Ieper Group

Ieper Group
Groupe d'Ypres
Ieper Group; Groupe d'Ypres
Stratigraphic range: Ypresian; ~54–50 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
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′N 4°18′E / 51.3°N 4.3°E
Approximate paleocoordinates	46°42′N 1°30′E / 46.7°N 1.5°E
Region	East Flanders, West Flanders, Antwerp, Hainaut, Flemish & Walloon Brabant
Country	Belgium
Extent	Campine Basin
Type section
Named for	Ypres (Ieper)
	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".

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	Group	Formation	Member	Lithologies	Maximum thickness	Notes
Ypresian	C22n	Zenne	Aalter	Oedelem Sand	Sandstone		^[14]
	C22r	Zenne	Aalter	Beernem Sand	Sandstone		^[14]
		Ieper	Gentbrugge	Aalterbrugge Lignite	Lignite	50 m (160 ft)	^[15]
				Vierzele Sand	Sandstone
				Pittem Clay	Claystone
				Merelbeke Clay	Claystone
				Kwatrecht Complex
			Mons-en-Pévèle		Micaceous sandstone	A few meters	^[16]
	C23n		Hyon	Mont-Panisel	Sandstone	25 m (82 ft)	^[17]
				Bois-la-Haut Sand	Sandstone
				Egem	Claystone
			Tielt	Egemkapel	Sandstone	25 m (82 ft)	^[18]
			Tielt	Kortemark	Siltstone	25 m (82 ft)	^[18]
	C23r		Kortrijk	Aalbeke	Claystone	125 m (410 ft)	^[19]
	C24n			Roubaix	Claystone
	C24r			Orchies
				Mt. Héribou	Claystone
				Het Zoute	Siltstone
		Landen	Tienen	Oosthoek Sand	Sandstone		^[20]
				Knokke Clay	Claystone
				Dormaal Sand	Sandstone

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]

References

^ Steurbaut, 2006, p.74
^ Molina et al., 2006, p.15
^ Ypresian Stage at Encyclopedia Britannica
^ Dupuis et al., 2003, p.44
^ ^a ^b Ypresian/Lutetian boundary stratotype - University of Zaragoza
^ Bernaola et al., 2006, p.75
^ Larrasoaña et al., 2008, p.396
^ Larrasoaña et al., 2008, p.411
^ Molina et al., 2006, p.8
^ Guerrera et al., 2014, p.172
^ Molina et al., 2006, p.2
^ Steurbaut, 2006, p.76
^ Ieper Group - National Commission for the Stratigraphy of Belgium
^ Aalter Formation at Fossilworks.org
^ Gentbrugge Formation
^ Mons-en-Pévèle Formation
^ Hyon Formation - National Commission on the Stratigraphy of Belgium
^ Tielt Formation - National Commission on the Stratigraphy of Belgium
^ Kortrijk Formation - National Commission on the Stratigraphy of Belgium
^ Tienen Formation at Fossilworks.org
^ Smith & Smith, 2003

Bibliography

Steurbaut, Etienne; De Ceukelaire, Marleen; Lanckacker, Tim; Matthijs, Johan; Stassen, Peter; Van Baelen, Hervé; Vandenberghe, Noël (2017), An update of the lithostratigraphy of the Ieper Group (PDF), National Commission for the Stratigraphy of Belgium, pp. 1–79, retrieved 2020-09-07
Steurbaut, Etienne (2006), "Ypresian", Geologica Belgica, 9: 73–93, retrieved 2020-09-07
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
Laga, P.; Louwye, S.; Geets, S. (2001), "Paleogene and Neogene lithostratigraphic units (Belgium)", Geologica Belgica, 4 (1–2): 135–152, doi:10.20341/gb.2014.050, retrieved 2020-09-07
Willems, W (1974), "An aberrant Uvigerina from the Lower Eocene of Belgium", Micropaleontology, 20 (4): 478–479, Bibcode:1974MiPal..20..478W, doi:10.2307/1485134, JSTOR 1485134

Other Ypresian

Guerrera, F.; Mancheño, M.A.; Martín Martín, M.; Raffaelli, G.; Rodríguez Estrella, T.; Serrano, F. (2014), "Paleogene evolution of the External Betic Zone and geodynamic implications", Geologica Acta, 12: 171–192, retrieved 2020-09-07
Molina, Eustoquio; Gonzalvo, Concepción; Mancheño, Miguel A.; Ortiz, Silvia; Schmitz, Birger; Thomas, Ellen; von Salis, Katharina (2006), "Integrated stratigraphy and chronostratigraphy across the Ypresian-Lutetian transition in the Fortuna Section (Betic Cordillera, Spain)", Newsletters on Stratigraphy, 42: 1–19, doi:10.1127/0078-0421/2006/0042-0001, retrieved 2020-09-07
Larrasoaña, J.C.; Gonzalvo, C.; Molina, E.; Monechi, S.; Ortiz, S.; Tori, F.; Tosquella, J. (2008), "Integrated magnetobiochronology of the Early/Middle Eocene transition at Agost (Spain): Implications for defining the Ypresian/Lutetian boundary stratotype" (PDF), Lethaia, 41 (4): 395–415, Bibcode:2008Letha..41..395L, doi:10.1111/j.1502-3931.2008.00096.x, hdl:2158/253940, retrieved 2020-09-07
Dupuis, Christian; Aubry, Marie-Pierre; Steurbaut, Etienne; Berggren, William A.; Ouda, Khaled; Magioncalda, Roberto; Cramer, Benjamin S.; Kent, Dennis V.; Speijer and Claus Heilmann-Clausen, Robert P. (2003), "The Dababiya Quarry Section: Lithostratigraphy, clay mineralogy, geochemistry and paleontology", Micropalaeontology, 49: 41–59, Bibcode:2003MiPal..49S..41D, doi:10.2113/49.Suppl_1.41, retrieved 2020-09-07

[Steurbaut2006-p74-1] Steurbaut, 2006, p.74

[Molina2006-p15-2] Molina et al., 2006, p.15

[Britannica-3] Ypresian Stage at Encyclopedia Britannica

[Dupuis2003-p44-4] Dupuis et al., 2003, p.44

[Unizar-5] Ypresian/Lutetian boundary stratotype - University of Zaragoza

[Bernaola2006-p75-6] Bernaola et al., 2006, p.75

[Larrasoana2008-p396-7] Larrasoaña et al., 2008, p.396

[Larrasoana2008-p411-8] Larrasoaña et al., 2008, p.411

[Molina2006-p8-9] Molina et al., 2006, p.8

[Guerrera2014-p172-10] Guerrera et al., 2014, p.172

[Molina2006-p2-11] Molina et al., 2006, p.2

[Steurbaut2006-p76-12] Steurbaut, 2006, p.76

[NCSB-13] Ieper Group - National Commission for the Stratigraphy of Belgium

[FWAalter-14] Aalter Formation at Fossilworks.org

[NSCBGentbrugge-15] Gentbrugge Formation

[NSCBMons-16] Mons-en-Pévèle Formation

[NCSBHyon-17] Hyon Formation - National Commission on the Stratigraphy of Belgium

[NCSBTielt-18] Tielt Formation - National Commission on the Stratigraphy of Belgium

[NCSBKortrijk-19] Kortrijk Formation - National Commission on the Stratigraphy of Belgium

[FWTienen-20] Tienen Formation at Fossilworks.org

[Smith2003-21] Smith & Smith, 2003

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]

[10]

[11]

[12]

[13]

[14]

[15]

[16]

[17]

[18]

[19]

[20]

[21]