Colored dolomite
The colored dolomite is a lithostratigraphic unit in the Northern Limestone Alps. It often occurs in conjunction with the Gutenstein Formation and the Steinalm Formation . It gets its name from the strongly varying structure that emerges through clear banking . In the stratigraphic table of Austria, the colored dolomite is not shown as a separate unit. It is possible that the colored dolomite is a diagenetically modified Hallstatt limestone .
description
The colored dolomite is a coarse-grained, pebbly, gray to brown dolomite, which can be massive or coarse banked. The hues of the colored dolomite are distinctly colored and are distributed in fine lenses or greasy layers with green, turquoise, light red, rusty brown or purple color. They dominate the entire rock color precisely because of their fine distribution. According to Tollmann & Schlager, the pebble content and the colorful clays can be interpreted as tuffy scattering of volcanism in the time of the Illyrian . The layer thicknesses are a few tens of meters.
The colored dolomite has shell-like to smooth fracture surfaces and does not weather in a creepy manner, but, as with the dark variant of Gutenstein dolomite, in furrowed, lumpy shapes that stand out from the slopes when the weather is lighter.
When viewed microscopically in a thin section , the crystals alternate between fine and coarse-grained structures in an interlocked structure . They are often framed by brown iron hems , which provide reddish tones. The few fissures can be filled with calcite or also with brown or red material, which protrudes into the dolomite matrix as fibrous, matted crystals. A detailed examination at the Gosau ridge shows only a few enclosed fossils, most likely those of calcareous algae .
Educational conditions
Like the Gutenstein dolomite, the colored dolomite is a sediment formed in the Triassic period on the bottom of shallow seas. The deposits take place at sea depths up to a maximum of 200 m and mainly in the anisium . The climate at that time was warm, the formation area was a shallow basin in front of the reef complexes .
In the Dachstein region (Upper Austria-Salzburg) the two types of dolomite are closely interlinked and lithologically similar, but differ in the color of the thin layers of clay .
See also
literature
- Benno Plöchinger (with contributions by Heinz A. Kollmann) (Gosau deposits in the Gosau basin), Walter Kollmann (hydrogeology), Gerhard Schäfer (Hallstatt zone west of Plassen) and Dirk van Husen (Quaternary): Geological map of the Republic of Austria 1: 50,000 explanations to sheet 95 Sankt Wolfgang im Salzkammergut. 74 pp., Vienna 1982 PDF
Individual evidence
- ↑ Stratigraphic table of Austria 2004 PDF file ( Memento of the original from April 24, 2018 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Andreas Scheidleder u. a .: Project karst water Dachstein. Volume 2: Karst hydrology and risk of contamination of springs. Archive for deposit research, Volume 21, Vienna 2001, page 26. PDF file
