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
Overlies	Senonian formations
Thickness	Up to 26 m (85 ft)
Lithology
Primary	Sandstone (!)
Location
Coordinates	50°30′N 3°12′E / 50.5°N 3.2°E / 50.5; 3.2Coordinates: 50°30′N 3°12′E / 50.5°N 3.2°E / 50.5; 3.2
Approximate paleocoordinates	45°00′N 0°48′E / 45.0°N 0.8°E / 45.0; 0.8
Region	Nord, Pas-de-Calais
Country	France
Extent	Southernmost
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 .

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, , , Natica deshayesiana and Martesia cuneata. The Tuffeau is exposed near and , 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 ) 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 , 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

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[]

Bibliography[]

• Head, J.J.; J.I. Bloch; A.K. Hastings; J.R. Bourque; E.A. ; F.A. Herrera; P.D. Polly, and C.A. . 2009. Giant boid snake from the paleocene neotropics reveals hotter past equatorial temperatures. Nature 457. 715–718. Accessed 2020-03-08.
• Smith, T., and R. Smith. 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. Accessed 2020-03-08.
• Various, Authors. 1969. Carte geologique Saint-Omer 1:50.000 - Memoire explicative, 1–20. . Accessed 2020-03-08.