Tuffeau de St Omer

Tuffeau de Saint-Omer
Stratigraphic range: Mid Thanetian ~58  Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Type	Formation
Underlies	Sables et Grès de Grandgiise
Overlies	Senonian formations
Thickness	Up to 26 m (85 ft)
Lithology
Primary	Sandstone (!)
Location
Coordinates	50°30′N3°12′E / 50.5°N 3.2°E / 50.5; 3.2
Approximate paleocoordinates	45°00′N0°48′E / 45.0°N 0.8°E / 45.0; 0.8
Region	Nord, Pas-de-Calais
Country	France
Extent	Southernmost North Sea Graben
Type section
Named for	Saint-Omer
Location	Saint-Omer, Pas-de-Calais
Tuffeau de St Omer (France)

The "Tuffeau" de Saint-Omer is a geologic formation in northern France. The sandstones of the formation, named after Saint-Omer, preserve bird and primate fossils dating back to the middle Thanetian age of the Paleocene epoch of the Paleogene period, dating to about 58 Ma.

The European land mammal age, a continental biostratigraphic zonation for the Cenozoic, as ammonites for the Mesozoic and conodonts for the Paleozoic, classification starts after this age, the Thanetian is correlative with the MP2 to 5 of the Mammal Paleogene zone of Europe. At this time in geologic history the climate was at an all-time high with estimated tropical temperatures of 34 °C (93 °F) and 2000 ppm atmospheric CO₂. ^[1]

The formation is locally referred to and geologically known as tuff, although the lithology of the formation is glauconitic sandstone, deposited in a shallow marine environment at the southernmost edge of the North Sea Graben.

Description

The Tuffeau de Saint-Omer is described as a glauconitic well-sorted sandstone, with opal cement and the invertebrate fossils Pholadomya cuneata , P. konincki , Cyprina morrisi , Thracia prestwichi , Natica deshayesiana and Martesia cuneata . The Tuffeau is exposed near Molinghem and Doulac, north of Saint-Omer, after which the formation is named. Despite the siliciclastic lithology, the formation is locally referred to as "tuff"; volcaniclastic rock. ^[2]

The thickness of the unit varies from 10 metres (33 ft) (near Garbecque) to around 20 metres (66 ft) (in Arques, Quiestède, and Aire-sur-la-Lys) and sometimes more (24 metres (79 ft) at Helfaut and 26 metres (85 ft) at Blendecques). The thickness of the tuff intersperses with the Sables d'Ostricourt, giving a total thickness of the Landenian section of 35 to 40 metres (115 to 131 ft). ^[2]

Fossil content

At Templeuve, the following fossils were reported: ^{[3] [4]}

Primates

• Berruvius cf. lasseroni
• Sarnacius aff. gingerichi

Birds

• Lithornithidae indet.
• Pelagornithidae indet.

See also

• List of fossiliferous stratigraphic units in France
• Cerrejón Formation, contemporaneous fossiliferous formation in Colombia
• Itaboraí Formation, contemporaneous fossiliferous formation in Brazil
• European land mammal age

References

1. Head et al., 2009
2. Carte geologique Saint-Omer, 1969, p.8
3. Templeuve at Fossilworks.org
4. Smith & Smith, 2003

Bibliography

• Head, J.J.; Bloch, J.I.; Hastings, A.K.; Bourque, J.R.; Cadena, E.A.; Herrera, F.A.; Polly, P.D.; Jaramillo, C.A. (2009), "Giant boid snake from the paleocene neotropics reveals hotter past equatorial temperatures" , Nature , 457 (7230): 715–718, Bibcode:2009Natur.457..715H, doi:10.1038/nature07671, PMID   19194448 , retrieved 2020-03-08
• Smith, T.; Smith, R. (2003), "Terrestrial mammals as biostratigraphic indicators in upper Paleocene-lower Eocene marine deposits of the southern North Sea Basin", Geological Society of America Special Paper , 369: 513–520, retrieved 2020-03-08
• Various, Authors (1969), Carte geologique Saint-Omer 1:50.000 - Memoire explicative (PDF), BRGM, pp. 1–20, retrieved 2020-03-08