Results from a Multi-disciplinary Sedimentary Pilot Study of Tectonic Lake Iznik (NW Turkey) – Geochemistry and Paleolimnology of the Recent Past |
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Authors: | Sven O Franz Lorenz Schwark Cathrin Brüchmann Burkhard Scharf Ralf Klingel Jon D Van Alstine Nam?k Çagatay Umut B Ülgen |
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Institution: | 1. Institute of Geology, University of Bonn, Nussallee 8, 53115, Bonn, Germany 2. Institute of Geology and Mineralogy, University of Cologne, Zülpicher Stra?e 49a, 50674, Cologne, Germany 3. GeoForschungsZentrum Potsdam, Telegrafenberg, 14473, Potsdam, Germany 4. Burkhard Scharf, Emmericher Stra?e 27, 46286, Dorsten-Rhade, Germany 5. Department of Inland Water Research, Earlier: UFZ Centre for Environmental Research Leipzig-Halle, Brückstra?e 3a, 39114, Magdeburg, Germany 6. Kemski & Partner, Beratende Geologen, Alte Heerstra?e 1, 53121, Bonn, Germany 7. Large Lakes Observatory, University of Minnesota Duluth, 10 University Drive, 202 RLB, Duluth, MN, 55812-2496, USA 8. General Geology Division, Faculty of Mines, Istanbul Technical University, 34469, Maslak, Istanbul, Turkey 9. Eurasia Institute of Earth Science, Istanbul Technical University, Maslak, Istanbul, 34469, Turkey
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Abstract: | A limnogeological reconnaissance study was carried out on Lake Iznik, located in the southeast of the Marmara region of Turkey,
involving a seismic survey and collection of short sediment cores. This lake is located on the middle branch of the North
Anatolian Fault Zone (NAFZ), a transform plate boundary between the Eurasian and Anatolian Plates. It is, therefore, tectonically
active and offers an opportunity to investigate the interplay of sedimentary and seismo-tectonic processes, as well as climate
change and human impact in the region. Short cores of the three sub-basins, maximum length of 35.5 cm, recovered non-laminated,
blackish clays and silts with varying amounts of biogenic and minerogenic (allochthonous, autochthonous) material, which documented
almost the last 80 years of deposition and environmental history. High sedimentation rates in the deeper core sections are
accompanied by changes in land use (conversion of woodland to farmland) in the northern areas of Lake Iznik, which caused
the deposition of more weathered material (high K/Na ratios) and higher contents of Mn in the lake. A tendency towards eutrophic
conditions within the last 20 years is indicated by high nutrient content (N, TOC, P), decreasing C/N-ratios, and characteristic
diatom and cladoceran associations. Also increased pollution is revealed by higher Pb, Cu, and Zn contents and increased supply
of human and animal faeces (high coprostanol content) during the last two decades. But simultaneous lower sedimentation rates
towards the core tops complicate the reconstruction of recent and past eutrophication and pollution states of Lake Iznik.
This requires an extension of the pilot study and deeper sediment cores, to recover non-anthropogenic influenced sediment
levels. |
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Keywords: | Diatoms Geochemistry Human impact Lake Iznik Sedimentology Turkey |
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