Northern Europe II GO 568 Structural Geology James S. Aber

Tectonic overview

1. Halokinesis -- Buried Zechstein (Permian) salt was mobilized by overburden pressure and flowed into anticlines and diapirs. Salt flowage occurred as sediment accumulation continued in adjacent synclinal basins. Most movement took place during the Mesozoic, but minor movements continued through the Cenozoic and even today. Maximum uplift of salt has exceeded 5 km in some places. Salt structures are best developed in northern Germany and in northwestern Denmark.

2. Glaciotectonism -- Ice-push deformation took place across the southern Baltic region during Pleistocene glaciations. Relatively soft Mesozoic and Cenozoic sedimentary strata were most affected along with Quaternary deposits by shallow folding and faulting. Large ice-shoved hills were created and rafts of deformed strata were transported 10s to 100s of km in some cases. Glaciotectonic structures are well known in Ireland, England, the Netherlands, Denmark, Germany, Poland, the Baltic states, and parts of Russia.

Mesozoic Geology

	Triassic limestone quarry at Rudersdorf, near Berlin, eastern Germany. Limestone is used for making concrete products. Photo date 8/95, © J.S. Aber.
	Kaolinite mine on Dartmoor, southwestern England, United Kingdom. The kaolinite formed presumably during Mesozoic weathering of granite. Known as "china clay," this material is used for making china and other ceramic products. Photo date 9/92, © J.S. Aber.
	Former kaolinite mine, Rabekkeværket, island of Bornholm, Denmark. Kaolinite was formed by chemical breakdown of the Rønne Granite under a humid (tropical) climate during the Jurassic (Gry 1977a). The kaolinite still retains traces of structures found within the granite. Photo by Mona Hansen (1960); used by permission, © Varv (1977).
	Robbedale Formation, island of Bornholm, Denmark. Upper Jurassic shallow marine, littoral deposits are dominated by unconsolidated quartz sand. Photo date 6/79, © J.S. Aber.
	Jydegård Formation above the Robbedale Formation, island of Bornholm, Denmark. Lower Cretaceous Jydegård Formation consists of unconsolidated, interbedded sand, silt, and lignite beds that rest conformably on the underlying Robbedale Formation. The Jydegård Formation was deposited in a coastal lagoon behind a barrier island or spit (Gry 1977b). Photo date 6/79, © J.S. Aber.
	Arnager greensand, island of Bornholm, Denmark. An unconsolidated, glauconitic sand is rich in micro- and macro-fossils of Cenomanian age (late Cretaceous). Glauconite is an indicator for deposition in a shallow marine environment. Photo date 6/79, © J.S. Aber.
	Arnager chalk, island of Bornholm, Denmark. An unusual chalk that consists of about 45-70% chalk plus quartz sand, clay, and flint nodules (Christiansen 1977). This chalk was deposited near the eastern edge of the late Cretaceous marine basin that covered northwestern Europe, as indicated by the presence of land-derived sediments. Photo date 6/79, © J.S. Aber.

Geologic map of the pre-Quaternary bedrock of Denmark. Most of the country is underlain by Cretaceous (green) and Tertiary (orange-yellow) strata. The circular structures in the northwest mark salt diapirs. Pink regions in Sweden and the Danish island of Bornholm are parts of the Fennoscandian Shield.

	Stevns Klint, eastern Denmark. The upper gray limestone is Danian (lowermost Tertiary), and the lower white chalk is Maastrichtian (uppermost Cretaceous). This section includes the K/T boundary (see next photos). Photo date 5/79, © J.S. Aber.
	Stevns Klint, eastern Denmark. The K/T boundary is marked by the dark seam, known as the "fish clay," across the middle of this view (Håkanson 1971)). The fish clay contains high amounts of iridium and other indications of an unusual tectonic event. See closeup picture in next image. Photo date 5/79, © J.S. Aber.
	Closeup view of the K/T boundary at Stevns Klint, eastern Denmark. Some attribute the boundary layer (fish clay) to an asteroid impact in the Yucatan, Mexico; others ascribe it to a massive volcanic eruption, such as initiation of the Réunion or Iceland hot spot. Photo date 5/79, © J.S. Aber.

Cenozoic Geology

	Chalk quarry over Batum salt diapir, northern Jylland, Denmark. Normally buried beneath thick Tertiary sediments, the chalk is uplifted here over the crest of a salt diapir. Photo date 6/79, © J.S. Aber.
	Quarry in "mo-clay" strata of the Fur Formation, Harjøj, Denmark. The late Paleocene/early Eocene Fur Formation consists of interbedded diatomite (light beds) and volcanic ash (dark layers). The volcanic ash was derived presumably from the Skagerrak region as an offshoot of rifting and vulcanism in the North Atlantic region. Photo date 6/79, © J.S. Aber.
	Folded "mo-clay" strata of the Fur Formation, Feggeklit, northwestern Denmark. This sediment was particularly susceptible to ice-push deformation as shown by these folds. Photo date 7/87, © J.S. Aber.
	Nappe of mo-clay formation, Hanklit, island of Fur, Denmark. Glacial gravel is wrapped around an overturned, rootless fold of mo-clay, and the nappe rests on till. Note person at bottom of cliff. Photo date 6/79, © J.S. Aber.
	Jættebrink, a large slab of lower Maastrichtian (late Cretaceous) chalk thrust over Quaternary sediment by ice pushing, Møns Klint, southeastern Denmark. The chalk slab is an allochthonous nappe (Surlyk 1971). Photo date 5/79, © J.S. Aber.
	Ice-pushed masses of chalk stand as vertical cliff faces, Møns Klint, southeastern Denmark. Sommerspiret, the chalk pinancle in scene center, stood 102 m high at the time this photo was taken; it has since fallen down in a storm. Photo date 10/86, © J.S. Aber.
	Sheared and folded chalk-banded till. Hjelm Nakke, island of Møn, southeastern Denmark. Photo date 10/86, © J.S. Aber.
	Glacially transported raft of Oligocene "glimmersand" (micaeous sandstone) is the light-colored body at top of section. It rests on Pleistocene glacial sand. Freienwalde, northeastern Germany. Photo date 8/95, © J.S. Aber.
	Dark mass of Quaternary interglacial lacustrine or marine strata thrust along with glacial sand into an ice-shoved ridge at Kadyny, northern Poland. This structure is part of the Elblag Upland, a glaciotectonic region covering about 400 km² and rising almost 200 m above sea level. Photo date 7/93, © J.S. Aber.
	Barges moving upstream on the Rhine River, Andernach, western Germany. The Rhine River flows through a now-inactive rift zone in northwestern Europe. The rift zone developed during the Eocene, but has been largely quiet since the Miocene. An exception is the Eifel volcanic field (see next two photos). Photo date 8/95, © J.S. Aber.
	Section through the side of Wannenköpfe, a large cinder cone in the East Eifel volcanic field, western Germany. This cinder cone was built around 215,000 to 225,000 years ago of basaltic eruptions (van den Bogaard 1995). Photo date 8/95, © J.S. Aber.
	Tephra deposit of the Laacher See eruption, West Eifel volcanic field, western Germany. This eruption took place 13,000 years ago and involved about 5 km³ of magma (van den Bogaard 1995). The Laacher See tephra is found throughout northwestern Europe. Note people standing on left side. Photo date 8/95, © J.S. Aber.

References

• Bogaard, P. van den 1995. Quaternary volcanism. Field Guide Excursion A18, INQUA 24th International Congress.

• Christiansen, W.K. 1977a. Det marine Kridt. In, Geologi på Bornholm, p. 82-89. Varv, Ekskursionsfører Nr. 1.

• Gry, H. 1977a. Lokalitet 38. Rabekkeværket. In, Geologi på Bornholm, p. 71-72. Varv, Ekskursionsfører Nr. 1.

• Gry, H. 1977b. Lokalitet 39. A/S Carl Nielsens sandgrav, Robbedale. In, Geologi på Bornholm, p. 73-78. Varv, Ekskursionsfører Nr. 1.

• Håkanson, E. 1971. Stevns Klint. In, Geologi på Øerne p. 25-36. Varv, Ekskursionsfører Nr. 2.

• Surlyk, F. 1971. Skrivekridtklinterne på Møn. In, Geologi på Øerne p. 5-24. Varv, Ekskursionsfører Nr. 2.

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