Blytt-Sernander
Encyclopedia
The Blytt-Sernander classification, or sequence, is a series of north Europe
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 zone
s later defined by Lennart von Post
, one of the founders of palynology
.
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; 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 grenzhorizont, in German
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
and oxygen isotope ratio cycle
s. Currently geologists working in different regions are studying sea levels, peat bogs and ice core
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
and North America
.
The fluctuations of climatic change are more complex than Blytt-Sernander period can identify. For example, recent peat core sample
s at Roskilde Fjord
and also Lake Kornerup in Denmark
identified 40 to 62 distinguishable layers of pollen
, respectively. However, no universally accepted replacement model has been proposed.
dates obtained from peat. Earlier radiocarbon dates were often left uncalibrated; that is, they were derived by assuming a constant concentration of atmospheric radiocarbon. In fact the atmospheric radiocarbon concentration has varied over time and thus radiocarbon dates need to be calibrated
.
of Europe
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 Europe
ans should stop using bronze
and start using iron
abruptly at the lower boundary of the Subatlantic at 600 BC. In the warm Atlantic
period, Denmark
was occupied by Mesolithic
cultures, rather than Neolithic
, notwithstanding the climatic evidence. Moreover, the technology stages vary widely globally.
phases and approximate calibrated dates (see above) are
The Holocene
phases are
/species
studied in peat
are
More sphagnum
appears in wet periods. Dry periods feature more tree stumps, of birch and pine.
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
an climatic periods or phases based on the study of Danish
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
peat bogs by Axel Blytt (1876) and Rutger Sernander (1908). The classification was incorporated into a sequence of pollen zone
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 scientists, such as geologists, climatologisists, geographists and archaeologists, who study the...
s later defined by Lennart von Post
Lennart von Post
Ernst Jakob Lennart von Post 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 University 1929-1950.-Early life:Lennart von Post was born in Johannesberg, near...
, one of the founders of 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...
.
Description
Layers in peatPeat
Peat is an accumulation of partially decayed vegetation matter or histosol. Peat forms in wetland bogs, moors, muskegs, pocosins, mires, and peat swamp forests. Peat is harvested as an important source of fuel in certain parts of the world...
were first noticed by Heinrich Dau
Heinrich Dau
Johann Heinrich Christfried Dau 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-Sernander" sequences based on peat stratigraphy.He died at Altona,...
in 1829. A prize was offered by the Royal Danish Academy of Sciences and Letters
Royal Danish Academy of Sciences and Letters
Royal Danish Academy of Sciences and Letters is a Danish non-governmental science Academy, founded 13 November 1742 by permission of the King Christian VI, as a historical Collegium Antiquitatum...
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 grenzhorizont, in German
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
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
Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...
and oxygen isotope ratio cycle
Oxygen isotope ratio cycle
Oxygen isotope ratio cycles are cyclical variations in the ratio of the abundance of oxygen with an atomic mass of 18 to the abundance of oxygen with an atomic mass of 16 present in some substances, such as polar ice or calcite in ocean core samples. The ratio is linked to water temperature of...
s. Currently geologists working in different regions are studying sea levels, peat bogs and ice core
Ice core
An ice core is a core sample that is typically removed from an ice sheet, most commonly from the polar ice caps of Antarctica, Greenland or from high mountain glaciers elsewhere. As the ice forms from the incremental build up of annual layers of snow, lower layers are older than upper, and an ice...
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
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...
and 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 fluctuations of climatic change are more complex than Blytt-Sernander period can identify. For example, recent peat core sample
Core sample
A core sample is a cylindrical section of a naturally occurring substance. Most core samples are obtained by drilling with special drills into the substance, for example sediment or rock, with a hollow steel tube called a core drill. The hole made for the core sample is called the "core hole". A...
s at Roskilde Fjord
Roskilde Fjord
Roskilde Fjord is the fjord north of Roskilde, Denmark, and is located at . It is a long branch of the Isefjord.-Cities:The cities Frederiksværk, Frederikssund, Jægerspris, Jyllinge and Roskilde, , all have coastline at Roskilde Fjord...
and also Lake Kornerup in Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
identified 40 to 62 distinguishable layers of pollen
Pollen
Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...
, respectively. However, no universally accepted replacement model has been proposed.
Dating and calibration
Today the Blytt-Sernander sequence has been substantiated by a wide variety of scientific dating methods, mainly radiocarbonRadiocarbon dating
Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...
dates obtained from peat. Earlier radiocarbon dates were often left uncalibrated; that is, they were derived by assuming a constant concentration of atmospheric radiocarbon. In fact the atmospheric radiocarbon concentration has varied over time and thus radiocarbon dates need to be calibrated
Radiocarbon dating
Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...
.
Cross-discipline correlation
The Blytt-Sernander classification has been used as a temporal framework for the archaeological culturesArchaeology
Archaeology, or archeology , is the study of human society, primarily through the recovery and analysis of the material culture and environmental data that they have left behind, which includes artifacts, architecture, biofacts and cultural landscapes...
of Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
and America
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. 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 Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
ans should stop using bronze
Bronze
Bronze is a metal alloy consisting primarily of copper, usually with tin as the main additive. It is hard and brittle, and it was particularly significant in antiquity, so much so that the Bronze Age was named after the metal...
and start using iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
abruptly at the lower boundary of the Subatlantic at 600 BC. In the warm Atlantic
Atlantic (period)
The Atlantic in palaeoclimatology was the warmest and moistest Blytt-Sernander period, pollen zone and chronozone of Holocene northern Europe. The climate was generally warmer than today. It was preceded by the Boreal, with a climate similar to today’s, and was followed by the Sub-Boreal, a...
period, Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
was occupied by Mesolithic
Mesolithic
The Mesolithic is an archaeological concept used to refer to certain groups of archaeological cultures defined as falling between the Paleolithic and the Neolithic....
cultures, rather than Neolithic
Neolithic
The Neolithic Age, Era, or Period, or New Stone Age, was a period in the development of human technology, beginning about 9500 BC in some parts of the Middle East, and later in other parts of the world. It is traditionally considered as the last part of the Stone Age...
, notwithstanding the climatic evidence. Moreover, the technology stages vary widely globally.
The sequence
The PleistocenePleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
phases and approximate calibrated dates (see above) are
- Older DryasOlder DryasThe Older Dryas was a stadial period between the Bølling and Allerød oscillations during the Pleistocene glacial period of ~11,700—12,000 uncalibrated years ago...
stadial, 14,000–13,600 BP - AllerødAllerød OscillationThe Allerød period was a warm and moist global interstadial that occurred at the end of the last glacial period. The Allerød oscillation raised temperatures , before they declined again in the succeeding Younger Dryas period, which was followed by the present interglacial period.In some regions,...
interstadial, 13,600–12,900 BP - Younger DryasYounger DryasThe Younger Dryas stadial, also referred to as the Big Freeze, was a geologically brief period of cold climatic conditions and drought between approximately 12.8 and 11.5 ka BP, or 12,800 and 11,500 years before present...
stadial, 12,900–11,640 BP
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"...
phases are
- Preboreal
- BorealBoreal (period)In paleoclimatology of the Holocene, the Boreal was the first of the Blytt-Sernander sequence of north European climatic phases that were originally based on the study of Danish peat bogs, named for Axel Blytt and Rutger Sernander, who first established the sequence. In peat bog sediments, the...
, cool, dry, rising temperature, 11,500–8,900 BP - AtlanticAtlantic (period)The Atlantic in palaeoclimatology was the warmest and moistest Blytt-Sernander period, pollen zone and chronozone of Holocene northern Europe. The climate was generally warmer than today. It was preceded by the Boreal, with a climate similar to today’s, and was followed by the Sub-Boreal, a...
, warm, moist, maximum temperature, 8900–5700 BP - Subboreal, 5700–2600 BP
- Subatlantic, 2600–0 BP
Marker species
Some marker plant generaGenus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
/species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
studied in peat
Peat
Peat is an accumulation of partially decayed vegetation matter or histosol. Peat forms in wetland bogs, moors, muskegs, pocosins, mires, and peat swamp forests. Peat is harvested as an important source of fuel in certain parts of the world...
are
- SphagnumSphagnumSphagnum is a genus of between 151 and 350 species of mosses commonly called peat moss, due to its prevalence in peat bogs and mires. A distinction is made between sphagnum moss, the live moss growing on top of a peat bog on one hand, and sphagnum peat moss or sphagnum peat on the other, the...
- Carex limosaCarexCarex is a genus of plants in the family Cyperaceae, commonly known as sedges. Other members of the Cyperaceae family are also called sedges, however those of genus Carex may be called "true" sedges, and it is the most species-rich genus in the family. The study of Carex is known as...
- Scheuchzeria palustris, Rannock rush
- Eriophorum vaginatumEriophorum vaginatumEriophorum vaginatum L. is a species of perennial herbaceous plants in the family Cyperaceae, native to bogs and other acidic wetlands throughout the Holarctic Kingdom. It is a 30-60 cm high tussock-forming plant with erect solitary spikelets.-External links:* in Flora of North America*...
, cotton grass - Vaccinium oxycoccus, bog cranberry
- Andromeda polifolia, bog rosemary
- Erica tetralixErica tetralixErica tetralix is a species of heather found in Atlantic areas of Europe, from southern Portugal to central Norway, as well as a number of boggy regions further from the coast in Central Europe. In bogs, wet heaths and damp coniferous woodland, Erica tetralix can become a dominant part of the flora...
, cross-leaved heather - Calluna vulgaris, heather
- PinusPinePines are trees in the genus Pinus ,in the family Pinaceae. They make up the monotypic subfamily Pinoideae. There are about 115 species of pine, although different authorities accept between 105 and 125 species.-Etymology:...
, pine - BetulaBirchBirch is a tree or shrub of the genus Betula , in the family Betulaceae, closely related to the beech/oak family, Fagaceae. The Betula genus contains 30–60 known taxa...
, birch
More sphagnum
Sphagnum
Sphagnum is a genus of between 151 and 350 species of mosses commonly called peat moss, due to its prevalence in peat bogs and mires. A distinction is made between sphagnum moss, the live moss growing on top of a peat bog on one hand, and sphagnum peat moss or sphagnum peat on the other, the...
appears in wet periods. Dry periods feature more tree stumps, of birch and pine.