Currently, a widespread scientific confusion exists on the stratigraphic and geochronologic division of the Weichselian Lateglacial (cf. e.g. Usinger 1985, 1998; Hoek 1997; Björck et al. 1998; Litt & Stebich 1999; Litt et al. 2001, 2003; Eriksen 2002; De Klerk 2002, 2004; Terberger et al. 2004). In order to gain insights in the origins, development and extent of this confusion, the development of stratigraphical and geochronological schemes and concepts of the Lateglacial was studied in a historical and methodological context (De Klerk 2004).
Locations of the most important studied sites that contributed to the development of stratigraphic and geochronologic divisions of the Weichselian Lateglacial: A: Allerød; B: Bøllingsø; BR: Brøndmyra; F: Fjerritslev; G: Glüsing; M/S: Meiendorf and Stellmoor; NL: Nørre Lyngby; U: Usselo
The recognition that cold climates must have prevailed in northern Europe in former times started with the finds of macrofossils of Dryas octopetala in Scandinavia (cf. Iversen 1973; Joosten 1995). After a discovery at Allerød (Denmark) by Hartz & Milthers (1901) that different strata contained macrofossils indicative for various vegetation forms, i.e. open vegetation and closed forests, several climatic phases were deduced for the Lateglacial. The open vegetation, also referred to as Dryas flora, was interpreted as typical for a cool climate, the forested 'Allerød' was assumed to have been fairly warm. After the development of pollen analysis as scientific discipline, various palynostratigraphic schemes were developed which aimed to describe different vegetation phases. Among these, the division of Jessen (1935) had the greatest influence on the further development of stratigraphic schemes.
The investigations of Bøllingsø (Denmark) by Iversen (1942, 1954, 1973) and his colleagues are of special importance. Iversen interpreted to have found evidence of expansion of birch forests in central Denmark prior to the Allerød. He called this assumed warm period 'Bølling'. A critical review of his methods, however, proved that these are not completely suitable (cf. De Klerk 2004): it is demonstrated that Iversen's calculation basis for pollen diagrams - the so-called 'Iversen pollen sum' - is unsuitable for pollen diagrams covering the Lateglacial because it includes pollen types that are possibly produced by wetland herbs (e.g. Poaceae, Cyperaceae). These types might erroneously suggest an open upland vegetation when actually a wetland vegetation along the lake borders had expanded. A recalculation of the Bøllingsø-diagrams with an dryland pollen sum - i.e. effectively excluding types possibly produced by wetland herbs - lead to a different pollen diagram zonation and a different palaeoecological interpretation (cf. De Klerk 2004). In realtiy, the Bølling oscillation of Iversen might be a local phenomenon only without any (over)regional significance, although such a conclusion is not completely evident from the original data.
In The Netherlands, Van der Hammen (1951) found other palynological evidences of an earlier climatic oscillation which he and Iversen (1954) erroneously correlated with the Bølling at Bøllingsø. Van der Hammen further developed, redefined and revised the stratigraphic scheme of the Weichselian Lateglacial by introducing a 'Bølling sensu lato' (Van der Hammen 1957) and later by introduction of a 'Bølling sensu stricto' (Van der Hammen & Vogel 1966). The scheme of Van der Hammen (1957) was also applied in the chronostratigraphy of Mangerud et al. (1974) - which is actually an absolutely dated palynostratigraphy with palaeoclimatic implications - and found internationally the most widespread application.
Summary of the development of the stratigraphic and geochronological division of the Weichselian Lateglacial in the course of the 20th Century
Due to another correlation error between Danish, Dutch and NW German pollen diagrams, Menke (1968) introduced another warm period: the 'Meiendorf'. Taking into account the correlation mistakes and other misleading errors of Menke, Usinger (1985) proposed to introduce a 'Bølling-Allerød complex' and to abolish the term 'Meiendorf'. Reacting on criticism mainly by Usinger, Menke made some revisions in his palynostratigraphic scheme (cf. Bokelmann et al. 1983; Bock et al. 1985). Slightly modified, the views of Menke were used to propose a new biostratigraphic division for the Eifel region (and far beyond) by Litt & Stebich (1999) and Litt et al. (2001, 2003). In a later study, Usinger (1998) accepted the Meiendorf, but proposed to abolish the term 'Bølling'.
In the meantime, it had become clear that the palaeoclimate can much more accurately be reconstructed from Coleoptera (Coope 1986) and oxygen isotopes (Siegenthaler & Eicher 1986) than from botanical fossils. Several smaller fluctuations were deduced from oxygen isotopes from Swiss lakes, including the Aegelsee fluctuation, Gerzensee fluctuation and the Preboreal oscillation (Lotter et al. 1992). Björck et al. (1998) proposed to abolish all previously used schemes and to replace them with a scheme based on the oxygen isotope records from Greenland ice cores. Coleoptera from England and The Netherlands indicated that the highest summer temperatures were reached at the beginning of the Weichselian Lateglacial (after 12900 radiocarbon years BP), while pollen simultaneously showed an open upland vegetation; in other regions, however, a major temperature rise was indicated first after ca. 12450 radiocarbon years BP (cf. De Klerk 2004). In correlating de isotope data from Greenland with the Coleoptera data of England, Björck et al. (1998) probably included a correlation mistake of approximately 500 years between the annually laminated ice-cores and the radiocarbon-dated Coleoptera data (cf. Billwitz et al. 2000; De Klerk 2004). The latter prefers to assume that around 12900 radiocarbon years BP only a minor temperature rise occurred, whereas around 12450 radiocarbon years BP the temperature rose greatly.
The main conclusions are that:
1: the existing terminology is very unfortunate and should be completely abandonned;
2: an international discussion is necessary in order to solve the existing problems, especially with respect to correlation and (independant or integrated) interpretation of the various records and proxies;
3: it is best to develop - for the time being - regionally restricted schemes with an unambiguous terminology independently for various records and proxies and to refrain from still premature overregional correlations.
De Klerk, P. (2004): Confusing concepts in Lateglacial stratigraphy and geochronology: origin, consequences, conlusions (with special emphasis on the type locality Bøllingsø). Review of Palaeobotany and Palynology 129: 265-298.
Other Relevant literature:
Bennike, O., Sarmaja-Korjonen, K. & Seppänen, A. (2004): Reinvestigation of the classic late-glacial Bølling Sø sequence, Denmark: chronology, macrofossils, Cladocera and Chlydorid ephippia. Journal of Quaternary Science 19: 465-478.
Billwitz, K., Helbig, H., Kaiser, K., De Klerk, P., Kühn, P. & Terberger, T. (2000): Untersuchungen zur spätpleistozänen bis frühholozänen Landschafts- und Besiedlungsgeschichte in Mecklenburg-Vorpommern. Neubrandenburger Geologische Beiträge 1: 24-38.
Björck, S., Walker, M.J.C., Cwynar, L.C., Johnsen, S., Knudsen, K.-L., Lowe, J.J., Wohlfarth, B. & Intimate members (1998): An event stratigraphy for the Last Termination in the North Atlantic region based on the Greenland ice-core record: a proposal by the INTIMATE group. Journal of Quaternary Science 13: 283-292.
Bock, W., Menke, B., Strehl, E. & Ziemus, H. (1985): Neuere Funde des Weichselspätglazials in Schleswig-Holstein. Eiszeitalter und Gegenwart 35: 161-180.
Bokelmann, K., Heinrich, D. & Menke, B. (1983): Fundplätze des Spätglazials am Hainholz-Esinger Moor, Kreis Pinneberg. Offa 40: 199-239.
Coope, G.R. (1986): Coleoptera analysis. In: Berglund, B.E. (ed.): Handbook of Holocene Palaeoecology and Palaeohydrology. John Wiley & Sons Ltd, Chichester: 703-713.
De Klerk, P. (2002): Changing vegetation patterns in the Endinger Bruch area (Vorpommern, NE Germany) during the Weichselian Lateglacial and Early Holocene. Review of Palaeobotany and Palynology 119: 275-309.
Eriksen, B.V. (2002): Reconsidering the geochronological framework of Lateglacial hunter-gatherer colonization of southern Scandinavia. Jutland Archaeological Society Publications 39: 25-41.
Hartz, N. (1912a): Allerød-Muld: Allerød-Gytjens Landfacies. Foreløbig Meddelelse. Meddelelser fra Dansk Geologisk Forening 4: 61-68.
Hartz, N. (1912b): Allerød-Gytje und Allerød-Mull. Bemerkungen über die Moore der Holte-Gegend, der allgemeinen Versammlung der Deutschen Geologischen Gesellschaft 1912 gewidmet. Meddelelser fra Dansk Geologisk Forening 4: 85-92.
Hartz, N. & Milthers, V. (1901): Det senglaciale ler i Allerød Teglværksgrav. Meddelelser fra Dansk Geologisk Forening 8: 31-60.
Hoek, W.Z. (1997): Palaeogeography of Lateglacial vegetations. Aspects of Lateglacial and Early Holocene vegetation, abiotic landscape, and climate in The Netherlands. Nederlandse Geografische Studies 230: 1-147.
Iversen, J. (1942): En pollenanalytisk Tidsfæstelse af Ferskvandslagene ved Nørre Lyngby. Med Bemærkinger om de senglaciale Naturforhold i Danmark. Meddelelser fra Dansk Geologisk Forening 10: 130-151.
Iversen, J. (1954): The late-glacial flora of Denmark and its relation to climate and soil. Danmarks Geologiske Undersøgelse II. Række 80: 87-119.
Iversen, J. (1973): The development of Denmark's nature since the Last Glacial. Danmarks Geologiske Undersøgelse V. Række nr. 7-C: 1-126. Translated by M. Robson from Danmarks Natur 1: 345-445 (1967).
Jessen, K. (1935): Archaeological dating in the history on north Jutland's vegetation. Acta Archaeologica 5: 185-214.
Joosten, J.H.J. (1995): Between diluvium and deluge: the origin of the Younger Dryas concept (extended abstract). Geologie en Mijnbouw 74: 237-240.
Litt, T. & Stebich, M. (1999): Bio- and chronostratigraphy of the Lateglacial in the Eifel region, Germany. Quaternary International 61: 5-16.
Litt, T., Brauer, A., Goslar, T., Merkt, J., Balaga, K., Müller, H., Ralska-Jasiewiczowa, M., Stebich, M. & Negendank, J.F.W. (2001): Correlation and synchronisation of Lateglacial continental sequences in northern central Europe based on annually laminated lacustrine sediments. Quaternary Science Reviews 20: 1233-1249.
Litt, T., Schmincke, H.-U. & Kromer, B. (2003): Environmental responses to climatic and volcanic events in central Europe during the Weichselian Lateglacial. Quaternary Science Reviews 22: 7-32.
Lotter, A.F., Eicher, U., Siegenthaler, U. & Birks, H.J.B. (1992): Late-glacial climatic oscillations as recorded in Swiss lake sediments. Journal of Quaternary Science 7: 187-205.
Lowe, J.J. & Gray, J.M. (1980): The stratigraphic subdivision of the Lateglacial of NW Europe: a discussion. In.: Lowe, J.J., Gray, J.M. & Robinson, J.E. (eds.): Studies in the Lateglacial of North-West Europe. Including papers presented at a symposium of the Quaternary Research Association held at University College London, January 1979. Pergamon Press, Oxford: 157-175.
Mangerud, J., Andersen, S.T., Berglund, B.E. & Donner, J.J. (1974): Quaternary stratigraphy of Norden, a proposal for terminology and classification. Boreas 3: 109-128.
Menke, B. (1968): Das Spätglazial von Glüsing. Ein Beitrag zur Kenntnis der spätglazialen Vegetationsgeschichte in Westholstein. Eiszeitalter und Gegenwart 19: 73-84.
Sarmaja-Korjonen, K., Seppänen, A. & Bennike, O. (2006): Pediastrum algae from the classic late glacial Bølling Sø site, Denmark: response of aquatic biota to climate change. Review of Palaeobotany and Palynology 138: 95-107.
Siegenthaler, U. & Eicher, U. (1986): Stable oxygen and carbon isotope analyses. In: Berglund, B.E. (ed.): Handbook of Holocene Palaeoecology and Palaeohydrology. John Wiley and Sons Ltd., Chichester: 407-422.
Terberger, T., De Klerk, P., Helbig, H., Kaiser, K. & Kühn, P. (2004): Late Weichselian landscape development and human settlement in Mecklenburg-Vorpommern (NE Germany). Eiszeitalter und Gegenwart 54: 138-175.
Usinger, H. (1981): Pollen- und Großrestanalysen am limnischem Spätglazial aus dem Scharnhagener Moor, Schleswig-Holstein. Schr. Naturw. Ver. Schlesw.-Holst. 51: 85-105.
Usinger, H. (1985): Pollenstratigraphischer, vegetations- und klimageschichtlicher Gliederung des "Bölling-Alleröd Komplexes" in Schleswig-Holstein und ihre Bedeutung für die Spätglazial-Stratigraphie in benachbarten Gebiete. Flora 177: 1-43.
Usinger, H. (1998): Pollenanalytische Datierung spätpaläolithischer Fundschichten bei Ahrenshöft, Kr. Nordfriesland. Archäologische Nachrichten aus Schleswig-Holstein: Mitteilungen der Archäologischen Gesellschaft Schleswig-Holstein e.V. und des Archäologischen Landesamtes Schleswig-Holstein 8, 1997: 50-73.
Van der Hammen, T. (1951): Late-glacial flora and periglacial phenomena in the Netherlands. Leidse Geologische Mededelingen 17: 71-183.
Van der Hammen, T. (1957): The stratigraphy of the Late-Glacial. Geologie en Mijnbouw 19: 250-254.
Van der Hammen, T. & Vogel, J.C. (1966): The Susacá-Interstadial and the subdivision of the Late-Glacial. Geologie en Mijnbouw 45: 33-35.
Van Geel, B., Coope, G.R. & Van der Hammen, T. (1989): Palaeoecology and stratigraphy of the Lateglacial type section at Usselo (The Netherlands). Review of Palaeobotany and Palynology 60: 25-129.