Shifts in the Ediacaran to Lower Ordovician sedimentary zircon provenances of Northwest Gondwana : the Pyrenean files

Acknowledgments. This research was founded by the RGF program of the French Geological Survey (BRGM).Detrital zircon grains from Cambrian-Lower Ordovician sandstones and quartzites sampled in the Pyrenees were dated by LA-ICPMS in order to assess their provenance sources. Resulting age distributions are compared to other available datasets from neighbouring margins, such as Morocco, the Iberian Peninsula, southern France and Sardinia. Kolmogorov-Smirnov (K-S) test and Crystallization Age-Depositional Age (CA-DA) diagrams were used to compare zircon populations estimating their possible correlation with the arc/rift/drift geodynamic evolution of the northwestern Gondwana margin. During Terreneuvian times, zircon populations allowed the distinction of i) a southwesternmost edge (Anti-Atlas-Ossa-Morena Rift) mostly influenced by Panafrican and Anti-Atlasian sources (ca. 0.63-0.54), ii) a northeasternmost edge (Sardinia) recording the influence of the Saharan Metacraton and the Arabian Nubian Shield, with an distinct Stenian-Tonian shift (ca. 1.25-0.85Ga) and iii) an intermediate palaeogeographic transect, where lies the Central-Iberian, West Asturian-Leonese and Cantabrian Zones, the Montagne Noire and the Pyrenees sharing similar populations and a chronologically progressive influence from Anti-Atlasian/Panafrican to Saharan Metacraton/Arabian Nubian Shield sources. This gradual modification in zircon percentage populations supports similar trends based on climatically sensitive indicators, biogeographic patterns of Cambrian Epoch 2 archaeocyathan and microfossil assemblages, and laterally correlatable episodes of carbonate production, all of them pointing to a Cambrian setting for the Pyrenean Basin between the Montagne Noire (Occitan Domain) and the Sardinian margins of NW Gondwana. The Terreneuvian zircon patterns recorded in the Pyrenees gradually evolved from Cambrian Epoch 2 to Early Ordovician times, reflecting the geodynamic evolution from Panafrican and Cadomian arc-related to rift-dominant conditions. During Furongian and Ordovician times, the relative percentage of zircon populations led to a more spread age curve, characteristic of extensional settings and pointing to rift (passive margin) conditions

Shifts in the Ediacaran to Lower Ordovician sedimentary zircon provenances of Northwest Gondwana : the Pyrenean files

Acknowledgement. This research was founded by the RGF program of the French Geological Survey (BRGM). This paper is a contribution to project CGL2013-48877-P from Spanish MINECO. François Guillot, Olivier Blein, Cecilio Quesada and Cesar Witt are warmly thanked for stimulating discussions about Cadomian geodynamics. The authors appreciate revisions by Noel Moreira (Evora, Portugal) and an anonymous reviewer.Detrital zircon grains from Cambrian-Lower Ordovician sandstones and quartzites sampled in the Pyrenees were dated by LA-ICPMS in order to assess their provenance sources. Resulting age distributions are compared to other available datasets from neighbouring margins, such as Morocco, the Iberian Peninsula, southern France and Sardinia. Kolmogorov-Smirnov (K-S) test and Crystallization Age-Depositional Age (CA-DA) diagrams were used to compare zircon populations estimating their possible correlation with the arc/rift/drift geodynamic evolution of the northwestern Gondwana margin. During Terreneuvian times, zircon populations allowed the distinction of i) a southwesternmost edge (Anti-Atlas-Ossa-Morena Rift) mostly influenced by Panafrican and Anti-Atlasian sources (ca. 0.63-0.54), ii) a northeasternmost edge (Sardinia) recording the influence of the Saharan Metacraton and the Arabian Nubian Shield, with an distinct Stenian-Tonian shift (ca. 1.25-0.85Ga) and iii) an intermediate palaeogeographic transect, where lies the Central-Iberian, West Asturian-Leonese and Cantabrian Zones, the Montagne Noire and the Pyrenees sharing similar populations and a chronologically progressive influence from Anti-Atlasian/Panafrican to Saharan Metacraton/Arabian Nubian Shield sources. This gradual modification in zircon percentage populations supports similar trends based on climatically sensitive indicators, biogeographic patterns of Cambrian Epoch 2 archaeocyathan and microfossil assemblages, and laterally correlatable episodes of carbonate production, all of them pointing to a Cambrian setting for the Pyrenean Basin between the Montagne Noire (Occitan Domain) and the Sardinian margins of NW Gondwana. The Terreneuvian zircon patterns recorded in the Pyrenees gradually evolved from Cambrian Epoch 2 to Early Ordovician times, reflecting the geodynamic evolution from Panafrican and Cadomian arc-related to rift-dominant conditions. During Furongian and Ordovician times, the relative percentage of zircon populations led to a more spread age curve, characteristic of extensional settings and pointing to rift (passive margin) conditions

Shifts in the Ediacaran to Lower Ordovician sedimentary zircon provenances of Northwest Gondwana: the Pyrenean files

Detrital zircon grains from Cambrian–Lower Ordovician sandstones and quartzites sampled in the Pyrenees were dated by LA-ICPMS in order to assess their provenance sources. Resulting age distributions are compared to other available datasets from neighbouring margins, such as Morocco, the Iberian Peninsula, southern France and Sardinia. Kolmogorov-Smirnov (K-S) test and Crystallization Age-Depositional Age (CA-DA) diagrams were used to compare zircon populations estimating their possible correlation with the arc/rift/drift geodynamic evolution of the northwestern Gondwana margin. During Terreneuvian times, zircon populations allowed the distinction of i) a southwesternmost edge (Atlas-Ossa-Morena Rift) mostly influenced by Panafrican and Anti-Atlasian sources (ca. 0.63–0.54), ii) a northeasternmost edge (Sardinia) recording the influence of the Saharan Metacraton and the Arabian Nubian Shield, with an distinct Stenian–Tonian shift (ca. 1.25–0.85Ga) and iii) an intermediate palaeogeographic transect, where lies the Central Iberian, West Asturian-Leonese and Cantabrian Zones, the Montagne Noire and the Pyrenees sharing similar populations and a chronologically progressive influence from Anti-Atlasian/Panafrican to Saharan Metacraton/Arabian Nubian Shield sources. This gradual modification in zircon percentage populations supports similar trends based on climatically sensitive indicators, biogeographic patterns of Cambrian Epoch 2 archaeocyathan and microfossil assemblages, and laterally correlatable episodes of carbonate production, all of them pointing to a Cambrian setting for the Pyrenean Basin between the Montagne Noire (Occitan Domain) and the Sardinian margins of NW Gondwana. The Terreneuvian zircon patterns recorded in the Pyrenees gradually evolved from Cambrian Epoch 2 to Early Ordovician times, reflecting the geodynamic evolution from Panafrican and Cadomian arc-related to rift-dominant conditions. During Furongian and Ordovician times, the relative percentage of zircon populations led to a more spread age curve, characteristic of extensional settings and pointing to rift (passive margin) conditions

Shifts in the Ediacaran to Lower Ordovician sedimentary zircon provenances of Northwest Gondwana: the Pyrenean files

Detrital zircon grains from Cambrian–Lower Ordovician sandstones and quartzites sampled in the Pyrenees were dated by LA-ICPMS in order to assess their provenance sources. Resulting age distributions are compared to other available datasets from neighbouring margins, such as Morocco, the Iberian Peninsula, southern France and Sardinia. Kolmogorov-Smirnov (K-S) test and Crystallization Age-Depositional Age (CA-DA) diagrams were used to compare zircon populations estimating their possible correlation with the arc/rift/drift geodynamic evolution of the northwestern Gondwana margin. During Terreneuvian times, zircon populations allowed the distinction of i) a southwesternmost edge (Anti-Atlas-Ossa-Morena Rift) mostly influenced by Panafrican and Anti-Atlasian sources (ca. 0.63–0.54), ii) a northeasternmost edge (Sardinia) recording the influence of the Saharan Metacraton and the Arabian Nubian Shield, with an distinct Stenian–Tonian shift (ca. 1.25–0.85Ga) and iii) an intermediate palaeogeographic transect, where lies the Central-Iberian, West Asturian-Leonese and Cantabrian Zones, the Montagne Noire and the Pyrenees sharing similar populations and a chronologically progressive influence from Anti-Atlasian/Panafrican to Saharan Metacraton/Arabian Nubian Shield sources. This gradual modification in zircon percentage populations supports similar trends based on climatically sensitive indicators, biogeographic patterns of Cambrian Epoch 2 archaeocyathan and microfossil assemblages, and laterally correlatable episodes of carbonate production, all of them pointing to a Cambrian setting for the Pyrenean Basin between the Montagne Noire (Occitan Domain) and the Sardinian margins of NW Gondwana. The Terreneuvian zircon patterns recorded in the Pyrenees gradually evolved from Cambrian Epoch 2 to Early Ordovician times, reflecting the geodynamic evolution from Panafrican and Cadomian arc-related to rift-dominant conditions. During Furongian and Ordovician times, the relative percentage of zircon populations led to a more spread age curve, characteristic of extensional settings and pointing to rift (passive margin) conditions

Review of the Ediacaran-Lower Ordovician (pre-Sardic) stratigraphic framework of the Eastern Pyrenees, southwestern Europe

The Ediacaran-Lower Ordovician successions exposed in the Eastern Pyrenees are updated and revised based on recent U-Pb zircon radiometric ages, intertonguing relationships of carbonate-dominated strata, and onlapping patterns marking the top of volcano-sedimentary complexes. A stratigraphic comparison with neighbouring pre-Variscan outcrops from the Montagne Noire (southern French Massif Central) and Sardinia is related to i) the absence of Cadomian deformation close to the Ediacaran-Cambrian boundary interval; ii) the presence of an episodic, Cadomian-related, acidic-dominant volcanism related to carbonate production punctuating the Ediacaran-Cambrian transition, similar to that recorded in the northern Montagne Noire; and iii) the lack of Guzhangian (Cambrian Epoch 3) regressive shoal complexes present in the Montagne Noire and probably in Sardinia

Shifts in the Ediacaran to Lower Ordovician sedimentary zircon provenances of Northwest Gondwana: the Pyrenean files

Detrital zircon grains from Cambrian–Lower Ordovician sandstones and quartzites sampled in the Pyrenees were dated by LA-ICPMS in order to assess their provenance sources. Resulting age distributions are compared to other available datasets from neighbouring margins, such as Morocco, the Iberian Peninsula, southern France and Sardinia. Kolmogorov-Smirnov (K-S) test and Crystallization Age-Depositional Age (CA-DA) diagrams were used to compare zircon populations estimating their possible correlation with the arc/rift/drift geodynamic evolution of the northwestern Gondwana margin. During Terreneuvian times, zircon populations allowed the distinction of i) a southwesternmost edge (Anti-Atlas-Ossa-Morena Rift) mostly influenced by Panafrican and Anti-Atlasian sources (ca. 0.63–0.54), ii) a northeasternmost edge (Sardinia) recording the influence of the Saharan Metacraton and the Arabian Nubian Shield, with an distinct Stenian–Tonian shift (ca. 1.25–0.85Ga) and iii) an intermediate palaeogeographic transect, where lies the Central-Iberian, West Asturian-Leonese and Cantabrian Zones, the Montagne Noire and the Pyrenees sharing similar populations and a chronologically progressive influence from Anti-Atlasian/Panafrican to Saharan Metacraton/Arabian Nubian Shield sources. This gradual modification in zircon percentage populations supports similar trends based on climatically sensitive indicators, biogeographic patterns of Cambrian Epoch 2 archaeocyathan and microfossil assemblages, and laterally correlatable episodes of carbonate production, all of them pointing to a Cambrian setting for the Pyrenean Basin between the Montagne Noire (Occitan Domain) and the Sardinian margins of NW Gondwana. The Terreneuvian zircon patterns recorded in the Pyrenees gradually evolved from Cambrian Epoch 2 to Early Ordovician times, reflecting the geodynamic evolution from Panafrican and Cadomian arc-related to rift-dominant conditions. During Furongian and Ordovician times, the relative percentage of zircon populations led to a more spread age curve, characteristic of extensional settings and pointing to rift (passive margin) conditions

The geological-event reference system, a step towards geological data harmonization

The temporal dimension is an inherent component of geology. In this regard, traditional geological maps can represent a few geological events, yet they hardly account for the entire complex rock history whether sedimentary, crystalline or volcanic. Here, using the RGF research program (French Geological Reference platform) we propose a new methodology based on digital technology and the French historical collection of 1:50 000-scale geological maps. This innovative approach consists of describing, organizing and hierarchizing a series of geological events within a reference framework and linking it to GIS map geometries (polygons, faults, points). In this way, the complete history of geological features can be compiled and stored in digital maps, combining distinct geological events and properties. For a single event, all associated transformations can be represented on maps, facilitating the production of real “palaeo-geological” maps that consider not only traditional sedimentary environments but also possible synchronous weathering, metamorphism, and volcanism. We discuss here an example of French orogenic history. The approach demonstrated here on geological maps can be used with other geological data media (boreholes, seismic reflection profiles, etc.) and thus facilitate a 3D-to-4D scale, with a significant ability to address not only academic community needs, but also themes or issues related to applications required by politics, civil engineering, and society itself, to confront challenges such as natural and anthropic risk reduction and subsurface uses

Palaeozoic Basement of the Pyrenees

International audienceIn the Pyrenees, the Cambrian-Lower Ordovician strata represent a quiescent time span with no remarkable tectonic activity, followed by a late Early-Mid Ordovician episode of uplift and erosion that led to the formation of the Sardic unconformity. Silurian sedimentation was widespread and transgressive followed by a Devonian succession characterized by a complex mosaic of sedi-mentary facies. Carboniferous pre-Variscan sediments (Tournaisian-Viséan cherts and limestones) precede the arrival of the synorogenic siliciclastic supplies of the Culm flysch at the Late Serpukhovian. All this succession was subsequently affected by the Serpukhovian-Bashkirian (Variscan) collision, as a result of which, the Palaeozoic rocks were incorporated into the northeastern branch of the Ibero-Armorican Arc

Cadomian Influence on the pre-Sardic series of the Eastern Pyrenees : geochemical, stratigraphic and geochronological approach

La stratigraphie de l’Ediacarien-Ordovicien Inférieur des Pyrénées Orientales est révisée. Le découpage stratigraphique est similaire aux successions de la Montagne Noire (France) et de la Sardaigne (Italie) tenant compte de (1) l’absence de déformation cadomienne au cours de la transition Ediacarien-Cambrien, (2) la présence, comme dans la Montagne Noire septentrionale, d’un volcanisme acide proche de la limite Ediacarien-Cambrien, et (3) l’absence des corps régressifs du Guzhangien (Cambrien moyen terminal) comme au Sud-Ouest de la Sardaigne. Les analyses géochimiques du volcanisme de l’Ediacarien supérieur des Pyrénées Orientales suggèrent deux affinités distinctes, une tholéitique liée à un contexte d’extension (métabasites des Formations de Nyer et d’Olette) et une autre calco-alcaline et à dominance acide liée à l’orogénèse Cadomienne (sommet de la Formation d’Olette et Formation du Pic de la Clape). Une révision des zircons détritiques des dépôts terreneuviens de la partie nord-occidentale péri-gondwanienne (Maroc, massif Ibérique, Montagne Noire, Pyrénées et Sardaigne) reflète l’influence relative des principales sources de sédiments suivant une polarité SO-NE : les sources panafricaines et atlasiennes prédominent dans les successions les plus sud-occidentales, tandis que l’influence du craton Arabo-Nubien et du méta-craton Saharien augmente vers le NE. Cette tendance disparait ensuite, reflétant une possible homogénéisation géodynamique et des sources continentales le long de cette marge.The Ediacaran-Lower Ordovician stratigraphy of the Eastern Pyrenees is updated and revised. A similar stratigraphic framework is compared with neighbouring outcrops from the Montagne Noire (France) and Sardinia (Italy), which take into account: (i) the absence of Cadomian deformation close to the Ediacaran-Cambrian boundary interval, (ii) the presence, like in the northern Montagne Noire, of acidic-dominated volcanosedimentary complexes punctuating the Ediacaran-Cambrian transition, (iii) the lack of the Guzhangian (mid Cambrian) regression, also absent in SW Sardinia. The geochemical analysis of the uppermost Ediacaran volcanism in the Eastern Pyrenees suggest two distinct affinities linked to extensional conditions (metabasites of the Nyer and Olette formations) followed by the influence the Cadomian orogeny (acidic and calk-alkaline magmatism recorded at the top of the Olette Formation and in the overlying Pic de la Clape Formation). Detrital zircons from Terreneuvian siliciclastic sediments of West Gondwana (Morocco, Iberian Massif, Montagne Noire, Pyrenees and Sardinia) reflect a distinct SW-NE trend in the relative influence of major sediment sources: the Panafrican-Atlasian sources predominate throughout the southwesternmost successions, whereas the influence of the Arabian-Nubian Shield and the Sahara Metacraton sources increases northeastward. This trend tends to disappear afterwards, possibly reflecting a common geodynamic evolution throughout this margin

Volcanosedimentary complex encompassingthe Ediacaran- Cambrian boundary interval inthe Oriental Pyrenees

National audienceThe Pyrenees are part of the northeastern margin of the Ibero-Armorican Variscan Arc. They possess one of the most completeuppermost Ediacaran–Cambrian successions in West Gondwanawhich has been classically divided into two principal lithostratigraphicunits : the Canaveilles and Jujols Groups. In the southernflank of the Canigou massif (Puigmal Variscan tectonostratigraphicunit), a unique Fabert volcanic level is usually described atthe top of the Cabrils Formation (uppermost Canaveilles Group)which was recently dated around ca. 570 Ma. The overlying TreguràFormation (Jujols Group) is divided into a lower volcanoclasticbreccia member with limestone olistoliths and strong thicknessvariations, and an upper limestone member. The Tregurà Formationhas been considered to encompass the Ediacaran-Cambriantransition, however, until now, no geochronological data have supportedthis hypothesis. The present study has been aimed to providean up-to-date and detailed facies analyzes of the Ediacaran-Cambrian formations from the Pyrenees, and to test previouslypublished dating of above-mentioned volcanic and breccia levelsthrough new LA-ICPMS U–Pb dating of zircons. Therefore, theso-called Fabert volcanic level have been sampled in the FabertVillage and the nearby Pic de la Clape, yielding respective agesat ca.559.5 +1.7/-1.3 Ma and ca.542.9 +5/-1.3 Ma. The Treguràbreccia, sampled at the Pic du Finestrelles and the Pic dela Clape, have respectively yielded maximum depositional agesof ca.556±7Ma and ca.532.9±6.1 Ma.. These new dating arguefor a long-lasting volcanic episode with multiple pulses during theEdiacaran-Cambrian transition. As a consequence, an updatedstratigraphic framework is proposed