Subboreal

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series Climate level Pollen
zone 		Period
Holocene Subatlantic X 450 BC Until today
IX
Subboreal VIII 3,710-450 BC Chr.
Atlantic VII 7,270-3,710 BC Chr.
VI
Boreal V 8,690-7,270 BC Chr.
Preboreal IV 9,610-8,690 BC Chr.
Pleistocene
Younger dryas period III 10,730-9,700 ± 99 BC Chr.

The Subboreal according to the Blytt-Sernander classification in the geological the second youngest period of the Holocene in North-West Europe. It lasted from 3710-450 BC. Chr.

Definition of terms and stratigraphic position

The term subboreal ( Latin sub 'below, below, below' and Greek Βορέας Boreas 'god of the north wind'), often referred to as the late warm period or mixed oak forest alder period , was coined by Rutger Sernander to distinguish it from Axel Blytts Boreal . The subboreal follows the immediately preceding Atlantic and is in turn replaced by the sub- Atlantic .

The subboreal corresponds to the pollen zone VIII by Franz Firbas (1949), X in the diagram by Fritz Theodor Overbeck (1975), and IVa and IVb by WH Zagwijn.

In terms of climate stratigraphy, the subboreal can be divided into an older subboreal and a younger subboreal . It is assigned to either the Middle Holocene or the Young Holocene . In terms of cultural history, the subboreal encompasses most of the Neolithic and the entire Bronze Age (beginning at 4200 to 3800 years BP).

Chronological order

Mesolithikum Neolithikum Bronzezeit Eisenzeit Yoldia-Meer Ancylussee Littorinameer Flandrische Transgression Dünkirchen-Transgression Präboreal Boreal (Klimastufe) Atlantikum Subatlantikum

Note: Only the borders marked with a black dividing line are more or less exact; they are based on annual layers in lake sediments in north-central Europe and, strictly speaking, only apply to the climatic stages. The other boundaries are uncertain and not rigidly set. In particular, the boundary between the Middle and Young Holocene is very variable. Regarding the cultural levels, the regionally different development must be taken into account.

Age

The lower limit of the subboreal is 3710 BC. BC (5660 years  BP ). However, this limit is not to be regarded as rigid. For example, some authors put the beginning of the subboreal earlier at 6350 years BP (4400 BC) or in north-western Poland at 6780 years BP (4830 BC); others, on the other hand, estimate only 5000 years BP (3050 BC). Chr.). It ends at 450 BC. The upper limit (and thus the transition to the subatlantic) is also not rigidly fixed, but can be as early as 1170 to 830 BC. Take place. In varve years , the subboreal corresponds to the period 5660 to 2750 years BP.

The boundary between the Elderly and the Younger Subboreal is mostly believed to be 1350 BC. Chr. Indicated.

Climate history

The temperature curve in the Holocene

The climate during the subboreal was drier and slightly cooler (on average around 0.1  K ) compared to the preceding Atlantic , even if it was still warmer than today. The temperatures were on average 0.7 K higher than in the current subatlantic. A consequence was that during the subboreal the lower limit of the glaciers in Scandinavia was raised by 100 to 200 meters compared to the subatlantic. Overall, however, the annual average temperatures within the subboreal were generally declining with several fluctuations (they slowly cooled by up to 0.3 K).

The beginning of the subboreal is marked in the Aegean region by a hundred-year drought centered at 5600 years BP. However, this event is expected by the end of its significance far African humidity period ( Engl. African Humid Period ) have been exceeded at this time. In lakes in subtropical Africa (such as Lake Chad ), a rapid decline in the lake level was observed at that time. In southern Mesopotamia , too, an increasing aridity spread in the period from 6200 to 5000 years BP, which led to demographic upheavals and possibly brought about the end of Uruk .

In northwestern Europe ( Eifelmaare ) a climatic break can be observed from 5000 varven years BP. For example, the July temperatures during the previous Holocene optimum in the period 8200 to 5000 varven years BP were on average 1 K higher. Coupled with the drop in summer temperatures, however, was an increase in the January mean and an increase in annual precipitation .

The period 4700 to 4100 years BP is again characterized by persistent drought in northern Africa and the Middle East , underlined by lake level minima. The decline in monsoon rains between 4500 and 4000 years BP likely brought about the turmoil and eventually the end of the Old Kingdom of Egypt . A very similar development took place in the Levant . The drought peak in Mesopotamia at 4200 years BP is likely to have triggered the decline of the Akkadian Empire .

Greenhouse gas carbon dioxide

The greenhouse gas carbon dioxide had reached a Holocene minimum value of 260 ppm at the beginning of the subboreal  . This value then rose steadily with slight fluctuations to 293 ppm at the end of the subboreal.

Vegetation-historical developments

Beech stand in Zonienwoud near Brussels, Belgium

In Scandinavia , the transition between the Atlantic and the subboreal is a sharp and easily recognizable border based on the composition of the vegetation. The transition is less clear in Western Europe . A typical feature here is the rapid decline of elms and linden trees as part of the characteristic mixed oak forest (EMW). The reasons for the decline in the linden trees are not clear, possibly it was due to the colder climate or human influences. The decline in elms (so-called elm fall ), which can be attributed to a fungal disease transmitted by the elm splint beetle ( Scolytus scolytus , Scolytus multistriatus ) by an ascomycete ( Ceratocystis ulmi ), was probably also promoted by climatic changes and anthropogenic use ( e.g. snipping ) . The in Central and Northern Europe with about 4000 BC Elmenfall dated to the 4th century BC (in Eifelmaaren, for example, a decrease from 20 to 4% was observed) is more likely to have run diachronically and spread over the period 4350 to 3780 BC. Have extended.

Another forest-historical event of the subboreal is the immigration of the common beech ( Fagus sylvatica ) and the hornbeam ( Carpinus betulus ) from the refuges of the Balkan peninsula and south of the Apennines . These two processes were also diachronic - beech pollen was first used from 4340 to 3540 BC. And hornbeam pollen a little later from 3400 to 2900 BC Proven. With the onset of the younger subboreal, the actual expansion of the beeches began. During the establishment of the beech and hornbeam was under simultaneous occurrence of settlement pointers (. Eg Getreidetaxa and plantain - Plantago lanceolata ) a decrease in the hazel recorded.

The drier climate during the subboreal also caused the spread of heather plants .

Sea level

The postglacial sea level rise

As in the previous Atlantic, the sea ​​level continued to rise during the subboreal . The increase was only around 1 meter, or 0.3 millimeters / year, over the entire period. At the end of the subboreal, the sea level was then 1 meter below sea level.

Development in the Baltic Sea Region

The Baltic Sea had already developed into the Littorina Sea before the subboreal began . The second Littorina transgression took place in the older subboreal, reaching 1 meter below sea level. After the late Littorine regression , the 3rd Littorina transgression occurred towards the end of the younger subboreal, which was 60 centimeters below sea level (and later in the beginning subatlantic approached the current water level).

Development in the North Sea region

In the North Sea region , after the Flanders Transgression that had taken place in the Atlantic, at the beginning of the suboreal there was a slight drop in sea level or a sea level standstill.

See also

Individual evidence

  1. ^ Structure of the Holocene. Geocenter Hanover (PDF; 405 kB).
  2. ↑ R. Sernander: Om växtlämningar i Scandinavia marina bildningar . In: Bot. Not. 1889 . Lund 1889, p. 190-199 .
  3. ↑ A. BIytt: Immigration of the Norvegian Flora . Alb. Cammermeyer, Christiania (Oslo) 1876, p. 89 .
  4. ↑ Waldo Helio Door Zagwijn : Nederland in het Holoceen . In: Rijks Geologische Dienst Haarlem (Ed.): Geologie van Nederland . Deel 1. Staatsuitgeverij, 's-Gravenhage 1986.
  5. ^ CM Herking: Pollen analysis of the Holocene vegetation history along the eastern lower Oder valley and southern lower Warta valley in north-western Poland. Dissertation . Göttingen, Georg August University 2004.
  6. ↑ K. Tobolski: Paleo-ecological studies of the settlement area in Lednica Landscape Park (north-west Poland) . In: Offa . tape 47 , 1990, pp. 109-131 .
  7. ↑ S. Jahns: Late-glacial and Holocene woodland dynamics and land-use history of the lower Oder valley, north-eastern Germany, based on two, AMS 14C-dated, pollen profiles . In: Vegetation History and Archaeobotany . tape 9 (2) , 2000, pp. 111-123 .
  8. ↑ a b T. Litt et al .: Vegetation and climate history in the Westeifel Volcanic Field (Germany) during the past 11,000 years based on annually laminated lacustrine maar sediments . In: Boreas . tape 38 , 2009, p. 679-690 .
  9. ↑ SO Dahl, A. Nesje: A new approach to calculating Holocene winter precipitation by combining glacier equilibrium line altitudes and pine-tree limits: a case study from Hardangerjøkulen central southern Norway . In: The Holocene . tape 6 , 1996, pp. 381-398 .
  10. ↑ U. Kotthoff et al .: Lateglacial and Holocene vegetation dynamics in the Aegean region: an integrated view based on pollen data from marine and terrestrial archives . In: The Holocene . tape 18, 7 , 2008, pp. 1019-1032 .
  11. ↑ PB de Menocal et al .: Abrupt onset and termination of the African Humid Period: rapid climate responses to gradual insolation forcing . In: Quaternary Science Reviews . tape 19 , 2000, pp. 347-61 .
  12. ^ DJ Kennett, JP Kennett: Early state formation in southern Mesopotamia: sea levels, shorelines, and climate change . In: Journal of Island and Coastal Archeology . tape 1 , 2006, p. 67-99 .
  13. ^ F. Gasse, E. Van Campo: Abrupt post-glacial events in West Asia and North Africa monsoon domains . In: Earth and Planetary Science Letters . tape 126 , 1994, pp. 435-56 .
  14. ^ F. Gasse: Hydrological changes in the African tropics since the Last Glacial Maximum . In: Quaternary Science Reviews . tape 19 , 2000, pp. 189-211 .
  15. ↑ Y. Enzel et al .: Late Holocene climates of the Near East Documented from Dead Sea level variations and regional winter rainfall . In: Quaternary Research . tape 60 , 2003, p. 263-73 .
  16. ^ H. Weiss et al .: The genesis and collapse of third millennium North Mesopotamian civilization . In: Science . tape 261 , 1993, pp. 995-1004 .
  17. ↑ F. Parrenin, L. Loulergue, E. Wolff: EPICA Dome C Ice Core Time Scales . In: World Data Center for Paleoclimatology Data Contribution Series # 2007-083.NOAA / NCDC Paleoclimatology Program . Boulder CO, USA 2007.
  18. ↑ SM Peglar, HJB Birks: The mid-Holocene Ulmus fall at Diss Mere, South-East England - disease and human impact? In: Vegetation History and Archaeobotany . tape 2 , 1993, p. 61-68 .
  19. ↑ K.-E. Behre, D. Kucan: The history of the cultural landscape and agriculture in the settlement chamber Flögeln, Lower Saxony . In: Problems of coastal research in the southern North Sea area . tape 21 , 1994, p. 1-227 .
  20. ↑ B. Kubitz: The Holocene vegetation and settlement history in the West Eifel using the example of a high-resolution pollen diagram from the Meerfelder Maar . In: Dissertationes Botanicae . tape 339 , 2000, pp. 106 .