Stratigraphy of the Cordubian-Ovetian (Lower Cambrian) Transition in the Occidental Iberian Chain (Spain)

[Resumen] Este trabajo analiza los afloramientos de la Formación Embid (Cámbrico Inferior) existentes en el borde nororiental de la Cadena Ibérica Occidental, entre las localidades de Torrijo de la Cañada y Villalengua (unidad estructural de Moros). Con este objetivo se han realizado dos perfiles estratigráficos y estudiado sus litofacies. Asimismo, se pone de manifiesto el contenido paleoicnológico más representativo. La aparición de distintos ejemplares del icnogénero Astropolichnus separados 200 m. en la serie estratigráfica plantea la necesidad de reconsiderar la precisión de este incofósil como indicador bioestratigráfico. Debido a la ausencia de afloramientos superficiales de la Formación Bámbola, estos materiales constituyen las rocas más antiguas.de esta Cadena. Finalmente, se propone al perfil To1 como hipoestratotipo de la Formación Embid en la Cadena Ibérica Occidental.[Abstract] This work presents a study of the Embid Formation, the oldest formation cropped out in the Occidental Iberian Chain (NE Spain). This outcrop is placed in the nucleus of the Moros structural unit (ALVARO et al., 1992), located in the nonheastern contact of this Chain with the Calatayud-Teruel Teniary basin, between Villalengua and Torrijo de la Cañada localities (Zaragoza Province). We have studied two sections of the Embid Formation (To1 and T02). The first one, 250 m. thick, is the most complete and shows the best exposition of the area. It is proposed as the hipostratotype of the Embid Formation in this Chain. In To1, four terms (El to E4) of this formation and other at the beginning of the Jalón Formation al) have been recognized, according to the sandstone/shale ratio. The ichnofossils and other sedimentary structures studied here suggest, for terms E2 and E4-J1, a litoral to shallow sublitoral environment (tidal flat and tidal channels, influenced by tidal and wave effects), and a sublitoral (circalitoral) environment with episodic levels influenced by storms currents and/or hard tides, for the terms El and E3. The northeastwards To2 section, 150 m. thick, shows a similar evolution, but a more distal character. The wide development of subtidal sand bodies as well as the low diversity and wealth of biogenic structures, suggest a shoreface sedimentation, with a intercalated episode influenced by tidal action. The materials of this section are assigned to the Embid Formation for its lithology, the lack of white quarzites (that characterize the underlying Bámbola Formation) and the ichnofossil record. In spite of palichnological, lithological and sedjmentological affinities between both profils, we can not give an accurate correlation of both sequences. The section To1 records a shallower episode (E2), reaching subaerial exposure in the Cordubian-Ovetian transition. It is the first time this episode has been recognized in the Iberian Chains, and it is considered as a local process. A second shallower episode is placed in the transition of the Embid-Jalón Formations (E4-J1). It has been recognized in other outcrops of the Iberian Chains and LIÑAN & GAMEZ (in press) have proposed a correlation of this regressive episode with the Woodlands Regression (BRASIER, 1985). On the other hand, Astropolichnus ichnogenus is recorded in different levels of same section (200 m. separated), for the first-time in the Iberian Chains. This fact will force to reconsider the accuracy of this ichnofossil as biostratigraphical marker. Finally, a progresive eastwards distallity of the sediments is inferred by comparison with similar outcrops of the Oriental Iberian Chain, by the existence of the first local"shallower episode, placed in the more suroccidental outcrop of the basin (To1), and by the northeastwards paleocurrents directions. These data support the existence of an emerged area beside the occidental margin of the Cantabrian-Iberian Basin as was pointed by LOTZE (1961), and also proposed in the cantabrian sector of this basin by ARAMBURU el al. (1992)

First report of Crumillospongia (Demospongea) from the Cambrian of Europe (Murero biota, Spain)

The demosponge genus Crumillospongia, originally described from the Burgess Shale (middle Cambrian of Canada), has only been cited from lower and middle Cambrian localities of North America and China. The taxon is now also described from uppermost lower Cambrian rocks of the Murero Lagerstätte (Zaragoza Province, NE Spain). Crumillospongia mureroensis sp. nov. is a small to medium sized sack-shaped to elongate demosponge characterized by the presence of densely packed pores of three sizes, considerably larger than those in any other species of the genus. The Spanish material represents a link in the chronostratigraphical gap between the Chinese and North American material.Peer reviewe

Cambrian bioestratigraphy and environmental evolution of the Borobia area (Province of Soria, Oriental Iberian Chain, Spain)

[Resumen] Se estudian dos secciones estratigráficas en los afloramientos cámbricos más septentrionales de la Cadena Ibérica Oriental, las cuales incluyen a las formaciones Jalón, Ribota, Huérmeda, Daroca, Valdemiedes, Murero y Acón. Los datos estratigráficos, mineralógicos, petrológicos y paleontológicos sugieren la existencia de tres geoventos de tipo eustático. El primero de ellos (Transgresión del Cámbrico inferior) comienza con depósitos litorales en condiciones áridas y ambiente oxidante, para evolucionar a un medio sublitoral carbonatado y posteriormente a otro de plataforma siliciclástica abierta. El segundo geoevento (Regresión Hawke Bay) estaría representado por las areniscas y lutitas de la Formación Daroca. El inicio del tercer geoevento (transgresión generalizada del Cámbrico medio) produce la instauración de una plataforma mixta (terrígeno-carbonatada) con pulsos regresivos asociados, representados por la base de la Formación Acón. La presencia de los trilobites Strenuaeva ineondita, Aeadolenus sp., Asturiaspis inopinatus; Paradoxides (Eeeaparadoxides) suleatus; P. (Eee.) rouvillez: P. (Bee.) barehyrhaehis, Badulesia tenera, Badulesia pasehz: Badulesia granien: Solenopleuropsis verdiagana, Solenopleuropsis truneata y Pardazlhaina sp.; junto a los acritarcos Skiagia ezliosa, Heliosphaen'dium dissimzlare, Arehaeodiseina umbonulata, Cristallinium eambn'ensis, Eliasum Ilaniseum, Timofeevia fosfonOtiea y Timofeevia lanearae sugiere que los pisos Marianiense, Bilbiliense, Leoniense y Caesaraugustiense del Cámbrico inferior-medio están representados. Estos datos paleontológicos permiten una primera comparación entre la biozonación española de trilobites y la de acritarcos, y proceder así a la correlación de los materiales del Cámbrico inferior y medio de la Península Ibérica con los de la Plataforma Oriental Europea.[Abstract] Two stratigraphical sections from the more septentrional Cambrian outcrops of the Oriental Iberian Chain 'are studied, including theJalón, Ribota, Huérmeda, Daroca, Valdemiedes, Murero and Acón formations (Lower-Middle Cambrian). The stratigraphical, mineralogical, petrological and paleontological data suggest the presence of three eustatic geoevents. The first one (Lower Cambrian Transgression) started with litoral deposits on arid and oxidant conditions that changed to sublitoral deposits (carbonate shelf) and posteriorly to an open siliciclastic shelf. The second eustatic geoevent (Hawke Bay Regression) is represented by the sandstones and lutites of the Daroca formation. The third geoevent (Middle Cambrian Transgression) began with the establishment of a mixed shelf (terrigenous- carbonated) and shows sorne regressive pulses represented by the basal leveIs of the Acón Formation. The presence of the trilobites Strenuaeva ineondita, Aeadolenus sp., Asturiaspis inopinatus, Paradoxides (Eceaparadoxides) suleatus, P. (Eee.) rouvillei, P. (Bee.) barehyrhaehis, Badulesia tenera, Badulesia pasehz~ Badulesia granien', Solenopleuropsis verdiagana, Solenopleuropsis truneata and Paradazlhania sp.; and the acritarchs Skiagia ezliosa, Heiosphaen'dium dissimzlare, Arehaeodiseina umbonulata, Cristallinium eambn'ensis, Eliasum Ilaniseum, Timofeevia fosfontiea and timofeevia lanearae suggest a Lower-Middle Cambrian age (Marianian to Caesaraugustian stages). These biostratigraphical data allow a comparison between the trilobite and acritarch biozonations for the first time in Spain as well as the correlation of the Península Ibérica's Lower-Middle Cambrian materials with the East European Platform ones.

150 años del descubrimiento del yacimiento cámbrico de Murero (Cadenas Ibéricas, NE España).

The lower-middle Cambrian palaeontological site of Murero (Cadenas Ibéricas, NE Spain) is a classical locality of the Cambrian in Europe. The site was first reported by the French geologist Edouard de Verneuil in 1862, and now it achieves 150 years of geological works contributing to a better knowledge of the Cambrian Period. Murero is an exceptional Lagerstätte because the coexistence of both skeletal and soft-bodied groups along a continuous record of ca. 8 million years, which is subdivided into 14 trilobite zones. Murero was the first palaeontological site in Spain to obtain the highest protection figure (Bien de Interés Cultural, BIC) from the Spanish Administration in 1997. Since then, the educational and social projection of the site is continuously increasing

First soft-bodied fossil from the Ordovician of Peru

8 páginas.Konservat-Lagerstätten are a source of insurmountable information on the diversity of fossil assemblages during the lower Palaeozoic. Soft-bodied fossils are especially rare in South America, but a new locality has been discovered from the Middle Ordovician of Peru that has produced the fairly well-preserved possible palaeoscolecidan Juninscolex ingemmetianum gen. et sp. nov. The distinctive characteristics of this worm make it similar to European taxa within the group.Peer reviewe