Palyno- and chronostratigraphy of a long sequence from Lac d'Annecy (northern outer Alps, France) |
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Authors: | F David G Farjanel MP Jolly |
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Institution: | (1) Laboratoire Botanique Historique et Palynologie, URA CNRS, Faculté des Sciences et Techniques St. Jérôme, 13397 Marseille, Cedex 13, France;(2) Service Géologique National, Bureau Recherche Géologique et Minière, BP 6009, 45060 Orléans, Cedex, France;(3) 2 rue de Vintué, 91580 Etrechy, France |
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Abstract: | Pollen analysis (absolute and relative frequencies) of a 44 m sedimentary sequence from Lac d'Annecy provides a record of vegetation history since deglaciation in the northern part of the French alpine foreland. Sixteen pollen zones are described and compared with those obtained from sites in adjacent areas, and 17 AMS radiocarbon dates provide a chronology which enables a minimum age for the termination of the last glaciation to be inferred. The pollen assemblages reflect the influence of a number of depositional processes, including selective sorting and sediment reworking, and thus illustrate some of the limitations inherent in the AMS radiocarbon dating of macroscopic plant remains. For instance, the basal Picea pollen assemblage zone corresponds to a lithological unit that contains reworked material, attributed to deposits older than St Germain II, which makes the 14C AMS radiocarbon date of 25 Ka BP obtained for this zone rather questionable. The existence of two climatic events prior to the Younger Dryas is confirmed. An influx of pollen from the nearby river inlet may explain why these events are well expressed in the pollen stratigraphy. |
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Keywords: | pollen stratigraphy deglaciation northwestern Alps late Pleistocene Holocene |
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