Episodic development of Cambrian eocrinoid-sponge meadows in the Iberian Chains (NE Spain)

Álvaro, J. Javier; Vennin, Emmanuelle

doi:10.1007/bf02537370

Cited by 42 publications

(29 citation statements)

References 15 publications

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“…The Murero Formation consists of siliciclastic shales with interbedded carbonate nodules (Liñán et al 2002), and has been interpreted as being deposited in transgressive conditions of offshore environments (Álvaro & Vennin 1997, Gámez Vintaned et al 2009). The majority of paradoxidid specimens come from the uppermost • B -map showing study locality in the northern part of the Eastern Iberian Chain (NE Spain), after Gozalo & Liñán (1988).…”

Section: Geographic and Geological Settingmentioning

confidence: 99%

Exoskeletal abnormalities in paradoxidid trilobites from the Cambrian of Spain, and a new type of bite trace

Zamora¹,

Mayoral²,

Esteve³

et al. 2011

Bull. Geosci.

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Exoskeletal abnormalities in middle Cambrian paradoxidid trilobites from Purujosa (Eastern Iberian Chain, NE Spain) are herein analyzed for the first time. Two distinct types are reported. The first is represented by triangular or asymmetrical V-to W-shaped breaks on margins of isolated sclerites (cranidia, free cheeks and hypostomes). The second group is represented by shortened thoracic pleural spines in complete or nearly complete individuals. Possible causes of these injuries are discussed, but in some cases a single cause/effect explanation is not apparent. A new ichnotaxon, Mandibulichnus serratus nov. ichnogen., nov. ichnosp., is erected to refer to serrated breakage of the margins of isolated trilobite sclerites produced by active predation or scavenging.•

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Section: Geographic and Geological Settingmentioning

confidence: 99%

Exoskeletal abnormalities in paradoxidid trilobites from the Cambrian of Spain, and a new type of bite trace

Zamora¹,

Mayoral²,

Esteve³

et al. 2011

Bull. Geosci.

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“…As envisaged by Álvaro & Vennin (1997) in the Iberian Chains (NE Spain), the ecological patterns of the nonreefal benthic communites were controlled by factors quite…”

Section: Resumementioning

confidence: 99%

“…The lower part of the formation contains stromatolitic limestones, whereas bioclastic limestones dominate its upper part. A lithofacies analysis of the Valdemiedes Formation and its palaeogeographical distribution throughout the Iberian platform were recently established (Álvaro et al 1993;Álvaro & Vennin 1996aÁlvaro & Vennin -b, 1997. The Lower-Middle Cambrian boundary is in the Valdemiedes Formation, the biostratigraphical chart of which has been established on the basis of trilobite zonation (Álvaro et al 1993;Liñán et al 1993).…”

Section: Geological Setting and Stratigraphymentioning

confidence: 99%

“…Such an interpretation (external silicification and internal carbonate cementation) is also possible for R.? mesonesensis even if the systematic observation of this character and the diagenetic pattern of the Valdemiedes Formation (Álvaro & Vennin 1998) make this point questionable. In addition, Cymbionites shares its general shape with the forms described herein.…”

Section: Holotype -Mpz 17070 (Pl I/1-4)mentioning

confidence: 99%

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New Early Cambrian eocrinoids from the Iberian Chains (NE Spain) and their role in nonreefal benthic communities

Clausen

2004

Eclogae geol. Helv.

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The Early Cambrian echinoderm-sponge meadows, which colonized shallow carbonate-siliciclastic platforms, have received relatively little study despite their widespread occurrence in several regions of Gondwana. Their taxa are generally preserved disarticulated, reworked and deposited through the action of waves and storms. Silicified echinoderm-rich packstones from the uppermost Bilbilian limestones (latest Early Cambrian in age) of the Valdemiedes Formation (Iberian Chains, NE Spain) formed through growth and destruction of echinoderm-sponge colonies by storm-wave action. This fauna has been studied in thin section and after etching by acetic acid. Eocrinoid remains include the thecal basal-ossicle of Rhopalocystis? mesonesensis n. sp. and other indeterminate species. Echinoderm columnals, visible in thin section, are associated with sponge spicules, trilobites, calcite-and phosphate-shelled brachiopods, chancelloriid sclerites, and foraminiferans. This finding suggests that stemmed eocrinoids were already present on the western Gondwana margin at the end of the Early Cambrian. RESUMEMalgré leur large distribution dans plusieurs régions du Gondwana, les colonies à échinodermes et éponges du Cambrien inférieur qui colonisèrent les plates-formes peu profondes en régime sédimentaire mixte demeurent relativement peu étudiées. Leur taxa sont généralement préservés désarticulés et remaniés au sein de dépôts hydrodynamiques sous l'influence des vagues et tempêtes. Des packstones silicifiés à échinodermes du Bilbilien terminal (fin du Cambrien inférieur) de la Formation de Valdemiedes (Chaînes Ibériques, Nord-Est de l'Espagne) ont été étudiés en lames minces et par dissolution à l'acide acétique. Ces bancs calcaires furent formés par la destruction répétée de colonies à éponges et échinodermes par l'action commune des vagues et tempêtes. Les restes d'éocrinoïdes extraits incluent la pièce basale de la thèque de Rhopalocystis? mesonesensis n. sp., ainsi que d'autres espèces indéter-minées. Des columnales d'échinodermes sont également visibles en lames minces. Ces fossiles sont associés à des spicules d'éponges, des trilobites, des brachiopodes à valves calcaires et phosphatées, des sclérites de chancelloriides et des foraminifères. Cette étude suggère que les échinodermes à tige étaient présents sur la marge occidentale du Gondwana dès la fin du Cambrien inférieur.

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“…The Valdemiedes Formation (20-150 m thick) consists of rhythmic, centimetric to decimetric beds of marly shales and limestones, the latter of bioclastic and stromatolitic character. The Lower-Middle Cambrian boundary subdivides the Valdemiedes Formation into two major sedimentary complexes : an uppermost Lower Cambrian peritidal (stromatolitedominated) platform episodically interrupted by the input of storm-induced deposits, and a lowermost Middle Cambrian subtidal platform colonized by eocrinoid-sponge meadows, in which peritidal environments disappeared progressively [Álvaro et al, 1993 ;Álvaro and Vennin, 1997]. The Valdemiedes high-frequency, Milankovitch-like cyclicity is arranged into low-frequency shallowing-upward sequences, forming a broad aggradational tendency [Álvaro et al, 2000].…”

Section: Geologic Setting and Stratigraphymentioning

confidence: 99%

Encrusting strategies in a Cambrian nonreefal epibenthic community

Clausen

Álvaro

2002

Bulletin De La Société Géologique De France

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Abstract. -Microfossils released by the action of acids from the Cambrian Valdemiedes Formation (Iberian Chains, NE Spain) contain evidence that encrusting microepifauna (foraminifers and serpulid tube worms) infested shelled hard substrates in nonreefal environments. They appear to have exploited parasitic and/or commensal ecological niches under medium-to low-energy bottom conditions. Despite the gregariousness character of the epifauna, skeletal overgrowths are rare, reflecting low-patterns on competitive interactions for space. Cambrian psammosphaerids (agglutinated foraminifers) were able to dissolve partly calcareous shells : although no evidence of pitting is observed, distinct depressed scars occur on the internal sides of host shells. The serpulids experienced a population bloom during the ecosystem recovery interval after the community turnover represented by the Valdemiedes event, and sharply disappeared during the ensuing return to background conditions. By contrast, the psammosphaerids are relatively abundant across the event, increasing in abundance during the same bloom of opportunistic taxa. Stratégies d'encroûtement dans une communauté épibenthique cambrienne non récifaleMots clés. -Foraminifères, Serpulidés, Epifaune, Paléoécologie, Cambrien, Chaînes ibériques.Résumé. -Les microfossiles extraits des calcaires de la formation cambrienne de Valdemiedes (Chaînes ibériques, NE Espagne) mettent en évidence l'essor d'une microfaune épibenthique à caractère encroûtant (composée de foraminifères et de serpulidés), qui a infesté les substrats durs fournis par des coquilles en milieu non-récifal. Elle semble avoir exploité les niches écologiques liées au parasitisme et/ou commensalisme sous des conditions environnementales d'énergie basse à modérée. Malgré le caractère grégaire de l'épifaune, la présence de recouvrements squelettiques est rare, ce qui traduit un taux faible de compétition spatiale. Les foraminifères à paroi agglutinée, de type psammosphaeridé, étaient capables de dissoudre partiellement les coquilles carbonatées qu'ils encroûtaient : malgré l'absence de perforations, des cicatrices de cet encroûtement sont visibles sur la face interne des coquilles. Ces deux taxons opportunistes ont réagi de façon différente au remplacement des communautés benthiques représenté par l'événement Valdemiedes : les psammosphaeridés ont traversé cet événement avec un pic d'abondance dans le niveau stratigraphique de reconquête de l'écosystème, tandis que les serpulidés, dominants à ce niveau, sont absents ou extrêmement rares en conditions normales.

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Episodic development of Cambrian eocrinoid-sponge meadows in the Iberian Chains (NE Spain)

Cited by 42 publications

References 15 publications

Exoskeletal abnormalities in paradoxidid trilobites from the Cambrian of Spain, and a new type of bite trace

Exoskeletal abnormalities in paradoxidid trilobites from the Cambrian of Spain, and a new type of bite trace

New Early Cambrian eocrinoids from the Iberian Chains (NE Spain) and their role in nonreefal benthic communities

Encrusting strategies in a Cambrian nonreefal epibenthic community

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