Tornquist Zone
The Tornquist Zone (named after the German geologist Alexander Tornquist , other names are Tesseire-Tornquist Zone or Tornquist Line ) is a geological deformation zone ( suture ) in the north and east of Central Europe . It is the plate tectonic border area between the Baltic Shield of Scandinavia (Baltika) and eastern Central Europe and, as a geological weakness zone, separates two areas of the large Eurasian continental plate .
location
The zone is up to 100 km wide and extends from the Dobrudscha , through Poland and the southern Baltic Sea via Bornholm , southern Sweden , North Jælland , the Kattegat to Vendsyssel and Thy in Denmark . North of Rügen it splits into a northern branch, the carefree zone or carefree Tornquist zone , and a southern branch, which together with the Tornquist zone forms the trans-European suture zone (also Dobruja-North Sea lineament ). Between the two branches there is an area in which the basement is only covered by relatively thin younger layers, the so-called Ringköbing-Fyn-Hoch .
Geological background
The Tornquist Zone was created by the collision of the two continents Avalonia and Baltica . The timing of the collision is controversial. It took place at the earliest in the highest Ordovician and was probably completed by the end of the Silurian . The maximum possible age of the Tornquist Zone is thus around 460 million years.
The Tornquist Zone separates two areas with different structures of the earth's crust : in the east the earth's crust is about 45 km thick and was essentially formed in the Precambrian ; in the west it has an average thickness of about 30 km and was welded into one whole during the Variskan mountain formation in the Carboniferous . On the earth's surface, the Tornquist Zone can almost only be verified by geophysical methods such as gravity measurements or seismics , as it is covered by, in some cases, thick younger deposits. With the exception of a few isolated occurrences (e.g. the Heiligkreuzgebirge , the Sudeten and the Dobruja ), direct outcrops of the deeper earth's crust are only given by the numerous deep boreholes that have reached the layers affected by the Ordovician collision. The zone is traced by a series of geological sedimentary basins in which thick Mesozoic sediments have accumulated. From northwest to southeast these are the Norwegian-Danish Basin , the Danish Trough and the Polish Trough . Along the southern border of Poland and Romania , the Tornquist Zone is affected by the mountain formation of the Carpathians .
Today's activity
Even today, weak, barely noticeable earthquakes often occur between Denmark and Sweden , which are attributed to this plate boundary. On June 15, 1985, a magnitude 4.5 quake occurred in the Danish Nordsjælland , the epicenter was determined in the sea north of Gilleleje . In 2008, on December 16 at 6:20 am, an earthquake with an epicenter east of Malmö in Skåne in southern Sweden with a magnitude of 4.8. There is historical evidence of a powerful earthquake in Thy. Due to the differences in the thickness of the earth's crust, the heat flow from the interior of the earth is significantly different on both sides of the Tornquist zone.
Individual evidence
- ^ Tornquist zones ( Memento of February 9, 2006 in the Internet Archive ) Geological Institute, Lund University, Sweden , last updated October 27, 2004.
- ↑ a b c d Trans-European Suture Zone: Phanerozoic Accretion and the Evolution of Contrasting Continental Lithosphere. EUROPROBE, archived from the original on July 23, 2012 ; accessed on January 6, 2010 (see also the linked PDF document for more detailed information).
- ↑ a b Roland Walter et al .: Geology of Central Europe . 5th edition. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart 1992, ISBN 3-510-65149-9 , pp. 4-5 .
- ↑ Jordskalv i Skåne ( Memento of June 4, 2009 in the Internet Archive ) Swedish geological service: Sveriges geologiska undersökning , published December 16, 2008.