A 200 year sedimentary record of progressive eutrophication in Lake Greifen (Switzerland): Implications for the origin of organic-carbon-rich sediments
- Inst. Francais de Petrole, Rueil-Malmaison (France)
- Geological Inst., Zuerich (Switzerland)
- TOTAL, St. Remy les Chevreuse (France)
Over the past 200 years Lake Greifen, a small lake in northeastern Switzerland, has undergone dramatic changes in primary productivity and eutrophication due to increased nutrient supply from agricultural activity and industrialization. A 40 year historical record of the water-column chemistry indicates that productivity and eutrophication reached a maximum in 1974, after which stricter regulations on the input of nutrients resulted in a progressive decrease. Collected cores show the sedimentary expression of this anthropogenically induced eutrophication by a well-developed annual sedimentation and by enhanced values of total organic carbon, organic-carbon accumulation rates, and hydrogen indices (HI) of the kerogens. Analyses of the carbon isotopic composition of sedimentary carbonates and organic matter reveal that the fractionation between these two phases varies with the HI of kerogens. This observation is explicable in terms of changing productivity and preservation of the organic matter, and the CO[sub 2 (aq)] budget of the water body. The authors propose that if high primary productivity were primarily responsible for the preservation and accumulation of organic matter, then a negative correlation will occur between [Delta][delta][sup 13]C[sub calcite-organic matter]([Delta][delta][sup 13]C[sub cal-om]) and HI values. In an environment with relatively low to moderate productivity but with bottom-water anoxia, a positive correlation will exist between [Delta][delta][sup 13]C[sub cal-om] and HI values. This study of Lake Greifen has implications for understanding paleoenvironmental controls on ancient organic-carbon-rich sediments.
- OSTI ID:
- 6937725
- Journal Information:
- Geology; (United States), Vol. 20:9; ISSN 0091-7613
- Country of Publication:
- United States
- Language:
- English
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