To install click the Add extension button. That's it.

The source code for the WIKI 2 extension is being checked by specialists of the Mozilla Foundation, Google, and Apple. You could also do it yourself at any point in time.

4,5
Kelly Slayton
Congratulations on this excellent venture… what a great idea!
Alexander Grigorievskiy
I use WIKI 2 every day and almost forgot how the original Wikipedia looks like.
Live Statistics
English Articles
Improved in 24 Hours
Added in 24 Hours
What we do. Every page goes through several hundred of perfecting techniques; in live mode. Quite the same Wikipedia. Just better.
.
Leo
Newton
Brights
Milds

Blytt–Sernander system

From Wikipedia, the free encyclopedia

The Blytt–Sernander classification, or sequence, is a series of north European 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 in peat were first noticed by Heinrich Dau in 1829.[1] 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[2] noticed the sharp boundary horizons, or Grenzhorizonte, 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 cycles. 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 periodizations can identify. For example, recent peat core samples at Roskilde Fjord and also Lake Kornerup in Denmark identified 40 to 62 distinguishable layers of pollen, respectively. [3] 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 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 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 Europeans 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.

Sequence

The Pleistocene phases and approximate calibrated dates (see above) are:

The Holocene phases are:

Marker species

Some marker plant genera or species studied in peat are

More sphagnum appears in wet periods. Dry periods feature more tree stumps, of birch and pine.

References

  1. ^ Dau, Allerunterthänigster Bericht an die Königliche Dänische Rentekammer über die Torfmoore Seelands nach einer im Herbste 1828 deshalb unternommenen Reise. (usually simply Über die Torfmoore Seelands) Copenhagen and Leipzig, 1829.
  2. ^ Weber, "Grenzhorizont und Klimaschwankungen" Abhandl. Naturwiss. Vereins, Bremen 26 (1926:98-106).
  3. ^ [1] 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

External links

This page was last edited on 7 September 2021, at 09:53
Basis of this page is in Wikipedia. Text is available under the CC BY-SA 3.0 Unported License. Non-text media are available under their specified licenses. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc. WIKI 2 is an independent company and has no affiliation with Wikimedia Foundation.