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2 2023

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Dinoflagellate cysts and benthic foraminifera from surface sediments of Svalbard fjords and shelves as paleoenvironmental indicators

Telesiński Maciej M., Pospelova Vera, Mertens Kenneth Neil, Kucharska Małgorzata, Zajączkowski Marek

Oceanologia

2023

Vol. 65 (4)

571--594

Due to the Arctic amplification effect, the Svalbard archipelago is an important area for studying ongoing environmental changes. However, its marine ecosystem is extremely complex. In this study, we analyze modern assemblages of dinoflagellate cysts (dinocysts) and benthic foraminifera from surface sediment samples around Svalbard. We use multivariate statistical analyses to examine relationships between environmental conditions (summer and winter sea surface temperature and salinity, sea-ice cover, etc.) and both microfossil groups to evaluate their use as proxies for reconstructions of the marine environment in the region. Our results show that the most important factor controlling the environment around Svalbard is the Atlantic Water which mostly impacts the western coast, but its influence reaches as far as the eastern coast of Nordaustlandet. However, on a local scale, such factors as the sea-ice cover, the presence of tidewater glaciers, or even the morphology and hydrology of fjords become increasingly important. We found that two dinocyst species, cysts of Polarella glacialis and Echinidinium karaense, can be considered regional winter drift ice indicators. The relationships between environmental parameters and benthic foraminiferal assemblages are much more difficult to interpret. Although statistical analysis shows a correlation of benthic foraminiferal species with various environmental parameters, this correlation might be somewhat coincidental and caused by other factors not analyzed in this study. Nevertheless, the use of two complementary microfossil groups as (paleo)environmental indicators can provide a more comprehensive picture of the environmental conditions.

Fate of swelling clay minerals during early diagenesis: a case study from Gdańsk Bay (Baltic Sea)

Kisiel Marta, Skiba Michał, Damrat Mateusz, Kuligiewicz Artur, Maj-Szeliga Katarzyna, Makiel Magdalena, Zajączkowski Marek, Salata Dorota

Annales Societatis Geologorum Poloniae

2023

Vol. 93, No. 3

305--322

The aim of the study was to recognize the early diagenetic transformations of clay minerals likely taking place in the brackish environment of Gdańsk Bay (Baltic Sea). The Vistula River loads and sediments of the Vistula delta front and prodelta were studied. The mineral compositions of the clay fractions were determined by X-ray diffractometry. The average layer charge (LC) of the expandable interlayers was determined using the O-D vibrational spectroscopy method. The major element content of the studied clays was determined by inductively coupled plasma optical emission spectrometry. The <0.2 μm clay fraction, separated from the river sediments, contained illite-smectite mixed layered minerals, rich in high-charge, dioctahedral smectite (Ilt-Sme), illite, and kaolinite. The same clay fraction, separated from the delta-front sediments, was also composed mainly of Ilt-Sme, illite, kaolinite, and hydroxy-interlayered minerals. The <0.2 μm clay fraction from the prodelta sediments was depleted in Ilt-Sme and enriched in illite and chlorite, relative to the clays from both the river and the delta-front sediments. The LCs (0.45 to 0.56 per formula unit) were higher for clays from the river and the delta front sediments, relative to the clays from the prodelta. The <0.2 μm clay fractions from the prodelta sediments were enriched in MgO, Fe2O3, and K2O, relative to the fine clay fraction from the river. The results indicated that the smectite component of Ilt-Sme, deposited by the Vistula in Gdańsk Bay, underwent chloritization and likely illitization. The chloritization most likely proceeded via formation of hydroxy-interlayers within the smectite. Illite-like minerals, formed at the expense of the smectite with high LC, due to selective adsorption and fixation of K+ from seawater.