Trace and soft body fossils from the Pedroche Formation (Ovetian, Lower Cambrian of the Sierra de Córdoba, S Spain) and their relation to the Pedroche event

Universidad de Huelva, Huelva, Andalusia, Spain
Geobios (Impact Factor: 1.24). 07/2006; 39(4):443-468. DOI: 10.1016/j.geobios.2005.04.004


The low Lower Cambrian rocks from the Sierra de Córdoba contain one of the best successions in Europe, which consists of well exposed mixed facies with abundant fossil assemblages showing long stratigraphical ranges throughout the Pedroche Formation. These assemblages include diverse Ovetian archaeocyaths, trilobites, small shelly fossils, calcimicrobes, trace fossils and stromatolites. Trace fossils are still poorly known, and thus they are the main objective of this work. Ichnological data are obtained from the Arroyo de Pedroche 1, Arroyo de Pedroche 2 and Puente de Hierro sections. Trace fossils include the ichnogenera Bergaueria, aff. Bilinichnus, Cochlichnus, aff. Cosmorhaphe?, Cylindrichnus, Dactyloidites, Dimorphichnus, Diplichnites, Monocraterion, Palaeophycus, aff. Phycodes, Planolites, Psammichnites, Rusophycus, Skolithos, Torrowangea and Treptichnus, as well as faecal pellets, meniscate trace fossils and others. They are abundant in shales and sandstones, and indicate important changes in the benthic conditions with respect to the underlying Torreárboles Formation. Changes in fossil assemblages within Member I of the Pedroche Formation indicate palaeoecological disruptions, which led to the disappearance of numerous archaeocyath species and the decrease of stromatolite biodiversity. This was followed by dominance of trilobite and brachiopod assemblages, accompanied by trace fossils of the Psammichnites ichnosp. A ichnoassociation. This biotic turnover (Pedroche event) occurred at the lower part of the archaeocyath Zone III, within the Bigotina bivallata biozone. The diagnoses of the ichnospecies Cochlichnus anguineus and Dactyloidites cabanasi are emended.

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    • "n. sp. is recorded 500 m below the Ovetian bigotinid trilobite Serrania sp. at La Rinconada, province of Salamanca, central Spain, and its occurrence coincides with the first record of Astropolichnus hispanicus in the region (Rodríguez Alonso et al. 1995; Fig. 4). Another ichnospecies associated with Lunagraulos tamamensis in the Salamanca area is Dactyloidites cabanasi (Meléndez in Cabanás, 1966), an ichnotaxon typical of the lower Ovetian Lemdadella linaresae trilobite Zone in Sierra Morena, province of Córdoba, southern Spain (Gámez Vintaned et al. 2006a). D. cabanasi is recorded in association with Psammichnites gigas (Torell, 1868) in Corduban rocks ( = Terreneuvian ; Landing et al. 2007) from the Toledo Mountains in central Spain (Seilacher & Gámez-Vintaned, 1995; Palacios et al. 1999). "
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    ABSTRACT: The type material of Agraulos antiquus Sdzuy, 1961 from the La Herrería Formation, northern Spain, is revised together with additional material and included in the new genus Lunagraulos. The stratigraphical range of Lunagraulos antiquus (Sdzuy, 1961) – occurring below that of the trilobite species of the genera Lunolenus, Metadoxides and Dolerolenus in the type locality of Los Barrios de Luna in the province of León, northern Spain – and the accompanying ichnofossil assemblage demonstrate an Ovetian age (lower part of Cambrian Stage 3, currently being discussed by the International Subcommission on Cambrian Stratigraphy) for this species. Moreover, the trilobite Lunagraulos tamamensis n. gen. n. sp. is found in the Tamames Sandstone near the village of La Rinconada in the province of Salamanca, central Spain. The biostratigraphical position of this new taxon and its accompanying ichnoassemblage is also analysed and assigned to the lowermost Ovetian Stage. The genus Lunagraulos is therefore the oldest agraulid found in the fossil record. The exceptional presence of Lunagraulos in a marine coarse siliciclastic succession – a facies rather typical for the ichnofossils Cruziana and Rusophycus, some of the oldest signs of trilobite activity – suggests that first trilobite representatives may have inhabited high- to middle-energy, marine environments. This hypothesis may also explain both the taxonomic and biostratigraphic heterogeneity of the first trilobite genera appearing across the world, due to preservation problems in this type of facies. Comparison of the Lunagraulos biostratigraphy with other coeval Spanish fossil assemblages allows us to propose its intercontinental correlation with the oldest records of currently known trilobites.
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    • "Bergaueria is regarded as a dwelling structure, and present specimen shows close resemblance with Bergaueria perata Prantl (1945). the specimen has global occurrences from Cambrian to Ordovician strata (häntzschel, 1975) but most common in lower cambrian (McKee, 1945; Seilacher, 1956; Crimes and Anderson, 1985; Gamez vintaned et al., 2006). It is also reported from the tethys himalaya (table 2). "
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