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

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

an climatic periods or phases based on the study of Danish peat bogs by Axel Blytt (1876) and Rutger Sernander (1908). The classification was incorporated into a sequence of pollen zones later defined by Lennart von Post, one of the founders of palynology.

Description

Layers of

peat Peat is an accumulation of partially Decomposition, decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, Moorland, moors, or muskegs. ''Sphagnum'' moss, also called peat moss, is one of the most ...

were first noticed by Heinrich Dau in 1829. A prize was offered by the Royal Danish Academy of Sciences and Letters to anyone who could explain them. Blytt hypothesized that the darker layers were deposited in drier times and 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 peat, which matched Blytt's classification. Sernander defined the 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 and oxygen isotope ratio cycles. Geologists working in different regions are studying sea levels, peat bogs, and ice core samples by a variety of methods, intending to further verify, and refine the Blytt–Sernander sequence. They find a general correspondence across

Eurasia Eurasia ( , ) is a continental area on Earth, comprising all of Europe and Asia. According to some geographers, Physical geography, physiographically, Eurasia is a single supercontinent. The concept of Europe and Asia as distinct continents d ...

and

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

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

Denmark Denmark is a Nordic countries, Nordic country in Northern Europe. It is the metropole and most populous constituent of the Kingdom of Denmark,, . also known as the Danish Realm, a constitutionally unitary state that includes the Autonomous a ...

identified 40 to 62 distinguishable layers of

pollen Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains (highly reduced Gametophyte#Heterospory, microgametophytes), which produce male gametes (sperm ...

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

and start using

iron Iron is a chemical element; it has symbol Fe () 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, forming much of Earth's o ...

abruptly at the lower boundary of the Subatlantic at 600 BC. In the warm Atlantic period,

was occupied by

Mesolithic The Mesolithic (Ancient Greek language, 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 i ...

cultures, rather than

Neolithic The Neolithic or New Stone Age (from Ancient Greek, Greek 'new' and 'stone') is an archaeological period, the final division of the Stone Age in Mesopotamia, Asia, Europe and Africa (c. 10,000 BCE to c. 2,000 BCE). It saw the Neolithic Revo ...

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

Sequence

The

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

phases and approximate calibrated dates (see above) are: * Older Dryas stadial, 14,000–13,600 BP (

Before Present Before Present (BP) or "years before present (YBP)" 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. Because ...

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

Younger Dryas The Younger Dryas (YD, Greenland Stadial GS-1) was a period in Earth's geologic history that occurred circa 12,900 to 11,700 years Before Present (BP). It is primarily known for the sudden or "abrupt" cooling in the Northern Hemisphere, when the ...

stadial, 12,900–11,640 BP The

Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

phases are: * Preboreal * Boreal, cool, dry, rising temperature, 11,500–8,900 BP * Atlantic, warm, moist, maximum temperature, 8900–5700 BP * Subboreal, 5700–2600 BP * Subatlantic, 2600–0 BP

Marker species

Some marker plant

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

studied in

are * ''

Sphagnum ''Sphagnum'' is a genus of approximately 380 accepted species of mosses, commonly known as sphagnum moss, also bog moss and quacker moss (although that term is also sometimes used for peat). Accumulations of ''Sphagnum'' can store water, since ...

'' * '' Carex limosa'' * '' Scheuchzeria palustris'', Rannock rush * '' Eriophorum vaginatum'', cotton grass * '' Vaccinium oxycoccos'', bog cranberry * '' Andromeda polifolia'', bog rosemary * '' Erica tetralix'', cross-leaved heather * '' Calluna vulgaris'', heather * ''

Pinus A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. ''World Flora Online'' accepts 134 species-rank taxa (119 species and 15 nothospecies) of pines as c ...

'', pine * '' Betula'', birch More

sphagnum ''Sphagnum'' is a genus of approximately 380 accepted species of mosses, commonly known as sphagnum moss, also bog moss and quacker moss (although that term is also sometimes used for peat). Accumulations of ''Sphagnum'' can store water, since ...

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