The Blytt–Sernander classification, or sequence, is a series of north

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

an climatic periods or phases based on the study of

Danish Danish may refer to: * Something of, from, or related to the country of Denmark People * A national or citizen of Denmark, also called a "Dane," see Demographics of Denmark * Culture of Denmark * Danish people or Danes, people with a Danish ance ...

peat bogs by

Axel Blytt Axel Gudbrand Blytt (19 May 1843 – 18 July 1898) was a Norwegian professor, botanist and geologist. He was the author of a number of books regarding the flora of Norway. Today he is most associated with his role in developing the Blytt-Sernan ...

(1876) and

Rutger Sernander Johan ''Rutger'' Sernander (2November 186627October 1944) was a Swedish botanist, geologist and archaeologist. He was one of the founders of the study of palynology which would later be developed by Lennart von Post, as well as a pioneer in the ea ...

(1908). The classification was incorporated into a sequence of

pollen zone Pollen zones are a system of subdividing the Last Glacial Period and Holocene paleoclimate using the data from pollen cores. The sequence provides a global chronological structure to a wide variety of researchers, such as geologists, climatologi ...

s later defined by

Lennart von Post Ernst Jakob Lennart von Post (16June 188411January 1951) was a Swedish naturalist and geologist. He was the first to publish quantitative analysis of pollen and is counted as one of the founders of palynology. He was a professor at Stockholm Uni ...

, one of the founders of palynology.

Description

Layers in

peat Peat (), also known as turf (), is an accumulation of partially decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, moors, or muskegs. The peatland ecosystem covers and is the most efficien ...

were first noticed by

Heinrich Dau Johann Heinrich Christfried Dau (1790–1831) was a Holstein-Danish geologist and writer, whose identification of peat layers led eventually to a system of classifying and dating post-glacial northern European paleoclimate periods, the Blytt–Sern ...

in 1829. A prize was offered by the

Royal Danish Academy of Sciences and Letters {{Infobox organization , name = The Royal Danish Academy of Sciences and Letters , full_name = , native_name = Det Kongelige Danske Videnskabernes Selskab , native_name_lang = , logo = Royal ...

to anyone who could explain them. Blytt hypothesized that the darker layers were deposited in drier times; the lighter, in moister times, applying his terms ''Atlantic'' (warm, moist) and ''Boreal'' (cool, dry). In 1926 C. A. Weber noticed the sharp boundary horizons, or ''Grenzhorizonte'', in

German German(s) may refer to: * Germany (of or related to) **Germania (historical use) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizens of Germany, see also German nationality law **Ger ...

peat, which matched Blytt’s classification. Sernander defined subboreal and subatlantic periods, as well as the late glacial periods. Other scientists have since added other information. The classification was devised before the development of more accurate dating methods, such as

C-14 dating Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon. The method was dev ...

and oxygen isotope ratio cycles. Geologists working in different regions are studying sea levels, peat bogs and

ice core An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier. Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper ones, and an ice core contains ic ...

samples by a variety of methods, with a view toward further verifying and refining the Blytt–Sernander sequence. They find a general correspondence across

Eurasia Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelago a ...

and

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

. The fluctuations of climatic change are more complex than Blytt–Sernander periodizations can identify. For example, recent peat core samples at Roskilde Fjord and also Lake Kornerup in

Denmark ) , song = ( en, "King Christian stood by the lofty mast") , song_type = National and royal anthem , image_map = EU-Denmark.svg , map_caption = , subdivision_type = Sovereign state , subdivision_name = Danish Realm, Kingdom of Denmark ...

identified 40 to 62 distinguishable layers of

pollen Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...

, respectively.
N. Schrøder et al, 2004. 10,000 Years of Climate Change and Human Impact on the Environment in the Area Surrounding Lejre. Journal - TES vol. 3, no. 1, 2004 However, no universally accepted replacement model has been proposed.

Problems

Dating and calibration

Today the Blytt–Sernander sequence has been substantiated by a wide variety of scientific dating methods, mainly Radiocarbon dating, radiocarbon dates obtained from peat. Earlier radiocarbon dates were often left uncalibrated; that is, they were derived by assuming a constant concentration of atmospheric radiocarbon. The atmospheric radiocarbon concentration has varied over time and thus radiocarbon dates need to be calibrated.

Cross-discipline correlation

The Blytt–Sernander classification has been used as a temporal framework for the archaeological cultures of

and

America The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

. Some have gone so far as to identify stages of technology in north Europe with specific periods; however, this approach is an

oversimplification The fallacy of the single cause, also known as complex cause, causal oversimplification, causal reductionism, and reduction fallacy, is an informal fallacy of questionable cause that occurs when it is assumed that there is a single, simple cause of ...

not generally accepted. There is no reason, for example, why the north

ans should stop using

bronze Bronze is an alloy consisting primarily of copper, commonly with about 12–12.5% tin and often with the addition of other metals (including aluminium, manganese, nickel, or zinc) and sometimes non-metals, such as phosphorus, or metalloids such ...

and start using

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...

abruptly at the lower boundary of the

Subatlantic The Subatlantic is the current climatic age of the Holocene epoch. It started about 2,500 years BP and is still ongoing. Its average temperatures are slightly lower than during the preceding Subboreal and Atlantic. During its course, the tempe ...

at 600 BC. In the warm

Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...

period,

was occupied by

Mesolithic The Mesolithic (Greek: μέσος, ''mesos'' 'middle' + λίθος, ''lithos'' 'stone') or Middle Stone Age is the Old World archaeological period between the Upper Paleolithic and the Neolithic. The term Epipaleolithic is often used synonymous ...

cultures, rather than

Neolithic The Neolithic period, or New Stone Age, is an Old World archaeological period and the final division of the Stone Age. It saw the Neolithic Revolution, a wide-ranging set of developments that appear to have arisen independently in several parts ...

, notwithstanding the climatic evidence. Moreover, the technology stages vary widely globally.

Sequence

The

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

phases and approximate calibrated dates (see above) are: *

Older Dryas The Older Dryas was a stadial (cold) period between the Bølling and Allerød interstadials (warmer phases), about 14,000 years Before Present, towards the end of the Pleistocene. Its date is not well defined, with estimates varying by 400 years, ...

stadial, 14,000–13,600 BP (

Before Present Before Present (BP) years, or "years before present", is a time scale used mainly in archaeology, geology and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Becaus ...

) * Allerød interstadial, 13,600–12,900 BP *

Younger Dryas The Younger Dryas (c. 12,900 to 11,700 years BP) was a return to glacial conditions which temporarily reversed the gradual climatic warming after the Last Glacial Maximum (LGM, c. 27,000 to 20,000 years BP). The Younger Dryas was the last stage ...

stadial, 12,900–11,640 BP The

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...

phases are: *

Preboreal The Preboreal is an informal stage of the Holocene epoch. It is preceded by the Tarantian and succeeded by the Boreal. It lasted from 10,300 to 9,000 BP in radiocarbon years or 8350BC to 7050BC in Gregorian calendar years (8th millennium BC). I ...

Boreal Boreal may refer to: Climatology and geography *Boreal (age), the first climatic phase of the Blytt-Sernander sequence of northern Europe, during the Holocene epoch *Boreal climate, a climate characterized by long winters and short, cool to mild ...

, cool, dry, rising temperature, 11,500–8,900 BP *

, warm, moist, maximum temperature, 8900–5700 BP *

Subboreal The Subboreal is a climatic period, immediately before the present one, of the Holocene. It lasted from 3710 to 450 BCE. Etymology The composite scientific term ''Subboreal'', meaning "below the Boreal," is derived from the Latin ''sub'' (bel ...

, 5700–2600 BP *

, 2600–0 BP

Marker species

Some marker plant

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

studied in

are * '' Sphagnum'' * ''

Carex limosa ''Carex limosa'' is a species of sedge known as bog-sedge, mud sedge, and shore sedge. Distribution This sedge is an aquatic or shore plant which can most often be found in peat bogs in mountains. It is widely distributed across North America ...

'' * ''

Scheuchzeria palustris ''Scheuchzeria palustris'' (Rannoch-rush, or pod grass), is a flowering plant in the family Scheuchzeriaceae, in which there is only one species and ''Scheuchzeria'' is the only genus. In the APG II system it is placed in the order Alismatales of ...

'', Rannock rush * ''

Eriophorum vaginatum ''Eriophorum'' (cottongrass, cotton-grass or cottonsedge) is a genus of flowering plants in the family Cyperaceae, the sedge family. They are found throughout the arctic, subarctic, and temperate portions of the Northern Hemisphere in acid bog ha ...

'', cotton grass * ''

Vaccinium oxycoccos ''Vaccinium oxycoccos'' is a species of flowering plant in the heath family. It is known as small cranberry, marshberry, bog cranberry, swamp cranberry, or, particularly in Britain, just cranberry. It is widespread throughout the cool temperate ...

'', bog cranberry * ''

Andromeda polifolia ''Andromeda polifolia'', common name bog-rosemary, is a species of flowering plant in the heath family Ericaceae, native to northern parts of the Northern Hemisphere. It is the only member of the genus ''Andromeda'', and is only found in bogs in ...

'', bog rosemary * ''

Erica tetralix ''Erica tetralix'', the cross-leaved heath, is a species of flowering plant in the family Ericaceae, native to western Europe, from southern Portugal to central Norway, as well as a number of boggy regions further from the coast in Central Europe ...

'', cross-leaved heather * ''

Calluna vulgaris ''Calluna vulgaris'', common heather, ling, or simply heather, is the sole species in the genus ''Calluna'' in the flowering plant family Ericaceae. It is a low-growing evergreen shrub growing to tall, or rarely to and taller, and is found wid ...

'', heather * '' Pinus'', pine * '' Betula'', birch More sphagnum appears in wet periods. Dry periods feature more tree stumps, of birch and pine.

References

External links

the Holocene

{{DEFAULTSORT:Blytt-Sernander system Chronology Holocene Paleoclimatology Paleoecology Palynology Dating methodologies in archaeology