Alleröd Interstadial

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Series /
( Glacial ) 		  Climatic levels   Period
v. Chr.
Holocene
Preboreal 9,610-8,690
Pleistocene
( Vistula
- Late Glacial )
Younger dryas period 10,730-9,700 ± 99
Alleröd Interstadial 11,400-10,730
Older dryas period 11,590-11,400
Bölling-Interstadial 11,720-11,590
Oldest dryas period 11,850-11,720
Meiendorf-Interstadial 12,500-11,850
( Vistula
- high glacial )
Mecklenburg phase

The Alleröd interstadial , also Allerød interstadial or Alleröd fluctuation , is the last warm phase ( interstadial ) shortly before the end of the last cold period ( Quaternary ). It lasted from 13,350 to 12,680 varve years BC. i.e., this corresponds to 11,400 to 10,730 BC. Chr.

Naming and conceptual history

The name was suggested by Nikolaj Hartz and Vilhelm Milthers in 1901 for late soft glacial, interstadial deposits. The interstadial conditions were developed on the basis of large plant residues. This warm phase was named after the type locality Allerød in Sjælland ( Denmark ), northwest of Copenhagen. Johannes Iversen was able to record this warmer phase using pollen and called it the Alleröd oscillation or Alleröd period .

definition

The beginning of the Alleröd Interstadial is defined by the expansion of the birch forests . At the end of the Alleröd Interstadial (and thus the beginning of the Younger Dryas Period ) they disappeared again and were replaced by a Strauchtundra .

Regional equivalents are the Windermere Interstadial in Great Britain (11,900 to 11,150 BC), the Woodgrange Interstadial in Ireland (11,800 to 11,000 BC) and the Two Creeks Interstadial in North America (11,350 to 10,050 BC). ).

The original type profile at Allerød (Zealand, Denmark) no longer exists today. Bølling Sø ( Jutland , Denmark) is therefore considered a parastratotype .

stratigraphy

The onset and duration of the Alleröd interstadial may vary slightly from region to region. The Older Dryas Period went ahead , while the Younger Dryas Period followed. With the Younger Dryas Period, the Pleistocene ended and the Holocene began.

According to Rasmussen et al. a. In 2006 the Alleröd-Interstadial includes the periods (from young to old):

  • GS-1 Greenland Stadial - 10,946 to 9,753 BC Chr .: Younger Dryas
  • GI-1a Greenland-Interstadial 1a - 11,149 to 10,946 BC Chr. - warm: warm-up phase before the onset of the younger dryas
  • GI-1b Greenland Interstadial 1b - 11,361 to 11,149 BC Chr. - cool: Gerzensee fluctuation
  • GI-1c Greenland-Interstadial 1c - 12,004 to 11,361 BC Chr. - warm: Alleröd biozone
    The Greenland Interstadial 1c can also be further subdivided (from young to old):
    • GI-1c1 - 11,572 to 11,324 BC Chr. - warm
    • GI-1c2 - 11,674 to 11,572 BC Chr. - cold: Aegelsee fluctuation or older dryas
    • GI-1c3 - 11,958 to 11,674 BC Chr. - warm

The Alleröd Interstadial usually follows the Older Dryas with the period GI-1c1. Occasionally, however, its duration is understood longer; For example, it begins in southern Germany, Switzerland, North America and the North Atlantic region immediately after the Elder Dryas with the period GI-1c3.

For a detailed stratigraphy see van Raden u. a. 2012.

Dating

The dating is secured with the help of the dendrochronology and the warven chronology attached to it . According to varven chronology, the Alleröd interstadial lasted from 13,350 to 12,680 varven years BC. H. Converted this means 11,400 to 10,730 BC. The Geozentrum Hannover dates this interval to 13,350 to 12,700 BC. H.

The evaluation of the annual conditions in the Greenland ice, however, showed a significantly longer period of 971 ± 31 years for GRIP and 1091 ± 29 years for NGRIP for the Alleröd interstadial . The GISP2 core even suggests 1120 ± 56 years. This discrepancy in the duration of the Alleröds can be explained by its extension to the Elder Dryas, already mentioned above.

In Scandinavia, Mangerud et al. a. In 1974 the Alleröd Interstadial was defined as 11,800 to 11,000 radiocarbon years (corresponding to 11,757 to 10,973 BC).

volcanic eruptions

The eruption of the Laacher volcano ( Laacher See ) is an outstanding geological event (large-scale deposition of pumice , detectable as far as Northern Europe) that took place in this time interval. It is located in the middle of the Gerzensee fluctuation (GI-1b). The volcanic ash , which is carried far away by the wind, allows correlation over long distances within Western, Central and Northern Europe. According to the dating, the eruption occurred 12,880 varven years BC. H. (based on 1950), d. H. in 10,930 BC Chr.

A regionally much more limited eruption occurred at the Puy de la Nugère in the French Massif Central , the tephren of which can at least be detected in the French Jura . Two tephra layers are assigned to the intervals from 13,420 to 13,010 and from 13,300 to 12,880 a BP.

A smaller eruption had started in the Chaîne des Puys around 13,200 ± 1,300 years BP from the Puy de Gorce .

Three reconstructions of past temperatures. The red grip sequence of the northern hemisphere shows the Dryas event (younger and older Dryas) around 13,000 years ago (1.3 × 10 4 ) with a group of clear rashes . In the curves of the southern hemisphere ( Vostok , EPICA from Antarctica ) a drop in the isotope ratio can be seen almost simultaneously.

Development of vegetation history

In Alleröd, which was very similar to today's climate, there was the first extensive reforestation in Eurasia and Central Europe after the last Ice Age (= Vistula high glacial ). Mainly mixed deciduous / coniferous forests were installed, with deciduous forests predominating in southern regions. The first section of the Alleröd was characterized by light birch forests, later there was a closed, but not too dense forest, in which the pine dominated (pine maximum around 11,000 BC). There were also aspen , spruce , larch and juniper mixed with oak , willow and hazel . Clear grasses (Poaceae), foxtail plants (Chenopodiaceae) and Artemisia were populated by clearings and open areas . Around 11,000 BC The so-called pine fall occurred in northern Italy , d. H. the pine forests that had dominated up to that point were noticeably thinning. The birch benefited from this as it regained dominance. The birch peak was not reached until the beginning of the Younger Dryas (around 10,300 BC).

Environmental parameters

Temperatures

According to Johnsen et al. a. In 1995 the temperatures during the Alleröd Interstadial in Greenland were 5 to 12  K colder than today, for Ireland the figure is 4 to 5 K towards the end of the Alleröd.

After the maximum temperature in the Bölling-Interstadial, a general cooling trend began, which gradually continued in the Alleröd-Interstadial. For example, if the summer average temperatures (July) for Ireland at the beginning of the Alleröd were still 13 ° C, by the beginning of the Younger Dryas they had cooled to around 10 ° C.

The around 11,950 BC The Alleröd Biozone (GI-1c), beginning in BC, was warm, but showed a slight decrease in temperature with several oscillations. The Gerzensee fluctuation (GI-1b), English Intra Allerød Cold Period , brought about from 11,300 BC. A significant cooling of up to 2 K. The from 11.100 BC. The beginning of the warm-up phase before the beginning of the Younger Dryas (GI-1a), English pre Younger Dryas Warming , also with 2 K restored the temperature conditions prevailing towards the end of the Alleröd Biozone, and then with a significant drop in temperature of just 3 K to the younger one To pass dryas.

Oxygen isotopes

The δ 18 O values go up to 11,000 BC. BC steadily and significantly decreased by 12% (from - 36 ‰ to - 41 ‰), and then rose again to - 38 ‰ by the end of the Alleröd interstadial (in GI-1a).

Carbon isotopes

The δ 13 C values ​​also steadily decrease by 57% during the Alleröds (from 3.5 to 1.5 ‰), whereby the Gerzensee fluctuation slows this down somewhat.

Cultural history

At the type locality Allerød in Denmark , northwest of Copenhagen (Denmark), archaeological remains from this period, which was important for the development of European settlements in the late Paleolithic ( late Paleolithic ), were found for the first time at the end of the 19th century . Due to the increasing forest cover in Central Europe, the large herds of the open country were displaced as the livelihood of the Magdalenian hunters . As a result, settlements and hunting camps became smaller; Archaeological remains of the Alleröd are called penknife groups in northern Germany after the typical stone tool shape . In southern Germany there is a contact zone with the late Magdalenian period. At about the same time, the Bromme culture developed in southern Scandinavia (11,400 to 10,500 BC) and the Swideria in Poland and Hungary (13,000 to 9,500 BC). The Ahrensburg culture began towards the end of the Alleröd Interstadial (10,760 to 9,650 BC). The Neolithic had already begun in the southeastern Mediterranean .

literature

Individual evidence

  1. ↑ Litt et al., 2007, pp. 62/3.
  2. ^ N. Hartz, V. Milthers: Det senglaciale Ler i Allerød Teglværksgrav. In: Meddelelser fra Dansk geologisk Forening , Volume 8, 1901, pp. 31-60.
  3. ↑ SO Rasmussen u. a .: A new Greenland ice core chronology for the last glacial termination . In: Journal of Geophysical Research . tape 111 , 2006.
  4. ↑ UJ van Raden et al .: High-resolution late-glacial chronology for the Gerzensee lake record (Switzerland): δ18O correlation between a Gerzensee-stack and NGRIP . In: Palaeogeography, Palaeoclimatology, Palaeoecology . 2012.
  5. ↑ The Quaternary in Lower Saxony and neighboring areas (PDF) ( Memento of the original from January 14, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / www.lbeg.niedersachsen.de
  6. ↑ Kathrine Seierstad: Annual layer counting in the Bølling-Allerød and Younger Dryas sections of the GRIP ice core using deconvoluted isotope data, dust and chemical data. Diploma thesis, University of Copenhagen . 2005, p. 120 .
  7. ↑ J. Mangerud, ST Andersen, BE Berglund, JJ Donner: Quaternary stratigraphy of Norden, a proposal for terminology and classification . In: Boreas . tape 3 , 1974, p. 109-128 .
  8. ↑ Jouannic, G. u. a .: Feldspar composition as an efficient tool for tephra identification: a case study from Holocene and Lateglacial lacustrine sequences (Jura, France) . In: Journal of Quaternary Science . tape 30 (6) , 2015, pp. 569-583 , doi : 10.1002 / jqs.2803 .
  9. ↑ Guérin, G .: Thermoluminescence des plagioclases. Méthode de datation du volcanisme. Applications au domaine volcanique français: Chaîne des Puys, Mont Dore et Cézallier, Bas Vivarais. Thèse d'Etat . Université Pierre et Marie Curie, Paris 1983, p. 253 .
  10. ↑ Manfred Rösch et al.: Pollen analyzes on three drill cores from the Profundal of Lake Orta. In: Astrid Stobbe, Ursula Tegtmeier (Ed.): Branches. An appreciation for Arie J. Kalis and Jutta Meurers-Balke (= Frankfurter Archäologische Schriften . Volume 18). Habelt, Bonn 2012, pp. 225–247.
  11. ↑ SJ Johnsen et al .: Greenland palaeotemperatures derived from GRIP bore hole temperature and ice core isotope profiles . In: Tellus . 47B, 1995, pp. 624-629 .
  12. ^ MJC Walker et al .: The Devensian / Weichselian Late-glacial in northwest Europe (Ireland, Britain, north Belgium, The Netherlands, northwest Germany) . In: Journal of Quaternary Science . tape 9 , 1994, pp. 109-118 .
  13. ^ SJ Johnsen et al .: Oxygen isotope and palaeotemperature records from six Greenland ice-core stations: Camp Century, Dye-3, GRIP, GISP2, Renland and NorthGRIP . In: Journal of Quaternary Science . tape 16 (4) , 2001, p. 299-307 .
  14. ↑ MCH Duijkers: Lateglacial climate and timing derived from multiproxy and microtephra analysis at Lurga, western Ireland. Thesis. 2009.

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