The effect of heating on mineral composition and grain size distribution of flux calcined porcelanites from the Gafsa-Metlaoui basin, southwestern Tunisia

2016 ◽  
Vol 124 ◽  
pp. 189-198 ◽  
Author(s):  
Raja Saidi ◽  
Ali Tlili ◽  
Fakher Jamoussi
Author(s):  
Rasma Tretjakova ◽  
Andris Karpovičs

Our research is focused on sedimentological conditions and postdepositional changes of recent fine grained lake sediments. We used bulk sediment mineralogical composition and grain size distribution as indicators to identify sediment source areas and possible changes during Holocene. We analysed fine grained (clayey) sediments from three Latgale lakes - Zeili, Pauguļi and Plusons, situated in Latgale upland. Lake sediments cover Late Pleistocene glacial deposits – loam and sandy loam. Bulk mineral composition of 6 sediment samples was determined by X-ray diffraction (XRD). Sediments contained typical minerals found in surrounding glacial sediments: rock-forming minerals as quartz, plagioclase, albite, enstatite, dolomite, calcite, and clay minerals - illite, kaolinite. To identify postdepositional changes in lake sediments of Holocene age clay minerals in clay fraction (<2 mkm) should be analysed. Particularly illite, smectite mixed layered minerals - illite/smectite (I/Sm) and chlorite. Additionally, grain size distribution of studied lake sediments was analysed. Accordingly, our studied sediments are clays, silty clays and clayey silts with bimodal particle distribution, except two samples from Zeiļi and Plusons with unimodal distribution.


1961 ◽  
Vol S7-III (4) ◽  
pp. 379-382
Author(s):  
Gian Clemente Parea ◽  
F. C. Wezel

Abstract Twelve samples of muds were collected from the bottom of Maggiore lake (northern Italy), at approximately equal intervals throughout the length of the lake in order to index the grain-size distribution and mineral composition of the muds. Most of the samples are typically lacustrine; some are typically fluviatile. The data indicate the presence of a significant amount of mineral matter in suspension throughout the lake as a result of strong currents generated by winds and by thermal variations in the lake waters.


2012 ◽  
Vol 45 (5) ◽  
pp. 487-502 ◽  
Author(s):  
Su Jeong Song ◽  
Chang Oh Choo ◽  
Chun-Joong Chang ◽  
Tae Woo Chang ◽  
Yun Deuk Jang

2021 ◽  
Vol 9 ◽  
Author(s):  
Denis Shmelev ◽  
Maria Cherbunina ◽  
Victor Rogov ◽  
Sophie Opfergelt ◽  
Arthur Monhonval ◽  
...  

Cryogenic weathering is a key driver of periglacial sediment composition and properties. Selective mineral-grain weathering caused by freeze-thaw cycles in permafrost environments has the ability to dominate this process, leading to silt-rich grain-size distributions. The cryogenic weathering index (CWI) is a promising tool to quantify cryogenic weathering and freezing conditions. It considers the low resistance of quartz to freeze-thaw cycles compared to feldspars. Using this approach, this study aims to decipher post-depositional weathering by reconstructing cryogenic late Pleistocene Yedoma origins of the Yedoma stratotype exposure Duvanny Yar. To estimate the recent environmental endmember and to determine the initial mineral composition of sediment until freezing, the distribution of CWI in the active layer was studied. In addition to CWI, we studied mineral composition, heavy mineral distribution, grain size distribution and grain morphology. We suggest that cryogenic weathering likely altered polygenetic deposits (fluvial, nival, colluvial, lacustrine, alluvial, and aeolian processes) during sediment and ground ice accumulation. Moreover, we found two CWI distribution peaks in the late Pleistocene - Holocene sediments at the boundaries between glacial and interglacial ages. In conclusion, we see that the Duvanny Yar sediment facies varied by CWI, but also with grain-size distribution, suggesting environmental changes during formation. Nevertheless, post-depositional processes like cryogenic weathering have influenced sediment characteristics and should be considered in paleoenvironmental reconstructions.


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