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Eemian interglacial

Eemian interglacial

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The Eemian was an interglacial period which began about 130,000 years ago and ended about 114,000 years ago. It was the second-to-latest interglacial period of the current Ice Age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...

, the most recent being the Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...

 which extends to the present day. The prevailing Eemian climate is believed to have been similar to that of the Holocene. The Eemian is also known as the Sangamonian Stage
Sangamonian Stage
The Sangamonian Stage, also known as the Sangamon interglacial, is the name used by Quaternary geologists to designate the last interglacial period in North America from 125,000—75,000 years ago, a period of...

 in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, the Ipswichian Stage in the UK
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, Mikulin interglacial in East European Plain
East European Plain
The East European Plain is a plain comprising a series of river basins in Eastern Europe. Together with the Northern European Plain it constitutes the European Plain. It is the largest mountain-free part of the European landscape.The plain spans approximately and averages about in elevation...

, the Valdivia interglacial in Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...

 and the Riss-Würm interglacial in the Alps
Alps
The Alps is one of the great mountain range systems of Europe, stretching from Austria and Slovenia in the east through Italy, Switzerland, Liechtenstein and Germany to France in the west....

.

Global temperatures


The Eemian climate is believed to have been about as stable as that of the Holocene. Changes in the earth's orbital parameters from today (greater obliquity and eccentricity, and perihelion), known as the Milankovitch cycle, probably led to greater seasonal temperature variations in the Northern Hemisphere, although global annual mean temperatures were probably similar to those of the Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...

. The warmest peak of the Eemian was around 125,000 years ago, when forests reached as far north as North Cape
North Cape, Norway
North Cape is a cape on the island of Magerøya in Northern Norway, in the municipality of Nordkapp. Its 307 m high, steep cliff is often referred to as the northernmost point of Europe, located at , 2102.3 km from the North Pole. However, the neighbouring point Knivskjellodden is actually...

 (which is now tundra
Tundra
In physical geography, tundra is a biome where the tree growth is hindered by low temperatures and short growing seasons. The term tundra comes through Russian тундра from the Kildin Sami word tūndâr "uplands," "treeless mountain tract." There are three types of tundra: Arctic tundra, alpine...

) in northern Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

 well above the Arctic Circle at 71°10′21"N 25°47′40"E. Hardwood
Hardwood
Hardwood is wood from angiosperm trees . It may also be used for those trees themselves: these are usually broad-leaved; in temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen.Hardwood contrasts with softwood...

 trees like hazel
Hazel
The hazels are a genus of deciduous trees and large shrubs native to the temperate northern hemisphere. The genus is usually placed in the birch family Betulaceae, though some botanists split the hazels into a separate family Corylaceae.They have simple, rounded leaves with double-serrate margins...

 and oak
Oak
An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...

 grew as far north as Oulu
Oulu
Oulu is a city and municipality of inhabitants in the region of Northern Ostrobothnia, in Finland. It is the most populous city in Northern Finland and the sixth most populous city in the country. It is one of the northernmost larger cities in the world....

, Finland
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

.

At the peak of the Eemian, the northern hemisphere winters were generally warmer and wetter than now, though some areas were actually slightly cooler than today. The Hippopotamus
Hippopotamus
The hippopotamus , or hippo, from the ancient Greek for "river horse" , is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest...

 was distributed as far north as the rivers Rhine and Thames. Trees grew as far north as southern Baffin Island
Baffin Island
Baffin Island in the Canadian territory of Nunavut is the largest island in the Canadian Arctic Archipelago, the largest island in Canada and the fifth largest island in the world. Its area is and its population is about 11,000...

 in the Canadian
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 Arctic Archipelago instead of only as far north as Kuujjuaq in northern Quebec
Quebec
Quebec or is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking population and the only one whose sole official language is French at the provincial level....

, and the prairie-forest boundary in the Great Plains
Great Plains
The Great Plains are a broad expanse of flat land, much of it covered in prairie, steppe and grassland, which lies west of the Mississippi River and east of the Rocky Mountains in the United States and Canada. This area covers parts of the U.S...

 of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 lay further west — near Lubbock, Texas
Lubbock, Texas
Lubbock is a city in and the county seat of Lubbock County, Texas, United States. The city is located in the northwestern part of the state, a region known historically as the Llano Estacado, and the home of Texas Tech University and Lubbock Christian University...

, instead of near Dallas, Texas
Dallas, Texas
Dallas is the third-largest city in Texas and the ninth-largest in the United States. The Dallas-Fort Worth Metroplex is the largest metropolitan area in the South and fourth-largest metropolitan area in the United States...

, where the boundary now exists. The era closed as temperatures steadily fell to conditions cooler and drier than the present, with 468-year long aridity pulse in central Europe, and by 114,000 years ago, a glacial era had returned.

Kaspar et al. (GRL, 2005) perform a comparison of a coupled general circulation model (GCM) with reconstructed Eemian temperatures for Europe. Central Europe (north of the Alps) was found to be 1–2 °C warmer than present; south of the alps conditions were 1–2 °C cooler than today. The model (generated using observed GHG concentrations and Eemian orbital parameters) generally reproduces these observations, and hence they conclude that these factors are enough to explain the Eemian temperatures.

Sea level


Sea level at peak was probably 4 to 6m (13 to 20 feet) higher than today (references in Overpeck et al., 2006), with much of this extra water coming from Greenland but some likely to have come from Antarctica. Global mean sea surface temperature
Sea surface temperature
Sea surface temperature is the water temperature close to the oceans surface. The exact meaning of surface varies according to the measurement method used, but it is between and below the sea surface. Air masses in the Earth's atmosphere are highly modified by sea surface temperatures within a...

s are thought to have been higher than in the Holocene, but not by enough to explain the rise in sea level through thermal expansion alone, and so melting of polar ice caps must also have occurred. Because of the sea level drop since the Eemian, exposed fossil coral reefs are common in the tropics, especially in the Caribbean and along the Red Sea coastlines. These reefs often contain internal erosion surfaces showing significant sea level instability during the Eemian.

A 2007 study found evidence that the Greenland ice core site Dye 3
Dye 3
Dye 3 is an ice core site and previously part of the Distant Early Warning line, located at in Greenland. As a DEW line base, it was disbanded in years 1990/1991....

 was glaciated during the Eemian, which implies that Greenland could have contributed at most 2 m (6.6 ft) to sea level rise. Scandinavia
Scandinavia
Scandinavia is a cultural, historical and ethno-linguistic region in northern Europe that includes the three kingdoms of Denmark, Norway and Sweden, characterized by their common ethno-cultural heritage and language. Modern Norway and Sweden proper are situated on the Scandinavian Peninsula,...

 was an island due to the inundation of vast areas of northern Europe
Northern Europe
Northern Europe is the northern part or region of Europe. Northern Europe typically refers to the seven countries in the northern part of the European subcontinent which includes Denmark, Estonia, Latvia, Lithuania, Norway, Finland and Sweden...

 and the West Siberian Plain
West Siberian Plain
The West Siberian Plain is a large plain that occupies the western portion of Siberia, between the Ural Mountains in the west and the Yenisei River in the east, and by the Altay Mountains on the South-East. Much of the plain is poorly drained and consists of some of the world's largest swamps and...

.

Definition of the Eemian


The Eemian Stage was first recognized from borehole
Borehole
A borehole is the generalized term for any narrow shaft bored in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes, including the extraction of water or other liquid or gases , as part of a geotechnical investigation, environmental site...

s in the area of the city of Amersfoort
Amersfoort
Amersfoort is a municipality and the second largest city of the province of Utrecht in central Netherlands. The city is growing quickly but has a well-preserved and protected medieval centre. Amersfoort is one of the largest railway junctions in the country, because of its location on two of the...

, Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

 by Harting (1875). He named the beds "Système Eémien", after the river Eem
Eem
The Eem is a river in the north of the Utrecht Province in the Netherlands with a length of approximately .The river is fed by the Vallei Canal and a number of Veluwe creeks, the most important of which are the Heiligenberger Beek, the Barneveldse Beek and the Lunterse Beek, all of which come...

 on which Amersfoort is located. Harting noticed the marine molluscan assemblages to be very different from the modern fauna of the North Sea
North Sea
In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...

. Many species from the Eemian layers nowadays show a much more southern distribution, ranging from South of the Strait of Dover
Strait of Dover
The Strait of Dover or Dover Strait is the strait at the narrowest part of the English Channel. The shortest distance across the strait is from the South Foreland, 6 kilometres northeast of Dover in the county of Kent, England, to Cap Gris Nez, a cape near to Calais in the French of...

 to Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...

 (Lusitanian
Lusitanian
Lusitanian may refer to:*Lusitanians, an ancient people of western Iberian Peninsula.**Lusitanian language, the language of the ancient Lusitanians.**Lusitanian mythology, the mythology of the ancient Lusitanians....

 faunal province) and even into the Mediterranean (Mediterranean faunal province). More information on the molluscan assemblages is given by Lorié (1887), and Spaink (1958). Since their discovery, Eemian beds in the Netherlands have mainly been recognized by their marine molluscan content combined with their stratigraphical position and other palaeontology. The marine beds there are often underlain by till
Till
thumb|right|Closeup of glacial till. Note that the larger grains in the till are completely surrounded by the matrix of finer material , and this characteristic, known as matrix support, is diagnostic of till....

s that are considered to date from the Saalian, and overlain by local fresh water or wind-blown deposits from the Weichselian. In contrast to e.g. the deposits in Denmark, the Eemian deposits in North America have never been found overlain by tills, nor in ice-pushed positions.

Van Voorthuysen (1958) described the foraminifera
Foraminifera
The Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...

 from the type site, whereas Zagwijn (1961) published the palynology
Palynology
Palynology is the science that studies contemporary and fossil palynomorphs, including pollen, spores, orbicules, dinoflagellate cysts, acritarchs, chitinozoans and scolecodonts, together with particulate organic matter and kerogen found in sedimentary rocks and sediments...

, providing a subdivision of this stage into pollen stages. At the end of the 20th century, the type site
Type site
In archaeology a type site is a site that is considered the model of a particular archaeological culture...

 was re-investigated using old and new data in a multi-disciplinary approach (Cleveringa et al., 2000). At the same time a parastratotype was selected in the Amsterdam
Amsterdam
Amsterdam is the largest city and the capital of the Netherlands. The current position of Amsterdam as capital city of the Kingdom of the Netherlands is governed by the constitution of August 24, 1815 and its successors. Amsterdam has a population of 783,364 within city limits, an urban population...

 glacial basin in the Amsterdam-Terminal borehole and was the subject of a multidisciplinary investigation (Van Leeuwen, et al., 2000). These authors also published a U/Th
Uranium-thorium dating
Uranium-thorium dating, also called thorium-230 dating, uranium-series disequilibrium dating or uranium-series dating, is a radiometric dating technique commonly used to determine the age of calcium carbonate materials such as speleothem or coral...

age for late Eemian deposits from this borehole of 118,200 ± 6,300 years ago. A historical review of Dutch Eemian research is provided by Bosch, Cleveringa and Meijer, 2000.

Further reading


/ Netherlands Journal of Geosciences |volume=79 |issue=2/3 |pages=135–145 |id= |url=http://www.njgonline.nl/publish/articles/000085/article.pdf |accessdate= |quote= }}
  • Cleveringa, P., Meijer, T., van Leeuwen, R.J.W., de Wolf, H., Pouwer, R., Lissenberg T. and Burger, A.W., 2000. The Eemian stratotype locality at Amersfoort in the central Netherlands: a re-evaluation of old and new data. Geologie & Mijnbouw / Netherlands Journal of Geosciences, 79(2/3): 197-216.
  • Harting, P., 1875. Le système Éemien Archives Néerlandaises Sciences Exactes et Naturelles de la Societé Hollandaise des Sciences (Harlem), 10: 443-454.
  • Harting, P., 1886. Het Eemdal en het Eemstelsel Album der Natuur, 1886: 95-100.
  • Lorié, J., 1887. Contributions a la géologie des Pays Bas III. Le Diluvium plus récent ou sableux et le système Eémien Archives Teyler, Ser. II, Vol. III: 104-160.
  • Spaink, G., 1958. De Nederlandse Eemlagen, I: Algemeen overzicht. Wetenschappelijke Mededelingen Koninklijke Nederlandse Natuurhistorische Vereniging 29, 44 pp.
  • Van Leeuwen, R.J. , Beets, D., Bosch, J.H.A., Burger, A.W., Cleveringa, P., van Harten, D., Herngreen, G.F.W., Langereis, C.G., Meijer, T., Pouwer, R., de Wolf, H., 2000. Stratigraphy and integrated facies analysis of the Saalian and Eemian sediments in the Amsterdam-Terminal borehole, the Netherlands. Geologie en Mijnbouw / Netherlands Journal of Geosciences 79, 161-196.
  • Van Voorthuysen, J.H., 1958. Foraminiferen aus dem Eemien (Riss-Würm-Interglazial) in der Bohrung Amersfoort I (Locus Typicus). Mededelingen Geologische Stichting NS 11(1957), 27-39.
  • Zagwijn, W.H., 1961. Vegetation, climate and radiocarbon datings in the Late Pleistocene of the Netherlands. Part 1: Eemian and Early Weichselian. Mededelingen Geologische Stichting NS 14, 15-45.

External links