Аннотация:Cambrian outcrops in Spain are some of the most extensive in Europe. They show a high biostratigraphic and intercontinental value because of their continuous and diverse fossil record and facies. (LOTZE, 1961; LIÑÁN et al., 2002).
The aim of this field trip is to visit the two more important Cambrian trilobite localities in Cadenas Ibéricas (NE Spain), Jarque and Murero, located some 80 km west from the city of Zaragoza (Fig. 1).
The Jarque section is the most continuous Lower-Middle Cambrian succession in Cadenas Ibéricas, where trilobites from Marianian to Languedocian stages have been found. The Murero fossiliferous site (spanning late Bilbilian through early Languedocian age) is known since the 19th century, when trilobites where first reported by De Verneuil. Many studies have been carried out since then in the area, including those dealing with Burgess Shale-type taxa, found at numerous horizons of this uppermost Lower through Middle Cambrian Lagerstätte (LIÑÁN, GÁMEZ VINTANED and GOZALO, 1996b). Murero is also the type section for the Valdemiedes Event, an extinction event located at the classical Lower/Middle Cambrian boundary, preceding the radiation of paradoxidids at the beginning of the early Middle Cambrian. Many other groups, such as bradoriid arthropods, brachiopods, echinoderms, sponges, palaeoscolecid worms, lobopodans, algae and ichnofossils have also been found in both the Jarque and Murero sections.
The two localities were visited by the International Subcommission on Cambrian Stratigraphy (ISCS) during its Annual Meeting in 1996. Thorough descriptions of the Jarque and Murero sections and their trilobite assemblages can be found in the guide- book edited for that conference (LIÑÁN, GÁMEZ VINTANED and GOZALO, 1996a) which is the base of this field trip. A complementary synthesis on the stratigraphy, biochronology and trilobite record of the Cadenas Ibéricas with photographs of selected specimens is also present in the Trilo 08 Conference book (GOZALO et al., 2008).
Recent works in the Rambla de Valdemiedes 2 section have pointed out the potential of this section as the standard for the Lower/Middle Cambrian boundary (GSSP and Series) because of its good international correlation (GOZALO et al., 2007).
Murero was the first palaeontological locality to be legally protected in Spain (ANDRÉS et al., 1999; Fig. 16.f) and one of the internationally renowned Spanish geosites because of the excellence of its palaeontological record (DIES ÁLVAREZ et al., 2008).