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Sandstone, what ist that ?
(Source: Geowissenschaftlicher Dienst, Dr. Olaf Otto Dillmann)
Sandstone is a bedrock from rounded to sharp-edged grains, whose diameter lies in between 0,063mm to 2mm according to the DIN 4022. The term sand thus describes a defined grain size interval. In contrary to most other rocks the sandstone is not defined by a certain mineral constituent. Quartz is generally regarded as the main mineral. The various grains of sand, the components, can also consist of other minerals or rock fragments. A sandstone, whose components consist to more than 90% of quartz grains, is called quartz sand stone. If a sandstone component leads, whose diameter exceeds 2mm, then it is called conglomerate sandstone (e.g. OLSBRUECKER SANDSTONE). Sandstones with portions of grain sizes under 0,063mm or 0,002mm are called silty and/or clayey sandstones.
Sandstones are deposit or sedimentary rocks, resulting from the solidification of loose sand, the sediment. After CORRENS sediments are regarded as deposited products of mechanical and chemical decomposition after transport. Means of transport are essentially water, wind and ice. The deposit of the sand takes place due to the force of gravity via mechanical sedimentation. All components of a sandstone set off mechanically after transport are called detritus. Characteristic for all sedimentary rocks is the layering. It results from changes in the sedimentation conditions, e.g. the supply of materially different detritus or the change of the grain size of the depositing substances. The banking which can be observed in sandstone sequences is to be due to repeated sedimentation interruptions. The emergence of sandstones is possible in different deposit areas. The deposit of sand can take place within by streams nerved lowlands, within the muzzle range of rivers (delta levels) as well as within the sea range in direct proximity of the coast or on shallows. The diversity of the deposit areas mentioned with their specific deposit conditions, which experienced their unmistakable development in the temporal succession of earth-historical procedures, lead to different sandstones, which arrive into the trade with a large sort-variety.
Layer sequence in the sandstone
Today the sandstone of this region shapes the landscape which was the sea bottom millions of years ago. Large rivers rinsed sand and decomposition debris into the Cretaceous sea. Rough quartz sand, clay and fine marl sank and solidified themselves layer for layer. A compact sandstone plate developed, about 20 x 30 kilometres wide and up to 600 meters thick.
- Bohemian massif
- Lusatian-Saxonian block
- Elbe Sandstone territory
- Rhenish massif
- prehistoric sea of the Cretaceous period
When the sea left approx 80 million years ago, the mountainforming decay began. At first bursts developed. From the north coming the Lusatian granite massif pushed itself gradually onto the sandstone plate. From the south the lifting mountains of the todays Erzgebirge caused counterpressure which slanted the brittle sandstone plate and bursted it. From the nearly right-angled break lines later the typical, cuboid-like fissure of the Elbe sandstone developed.
-fissure systems in the sandstone
(Source: Norbert Marwan, Internet)
In the lower upper-cretaceous (Cenoman) began one of the largest transgressions of the geologic history, which also flooded the regarded area. At first the deposits still originate from a river system coming from the west (embouchure), then later from the change of transgression and involution. The change causes a variety of different rock formations (fine to coarse-grained sandstones, clay, transgression-horizons).
This stratigraphical table gives an exact demonstration.
At the beginning of the Tertiary period the Cretaceous sea leaves completely and the erosion begins to shape typical landscape as we know it today. Due to the rock slip in the Erzgebirge (Egertalgraben) and the involved skew of the mountains, also the sandstone plate of the Elbsandstein is somewhat put up (with northern breaking in), what entails an even faster erosion (especially due to the Elbe coming from the south). At the same time it comes to a multiplicity of basalt volcanism, which formed many basalt crests (like Gohrisch, Hausberg and Eisenhübel) as well as countless basalt courses and brown-iron rinds in the sandstone. During the ice age two ice raids arrive in the Elbsandstein territory. Ground moraines and rope sea deposits on the edge of the ice. Since the ice retreat soil-formation and further destruction of the sandstone take place.