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Roeser, Patricia; Franz, Sven-Oliver; Litt, Thomas (2016): Carbonates and selected geochemistry composition for sediments from Lake Iznik for the past 31 ka cal BP. PANGAEA, https://doi.org/10.1594/PANGAEA.863235, Supplement to: Roeser, Patricia; Franz, Sven-Oliver; Litt, Thomas; Ariztegui, Daniel (2016): Aragonite and calcite preservation in sediments from Lake Iznik related to bottom lake oxygenation and water column depth. Sedimentology, 63(7), 2253-2277, https://doi.org/10.1111/sed.12306

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Abstract:
This study examines the forcing mechanisms driving long-term carbonate accumulation and preservation in lacustrine sediments in Lake Iznik (northwestern Turkey) since the last glacial. Currently, carbonates precipitate during summer from the alkaline water column, and the sediments preserve aragonite and calcite. Based on X-ray diffraction data, carbonate accumulation has changed significantly and striking reversals in the abundance of the two carbonate polymorphs have occurred on a decadal time scale, during the last 31 ka cal BP. Different lines of evidence, such as grain size, organic matter and redox sensitive elements, indicate that reversals in carbonate polymorph abundance arise due to physical changes in the lacustrine setting, for example, water column depth and lake mixing. The aragonite concentrations are remarkably sensitive to climate, and exhibit millennial-scale oscillations. Extending observations from modern lakes, the Iznik record shows that the aerobic decomposition of organic matter and sulphate reduction are also substantial factors in carbonate preservation over long time periods. Lower lake levels favour aragonite precipitation from supersaturated waters. Prolonged periods of stratification and consequently enhanced sulphate reduction favour aragonite preservation. In contrast, prolonged or repeated exposure of the sediment-water interface to oxygen results in in situ aerobic organic matter decomposition, eventually leading to carbonate dissolution. Notably, the Iznik sediment profile raises the hypothesis that different states of lacustrine mixing lead to selective preservation of different carbonate polymorphs. Thus, a change in the entire lake water chemistry is not strictly necessary to favour the preservation of one polymorph over another.
Coverage:
Latitude: 40.433300 * Longitude: 29.541700
Minimum Elevation: -50.0 m * Maximum Elevation: -50.0 m
Event(s):
IZN09/LC2+LC3 * Latitude: 40.433300 * Longitude: 29.541700 * Elevation: -50.0 m * Recovery: 45 m * Location: Turkey * Method/Device: Composite Core (COMPCORE) * Comment: Core IZN09/LC2: 14 meters piston core in succesive 2 meter sections at (40° 26.57' N, 29° 32.35' E), 50 meter water depth
Core IZN09/LC3: 14 meters piston core in succesive 2 meter sections at (40° 26.92' N, 29° 32.61' E), 50 meters water depth
Parameter(s):
#NameShort NameUnitPrincipal InvestigatorMethod/DeviceComment
1Sample code/labelSample labelRoeser, Patriciasample id from the geochemistry laboratory of uni bonn
2Depth, compositeDepth compmcdRoeser, PatriciaIntercore correlationdepth given in meters of composite depth. Details on the composite profile see Roeser et al. 2012
3AGEAgeka BPRoeser, PatriciaAge, calibratedGeocode – ka cal BP
4CalciteCal%Roeser, Patriciaweight %
5Calcite, standard deviationCal std dev±Roeser, Patricia
6AragoniteArg%Roeser, Patriciaweight %
7Aragonite, standard deviationArg std dev±Roeser, Patricia
8Calcite, lattice parameter aCalcite aÅRoeser, PatriciaLatice parameters for Calcite concentrations smaller than 2% are not given
9Standard deviationStd dev±Roeser, PatriciaCalcite a
10Calcite, lattice parameter cCalcite cÅRoeser, PatriciaLatice parameters for Calcite concentrations smaller than 2% are not given
11Standard deviationStd dev±Roeser, PatriciaCalcite c
12ManganeseMn%Roeser, Patricia
13ManganeseMn%Roeser, Patricia<63 µm, concentrations for the fraction smaller than 63 micron were obtained only for unit IV
14IronFe%Roeser, Patricia<63 µm, concentrations for the fraction smaller than 63 micron were obtained only for unit IV
15Carbon, organic, totalTOC%Roeser, Patricia
16Nitrogen, totalTN%Roeser, Patricia
Size:
3897 data points

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