Older dryas period

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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

In geological history, the older Dryas period is the name for a cool period between the Bölling interstadial and the Alleröd interstadial of the late Weichselian glacial period ( Quaternary ). The older dryas period began 13,540 years ago and ended around 13,350 years ago (according to the varven chronology in the Meerfelder Maar ). The time period was marked by a renewed, significant cooling with a relapse into a strauchtundra or thickened birch forest.

Naming and conceptual history

The name Older Dryaszeit, often just Older Dryas , also Middle Tundra Time or Dryas 2 , was coined by Johannes Iversen in 1942. Dryas is the botanical generic name of the white silver arum ( Dryas octopetala) , which was common throughout Germany and Scandinavia during this time.

definition

The Older Dryas period was defined by Johannes Iversen in the type profile Bølling Sø . In general, this interval is characterized by a sharp decrease in (tree) birch pollen and an increase in non-tree pollen.

stratigraphy

The Older Dryas Period, also known in the North Atlantic as Inter Allerød Cold Period I (IACP I), forms the cool central part of the three-part Greenland Interstadial  1c  (GI-1c) and therefore corresponds to the Greenland Interstadial 1c2  (GI-1c2). It follows the relatively warm Greenland Interstadial 1c3  (GI-1c3), which is already part of the Bölling Interstadial . The warm Greenland Interstadial 1c1  (GI-1c1), which forms the beginning of the Alleröd Interstadial , joins it.

In North America and the North Atlantic area, the 400 years older oldest  dryas period or the Aegelsee fluctuation - Greenland-Interstadial 1d (GI-1d) - is referred to as the older dryas. Because of the risk of stratigraphic confusion, caution is advised when using the term Older Dryas.

Dating

The Older Dryas Period has now been widely documented in northern Germany. According to the varven chronology in the Meerfelder Maar, it is dated from 13,540 varven years vh to around 13,350 varven years vh, ie this is converted from 11,590 to 11,400 BC. The Geozentrum Hannover, however, dates the older Dryas period with 13,480 to 13,350 cal. Vh Van Raden (2012) has recently also used the somewhat older period 11674 to 11572 BC. Considered.

Environmental parameters

Oxygen isotopes

During the Older Dryas Period, the δ 18 O values experienced a decrease of 2.5 ‰ SMOW , they fell from -37.5 to just under -40 ‰ SMOW. The minimum comes around 11600 BC. To lie.

Paleogeography

The Baltic Ice Reservoir was located in northwest Europe and was cut off by the edge of the ice sheet. Denmark and southern Sweden were ice-free and could therefore be colonized by pioneer plants. Northern Scandinavia was completely iced over, most of Finland was buried under ice and the Baltic countries were inundated by the ice reservoir. Between the British Isles and the European mainland, which at that time were still connected due to the low sea level, lay the so-called Doggerland , a rolling hilly landscape rich in game; hundreds of tons of bone material were recovered from the bottom of the North Sea here.

vegetation

Depending on the permafrost boundary and the latitude , northern Europe was covered by steppe or tundra vegetation . Wetlands on lakes and rivers were dense with dwarf birch , willow , sea ​​buckthorn and juniper . In the river lowlands and higher altitudes further south, sparse birch forests grew .

Birch and pine were the first trees to migrate to Northern Europe during the Bölling Interstadial. Due to the cooling in the Elder Dryas, there was a renewed advance of the ice masses. As a consequence, the forests withdrew again to the south and were replaced by open grasslands with alpine, cold-resistant plants. A comparable, arctic park tundra can be found today in Siberia in the transition zone between taiga and tundra. In the Older Dryas, however, it stretched in an almost uninterrupted band from Siberia to Great Britain.

The following are to be mentioned for alpine indicator plants:

Under the trees are:

The following should be mentioned as regards grassland taxa:

Cultural history

The humans (Homo sapiens sapiens of the Cro-Magnon type) were still in the late Upper Paleolithic during the Older Dryas . They were organized in groups and survived in the plains of Eurasia by hunting reindeer (Northern Europe) or woolly mammoths (Ukraine). They are already using dogs (Canis familiaris) on their hunting expeditions. The culture of the late Upper Palaeolithic was not uniform; rather, several regional traditions had developed. For example, the Azilien (12300 to 9600 BC) in France , the penknife groups (12000 to 10800 BC) in north-western Central Europe , the Bromme culture (11400 to 10500 BC) in southern Scandinavia , the Creswellia (12,500 to 8,000 BC) in southern England and Wales and the Swideria (13,000 to 9,500 BC) in Poland and Hungary .

See also

swell

literature

  • Thomas Litt, Karl-Ernst Behre, Klaus-Dieter Meyer , Hans-Jürgen Stephan and Stefan Wansa: Stratigraphic terms for the Quaternary of the northern German glaciation area. Ice Age and Present (Quaternary Science Journal), 56 (1/2): 7-65, Hannover 2007 ISSN  0424-7116 doi : 10.3285 / eg.56.1-2.02

Individual evidence

  1. ↑ Litt et al. (2007): p. 62
  2. ↑ Brauer, A. et al.: Land – ice teleconnections of cold climatic periods during the last Glacial / Interglacial transition . In: Climate Dynamics . tape 16 (2-3) , 2000, pp. 229-239 .
  3. ↑ a b van Raden, UJ 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, p. 1-12 .
  4. ↑ Page no longer available , search in web archives: The Quaternary in Lower Saxony and neighboring areas (PDF)@1@ 2Template: Toter Link / cdl.niedersachsen.de
  5. ↑ Hoek, Wim Z .: The last Glacial-Interglacial Transition . In: Episodes . 31, N ° 2, 2008, p. 226-229 .