Segregation (geology)
Separation means in geology the internal dissection of a rock by fissures, which is not caused by simple mechanical sedimentary deposits and to which both stratification and foliation can be traced back. In the case of igneous rocks, the secretion occurs through cooling shrinkage, in the case of sedimentary rock through desiccation and leads to a variety of shapes, for example columns in the case of basalt , cuboids in the case of sandstone and limestone or banks in the case of granite .
The cuboid term
The term cuboid entered the geological terminology early on from the quarrymen's language. A parallelepipedic shape of the sediment layer in question is decisive for this. Bernhard Cotta noted in 1839 in his explanations on the geognostic map of the ashlar sandstone: "Vertical fissures and crevices cut through, at a fairly right angle, the horizontal layers, and this creates that segregation into parallelepipedic bodies that gave rise to the name ashlar sandstone." In geological literature the term work stone bench appears in these contexts because it forms a rock layer preferred by stone crushers because of its compactness.
Because "ashlar sandstone" often occurs in the Cretaceous deposits, ashlar sandstone had become a synonym for the chalk formation in historical parlance . In this context, however, it should be noted that other types of rock, such as marl rocks or mudstones , can also occur in Cretaceous sediments .
In the case of sediment layers in which two parallel banks of further intermediate layers stand out, the terms lower and upper cuboid are used . If there are other square banks, they were called intermediate cuboid and cross cuboid . Later, an abstract terminology developed in geoscientific language that differentiated such banks of blocks with letters and numbers.
In this sense, the ashlar bench always establishes a specific reference to the depository or stratigraphic location by pointing to something above or below it. In 1844 , August Emanuel Reuss points to the merit of Carl Friedrich Naumann that he recognized the age difference in individual sandstone layers and therefore referred to them as upper and lower blocks.
See also
Individual evidence
- ↑ Bernhard Cotta: Explanations on Section VI of the geognostic chart of the Kingdom of Saxony and the adjacent federal states, or: Geognostic sketch of the area between Neustadt, Bischoffswerda, Wittichenau, Rothenburg, Görlitz, Ostritz, Rumburg and Schluckenau . Arnoldische Buchhandlung, Dresden and Leipzig, 1839, pp. 49–50.
- ↑ August Emanuel Reuss: The chalk formation of western Bohemia, a monographic attempt . Prague 1844, pp. 5-6