Subboreal

The Subboreal is in the earth's the second youngest period of the Holocene in northwestern Europe. It lasted from 3710-450 BC

• 3.1 greenhouse gas carbon dioxide

• 5.1 Development in the Baltic region
• 5.2 Development in the North Sea area

Definition and stratigraphic position

The term Subboreal ( ie below the Boreal derived from Latin sub - under, beneath, below, and the Greek god of the north wind Βορέας - boreas ), often referred to as Late heat time or mixed oak forest alder time, was by Rutger Sernander to distinguish Axel Blytts Boreal marked. The Subboreal following the immediately preceding Atlantic period and is in turn replaced by Subatlantic.

Klimastratigraphisch the Subboreal can be divided into a mature Subboreal and in a junior Subboreal. It is attributed to either the middle Holocene or the young - Holocene.

Culture History the Subboreal covers most of the Neolithic and the entire Bronze Age ( beginning in 3800-4200 years BP).

Temporal classification

Note: Only the fields marked with a black dividing line boundaries are more or less exactly; they are based on annual layers in lake sediments in north-central Europe and are, strictly speaking, only for air levels. The other boundaries are determined unsafe and not rigid. In particular, the boundary between Central and Jungholozän is highly variable. In the stages of culture the different regional development is observed.

Age

The lower limit of the Sub-boreal located at 3710 BC or in 5660 years BP. This limit is, however, not be regarded as rigid. For example, some authors use the beginning of the Sub-boreal earlier at 6350 years BP (or 4400 BC ) and in north-west Poland in 6780 years BP ( 4830 BC) on, while others expect only 5000 calendar years BP, ie 3050 BC It ends at 450 BC the upper limit (and thus the transition to Subatlantic ) but is also not rigidly fixed, but could be carried out in the period 1170-830 BC. In Warvenjahren the Subboreal corresponds to the period 5660-2750 BP Jahre.

The boundary between elder and younger Subboreal is usually given as 1350 BC.

Historical Climate History

The climate was during the Sub-boreal compared to the previous Atlantikum dry and slightly cooler (on average by 0.1 ° C ), even if it was still warmer than today. Thus, the temperatures were on average 0.7 ° C higher than under the current Subatlantic. The corollary was that the lower limit of the glaciers in Scandinavia was raised compared to Subatlantic by 100 to 200 meters during the Sub-boreal. Overall, however, annual average temperatures were within the Sub-boreal under several variations generally declining ( they cooled slowly by up to 0.3 ° C. ).

The beginning of the Sub-boreal is highlighted in the Aegean area from a hundred -year drought period, which is centered at 5600 years BP. However, this event may have been surpassed in importance by far from the end of the African humidity period ( engl. the African Humid Period) at this time. Thus, in lakes of the subtropical Africa was ( such as the Lake Chad ) then observed a rapid decline in the water level. Also in southern Mesopotamia a -increasing aridity made ​​in the period 6200-5000 Jahre BP wide, which led to demographic changes and possibly conjured up the end of Uruk.

In North West Europe ( Eifelmaare ) can be observed from 5000 BP Warvenjahren a climatic incision. For example, the July temperatures were on average above during the Holocene optimum vorangangenen in the period 8200-5000 Warvenjahre BP by 1 ° C higher. However, coupled with the drop in summer temperatures was an increase in the January mean and an increase in annual precipitation.

The period 4700-4100 Jahre BP is in northern Africa and the Middle East once again characterized by prolonged drought, underlined by Seespiegelminima. The decrease in monsoon rainfall 4500-4000 years BP has probably caused the confusion and finally the end of the Old Kingdom of Egypt. In the area of the Levant a very similar development proceeded. So likely to have caused the decline of the Akkadian Empire in Mesopotamia located at 4200 years BP dryness maximum.

Greenhouse gas carbon dioxide

The greenhouse gas carbon dioxide had at the beginning of the Sub-boreal Holocene reached a minimum value of 260 ppm. This value increased with slight variations then steadily to 293 ppm at the end of the Sub-boreal to.

Vegetation history developments

In Scandinavia, the transition between Atlantikum and Subboreal is a reference to the composition of the vegetation sharp and easily recognizable boundary. The transition can take less pronounced in Western Europe. A typical feature here is the rapid decline of elm and lime trees as components of the characteristic oak mixed forest (EMW ). The reasons for the decline in Linden are not clear, perhaps it was the colder climate or influences of man. The decline of elm trees ( so-called elm case ), the transferred to a by the elm bark beetle ( Scolytus scolytus, Scolytus multistriatus ) fungal disease caused by an ascomycete ( Ceratocystis ulmi ) is due, was probably also due to climatic changes and anthropogenic (eg pollarding ) promoted. The dated in Central and Northern Europe with about 4000 years BC elm case ( in Eifelmaaren was, for example, a decrease from 20 to 4 % observed) is probably rather run diachronically and extends over the period 4350-3780 years BC have

Another forest historical event of the Sub-boreal, the immigration of European beech (Fagus sylvatica) and hornbeam (Carpinus betulus ) from the refuges of the Balkan Peninsula and south of the Apennines dar. These two processes were diachronically - Book pollen for the first time from 4340-3540 BC. hornbeam pollen and demonstrated a little later from 3400-2900 BC. With the onset of the Younger Sub-boreal then began the actual spread of the book. During the establishment of beech and hornbeam with simultaneous occurrence of settlement was pointers (eg Getreidetaxa and Plantain - Plantago lanceolata) experienced a decline in hazel.

The drier climate during the Sub-boreal also caused the spread of ericaceous.

Sea ​​level

As in the previous Atlantikum the sea level rose during the Sub-boreal to continue. The increase was, however, now only about 1 meter, or 0.3 mm / year. At the end of the Sub-boreal, the sea level was then at 1 meter below sea level.

Development in the BSR

The Baltic had become the Littorinameer already before the beginning of the Sub-boreal. In older Subboreal was the second Littorina transgression, which reached 1 meter below sea level. After Spätlittorinen regression it came towards the end of the Younger Sub-boreal to 3 Littorina transgression, which was 60 centimeters below sea level ( and later in the early Subatlantic was heading the current water level ).

Development in the North Sea area

In the North Sea it had come to the meetings held in the Atlantic period Flandrischen transgression at the beginning of Suboreals to a slight decline in sea level or to a sea-level standstill.