Insights on the bio-geochemical processes that control sedimentation in Lake Iznik based on compositional data analysis

• Autores: P.A. Roeser, S. Franz, T. Litt
• Localización: Proceedings of the 6th International Workshop on Compositional Data Analysis: Girona, 1-7 de juny de 2015 / coord. por Santiago Thió Fernández de Henestrosa, Josep Antoni Martín Fernández, 2015, ISBN 978-84-8458-451-3
• Idioma: español
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• Resumen

  • Exploratory compositional data analysis allows insights to the bio-geochemical and physical processes controlling sedimentation in Lake Iznik (NW, Turkey). Based on the pattern investigation of clr-biplots from geochemical data, generally three main groups of elements are identified: (a) siliciclastic elements, (b) elements related to the carbonate accumulation; (c) elements related to organic productivity. The first group originates from the detrital input to the lake, i.e. catchment derived material that is transported by rivers as particles. The high variance between the siliciclastic elements and the second group, represented by calcium, indicates that a different process controls the majority of calcium accumulation in the sediments. Most of the calcium reaches the lake in dissolved form, originating from carbonate occurrences in the catchment, and further re-precipitates as carbonate from the water column. The third group, characterized by the total organic carbon content, represents the organic productivity within the lacustrine system. Some elements are unrelated to these three groups, such as Mn, Na, S, P, and therefore other processes than the fluvial transport, carbonate accumulation, or organic production of the lake control the behaviour of such elements. Based on the pattern investigation of clr-biplots of mineral data, we conclude that calcite has a distinct origin from aragonite, as from the siliciclastics. Additionally, kaolinite displays relative higher variance to the other aluminosilicates. One source of kaolinite is the weathering of albite. The evaluation of balance-dendograms reveals that the calcium accumulation, i.e. carbonate precipitation in the lake, retains most of the variability within the data-sets. A pattern comparison between ternary subcompositions of elements and minerals leads to the conclusion of increased chemical weathering since the middle Holocene, implying increased moist conditions. Such conclusions are of importance for further investigations in which the paleo-environment for the Marmara region is reconstructed for the past 31 ka calBP.