Browsing by Author "Zajączkowski, Marek"
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- ItemLate Holocene Vistula River floods recorded in grain size distributions and diatom assemblages of marine sediments of the Gulf of Gdańsk (Baltic Sea)(Elsevier, 2023-05-01) Szcześniak, Marta; Kokociński, Mikołaj; Jagodziński, Robert; Pleskot, Krzysztof; Zajączkowski, Marek; Szczuciński, WitoldDuring the large flood of the Vistula River in 2010, the riverine brackish water surface plume extended up to 70 km into the Gulf of Gdańsk (Baltic Sea), leaving a thin layer of medium-grained sand deposits. It inspired a search for palaeoflood records in marine sediments. Thus, we aimed to identify the most useful flood indicators and apply them to reveal palaeoflood records in sediment cores from the Gulf of Gdańsk. The study is based on analyses of surface samples, collected during and one year after the 2010 flood, and two long sediment cores, which were subjected to high-resolution grain size, diatom, and geochemical analyses, while chronology was based on the combined AMS 14C, 210Pb and 137Cs dating. It was found that, in a water depth of less than 30 m, modern large flood deposits were not preserved after a year. Sediment cores retrieved from greater water depths (over 60 m) were composed of sandy mud, and most of the 1 cm thick sediment samples were characterized by unimodal grain size distribution. However, some of the samples were bimodal, with the additional mode in fine-grained fractions, which is interpreted to be the result of direct deposition from riverine flood surface water plume. The diatom assemblages revealed a moderate downcore variability, except for the intervals characterized by bimodal grain size distributions. They contained elevated amounts of benthic oligohalobous (freshwater) and decreased euhalobous and mesohalobous taxa, supporting the likely interpretation of these layers as deposited during river flood events. During the last c. 4 ka, a dozen major flood events were identified. However, their application to flood climate reconstruction is challenging because of relatively frequent and partly unknown changes in major river mouth positions in the past. We suggest that thin deposits of major floods left on the seafloor and subjected to further mixing maybe still recognized using a combination of high-resolution grain size distribution and diatom analyses supplemented by a good understanding of the depositional system history.
- ItemLate Weichselian and Holocene palaeoceanography of Storfjordrenna, southern Svalbard(2015) Łącka, Magdalena; Zajączkowski, Marek; Forwick, Matthias; Szczuciński, WitoldMultiproxy analyses (including benthic and planktonic foraminifera, δ18O and δ13C records, grain-size distribution, ice-rafted debris, XRF geochemistry and magnetic susceptibility) were performed on a 14C-dated marine sediment core from Storfjordrenna, located off of southern Svalbard. The sediments in the core cover the termination of Bølling–Allerød, the Younger Dryas and the Holocene and reflect general changes in the oceanography/climate of the European Arctic after the last glaciation. Grounded ice of the last Svalbard–Barents Sea Ice Sheet retreated from the coring site ca. 13 950 cal yr BP. During the transition from the subglacial to glaciomarine setting, Arctic Waters dominated the hydrography in Storfjordrenna. However, the waters were not uniformly cold and experienced several warmer spells. A progressive warming and marked change in the nature of the hydrology occurred during the early Holocene. Relatively warm and saline Atlantic Water began to dominate the hydrography starting from approximately 9600 cal yr BP. Although the climate in eastern Svalbard was milder at that time than at present (smaller glaciers), two periods of slight cooling were observed in 9000–8000 and 6000–5500 cal yr BP. A change in the Storfjordrenna oceanography occurred at the beginning of the late Holocene (i.e. 3600 cal yr BP) synchronously with glacier growth on land and enhanced bottom current velocities. Although cooling was observed in the Surface Water, Atlantic Water remained present in the deeper portion of the water column of Storfjordrenna.
- ItemMultiproxy paleoceanographic study from the western Barents Sea reveals dramatic Younger Dryas onset followed by oscillatory warming trend(Springer Nature, 2020-09) Łącka, Magdalena; Michalska, Danuta; Pawłowska, Joanna; Szymańska, Natalia; Szczuciński, Witold; Forwick, Matthias; Zajączkowski, MarekThe Younger Dryas (YD) is recognized as a cool period that began and ended abruptly during a time of general warming at the end of the last glacial. New multi-proxy data from a sediment gravity core from Storfjordrenna (western Barents Sea, 253 m water depth) reveals that the onset of the YD occurred as a single short-lived dramatic environment deterioration, whereas the subsequent warming was oscillatory. The water masses in the western Barents Sea were likely strongly stratified at the onset of the YD, possibly due to runoff of meltwater combined with perennial sea-ice cover, the latter may last up to several decades without any brake-up. Consequently, anoxic conditions prevailed at the bottom of Storfjordrenna, leading to a sharp reduction of benthic biota and the appearance of vivianite microconcretions which formation is favoured by reducing conditions. While the anoxic conditions in Storfjordrenna were transient, the unfavorable conditions for benthic foraminifera lasted for c. 1300 years. We suggest that the Pre-Boreal Oscillation, just after the onset of the Holocene, may have been a continuation of the oscillatory warming trend during the YD.