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EUROPE/Holocene 147 Holocene W Lemke and J Harff, Baltic Sea Research Institute Warnemuănde, Rostock, Germany ò 2005, Elsevier Ltd All Rights Reserved Introduction The Quaternary period comprises the shortest time interval of all geological systems Compared to the preceding climatically stable and warm Tertiary, it is characterised by a multiple alternation of large-scale glaciations and short warm intervals in between The latest interglacial period, which is still ongoing, is called Holocene after the Greek words ‘holos’ (entire) and ‘ceno’ (new) According to recent understanding, it began ca 11 600 calendar years before present In contrast to other epochs of the Earth’s history, it is not defined and subdivided by certain floral or faunal assemblages but by climatic features Another basic difference from former geological periods is the increasing human impact on the geosphere In fact, some authors claim that the properties of the ‘system Earth’ have changed by human influence to an extent that it cannot be called natural anymore Reconstructing the geological past, therefore, requires consideration of natural processes, as well as the results of human activity and to separate them from each other Thus, Holocene geology is intensely interrelated not only with other natural sciences but also with human history, archaeology, and further social sciences This adds a wealth of additional information to the data stored within geological archives On the other hand, geological problems during the Holocene are not only a matter of actualism in the classical sense anymore Due to the increasingly closer connection between geological processes and the development of the human society, forecasting of geological trends becomes more and more important In this way, Charles Lyell’s (see Famous Geologists: Lyell) statement about the principle of actualism could be extended to: ‘‘The knowledge about present and past is the key to the future.’’ Dating When aiming for an accurate reconstruction of the geological past, dating becomes an essential issue Looking back from recent times to the near past, dating of geological events is simply done on a high resolution by analysing the written historical archives Further back in time, indirect methods (by using socalled proxy data) have to be used Proxy data with a yearly resolution are related to processes which result in persistent and regularly successive yearly structures within sediments (e.g., varve sequences) or organic material like wood (dendrochronology) The latter is based on the study of tree ring patterns which are controlled mainly by climatic factors In Europe it was used particularly for oaks in central and western Europe and for pines in northern Europe Regionally generalised curves for these two tree species cover nearly all of the European Holocene Dendrochronological dates are highly valuable for calibrating dating results produced by other methods This refers especially to isotopic dating by radiocarbon, which is widely used as a standard method for the dating of organic material within the Holocene By comparing dendrochronological or varve counting dates with radiocarbon dating, inconsistencies within the later ones, particularly within the early Holocene, became obvious Therefore, when looking at dates in the literature, it is crucial to consider if calibrated (calendar) years or radiocarbon years are referred to Within this article calendar years before present (BP) are used (except for Figure 10) Other short-lived isotopes, such as 210Pb are used to date processes and events in the more recent past on time-scales of decades and centuries Once the environmental history of a specific region is well known, assemblages of plants or animals might also help to assess the age of the deposits they are found in Climate One of the most intensively studied subjects of Holocene development is climate Ice and marine sediment cores have been used to assess climatic changes and they provide smoothed background data to more regional, or local and mostly more dramatic, climatic variations on the European continent The onset of the Holocene is marked by a global drastic temperature increase of about 7 C at the end of the Younger Dryas, about 11 600 calendar years BP This climate reorganisation happened during a period of not more than a few decades Since then, the Holocene climate has been stable by comparison with the preceding glacial period Nevertheless, minor climate fluctuations have been reconstructed Several periods with cooler and warmer temperatures than the last century have left their traces in the geological and biological archives and also in human history (Figure 1)
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