Geneza i klasyfikacja wapiennych osadów martwicowych

Joachim Szulc

Abstrakt


GENESIS AND CLASSIFICATION OF CALCAREOUS SINTER DEPOSITS

Summary
The paper presents genetic-environmental classification of authigenic limestones originating in agitated fresh water, based on data concerning chemistry of environment and contribution of lower plants in precipitation of calcium carbonate. There were differentiated:
1) calcareous tufa, precipitated by algae in environments varying in pH values. It originates in waters with layer movement and stagnant and, sometimes, agitated ones. Tufa is built of light, highly but uniformly porous, often friable limestone composed of micritic and microsparitic calcite, concentrically arranged around thallus. Seasonal and annual increments, up to 2 cm in width, are well visible.
2) Travertine - hard, highly but nonuniformly porous limestone, precipitating on mosses preferring waters with low pH values (about 5-7), i.e. more acid than those favourable for algae - springs and waterfalls. Travertine forms layers 10-40 cm thick, sloping upstream under varying angle. Free spaces are soon infilled with diagenetic deposit. This limestone is built of calcite grains varying in size.
3) Sinter - hard, not porous limestone formed by dripping water, i.e. by chemical precipitation only, mainly in spring (including thermal spring) zones and forming secondary dripstone and incrustations in free spaces in travertines. It originates in lower pH than fresh-water limestones and it is built of calcite crystals varying in size from micrite to 5 mm sparite.
4) Oncoids, varying in size and mode of development depending on the rate and type of transport. They are built of micrite precipitating on radially arranged or laying algal filaments and they are strongly porous.
5) Pelloids and calcareous muds, forming a large part of fresh-water limestone deposits. They are usually structureless and their origin is connected with direct precipitation of CaCO3 from water or destruction of older limestones. Algae and heterotrophic bacteriae have important contribution in their formation.

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