Varven chronology

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The varven chronology (also band tone dating or band tone calendar , from Swedish varvig lera - German  "layered clay" ) is based on the counting of layered deposits of varva ( sediments ) in lakes ( limnic sediments), moors, rivers or the sea ( marine sediments ), e.g. B. so-called band tones. If it is possible to classify the count in an absolute time frame using additional clues, the age is given in varve years . The Swedish geologist Gerard Jakob De Geer (1858–1943) is considered to be the founder of varven chronology .

Basics

In spring and summer, light, coarse-grained and sandy sediments settle, as the water supply is high due to large amounts of meltwater from glaciers or snowmelt , and thus both the transportability of the waters increases, and the proportion of fine-grain, humus clays in the background occurs. In winter mainly dark, humus clays are deposited. Depending on the precipitation and temperatures, this results in deposits of different thicknesses and colors. This annual deposit (two layers) is called a warve , the thickness of which can vary.

A band-tone calendar can be set up by counting the varves, similar to the dendrochronology (tree ring calendar ). Profiles from different regions can be combined by overlapping. Using this method, the Swedish baron Gerard Jakob De Geer succeeded in creating an absolute calendar for southern Sweden up to 10,000 BC even before the First World War . To set up. In the meantime, individual layer sequences, if they contain carbon, can be absolutely dated using radiocarbon dating (14C method) . It is also possible to carry out archaeomagnetic measurements on the clays in order to be able to date them absolutely.

For the Eifel region there is a chronology of the last 23,000 ( Meerfelder Maar , Holzmaar ), for a Japanese lake for 45,000 and for the Lago Grande di Monticchio on Monte Vulture in southern Italy even for the last 76,000 years.

This article or the following section is not adequately provided with supporting documents ( e.g. individual evidence ). Information without sufficient evidence could be removed soon. Please help Wikipedia by researching the information and including good evidence.

Warv sediments from small northern alpine lakes are archives from which agricultural activities can be read.

The varves of Lake Van in Turkey go back 14,570 years.

With regard to the varve counts, it should be noted that at least in German-speaking countries the term “varven years vh” (before today, before present, BP ) mostly refers to the year 1950.

See also

  • Stratigraphy - the general method of relative dating according to strata (layers)

swell

literature

  • Brewer, Achim; Hajdas, Ilka; Negendank, Jörg FW; Rein, Bert; Vos, Heinz; Zolitschka, Bernd, 1994: Warvenchronology - A method for the absolute dating and reconstruction of short and medium solar periodicities . Earth sciences; 12, 10-11; 325-332, doi : 10.2312 / geosciences . 1994.12.325 .
  • Herbert W. Franke: Methods of Geochronology. The search for the dates of the earth's history. Springer, Berlin et al. 1969 ( Understandable Science. Vol. 98, ISSN  0083-5846 ).
  • H. Wolfgang Wagner et al., 2012: Trier und Umgebung, Sammlung geologischer Führer , Vol. 60, 3rd edition, Bornträger, ISBN 978-3-443-15094-5 .
  • Bernd Zolitschka : Paleoclimatic Significance of Laminated Sediments. Holzmaar (Eifel, Germany), Lake C2 (Northwest Territories, Canada) and Lago Grande di Monticchio (Basilicata, Italy) . Bornträger, Berlin et al. 1998, ISBN 3-443-09013-3 ( Relief, Boden, Paläoklima 13), (At the same time: Potsdam, Univ., Habil.-Schr., 1996).

Individual evidence

  1. ↑ H. Wolfgang Wagner et al., 2012: Trier und Umgebung, Sammlung geologischer Führer , Vol. 60, 3rd edition, Bornträger, ISBN 978-3-443-15094-5 , [(see) http: // www. schweizerbart.de/publications/detail/artno/011006040 ].
  2. ↑ Günter Landmann, Andreas Reimer, Gerry Lemcke, Stephan Kempe: Dating Late Glacial abrupt climate changes in the 14,570 yr long continuous varve record of Lake Van, Turkey . Palaeogeography, Palaeoclimatology, Palaeoecology, 122, 1996, p. 116, doi : 10.1016 / 0031-0182 (95) 00101-8 .
  3. ↑ Mike Walker, Sigfus Johnson, Sune Olander Rasmussen, Trevor Popp, Jørgen-Peder Steffensen, Phil Gibbard, Wim Hoek, John Lowe, John Andrews, Svante Björck, Les C. Cwynar, Konrad Hughen, Peter Kershaw, Bernd Kromer, Thomas Litt , David J. Lowe, Takeshi Nakagawa, Rewi Newnham and Jakob Schwander: Formal definition and dating of the GSSP (Global Stratotype Section and Point) for the base of the Holocene using the Greenland NGRIP ice core, and selected auxiliary records . Journal of Quaternary Science, 24 (1), 2008, pp. 3-17 doi : 10.1002 / jqs.1227 .