Czy holoceńska kreda jeziorna jest osadem słodkowodnym?
Abstract
Holoceńska kreda jeziorna występująca w Polsce jest zaliczana do osadów słodkowodnych. W jej tworzeniu mają jednak decydujący udział trzy rodzaje wód. Pierwsze to wody descenzyjne, które podziemnie zasilały basen sedymentacyjny w Ca(HCO3)2. Ich mineralizacja przekraczała 1g/dm3 górną granicę wód słodkich. Strącanie, głównie przy udziale roślin i depozycja CaCO3 powodowały, że wody jeziora stale były słodkie. Innym rodzajem są wody, które dziś wchodzą w skład wapiennego osadu w przeciętnej ilości 5060% wag. Wody te są polijonowym roztworem, w którym ilościowo dominują SO42- i Ca2+. Wykonana metodą ekstrakcji analiza wody kredy jeziornej 2 złóż wykazała duże zróżnicowanie mineralizacji w obrębie warstw, profili i złóż. Potwierdziła to analiza przypuszczalnej mineralizacji oparta na zawartości SO3 w kredzie. Woda części złóż zmineralizowana jest dodatkowo NaCl. Wysoka mineralizacja wód, zdaniem autora, jest rezultatem zasilania jezior wodami ascenzyjnymi.
HAS LACUSTRINE CHALK ORIGINATED IN FRESHWATER ENVIROMENT?
Summary
Holocene lacustrine chalk is commonly considered as a freshwater sediment. However, the actual origin of lacustrine chalk is closely related to three different types of water. The first one is underground descenting water, which supplies sedimentary basin with Ca(HCO3)2. Its potential of mineralization equals 1g/dm3 and is higher than upper limit of fresh water mineralization. Thesecond type of water is the lake water which stays fresh due to permanent precipitation and deposition of CaCO3, due to the vegetation of plants. The third type is water presently included in calcareous sediment. The average content of such water in the sediment varies between 50 and 60 weight percent. Such water is a multi-ion solution (tab. 1) with SO2-n and Ca2+ as the main cations. The analysis of water included in lacustrine chalk taken from two deposits (tab. 2, fig. 1, 2) shows quite distinct differentiation of mineralization not only between particular deposits, but profiles and beds as well. These results have been confirmed by the analysis of probable mineralization calculated on the base of the content of SO3 in the chalk (tab. 3, fig. 3). Water taken from some deposits is additionally mineralized with NaCl (tab.4, fig.4). Accordingly to the author’s opinion, relatively high level of mineralization is caused by permanent feed of lakes by ascending water.
HAS LACUSTRINE CHALK ORIGINATED IN FRESHWATER ENVIROMENT?
Summary
Holocene lacustrine chalk is commonly considered as a freshwater sediment. However, the actual origin of lacustrine chalk is closely related to three different types of water. The first one is underground descenting water, which supplies sedimentary basin with Ca(HCO3)2. Its potential of mineralization equals 1g/dm3 and is higher than upper limit of fresh water mineralization. Thesecond type of water is the lake water which stays fresh due to permanent precipitation and deposition of CaCO3, due to the vegetation of plants. The third type is water presently included in calcareous sediment. The average content of such water in the sediment varies between 50 and 60 weight percent. Such water is a multi-ion solution (tab. 1) with SO2-n and Ca2+ as the main cations. The analysis of water included in lacustrine chalk taken from two deposits (tab. 2, fig. 1, 2) shows quite distinct differentiation of mineralization not only between particular deposits, but profiles and beds as well. These results have been confirmed by the analysis of probable mineralization calculated on the base of the content of SO3 in the chalk (tab. 3, fig. 3). Water taken from some deposits is additionally mineralized with NaCl (tab.4, fig.4). Accordingly to the author’s opinion, relatively high level of mineralization is caused by permanent feed of lakes by ascending water.