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Guzhangian (mid Cambrian) trilobites from siliceous concretions of the Valtorres Formation, Iberian Chains, NE Spain

Published online by Cambridge University Press:  19 July 2012

J. JAVIER ÁLVARO ,
SAMUEL ZAMORA ,
DANIEL VIZCAÏNO  and
PER AHLBERG
J. JAVIER ÁLVARO*
Affiliation:
Centre of Astrobiology (CSIC/INTA), Ctra. de Torrejón a Ajalvir km 4, 28850 Torrejón de Ardoz, Spain
SAMUEL ZAMORA
Affiliation:
Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK
DANIEL VIZCAÏNO
Affiliation:
7 Jean-Baptiste Chardin, Maquens, 11090 Carcassonne, France
PER AHLBERG
Affiliation:
Division of Geology, Department of Earth and Ecosystem Sciences, Lund University, Sölvegatan 12, 223 62 Lund, Sweden
*
†Author for correspondence: alvarobjj@cab.inta-csic.es
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Abstract

In the carbonate-siliciclastic strata of West Gondwana (e.g. in the Montagne Noire, France), the aftermath of the mid Languedocian (mid Cambrian) regression is characterized by a late Languedocian major turnover of trilobite families and a Furongian–early Tremadocian radiation related to the stepwise immigration of trilobite invaders from East Gondwana under persistent transgressive conditions. The scarcity of upper Languedocian fossil accumulations in clayey substrates has inspired the sampling of the palaeogeographically most distal parts of the Iberian Chains (Spain), where diagenetic dissolution of ubiquitous hexactinellid sponge spicules has favoured the formation of siliceous concretions. These have yielded the trilobites Peronopsis cf. insignis, Oidalagnostus trispinifer, Proampyx difformis (= Proampyx aculeatus), Bailiaspis? glabrata (= Holocephalina agrauloides, by ontogeny), Holasaphus cf. centropyge and a paradoxidid gen. et sp. indet. Despite preservation and sampling biases, the identification of this taphonomic window in offshore clayey substrates of West Gondwana allows the recognition of a strong biogeographical link with Baltica, and the correlation of the global Guzhangian Stage and the Solenopleura? brachymetopa Zone of Scandinavia with part of the Mediterranean upper Languedocian Substage.

Keywords

taphonomybiogeographyLanguedocianBalticaGondwana
Type
Original Articles
Information
Geological Magazine , Volume 150 , Issue 1 , January 2013 , pp. 123 - 142
Copyright
Copyright © Cambridge University Press 2012

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