Azuara impact structure
{{Infobox terrestrial impact site
| name = Azuara structure
| other_name =
| photo = Azuara-impact-structure-Map.jpg
| photo_size =
| photo_alt =
| photo_caption = Morphological signature of the Azuara structure taken from the digital map of Spain, 1:250,000
| map = Spain
| map_alt =
| map_caption = Location of the crater in Spain
| map_size =
| location =
| label =
| label_position =
| coordinates = {{coord|41.18|N|0.88|W|display=inline,title}}
| confidence = Unlikely
| diameter = Supposedly ~{{convert|30|km|mi|abbr=on}}
| depth =
| rise =
| imp_size =
| age = 32 to 40 Ma
Late Eocene or Early Oligocene
| exposed = Yes
| drilled = No
| bolide =
| translation =
| language =
| pronunciation =
| topo =
| access =
| country = Spain
| state = Aragon
| province = Zaragoza Province
| district =
| municipality = Azuara
}}
The Azuara structure is a structural feature of about {{convert|30|km|mi}} diameter,Mikheeva, 2017 located in northeastern Spain, roughly {{convert|50|km|mi}} south of Zaragoza.[http://labmpg.sscc.ru/a.html Azuara] The name is attributed to the small town of Azuara located near the center of the structure. It has been subject to controversial, generally rejected claims that it represents an impact feature. It was formerly listed in the Earth Impact Database, but was subsequently removed.
History
The first claims of an impact origin was given by Wolfgang Hammann as early as 1980, and the first field work was done by Johannes Fiebag in the early eighties. In 1985, Ernstson et al.{{cite journal |last1=Ernstson |first1=K. |last2=Hammann |first2=W. |last3=Fiebag |first3=J. |last4=Graup |first4=G. |date=1985 |title=Evidence of an impact origin for the Azuara structure (Spain) |journal=Earth and Planetary Science Letters |volume=74 |issue=4 |pages=361–370 |doi=10.1016/S0012-821X(85)80008-X|bibcode=1985E&PSL..74..361E }} published the purported occurrence of shock metamorphism.
Reception
Mainstream scientific opinion rejects the Azuara structure as being of impact origin, with the shock effects being tectonic features, the supposed impact ejecta (Pelarda Formation) actually being Quaternary alluvial fans and supposed impact breccias and dike breccias are generally interpreted as karst features and soil formations.{{cite journal |last1=Cortés |first1=A. L. |last2=Díaz-Martínez |first2=E. |last3=Sanz-Rubio |first3=E. |last4=Martínez-Frías |first4=J. |last5=Fernández |first5=C. |title=Cosmic impact versus terrestrial origin of the Azuara structure (Spain): A review |journal=Meteoritics & Planetary Science |date=2002 |volume=37 |issue=6 |pages=875–894 |doi=10.1111/j.1945-5100.2002.tb00862.x|doi-access=free |bibcode=2002M&PS...37..875C |hdl=10261/35962 |hdl-access=free }} The opposition against the impact origin for Azuara has been supported by an analysis and paper (Langenhorst & Deutsch 1996) rejecting the occurrence of shock metamorphism in Azuara rocks.{{cite journal|last1=Langenhorst|first1= F. |last2= Deutsch|first2= A.|date=1996|title=The Azuara and Rubielos structures, Spain: Twin impact craters or Alpine thrust systems? TEM investigations on deformed quartz disprove shock origin|journal=Lunar and Planetary Science|volume=27|pages=725–726|bibcode=1996LPI....27..725L}} Based on this paper and analysis, Azuara was removed from the Canadian Impact Data Base when its management changed to the University of New Brunswick.[http://tsun.sscc.ru/nh/impact.php?iname=&country=spain&min_age=0.0&max_age=3400.0&min_valid=0&max_valid=4&min_lat=-90&max_lat=90&min_lon=-180&max_lon=180&min_dia=0.0&max_dia=2250.0&search=Search+Database EDEIS Expert Database on Earth Impact Structures] {{webarchive |url=https://web.archive.org/web/20110727124028/http://tsun.sscc.ru/nh/impact.php?iname=&country=spain&min_age=0.0&max_age=3400.0&min_valid=0&max_valid=4&min_lat=-90&max_lat=90&min_lon=-180&max_lon=180&min_dia=0.0&max_dia=2250.0&search=Search+Database |date=July 27, 2011 }}
See also
References
{{Reflist}}
= Bibliography =
- {{citation |last=Mikheeva |first=Anna |year=2017 |title=The Complete Catalog of the Earth's Impact structures |url=http://labmpg.sscc.ru/impact/index1.html |publisher=Russian Academy of Sciences |pages=1 |accessdate=2019-04-02}}
External links
- [https://web.archive.org/web/20110727124028/http://tsun.sscc.ru/nh/impact.php?iname=&country=spain&min_age=0.0&max_age=3400.0&min_valid=0&max_valid=4&min_lat=-90&max_lat=90&min_lon=-180&max_lon=180&min_dia=0.0&max_dia=2250.0&search=Search+Database EDEIS Expert Database on Earth Impact Structures ]
{{Impact cratering on Earth}}
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{{DEFAULTSORT:Azuara Impact Structure}}
Category:Impact craters of Spain
Category:Possible impact craters on Earth