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Rubielos de la Cérida impact structure
The c. 80 km x 40 km sized Rubielos de la Cérida impact structure (impact basin, resp.) is located in Aragon, northeast Spain, north of Teruel and is considered〔Ernstson, K., Anguita, F., and Claudin, F. 1994. 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: 25..〕〔(), Hradil, K., Schüssler, U., and Ernstson, K. 2001. Silicate, phosphate and carbonate melts as indicators for an impact-related high-temperature influence on sedimentary rocks of the Rubielos de la Cérida structure, Spain, in: Impact markers in the stratigraphic record, 6th ESF-IMPACT workshop Granada, abstract book: 49-50.〕〔(), Claudin, F., Ernstson, K., Rampino, M.R., and Anguita, F. 2001. Striae, polish, imprints, rotated fractures, and related features from clasts in the Puerto Mínguez impact ejecta, in: Impact markers in the stratigraphic record, 6th ESF-IMPACT workshop Granada, abstract book: 15-16.〕〔(), Ernstson, K., Claudin, F., Schüssler, U. & Hradil, K. (2002): The mid-Tertiary Azuara and Rubielos de la Cérida paired impact structures (Spain). - Treb. Mus. Geol. Barcelona, 11, 5 - 65.〕〔(), Ernstson, K., Claudin, F., Schüssler, U., Anguita, F. and Ernstson, T. 2001. Impact melt rocks, shock metamorphism, and structural features in the Rubielos de la Cérida structure, Spain: evidence for a companion to the Azuara impact structure, in: Impact markers in the stratigraphic record, 6th ESF-IMPACT workshop Granada, abstract book: 23-24.〕〔Ernstson, K., Rampino, M. R., and Hiltl, M. 2001. Cratered cobbles in Triassic Buntsandstein conglomerates in northeastern Spain: An indicator of shock deformation in the vicinity of large impacts. Geology, 29: 11-14.〕 a companion of the Azuara impact structure and part of a large multiple impact event, the Azuara impact event, that from stratigraphic considerations and paleontological dating happened in the Upper Eocene or Oligocene (roughly 30 - 40 Mill. years ago). The name is attributed to the village of Rubielos de la Cérida located in the central uplift of the most northerly part of the structure.
Originally the Rubielos de la Cérida structure was limited to and described as a 40 km-diameter circular impact crater with a prominent central uplift but is now considered to comprise a whole crater chain forming an impact basin accompanied by a central uplift chain.〔(), Ernstson, K., Schüssler, U., Claudin, F., and Ernstson, T. (2003). An impact crater chain in northern Spain. Meteorite, 9, no 3, 35-39.〕 In the eastern part, the morphology of the original basin is in parts buried beneath post-impact Neogene sediments.
Conventionally, the impact basin is considered to represent tectonic structures, the Jiloca-Calatayud graben and the Alfambra-Teruel graben. Since a tectonic graben is typically characterized by tensional features, the common interpretation meets basic difficulties with the structurally dominant compressive style that is almost everywhere to be observed〔 and easily explained by an impact origin.〔[Melosh, H.J. 1989. Impact Cratering. A Geologic Process. 245 pp., New York (Oxford University Press).〕
==Impact features==
The impact nature is documented by impact melt rocks, suevite, abundant polymictic and monomictic breccias, breccia dikes (dike breccias), extensive megabreccias, impact ejecta, dislocated megablocks, peculiar geological structures in the rim and central uplift zones, and shock metamorphism.〔〔〔〔 Shock effects comprise melt glass, diaplectic glass from quartz and feldspar, planar deformation features (PDFs) in quartz and feldspar and moderate shock effects like intense kink banding and multiple sets of planar fractures (PFs) in quartz, multiple sets of kink bands in mica, and intense micro-twinning in calcite. Moderately developed shatter cones〔(),.〕 add to the impact signature.
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