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1 2007

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Cementacja węglanowa osadów piaszczystych klifu w Gdyni-Orłowie

Ciborowski T., Jankowski M.

Przegląd Geologiczny

2007

Vol. 55, nr 2

140-145

Carbonate cementation of sandy sediments is most common in tropical and subtropical climate, and quite rare in temperate climate. About 20 sites where carbonate cemented sandstones occur are known throughout the Polish Lowlands. A new outcrop of carbonate cemented sandstone was found near Gdynia-Orłowo (coast of the Gulf of Gdańsk). Field studies and microscopic analyses [optical microscopy and SEM] let to recognise the pattern of cementation of sandy sediments. Origin of the sandstones is connected with infiltration of rain water into glacial till (partially cracked). This till is the source of calcium carbonate transported by water into underlying fluvioglacial sands. Because of different sediments porosity and resulting degassing of CO2, CaCO3 precipitated. Additionally, elevated temperature and evaporation of water may also create favorable condition for precipitation. The process of cementation is related to the exposition of fluvioglacial sands layer caused by cliff abrasion (about 1 m per year). The best geochemical conditions for precipitation of CaCO3 are in the zone of contact with atmosphere, so this cementation seems to be recent. Carbonate cemented sandstones formed below the glacial till fall down and may be found in the colluvium of the cliff slope.