Ieper Group

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Ieper Group
Groupe d'Ypres
Stratigraphic range: Ypresian
~54–50  Ma
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Type Geologic group
Sub-units Kortrijk, Mons-en-Pévèle, Tielt, Hyon & Gentbrugge Formations
Underlies Zenne Group
  Aalter Formation
Overlies Landen Group
  Tienen Formation
Thickness>225 m (738 ft)
Lithology
Primary Sandstone, claystone
Other Siltstone
Location
Coordinates 51°18′N4°18′E / 51.3°N 4.3°E / 51.3; 4.3
Approximate paleocoordinates 46°42′N1°30′E / 46.7°N 1.5°E / 46.7; 1.5
Region East Flanders, West Flanders, Antwerp, Hainaut, Flemish & Walloon Brabant
CountryFlag of Belgium (civil).svg  Belgium
Extent Campine Basin
Type section
Named for Ypres (Ieper)
Belgium relief location map.jpg
Orange pog.svg
Ieper Group (Belgium)

The Ieper Group (Dutch : Ieper Groep; French : Groupe d'Ypres) is a group of rock strata in the subsurface of northwest Belgium. The group is subdivided into three marine formations, all formed during the Ypresian, a single age of the geologic timescale (55.8 to 48.6 million years ago, the oldest age of the Eocene epoch). Both age and group are named after the West Flemish town of Ypres, for which the Dutch name is "Ieper".

Contents

History of definition

Ypresian

In the original description of his newly introduced Ypresian stage Dumont (1850) did mention neither stratotype nor type locality. He simply referred to the "collines d'Ypres" or Ieper Hills, as the area where the unit is best developed. However, it remains unclear what is meant by this term. The town of Ieper is situated in western Belgium, at the southern end of a small, NW-SE oriented depression (15 to 20 metres (49 to 66 ft) above mean sea level), surrounded from north to south by a series of low hills (between 25 and 45 metres (82 and 148 ft)). Dumont probably envisaged the elevated zones a few km north and east of Ieper (St.-Jan, Zillebeke, etc.), where clay beds have been quarried for brick and tile making for quite a long time. [1]

A new stratotype for the Lutetian was proposed by Blondeau (1981) about 50 kilometres (31 mi) north of Paris. The neostratotype is located on the right bank of the river Oise at St. Leu d'Esserent and the large quarry at St. Vaast-les-Mello (Oise). [2]

Since 2003, the Global Stratotype Section and Point (GSSP) defined by the International Commission on Stratigraphy (ICS) for the Ypresian is set in the Dababiya section close to Luxor, Egypt, [3] where the uppermost Tarawan Limestone, the Esna Formation and the lowermost Thebes Limestone define the Ypresian sequence. [4] Several other proposals for the lithostratigraphic redefinition of the top of the Ypresian exist; [5] among others the Punta Torcida Formation of the Austral or Magallanes Basin in Tierra del Fuego, the Azkorri Sandstone in the Gorrondatxe section of the North Pyrenean Foreland or Basque–Cantabrian Basin, [6] [7] the Agost section close to Alicante in the Agost Basin in the Betic Cordillera, [8] and the Fortuna section north of Murcia in the Prebetic realm of the Betic Cordillera, [9] [10] all in Spain. Other proposed type sections for the Ypresian-Lutetian boundary are located in France, Italy, Israel, Tunisia, Morocco, Cuba and Mexico. [5] [11]

Stratigraphy

The Ieper Group was redefined by Steurbaut in 2006, [12] and is since 2017 subdivided into five formations by the National Commission for the Stratigraphy of Belgium, from youngest to oldest: [13]

Age Chron GroupFormationMemberLithologiesMaximum thicknessNotes
Ypresian C22n Zenne Aalter Oedelem Sand Sandstone [14]
C22rBeernem SandSandstone
Ieper Gentbrugge Aalterbrugge Lignite Lignite 50 m (160 ft) [15]
Vierzele SandSandstone
Pittem Clay Claystone
Merelbeke ClayClaystone
Kwatrecht Complex
Mons-en-Pévèle Micaceous sandstoneA few meters [16]
C23n Hyon Mont-PaniselSandstone25 m (82 ft) [17]
Bois-la-Haut SandSandstone
EgemClaystone
Tielt EgemkapelSandstone25 m (82 ft) [18]
Kortemark Siltstone
C23r Kortrijk AalbekeClaystone125 m (410 ft) [19]
C24nRoubaixClaystone
C24rOrchies
Mt. HéribouClaystone
Het ZouteSiltstone
Landen Tienen Oosthoek SandSandstone [20]
Knokke ClayClaystone
Dormaal SandSandstone

Outcrops

The Kortrijk Formation predominantly consists of marine clay. It occurs in the west and north of Belgium, the Tielt Formation, consisting of fine sand, is found in the subsurface of western and central Belgium and the Gentbrugge Formation, which comprises an alternation of clay, silt and fine sand, crops out in East and West Flanders.

The Ieper Group lies stratigraphically on top of the Landen Group (upper Paleocene) and below the Zenne Group (like the Ieper Group early Eocene in age). Unlike the Zenne Group, the Ieper Group can also occur in more southern parts of Belgium, for example in the Mons Basin.

Paleontology

The Tielt Formation has provided fossils of mammals, birds and reptiles. [21]

See also

Related Research Articles

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The Thanetian is, in the ICS Geologic timescale, the latest age or uppermost stratigraphic stage of the Paleocene Epoch or Series. It spans the time between 59.2 and56 Ma. The Thanetian is preceded by the Selandian Age and followed by the Ypresian Age. The Thanetian is sometimes referred to as the Late Paleocene.

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The Lutetian is, in the geologic timescale, a stage or age in the Eocene. It spans the time between 47.8 and41.2 Ma. The Lutetian is preceded by the Ypresian and is followed by the Bartonian. Together with the Bartonian it is sometimes referred to as the Middle Eocene Subepoch.

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The Opglabbeek Formation is a geologic formation in the subsurface of the eastern part of Belgian Limburg. The heterogeneous formation consists of clay and sand that was deposited lagoonally and fluvially during the early Selandian. The formation is named after the town of Opglabbeek in Limburg.

The Landen Group is a lithostratigraphic unit in the Belgian subsurface. The group consists of two formations of Thanetian to Ypresian age. The Landen Group is named after the town of Landen in Flemish Brabant.

The Tienen Formation is a geologic formation in the subsurface of northern Belgium. The formation crops out in the province of Hainaut and the Hesbaye region in the province of Limburg. It has a late Thanetian (Paleocene) to early Ypresian (Eocene) age.

The Dongen Formation is a geologic formation in the subsurface of the Netherlands. The formation consists of early Eocene marine clay and sand. It is named after the town of Dongen in North Brabant.

The Zenne Group is a group of rock strata in the subsurface of central and northwest Belgium. The group consists of three formations, all from the Ypresian and Lutetian ages. These formation have their shallow marine facies in common.

The Aalter Formation is a geologic formation in the subsurface of northwest Belgium. The formation consists of marine clay and sand, deposited in the shallow sea that covered northern and central Belgium in the Eocene epoch.

The Gentbrugge Formation is a geologic formation in the west of Belgium. The formation crops out in East Flanders and West Flanders and also occurs in the subsurface of the Province of Antwerp. It consists of marine clay, silt and sand, deposited in the shallow sea that covered northern Belgium during the Ypresian age.

The Tielt Formation is a geologic formation in the subsurface of Belgium. The formation crops out in the north of Hainaut, in the southern and central parts of West- and East Flanders and in Walloon and Flemish Brabant. It consists of marine very fine sand and silt, deposited in the shallow sea that covered Belgium during the middle and late Ypresian age.

The Kortrijk Formation is a geologic formation in the Belgian subsurface. This formation crops out in northern Hainaut, southern West and East Flanders and in Walloon Brabant. The formation consists of marine clay from the Ypresian age.

The Brussel Formation is a geologic formation in the subsurface of central Belgium. The formation is named after the Belgian capital, Brussels. It consists of shallow marine sandstone and calcareous sands, deposited in the sea that covered Belgium 45 million years ago, in the Eocene.

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The Lignites de Soissonais is a geologic formation in the Var, Marne departments of France. It preserves fossils dating back to the Ypresian stage of the Eocene period.

References

  1. ↑ Steurbaut, 2006, p.74
  2. ↑ Molina et al., 2006, p.15
  3. ↑ Ypresian Stage at Encyclopedia Britannica
  4. ↑ Dupuis et al., 2003, p.44
  5. 1 2 Ypresian/Lutetian boundary stratotype - University of Zaragoza
  6. ↑ Bernaola et al., 2006, p.75
  7. ↑ Larrasoaña et al., 2008, p.396
  8. ↑ Larrasoaña et al., 2008, p.411
  9. ↑ Molina et al., 2006, p.8
  10. ↑ Guerrera et al., 2014, p.172
  11. ↑ Molina et al., 2006, p.2
  12. ↑ Steurbaut, 2006, p.76
  13. ↑ Ieper Group - National Commission for the Stratigraphy of Belgium
  14. ↑ Aalter Formation at Fossilworks.org
  15. ↑ Gentbrugge Formation
  16. ↑ Mons-en-Pévèle Formation
  17. ↑ Hyon Formation - National Commission on the Stratigraphy of Belgium
  18. ↑ Tielt Formation - National Commission on the Stratigraphy of Belgium
  19. ↑ Kortrijk Formation - National Commission on the Stratigraphy of Belgium
  20. ↑ Tienen Formation at Fossilworks.org
  21. ↑ Smith & Smith, 2003

Bibliography

Other Ypresian
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