * Gervais, Oregon * Gervais Lake, a lake in Minnesota * Gervais Township, Minnesota * Gervais Road, part of 170 Street, Edmonton, Alberta, Canada ...

noted that the Issel Member likely dated to the

Early Eocene In the geologic timescale the Ypresian is the oldest age (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by th ...

, while the Villeneuve-la-Comptal Member likely dated to the

Middle Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', "d ...

. Caraven-Cachin (1898) was the first to assign the Sables du Castrais Formation to the

Stehlin Stehlin is a surname. Notable persons by this name include: *Benoist Stehlin (c.1732–1774), French harpsichord builder *Hans Georg Stehlin (1870–1941), Swiss paleontologist and geologist *Johann Jakob Stehlin (1803–1879), Swiss politician *K ...

(1910) and Escarguel (1999) dated the formation to the

Lutetian The Lutetian is, in the geologic timescale, a stage (stratigraphy), stage or age (geology), age in the Eocene. It spans the time between . The Lutetian is preceded by the Ypresian and is followed by the Bartonian. Together with the Bartonian it ...

and found it to overlie the Molasses de Saix et de Lautrec Formation. Fauré (2011) agreed with the more recent dating of the formation to the

Geology

The base of the Sables du Castrais Formation, which overlies

Danian The Danian is the oldest age or lowest stage of the Paleocene Epoch or Series, of the Paleogene Period or System, and of the Cenozoic Era or Erathem. The beginning of the Danian (and the end of the preceding Maastrichtian) is at the Creta ...

rocks, is made up of

gravel clays and the Issel Sandstones, which range from , and the Argiles rutilants d'Issel et de Saint-Papoul Member is deposited within the gravel clays, and is between thick. The Argiles rutilants d'Issel et de Saint-Papoul Member is overlain by the

Grès d'Issel Member, which is between thick, and is overlain by the

Molasses du Castelnaudary Member. The whole formation underlies the Molasses de Saix et de Lautrec Formation. The Grès de Carcassonne Member also appears to be slightly younger than the Grès d'Issel Member, likely dating to the late

or early

. The Sables du Castrais Formation was described by Capera and Baillet (2014) as a typical fluviatile formation, with lenticular channels, formed by conglomerates and

sandstones Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

, with calcareous cement and large trough cross-strata.Capera, J-C., Baillet, L. (2014). Carrière de grès éocènes de Carcassonne. ''Inventaire du patrimoine géologique du Languedoc-Roussilon, LRO-1052, DREAL Languedoc-Roussillon, 4 pp.''

Paleofauna

Mammals

; Artiodactyl ; Lipotyphia ; Marsupial ; Pan-Carnivora ; Perissodactyl ; Primates ; Rodent

Reptiles

; Crocodilians ; Turtles

References

{{reflist Geologic formations of France Eocene France