Cornbrash sandstone
The Cornbrash sandstone (also iron limestone ) was quarried around Lübbecke and Minden to Lemgo , Osnabrück , Hanover , Braunschweig and Fallersleben . It is a mainly carbonate - and also glauconitic - bound sandstone that contains iron. It originated in the Middle Jura .
Emergence
With the beginning of the Jura (195 million years ago) the sea level rose and the areas that had fallen dry in the Upper Triassic were flooded. In the Osnabrück region, at the beginning of the Jura (195 million years ago), thick layers of clay were deposited. They were deposits of a tropical to subtropical sea with a water depth of 20 to 100 meters and a water temperature of around 17–24 ° C. These conditions were the habitat of many ammonites and belemnites . In the Middle Jurassic, the sequence of layers changes, because the claystones slowly change into sandstone that came from a mainland to the north. The so-called Cornbrash was created. The Cornbrash is an excellent oil storage rock and in addition, an iron ore deposit up to 2 meters thick was created in certain areas of the Cornbrash. The banks in the rock are 1 meter high and the entire layer up to 20 meters.
Description and use
The Cornbrash sandstone is medium to coarse-grained, rarely fine-grained. Its bond is chalky or glaconitic. The iron content is always present and there are also veins of iron. Its qualities are very different depending on the proportion of the bond and the break position. At Porta the deposit is up to 80 meters thick and at Hanover about 18 meters. The small deposits near Hanover and Fallersleben have been exploited.
Larger workpieces were difficult to extract due to the fissures in the sandstone deposits. This stone was therefore mainly used as quarry and curb stone, also for grit , for road construction and in building construction as a foundation stone . This stone is no longer broken today (2008).
literature
- Otto Sickenberg: stones and earth. The deposits and their management. Geology and Deposits of Lower Saxony , 5th volume. Dorn-Verlag, Bremen, Horn 1951, p. 100ff.