Bølling oscillation

The Bolling interstadial, also Bølling interstadial, is in the Earth's history, a relatively warm period in the last phase of the Weichselian cold period ( Quaternary ). It followed on the chilly time period of the elders Dryas and was replaced by the also quite cool period of the older Dryas. After Warvenjahren the Bolling interstadial lasted from 13,670 to 13,540 Warvenjahre vh vh Warvenjahre Converted this is the period 11720-11590 BC It is characterized in Central Europe through a birch forest.

Naming and conceptual history

The name was introduced by John Iversen 1942 Bölling oscillation or Bölling period ( Bölling period ) in the scientific literature. It is named after the Bølling Sø ( Jutland, Denmark) named.

Definition

The lower limit of the Bolling Interstadial is defined at its type locality on the Bølling Sø by a marked rise in birch pollen (mainly from birch tree ) and a significant decrease of pollen from sand spikes ( Hippophaë ). The upper limit is characterized by a renewed decline in tree pollen and an increase in non- arboreal pollen.

Stratigraphy and correlation

In northern Germany the Bolling interstadial following the Oldest Dryas and the Aegelsee variation and will be completed by the older Dryas. It thus corresponds to the Greenland interstadial 1c3 (GI - 1c3 ). Deviating from the period between the Pleniglacial and the Oldest Dryas is considered Bolling interstadial in southern Germany, in Switzerland, in North America and the North Atlantic region, corresponding to the period GI -1e. In northern Germany, however, this is equivalent to Meiendorf interstadial. In Norway, the Bolling interstadial begins immediately after the Pleniglacial ( here Oldest Dryas ) and lasts until the older Dryas I, interrupted by the two cold phases BCP I ( engl. Bölling Cold Phase I) and BCP II ( Bölling Cold Phase II, also called IBCP and equivalent to Aegelsee fluctuation ).

The Bolling interstadial in the strict sense corresponds to the Hook (1997) the pollen zone 2a1, the extended Bolling interstadial however 1b of the pollen zone.

Dating

After Warvenjahren in Meerfelder the Bolling interstadial lasted from 13,670 to 13,540 Warvenjahre vh vh Warvenjahre, this represents the interval 11720-11590 BC. According to the Hannover Geozentrum it took, however, 13730-13480 cal BP or 11780 to 11530 BC. Lowe et al ( 2008) set the beginning already in 11954 BC and according to van Raden et al ( 2012) took the Bolling interstadial 11958-11674 BC.

Van Raden use for the extended Bolling interstadial including the period 12640-12094 BC.

Environmental parameters

Oxygen isotopes

Based on the NGRIP ice core, the Bolling interstadial draws against the two confining cold phases by up to 2 ‰ higher δ18O values ​​, which between - 39 ‰ SMOW oscillate ( VPDB ) - 38 and. The extended Bolling interstadial had its maximum value - 36% VPDB at the beginning and then shows later in a steady decline down to - 38 ‰ VPDB.

Temperatures

On the basis of Coleoptera Atkinson determined and others ( 1987) for the UK annual average temperatures 3-5 ° C during the Bolling Interstadial. The previous Advanced Bolling interstadial was even warmer, it has already been reached at its beginning up to 7 ° C. Thus, it was the warmest part of the Late Glacial with an enormous and very rapid temperature rise of about 10 ° C compared to the ratios in Pleniglacial. In the Netherlands (July) were determined by Heiri et al ( 2007) using Chironomidae summer temperatures. They showed for the Bolling interstadial slightly oscillating values ​​of 16.5 ° C and an increase of 14 to 17 ° C for the extended interstadial.

Sea ​​level

Measurements on coral reefs in Barbados by Peltier & Fairbanks ( 2006) refer to the Bolling interstadial to a sea level by 70 meters below sea level with a slightly rising trend. During the Meiendorf interstadial he had still 93-90 meters below sea level.

Vegetation development

Striking for the Bolling interstadial compared to the previous Oldest Dryas is the sudden increase in tree pollen due to ( over 80% ), especially the birches ( with a total of 60%). Willow and juniper experienced a decline, but the latter was able to maintain its importance and shrubby pass through the relatively open birch forest. Helio Audiophile herbs such as plantain and Helianthemum lost their former position. Also, grasses, Cyperaceae, and the taxa buckthorn and Artemisia were rapidly declining. Towards the end of the interstadial occurred in favor of pine ( 15%) to a decline in birch proportion.

In the extended Bolling interstadial tree pollen had first reached over 50 % in the total pollen, mainly supported by birch trees, especially dwarf birch (Betula nana ). The predominantly open grassy landscape of Pleniglazials was thus after colonization by dwarf birch increasingly interspersed with birch stands, which developed into a sparse birch forests on.

Cultural History

In the Levant, the Natufian had ( 12300-10200 BC) developed during the Bolling Interstadial. This protoagrarische culture stage was based on the use of wild cereals such as emmer and barley zweihreihige. Foothills of the Paleolithic in Central Europe were still to be found, as in the Paris region, the Magdalenian ( 16000-8000 BC) and in Italy and Eastern Europe, the Epigravettian. Further north, the hamburger culture unfolded ( 13500-11100 BC), the penknife groups ( 12000-10800 BC), the Tjonger group in the Netherlands and the Creswellien ( 12500-8000 BC) in England and Wales.