Late Ordovician (post–Sardic) rifting branches in the North Gondwanan Montagne Noire and Mouthoumet massifs of southern France

Upper Ordovician–Lower Devonian rocks of the Cabrières klippes (southern Montagne Noire) and the Mouthoumet massif in southern France rest paraconformably or with angular discordance on Cambrian–Lower Ordovician strata. Neither Middle–Ordovician volcanism nor associated metamorphism is recorded, and the subsequent Middle Ordovician stratigraphic gap is related to the Sardic phase. Upper Ordovician sedimentation started in the rifting branches of Cabrières and Mouthoumet with deposition of basaltic lava flows and lahar deposits (Roque de Bandies and Villerouge formations) of continental tholeiite signature (CT), indicative of continental fracturing. The infill of both rifting branches followed with the onset of: (1) Katian (Ka1–Ka2) conglomerates and sandstones (Glauzy and Gascagne formations), which have yielded a new brachiopod assemblage representative of the Svobodaina havliceki Community; (2) Katian (Ka2–Ka4) limestones, marlstones and shales with carbonate nodules, reflecting development of bryozoan-echinoderm meadows with elements of the Nicolella Community (Gabian and Montjoi formations); and (3) the Hirnantian Marmairane Formation in the Mouthoumet massif that has yielded a rich and diverse fossil association representative of the pandemic Hirnantia Fauna. The sealing of the subaerial palaeorelief generated during the Sardic phase is related to Silurian and Early Devonian transgressions leading to onlapping patterns and the record of high-angle discordances.Research was funded by projects CGL2010-39417, CGL2012-39471 and CGL2013-48877-P from Spanish MINECO.Peer reviewe

Cambrian–early Ordovician volcanism across the South Armorican and Occitan domains of the Variscan Belt in France: Continental break-up and rifting of the northern Gondwana margin

The Cambrian–lower Ordovician volcanic units of the South Armorican and Occitan domains are analysed in a tectonostratigraphic survey of the French Variscan Belt. The South Armorican lavas consist of continental tholeiites in middle Cambrian–Furongian sequences related to continental break-up. A significant volcanic activity occurred in the Tremadocian, dominated by crustal melted rhyolitic lavas and initial rifting tholeiites. The Occitan lavas are distributed into five volcanic phases: (1) basal Cambrian rhyolites, (2) upper lower Cambrian Mg-rich tholeiites close to N-MORBs but crustal contaminated, (3) upper lower–middle Cambrian continental tholeiites, (4) Tremadocian rhyolites, and (5) upper lower Ordovician initial rift tholeiites. A rifting event linked to asthenosphere upwelling took place in the late early Cambrian but did not evolve. It renewed in the Tremadocian with abundant crustal melting due to underplating of mixed asthenospheric and lithospheric magmas. This main tectono-magmatic continental rift is termed the “Tremadocian Tectonic Belt” underlined by a chain of rhyolitic volcanoes from Occitan and South Armorican domains to Central Iberia. It evolved with the setting of syn-rift coarse siliciclastic deposits overlain by post-rift deep water shales in a suite of sedimentary basins that forecasted the South Armorican–Medio-European Ocean as a part of the Palaeotethys Ocean.This research was funded by project CGL2013-48877-P from Spanish MINECO.Peer reviewe

Aperçu paléogéographique de la transition cambro-ordovicienne dans la Montagne Noire méridionale (France) : résultats préliminaires

La transition cambro-ordovicienne de la Montagne Noire méridionale reflète une tendance regressive en milieux silicoclastiques, comprenant les complexes de barres hydrauliques de la formation de la Dentelle, délimités par deux systèmes sédimentaires mixtes (carbonato-silicoclastiques) transgressifs dominés par l’action des tempêtes. Ces systèmes correspondent respectivement aux formations sous-jacentes de la Gardie et de Val d’Homs, et à la formation sus-jacente de Mounio, qui ont enregistré une activité tectonique synsédimentaire importante. Les communautés fauniques les plus riches et diversifiées (comprenant des trilobites, échinodermes, conodontes, brachiopodes à coquilles carbonatées et phosphatiques, spicules d’éponges, etc.) occupent des emplacements très réduits. Ces communautés, associées à une forte productivité carbonatée, sont situées sur des rampes intra-plates-formes et des horsts. Malgré l’absence de traces d’activité volcanique au cours de la transition cambro-ordovicienne en Montagne Noire méridionale le régime distensif responsable du développement des paléotopographies en horsts peut être relié avec un régime géodynamique en extension. Ce dernier est reconnu dans d’autres secteurs du Massif central ayant enregistré des processus d’océanisation et une importante activité volcanique à la base de l’Ordovicien

The Ordovician of France and neighbouring areas of Belgium and Germany

The Ordovician successions of France and neighbouring areas of Belgium and Germany are reviewed and correlated based on international chronostratigraphic and regional biostratigraphic charts. The same three megasequences related to the rift, drift and docking of Avalonia with Baltica can be tracked in Belgium and neighbouring areas (Brabant Massif and Ardenne inliers), western (Rhenish Massif) and northeastern Germany (Rügen). The remaining investigated areas were part of Gondwana in the Ordovician. The Armorican Massif shares with the Iberian Peninsula a Furongian–Early Ordovician gap (Toledanian or Norman gap), and a continuous Mid–Late Ordovician shelf sedimentation. The Occitan Domain (Montagne Noire and Mouthoumet massifs), eastern Pyrenees and northwestern Corsica share with southwestern Sardinia continuous shelf sedimentation in the Early Ordovician, and a Mid Ordovician ‘Sardic gap’. In the Ordovician, the Maures Massif probably belonged to the same Sardo-Occitan domain. The Vosges and Schwarzwald massifs display compa-rable, poorly preserved Ordovician successions, suggesting affinities with the Teplá-Barrandian and/or Molda-nubian zones of Central Europe.This paper is a contribution to the International Geoscience Programme (IGCP) projects 653 "The onset of the Great Ordovician Biodiversification Event" and 735 “Rocks and the Rise of Ordovician Life: Filling knowledge gaps in the Early Palaeozoic Biodiversification". The authors are particularly grateful to Annalisa Ferretti, David A.T. Harper and Petr Kraft for their careful and constructive reviews, comments and suggestions, which greatly improved the quality and relevance of the paper

New fossil assemblages from the Early Ordovician Fezouata Biota

The Fezouata Biota (Morocco) is a unique Early Ordovician fossil assemblage. The discovery of this biota revolutionized our understanding of Earth’s early animal diversifications—the Cambrian Explosion and the Ordovician Radiation—by suggesting an evolutionary continuum between both events. Herein, we describe Taichoute, a new fossil locality from the Fezouata Shale. This locality extends the temporal distribution of fossil preservation from this formation into the upper Floian, while also expanding the range of depositional environments to more distal parts of the shelf. In Taichoute, most animals were transported by density flows, unlike the in-situ preservation of animals recovered in previously investigated Fezouata sites. Taichoute is dominated by three-dimensionally preserved, and heavily sclerotized fragments of large euarthropods—possibly representing nektobenthic/nektic bivalved taxa and/or hurdiid radiodonts. Resolving whether this dominance reflects a legitimate aspect of the original ecosystem or a preservational bias requires an in-depth assessment of the environmental conditions at this site. Nevertheless, Taichoute provides novel preservational and palaeontological insights during a key evolutionary transition in the history of life on Earth

Controverses géologiques sur le Cambro-Ordovicien de la Montagne Noire (France) à l'aube du XXe siècle : les contributions de Jean Miquel (1859-1940)

Jean Miquel fut un naturaliste amateur qui participa, à la charnière entre les XIX e et XX e siècles, à l\u27élaboration des premières chartes stratigraphiques du Cambro-Ordovicien du versant méridional de la Montagne Noire (Languedoc). Sa connaissance détaillée de la géologie régionale des environs de sa localité natale (Barroubio) lui a permis de subdiviser correctement les affleurements à partir de critères lithologiques et paléontologiques, plus précisément en ce qui concerne le Cambrien inférieur-moyen et l\u27Arenigien (Ordovicien inférieur). Il est l\u27inventeur de cinq espèces de trilobites et d\u27une espèce d\u27échinoderme cambriens. Le présent article retrace l\u27évolution des idées concernant la paléontologie et la stratigraphie du Paléozoïque inférieur en Languedoc au cours de la vie de Miquel, afin de mieux comprendre l\u27influence en Montagne Noire des découvertes paléontologiques réalisées, par ailleurs, au Pays de Galles, en Amérique du Nord, en Bohême et dans le massif Armoricain.Jean Miquel is one of the most important amateur naturalists who contributed, across the transition of the 19th and 20th centuries, to the improvement of the first Cambro-Ordovician stratigraphical charts on the southern Montagne Noire (Languedoc). A detailed knowledge of the regional geology on the area surrounding the locality where he was born (Barroubio) permitted him to subdivide properly these outcrops according to lithological and pale-ontological features, mainly the Lower-Middle Cambrian and the Arenigian (Lower Ordovician). He defined five Cambrian trilobite species and one echinoderm species. This paper offers a panorama of the evolution of historic concepts developed in the paleontology and stratigraphy of the Languedocian Lower Paleozoic during Miquel\u27s life. This allows a better understanding of the influence in Languedoc of the first paleontological findings that took place in other regions, such as Wales, North America, Bohemia and the Armorican Massif.</p

Controverses géologiques sur le Cambro-Ordovicien de la Montagne Noire (France) à l'aube du siècle: les contributions de Jean Miquel (1859-1940)

Álvaro, José Javier, Vizcaïno, Daniel (2002): Controverses géologiques sur le Cambro-Ordovicien de la Montagne Noire (France) à l'aube du siècle: les contributions de Jean Miquel (1859-1940). Geodiversitas 24 (4): 725-752, DOI: http://doi.org/10.5281/zenodo.537686

Rhizocrinidae Jaekel 1894

Family Rhizocrinidae Jaekel, 1894 &lt;p&gt; &lt;b&gt;Remarks.&lt;/b&gt; The distal face of the radial circlet (Fig. 2B) and the presence or absence of axillary brachials (Fig. 2D) have been shown to be highly useful for distinguishing the various rhizocrinid genera (Roux &lt;i&gt;et al&lt;/i&gt;. 2019). Those authors subdivided &lt;i&gt;Conocrinus&lt;/i&gt; (sensu lato) into three genera, namely &lt;i&gt;Conocrinus&lt;/i&gt; (sensu stricto), &lt;i&gt;Paraconocrinus&lt;/i&gt; and &lt;i&gt;Pseudoconocrinus&lt;/i&gt;. Although appearing as early as the Ypresian, &lt;i&gt;Conocrinus&lt;/i&gt; (sensu stricto) was not found in Ilerdian strata of Corbi&egrave;res. The proximal columnals that constitute the proxistele of rhizocrinids are more or less thick and disc shaped, usually with flat and smooth facets. They are rare or absent in the screen-washed residues that we picked by hand. The columnals of the mesistele and dististele have synarthrial articulations with a central ligamentary fossa that has a figure-8 shape. The fulcral ridges change orientation from one joint to the next, giving the columnals a twisted appearance (Fig. 2E&ndash;F). Most rhizocrinids are fixed by rhizoids developed from the distal part of the stalk (dististele). In the fauna described here, the columnal characters do not allow a clear distinction between the different genera. The external morphology of juvenile aboral cups occasionally shows clear, discriminating characters, which tend to disappear later during growth by morphological convergence (homoplasy; for example, see Fig. 14A&ndash;I). The abundance of material from some outcrops has allowed the recognition of juveniles and the reconstitution of ontogenic trajectories that have proved instrumental in clarifying the taxonomy (see Fig. 9, for example).&lt;/p&gt; &lt;p&gt; &lt;b&gt;Stratigraphical distribution.&lt;/b&gt; Campanian-Recent.&lt;/p&gt;Published as part of &lt;i&gt;Roux, Michel, Martinez, Alain &amp; Vizcaïno, Daniel, 2021, A diverse crinoid fauna (Echinodermata, Crinoidea) from the Lower Eocene of the Gulf of Languedoc (Corbières, Aude, southern France), pp. 201-242 in Zootaxa 4963 (2)&lt;/i&gt; on pages 211-212, DOI: 10.11646/zootaxa.4963.2.1, &lt;a href="http://zenodo.org/record/4700704"&gt;http://zenodo.org/record/4700704&lt;/a&gt

Cherbonniericrinus requiensis Roux & Martinez & Vizcaïno 2021, n. sp.

&lt;i&gt;Cherbonniericrinus requiensis&lt;/i&gt; n. sp. &lt;p&gt;Fig. 16A&ndash;G&lt;/p&gt; &lt;p&gt; &lt;b&gt;Type material.&lt;/b&gt; 5 aboral cups, the best-preserved of which is designated holotype (MNHN.F. A82013) (Fig. 16E&ndash;G), the others are paratypes 1 to 4.&lt;/p&gt; &lt;p&gt; &lt;b&gt;Etymology.&lt;/b&gt; From the type locality R&eacute;qui near Montlaur (Val de Dagne, Aude).&lt;/p&gt; &lt;p&gt; &lt;b&gt;Type stratum.&lt;/b&gt; Base of the blue marls of the middle Ilerdian, above the &lt;i&gt;Solenomeris&lt;/i&gt; limestones, late NP10, but maybe already NP11.&lt;/p&gt; &lt;p&gt; &lt;b&gt;Type locality.&lt;/b&gt; R&eacute;qui near Montlaur (Val de Dagne, Aude).&lt;/p&gt; &lt;p&gt; &lt;b&gt;Diagnosis.&lt;/b&gt; Small species; aboral cup an inverted truncated cone in shape, external surface slightly concave to convex; sutures between plates variable, weakly marked between basals; aboral end diameter equal to or slightly less than 0.5 Dc; adoral face of radial circlet with discrete interradial crests, muscular synarthries as wide as radials, broad central cavity.&lt;/p&gt; &lt;p&gt; &lt;b&gt;Description of type series&lt;/b&gt; (Fig. 16). Quantitative characters of aboral cups of type series given in Table 16. Holotype (Fig. 16E&ndash;G) with aboral cup almost twice as high as wide, slightly swollen in upper half of basal circlet, lower part of basal circlet moderately inverted conical, slight constriction at basal-radial transition, basals about three times higher than radials, sutures between basals discrete or inconspicuous, marked sutures between basal and radial circlets and between radials. Aboral end diameter half of the maximum diameter of cup (Dp&rsquo;/Dc 0.49). Adoral face of radial circlet with slight marginal interradial tips but without conspicuous interradial ridges, muscular synarthries with reduced aboral ligament fossa and well-developed muscular fossae with lateral edges erected (Fig. 16G), broad central cavity (Dd/Dc 0.49); pattern similar to that of extant specimen (Fig. 16H). Paratypes with aboral cup of variable flare and height, lateral profile slightly convex (Fig. 16A) to markedly concave (Fig. 16D); sutures between basals conspicuous (Fig. 16A) to absent (Fig. 16B); distal face of radial circlet imperfectly preserved in largest paratype (Fig. 16C).&lt;/p&gt; &lt;p&gt; &lt;b&gt;Remarks.&lt;/b&gt; The aboral cup of the holotype of &lt;i&gt;C. requiensis&lt;/i&gt; (Fig. 16E&ndash;G) is the closest to those of the extant species &lt;i&gt;C. cherbonnieri&lt;/i&gt; (Roux, 1976) (Fig. 16H), both lacking sutures between basals. The paratypes (Fig. 16A&ndash;D) have an aboral cup general shape that is similar to those from the Danian of Denmark, attributed to? &lt;i&gt;Cherbionniericrinus&lt;/i&gt; sp. (Roux &lt;i&gt;et al&lt;/i&gt;. 2019), which differ, however, by a larger adoral cavity like in the extant species. Columnals are unknown. The extant species &lt;i&gt;C. cherbonnieri&lt;/i&gt; is anchored to the substratum by rhizoids penetrating into the sediment (Roux 1977).&lt;/p&gt; &lt;p&gt; &lt;b&gt;Occurrence.&lt;/b&gt; Early Ypresian (middle Ilerdian) of Corbi&egrave;res; species known only from R&eacute;qui near Montlaur (Val de Dagne, Aude).&lt;/p&gt;Published as part of &lt;i&gt;Roux, Michel, Martinez, Alain &amp; Vizcaïno, Daniel, 2021, A diverse crinoid fauna (Echinodermata, Crinoidea) from the Lower Eocene of the Gulf of Languedoc (Corbières, Aude, southern France), pp. 201-242 in Zootaxa 4963 (2)&lt;/i&gt; on pages 230-232, DOI: 10.11646/zootaxa.4963.2.1, &lt;a href="http://zenodo.org/record/4700704"&gt;http://zenodo.org/record/4700704&lt;/a&gt