Alemonite

Alemonite is a type of rock that occurs mainly in the Altmühl area and in the Upper Palatinate .

The name is derived from Alemona , the Latin name for the Altmühl. It was first described in 1971 by the geologist Erwin Rutte . According to Rutte, the Alemonite was formed during the Ries impact around 15 million years ago: Pressure , temperatures and the action of silica of cosmic origin transformed Jurassic limestone and green sandstone from the Altmühlalb and Upper Palatinate into a diverse and characteristic new rock.

Depending on the chemistry and structure of the parent rock , breccias or crystalline pebbles were formed. In the meantime, the gneisses and granites of the Bavarian / Bohemian Forest , the sand-gravel sediments of South Bohemia and the silicified sandstones of Central Europe , which are affected by the same impact after Rutte, are referred to as Alemonitic or Alemonitized.

The interpretation of the alemonite as an impactite , as well as the size of the impact derived by Rutte from the distribution of this rock , were controversial from the start. In particular, the assumption of silicification of the rock at the moment of the impact met with opposition from the start.

In the more recent literature on meteorites and impacts in Bavaria, the alemonite is no longer associated with an impact event; rather, it is described there as the formation of a weathering period close to the surface with warm climatic conditions (and thus corresponds more to a freshwater quartzite or Kallmünzer (geology) ). In the current recommendations of the IUGS on the nomenclature of impact metamorphic rocks, neither the term "alemonite" and the description of a corresponding rock appear.

Individual evidence

↑ Heinz Beyer: On the question of the origin of the silica in the Alemonites . In: The opening . tape 25 , no. 7/8 , 1974, p. 427-433 .
↑ Bavarian State Office for the Environment (ed.): Not of this world - Bavaria's meteorite . Self-published, 2012, ISBN 978-3-936385-92-2 , p. 83 .
↑ Douglas Fettes, Jacqueline Desmons (Ed.): Metamorphic Rocks. A Classification and Glossary of Terms . Cambridge University Press, Cambridge 2011, ISBN 978-0-521-33618-5 .

literature

E. Rutte: Alemonite - the suevite-equivalent impact rock type of the southern Franconian Alb , in Die Naturwissenschaften , Volume 59 (1972), pp. 214-216.
E. Rutte: New findings on astro problems and alemonites in the tail region of the giant comet , in Oberrheinische geologische Abhandlungen , Volume 23 (1974), pp. 66-105
W.-D. Grimm: The Upper Miocene quartz conglomerate in Eastern Lower Bavaria is not an astro problem , in New Yearbook for Geology and Paleontology, MONTHS , 1977, pp. 373–384
R. Hüttner, W. Reiff: No accumulation of astro problems on the Franconian Alb , in New Yearbook for Geology and Palaeontology, monthly books, 1977, pp. 415-422

[1] Heinz Beyer: On the question of the origin of the silica in the Alemonites . In: The opening . tape 25 , no. 7/8 , 1974, p. 427-433 .

[2] Bavarian State Office for the Environment (ed.): Not of this world - Bavaria's meteorite . Self-published, 2012, ISBN 978-3-936385-92-2 , p. 83 .

[3] Douglas Fettes, Jacqueline Desmons (Ed.): Metamorphic Rocks. A Classification and Glossary of Terms . Cambridge University Press, Cambridge 2011, ISBN 978-0-521-33618-5 .