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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... more
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...
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The Fezouata Biota (Morocco) is an exceptionally well-preserved fossil community of Early Ordovician age and although its oldest units are comparable with Burgess Shale-type localities of the Cambrian Explosion, little attention has been... more
The Fezouata Biota (Morocco) is an exceptionally well-preserved fossil community of Early Ordovician age and although its oldest units are comparable with Burgess Shale-type localities of the Cambrian Explosion, little attention has been paid to the younger units despite potential to reveal the conditions of the Ordovician Radiation. Herein, we describe a new middle to upper Floian Fezouata locality (Taichoute) encompassing an assemblage dominated by large bivalved euarthropods and giant filter-feeding radiodonts, which were transported and preserved in concretions associated with density-flow deposits. Taichoute captures the closing of the taphonomic window that characterizes exceptional fossil preservation during the Cambrian Explosion (i.e., carbonaceous compressions) as well as the faunal transition to assemblages dominated by typical Palaeozoic taxa.
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Trabajo presentado en el 5th International Palaeontological Congress, celebrado en Paris (Francia) del 9 al 13 de julio de 2018
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Understanding variations in body size is essential for deciphering the response of an organism to its surrounding environmental conditions and its ecological adaptations. In modern environments, large marine animals are mostly found in... more
Understanding variations in body size is essential for deciphering the response of an organism to its surrounding environmental conditions and its ecological adaptations. In modern environments, large marine animals are mostly found in cold waters. However, numerous parameters can influence body-size variations other than temperatures, such as oxygenation, nutrient availability, predation or physical disturbances by storms. Here, we investigate trilobite size variations in the Lower Ordovician Fezouata Shale deposited in a cold-water environment. Trilobite assemblages dominated by small- to normal-sized specimens that are a few centimetres in length are found in proximal and intermediate settings, while those comprising larger taxa more than 20 cm in length are found in the most distal environment of the Fezouata Shale. Drill core material from distal settings shows that sedimentary rocks hosting large trilobites preservedin situare extensively bioturbated with a high diversity of t...
Research Interests: Geology, Taphonomy, Ordovician, Trilobite, Bioturbation, and 3 moreArthropod, Body Size, and Paleozoic
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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Interactions and coordination between conspecific individuals have produced a remarkable variety of collective behaviours. This co-operation occurs in vertebrate and invertebrate animals and is well expressed in the group flight of birds,... more
Interactions and coordination between conspecific individuals have produced a remarkable variety of collective behaviours. This co-operation occurs in vertebrate and invertebrate animals and is well expressed in the group flight of birds, fish shoals and highly organized activities of social insects. How individuals interact and why they co-operate to constitute group-level patterns has been extensively studied in extant animals through a variety mechanistic, functional and theoretical approaches. Although collective and social behaviour evolved through natural selection over millions of years, its origin and early history has remained largely unknown. In-situ monospecific linear clusters of trilobite arthropods from the lower Ordovician (ca 480 Ma) of Morocco are interpreted here as resulting either from a collective behaviour triggered by hydrodynamic cues in which mechanical stimulation detected by motion and touch sensors may have played a major role, or from a possible seasonal...
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Sedimentological, palynological, and micropalaeontological studies carried out throughout the first half of the Holocene, during the Mesolithic/Neolithic transition in the Bay of Brest (i.e. 9200–9000 and 6600–5300 cal. BP) and in the Bay... more
Sedimentological, palynological, and micropalaeontological studies carried out throughout the first half of the Holocene, during the Mesolithic/Neolithic transition in the Bay of Brest (i.e. 9200–9000 and 6600–5300 cal. BP) and in the Bay of Douarnenez (i.e. 9200–8400 cal. BP), allowed characterizing coastal environmental changes under the increasing influence of the relative sea-level rise. The gradual flooding of the two studied sites implied a transition from river valleys to oceanic bays as revealed by the gradual retreat of salt marsh environments, as detected through palynological analysis. In addition, these high-resolution studies highlight the regional imprint of the North Atlantic millennial climate variability in north-western coastal environments. Two cold climate events are indeed suggested to have been locally marked by a moisture increase, mainly detected by increases in Lingulodinium machaerophorum, Corylus, and Alnus percentages at 8550 cal. BP in the Bay of Douarne...
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To date, Holocene palaeoecological signatures on the Northwestern coast of France have not been thoroughly investigated. In this study, environmental changes related to both climate processes and human disturbances were reconstructed over... more
To date, Holocene palaeoecological signatures on the Northwestern coast of France have not been thoroughly investigated. In this study, environmental changes related to both climate processes and human disturbances were reconstructed over the last 7000 cal. yr BP, based on pollen and chironomid assemblages from four coastal cores retrieved in Western Brittany (Porsmilin beach, NW France). Pollen and chironomid records show an environmental response to both millennial- and centennial-scale climate changes. During the mid-Holocene (until around 4200 cal. yr BP), when human impact was low, Porsmilin’s landscape was characterized by a mixed oak forest dominated by Corylus trees. Comparison of our data with other palynological data from the NW French Atlantic coast shows that this dominance may be related to more humid conditions prevailing at Porsmilin. Furthermore, over the mid-Holocene, Corylus and Quercus patterns appear anti-correlated, with Quercus declines appearing synchronous wi...
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... The Late Ordovician glacio-eustatic record from a high-latitude storm-dominated shelf succession: The Bou Ingarf section (Anti-Atlas, Southern Morocco). ... Conversely, storm-dominated sandstones and subordinate shales characterise... more
... The Late Ordovician glacio-eustatic record from a high-latitude storm-dominated shelf succession: The Bou Ingarf section (Anti-Atlas, Southern Morocco). ... Conversely, storm-dominated sandstones and subordinate shales characterise the Upper Tiouririne Fm. ...
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... La largeur(trans.) du rachis, globalement inf6rieure au tiers decelle du thorax, diminue du quatri6me au huiti6mesegment. ... Ces derni6res sont ~ rapprocher decelles figur6es et attribu6es ~ Megalaspidella(Paramegalaspis) frequens... more
... La largeur(trans.) du rachis, globalement inf6rieure au tiers decelle du thorax, diminue du quatri6me au huiti6mesegment. ... Ces derni6res sont ~ rapprocher decelles figur6es et attribu6es ~ Megalaspidella(Paramegalaspis) frequens (THoRAL, 1935) parB6rard (1986, pl. 5, fig. ...
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National audienc
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ABSTRACT This contribution deals with the Middle to early Late Ordovician of the Armorican Massif (western France). The aim is to reconstruct a multi-order eustatic curve from the stratigraphic record. The studied section (Crozon... more
ABSTRACT This contribution deals with the Middle to early Late Ordovician of the Armorican Massif (western France). The aim is to reconstruct a multi-order eustatic curve from the stratigraphic record. The studied section (Crozon Peninsula area) shows sediments deposited in tidal to storm-dominated shelf environments. A sequence analysis (facies and stacking pattern analyses), combined with a gamma-ray record and a backstripping procedure, was carried out. Chitinozoan assemblages provide the biostratigraphic framework including time calibration. The stratigraphic succession is dominated by the stacking of sequences representing different orders of sea-level change i.e. very high- (< 400 kyr), high- (400 kyr) and low- (3rd order) frequencies. Atime-calibratedsea-level high frequency curve, corrected for compaction, sediment load and tectonic subsidence, has been calculated based on a backstripping procedure. The smoothing of this curve permits identification of eleven third-ordersequences with seven episodes of significant (50 to 80 m) and rapid (less than 100 kyr) sea-level falls during the Darriwilian and the Sandbian, and two major transgressive events located in the formosa and pissotensis biozones of the Darriwilian. The reconstructed sea-level curve reveals that most of the third-order cycles comprise three fourth-order cycles of assumed 400 kyr duration. This 1.2 myr duration of the Ordovician third-ordersequences suggests that they may be related to long-period obliquity cycles, an orbital forcing characteristic of icehousesequences in the late Cenozoic and the Quaternary. These results imply that the major part of the Middle and early Late Ordovician was characterized by icehouse conditions and third-orderglacio-eustatic cycles. A time calibration of the chitinozoan biozones was developed from the sequential analysis. It suggests that the early Darriwilian biozones (from henryi to calix biozones) have short durations of several 10 to several 100 kyr whereas the pissotensis Biozone has a temporal extent of several myr, extending into the early Sandbian.