Abstract
Varved clay deposits from ice-dammed lakes are a particularly important and broadly applied raw material used for the production of high-quality ceramics (red bricks, roof tiles, etc.), but the mineralogy and geochemistry of these sediments are not fully understood. The aim of the present study was to determine the chemical and mineralogical composition of ice-dammed lake sediments of the Lębork deposit. Major-element analysis of the compositions of selected samples from the ice-dammed lake clays was performed by X-ray fluorescence (XRF) and trace elements were determined by inductively coupled plasma-mass spectrometry. The mineralogical composition of clay samples was determined by X-ray diffraction (XRD). Analyses of the chemical composition of the ice-dammed lake clays of the Lębork deposit showed that the dominant component was SiO2 with a mean content of 56.13 wt.%; the second most abundant component was Al2O3, with a mean content for the entire deposit of 11.61 wt.%. Analysis by ICP-MS indicated the presence of rare earth elements (REE), e.g. cerium, neodymium, lanthanum, and praseodymium; their mean contents are: 56.9, 27.0, 26.3, and 7.3 ppm, respectively. Mineralogical analysis of the varved clays identified quartz, muscovite, calcite, and clay minerals – illite, kaolinite, and montmorillonite. The material filling the Lębork basin is characterized by small lateral and vertical variability in chemical composition. The results of the present study may be of considerable importance in determining the parent igneous, metamorphic, and sedimentary rocks, the weathering products of which supplied material to the ice-dammed lake, as well as in determining the mechanisms and character of the sedimentation process itself.
Highlights
Pleistocene extraglacial ice-dammed lakes were formed as a result of ice-barring of a river valley and damming up the river flowing toward the ice-dam
Ice-dammed lake sediment deposits develop in water bodies formed through the inhibition of runoff and damming waters flowing through the ice sheet terminus
The chemical compositions of the ice-dammed lake clays of the Lębork deposit showed that the dominant component of the clays is SiO2 (Table 2)
Summary
Pleistocene extraglacial ice-dammed lakes were formed as a result of ice-barring of a river valley and damming up the river flowing toward the ice-dam. Clay-silty varves formed in such lakes are distinctive glacial features, due to the rhythmic sequence of deposition of sediments over a single year and are useful for Pleistocene stratigraphy. Ice-dammed lake sediment deposits develop in water bodies formed through the inhibition of runoff and damming waters flowing through the ice sheet terminus. They are lithologically distinctive and characterized by a sequence of facies, from fluvioglacial sands through glaciolimnic deposits, to icedammed lake rhythmites (Paluszkiewicz 2004)
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