A sediment sequence (SP05, 12.5 m long) was taken from the deep zone of
Lake Saint-Point (850 m a.s.l.). Sedimentological analyses highlight two
main contrasted periods of sedimentation: the Last Glacial Maximum
(LGM)/Late Glacial characterized by high silicates and quartz contents
the Holocene dominated by the carbonated fraction. At the beginning of
the Holocene (11 400 years cal. BP), silicates fraction flux abruptly
decreased. The shift between the Late Glacial and the Holocene periods
may be explained by forest development in the catchment. From 10 200 to
6800 years cal. BP, silicates and detrital carbonate fractions remained
stable before they progressively increased steady till 5000 years cal.
BP Both increases cannot be totally attributed to an anthropic impact
since pollen data indicate continuous anthropic activities only dated
back from 3000 years cal. BP. They thus resulted from a dominant
climatic control. From 5000 years cal. BP, silicates content still
increased while detrital carbonates input became steady due to a change
in pedogenetic processes affecting the catchment. During the last
millennium, silicates and detrital carbonate decreased, probably due to
pastureland development. To cite this article: A. Leroux et al., C. R.
Geoscience 340 (2008). (C) 2008 Academie des sciences. Published by
Elsevier Masson SAS. All rights reserved.