Rubielos de la Cérida basin

The approximately 80 × 40 kilometer Rubielos de la Cérida Basin in northeastern Spain has recently been interpreted as an impact structure.

Location and description

Morphological printout of the Rubielos de la Cérida basin, digital elevation map of Spain, scale 1 / 250,000

The impact basin is located north of Teruel in Aragon . It is considered the twin structure of the Azuara impact structure and was likely caused by a multiple impact. It was named after the village of the same name Rubielos de la Cérida , which is located on the central bulge in the extreme north of the structure.

Originally, the impact structure was described as a circular meteorite crater with a diameter of 40 kilometers and a clear central elevation. Today it is assumed that a chain of craters is lined up and merged to form an elongated impact basin with a central protruding ridge. To the east, a large part of the original basin is covered by Neogene sediments , which were only deposited after the impact.

So far, the impact structure has been viewed as purely tectonic in origin and interpreted as trenches - the Jiloca-Calatayud Trench and the Alfambra-Teruel Trench . However, since tectonic trenches are usually characterized by dilation structures, the classical interpretation has great difficulty in correctly interpreting the prevailing compressions encountered.

Impact structures

The Sierra Palomera, part of the central overburden in the Rubielos-de-la-Cérida basin

The Impaktnatur of the pelvis is determined by the presence of Impaktschmelzen, Suevite polymictic spread far and monomikten Brecciated hardens breccia pipes, extensive megabreccias, ejecta, dislocated Mega blocks remarkable geological structures on the rim and in the central breaking-up zone as well as signs of shock metamorphosis.

The shock effects manifest themselves in fused glasses, diaplectic glasses made of quartz and feldspar, planar elements ( English planar deformation features or PDFs) in quartz, differently oriented kink bands in mica as well as in intensive micro-twinning in calcite . Moderately formed radiation cones also appear and in turn refer to the impact nature of the basin.

Controversial interpretation

Suevite of the Rubielos de la Cérida basin

The origin of the Rubielos de la Cérida Basin remains controversial as Spanish geologists continue to oppose a cosmic impact. In their opinion, the shock effects are tectonic, the ejecta are alluvial fans or conglomerates of the Cenozoic era and the alleged impact and vein breccias in their eyes are karst phenomena and soil formations.

This resistance to the impact nature of Rubielos de la Cérida (and also Azuara) was nourished in 1996 by a scientific study by Langenhorst and Deutsch, since these authors did not believe they recognized the presence of shock metamorphosis.

Despite the evidence presented for an impact event that is characterized by strong shock phenomena, the impact basin (like Azuara) is not listed in the Canadian Earth Impact Database . However, other databases such as the J. Moilanen database or EDEIS (Expert Database on Earth Impact Structures) do contain the Rubielos de la Cérida Basin.

Age

Thin section with diaplectic glass and three different planar elements in quartz

Stratigraphic considerations and palaeontological dating situate the meteorite impact in the Upper Eocene or the Oligocene , ie around 40 to 30 million years ago BP .

Individual evidence

↑ Ernstson, K., Anguita, F. and Claudin, F .: Shock cratering of conglomeratic quartzite pebbles and the search and identification of an Azuara (Spain) probable companion impact structure . In: Shock wave behavior of solids in nature and experiments, 3rd ESF-Impact Workshop Limoges, abstract book . tape 25 , 1994.
↑ Ernstson, K., Schüssler, U., Claudin, F. and Ernstson, T .: An impact crater chain in northern Spain . In: Meteorite . 9, no 3, 2003, p. 35-39 .
^ Ernstson, K., Claudin, F., Schüssler, U. and Hradil, K .: The mid-Tertiary Azuara and Rubielos de la Cérida paired impact structures (Spain). In: Treb. Mus. Geol. Barcelona . tape 11 , 2002, p. 5 - 65 .
↑ Cortés, AL, Diaz-Martínez, E., Sanz-Rubio, E., Martínez-Frías, J. and Fernández, C .: Cosmic impact versus terrestrial origin of the Azuara structure (Spain): A review. In: Meteoritics & Planetary Science . tape 37 , 2002, p. 875-894 .
^ Diaz Martínez, E., Sanz Rubio, E. and Martinez Frias, J .: Sedimentary record of impact events in Spain. In: Geological Society of America. Special paper . tape 356 , 2002, pp. 551-562 .
↑ Langenhorst, F. and Deutsch, A .: The Azuara and Rubielos structures, Spain: Twin impact craters or Alpine thrust systems? In: Lunar and Planetary Science . tape XXVII , 1996.

[1] Ernstson, K., Anguita, F. and Claudin, F .: Shock cratering of conglomeratic quartzite pebbles and the search and identification of an Azuara (Spain) probable companion impact structure . In: Shock wave behavior of solids in nature and experiments, 3rd ESF-Impact Workshop Limoges, abstract book . tape 25 , 1994.

[2] Ernstson, K., Schüssler, U., Claudin, F. and Ernstson, T .: An impact crater chain in northern Spain . In: Meteorite . 9, no 3, 2003, p. 35-39 .

[3] Ernstson, K., Claudin, F., Schüssler, U. and Hradil, K .: The mid-Tertiary Azuara and Rubielos de la Cérida paired impact structures (Spain). In: Treb. Mus. Geol. Barcelona . tape 11 , 2002, p. 5 - 65 .

[4] Cortés, AL, Diaz-Martínez, E., Sanz-Rubio, E., Martínez-Frías, J. and Fernández, C .: Cosmic impact versus terrestrial origin of the Azuara structure (Spain): A review. In: Meteoritics & Planetary Science . tape 37 , 2002, p. 875-894 .

[5] Diaz Martínez, E., Sanz Rubio, E. and Martinez Frias, J .: Sedimentary record of impact events in Spain. In: Geological Society of America. Special paper . tape 356 , 2002, pp. 551-562 .

[6] Langenhorst, F. and Deutsch, A .: The Azuara and Rubielos structures, Spain: Twin impact craters or Alpine thrust systems? In: Lunar and Planetary Science . tape XXVII , 1996.