Interactions between crustal tectonics, salt tectonics and sedimentation : the western tyrrhenian margin

Dans le Bassin Tyrrhénien Occidental, le rifting de la Marge Est-Sarde a eu lieu à partir du Miocène moyen-supérieur, par extension arrière-arc liée à la migration vers l’Est du système de subduction Apennin. Le Bassin Tyrrhénien Occidental a aussi été marqué par la Crise de Salinité Messinienne (CSM), à l’origine du dépôt de séries évaporitiques, dont localement une épaisse couche de sel mobile. À partir de l'interprétation des nouvelles données sismiques METYSS (Messinian Event in the TYrrhenian from Seismic Study), les objectifs de cette thèse consistent notamment à comprendre les modalités de la CSM, à préciser les relations entre tectoniques crustale et salifère et à contraindre l’évolution géodynamique de la Marge Est-Sarde. Les résultats de cette étude ont abouti à la cartographie détaillée des marqueurs de la CSM (unités de dépôts et surfaces remarquables), qui fournissent de bons indicateurs spatio-temporels. Ces marqueurs ont permis de contraindre l’analyse structurale qui révèle que la phase majeure d’activité crustale est pré-CSM. Le rifting de la marge est donc clairement pré-CSM et ne se prolonge pas jusqu’au Pliocène, comme cela avait été envisagé antérieurement. De plus, cette étude a mis en évidence des mouvements crustaux post-CSM bien distincts du rifting, liés à une phase de réactivation post-rift significative sur cette marge. Cette réactivation est complexe et diversifiée ; elle se manifeste non seulement par la réactivation en extension de failles nées du rifting, mais aussi localement par le développement de structures compressives et des basculements de socle, illustrant un couplage entre tectonique crustale et tectonique salifère.In the Western Tyrrhenian Basin, rifting of the Eastern-Sardinian margin started during the middle to late In the Western Tyrrhenian Basin, rifting of the Eastern-Sardinian margin started during the middle to late Miocene times, due to back-arc extension following the eastward migration of the Apennine subduction system. The Western Tyrrhenian Basin has also been affected by the Messinian Salinity Crisis (MSC), which generated evaporitic deposits, particularly a thick mobile salt layer. Based on the interpretation of the new METYSS seismic data (Messinian Event in the TYrrhenian from Seismic Study), this work aims at a better understanding the modalities of the MSC, the relationships between crustal tectonics and salt tectonics, and the geodynamic evolution of the Eastern-Sardinian margin.The results lead to a detailed map of the MSC seismic markers (depositional units and remarkable surfaces). These markers provide spatiotemporal indicators and allow to constrain the structural analysis. Along the margin the major crustal stage is pre-MSC. Thus rifting of the margin occurred before the MSC and did not continue until Pliocene times, as previously considered. Moreover, this study evidences post-MSC crustal motions, well distinct from the rifting stage and linked to post-rift reactivation of the margin. This second crustal stage is various and complex; it reactivated crustal normal fault that had formed during rifting, but also generated crustal compressional structures. In some places, tilting of the pre-MSC basement triggered some salt tectonics

Pre-Commercial Procurement framework and European funding sources for European Research Infrastructure Consortiums: Insights from the DiSSCo ERIC development

Mechanisms and sources of funding for European Research Infrastructure Consortiums (ERICs) are diverse, complex and can be challenging to identify and to use. This paper provides a roadmap for Research & Development (R&D) within the pre-commercial procurement (PCP) framework and the landscape of funding for ERICs available from the European Union with a perspective on other tracks of funding. Our objective is to offer a starting point and underline opportunities and challenges, for existing and future ERICs. The work presented in this paper results from the research carried-out for the business model of the DiSSCo (Distributed System of Scientific Collections) ERIC, which is currently in its transition phase and will be constructed in the following years

Interactions between salt tectonics and crustal tectonics on the Eastern Sardinian Margin (Western Tyrrhenian Sea)

International audienceThe METYSS project (Messinian Event in the Tyrrhenian from Seismic Study) is based on high-resolution seismic data acquired along the Eastern Sardinian margin. The main aim is to study the Messinian Salinity Crisis (MSC) in the Western Tyrrhenian Basin, but we also investigated the thinning processes of the continental crust and the timing of crustal vertical movements across this backarc domain. Our first results shown that rifting ended before the MSC, but that crustal activity persisted long after the end of the rifting. This has been particularly observed on the proximal margin, the East-Sardinia Basin, where the Mobile Unit (MU, mobile Messinian salt) is thin or absent. In this study, we examined the distal margin, the Cornaglia Terrace, where the MU accumulated during the MSC and acted as a décollement, thus potentially decoupling the basement from the sedimentary cover. Our observations provide evidence for lateral flow and gravity gliding of the salt and its brittle sedimentary overburden along local basement slopes generated by the post-MSC tilting of some basement blocks formerly generated during the rifting. We also investigated an intriguing wedge-shaped body of MU located in a narrow N-S half graben bounded to the west by a major, east-dipping, crustal normal fault. Classically, one could think that this salt wedge is related to the syn-tectonics deposition of the MU, but we propose an original scenario, in which the post-rift vertical motion of the major fault has been cushioned by lateral flow of an initially tabular salt layer, leaving the supra-salt series apparently unaffected by the crustal motions of the basement. We tested this scenario by comparing natural data and physical (analogue) modelling data. Our results reveal that salt tectonics provides a powerful tool to understand the deep crustal tectonics of the margin and to constrain the timing of vertical motions in the Western Tyrrhenian Basin, results that can be applied to rifted salt-bearing margins worldwide

A report on recommendations for the most suitable financial contribution model for the Distributed System of Scientific Collections Research Infrastructure (DiSSCo-RI)

A key consideration during the preparatory phase project DiSSCo Prepare – which laid the foundations for the future Research Infrastructure DiSSCo (Distributed System of Scientific Collections) – was the need to establish a small number of alternative viable financial contribution models and a scalable formula which could be presented to potential funders, with a view to obtaining the minimum financial contribution necessary for DiSSCo to operate, as well as considering how the RI could grow with increased national funding.This report briefly explains the ERIC funding framework – as chosen for DiSSCo – and its legal constraints, in order to explain the key role played by national member contributions in the viability of an ERIC. An essential annex of the statutes that will be signed by all members of the ERIC is the member fee calculation. A proposal for the DiSSCo member fee calculation is set out in this document and is based on three main indicators: economic power (GDP), annual spending in research and development and population size. In the context of DiSSCo – and to ensure the ERIC can function – these indicators are connected to a fixed baseline fee of €50,000, in order to guarantee a minimum significant annual contribution from each participating country and avoid contributions that will be more expensive to manage than to benefit from. This baseline is multiplied by contribution factors which propose different ways to weight the various indicators.The method is established on an ideal scenario, whereby all 27 EU members, as well as the UK, Iceland, Norway and Switzerland sign the DiSSCo statutes and agree to the proposed member contribution calculation, amounting to €4.5 million for the annual budget of the ERIC. This scenario remains highly unlikely; therefore, a scaled approach has been envisaged, meaning the initial engagement of some countries will allow DiSSCo to begin its operation and implement its business strategy, whilst the growth of the ERIC and its activities is likely to evolve proportionally to the number of national members it is able to engage.This report also looks at the ways in which funding could be distributed amongst the DiSSCo members in order to implement decentralised services

A report on recommendations for the most suitable financial contribution model for the Distributed System of Scientific Collections Research Infrastructure (DiSSCo-RI)

A key consideration during the preparatory phase project DiSSCo Prepare – which laid the foundations for the future Research Infrastructure DiSSCo (Distributed System of Scientific Collections) – was the need to establish a small number of alternative viable financial contribution models and a scalable formula which could be presented to potential funders, with a view to obtaining the minimum financial contribution necessary for DiSSCo to operate, as well as considering how the RI could grow with increased national funding.This report briefly explains the ERIC funding framework – as chosen for DiSSCo – and its legal constraints, in order to explain the key role played by national member contributions in the viability of an ERIC. An essential annex of the statutes that will be signed by all members of the ERIC is the member fee calculation. A proposal for the DiSSCo member fee calculation is set out in this document and is based on three main indicators: economic power (GDP), annual spending in research and development and population size. In the context of DiSSCo – and to ensure the ERIC can function – these indicators are connected to a fixed baseline fee of €50,000, in order to guarantee a minimum significant annual contribution from each participating country and avoid contributions that will be more expensive to manage than to benefit from. This baseline is multiplied by contribution factors which propose different ways to weight the various indicators.The method is established on an ideal scenario, whereby all 27 EU members, as well as the UK, Iceland, Norway and Switzerland sign the DiSSCo statutes and agree to the proposed member contribution calculation, amounting to €4.5 million for the annual budget of the ERIC. This scenario remains highly unlikely; therefore, a scaled approach has been envisaged, meaning the initial engagement of some countries will allow DiSSCo to begin its operation and implement its business strategy, whilst the growth of the ERIC and its activities is likely to evolve proportionally to the number of national members it is able to engage.This report also looks at the ways in which funding could be distributed amongst the DiSSCo members in order to implement decentralised services

Processes controlling very low sedimentation rates on the continental slope of the Gonone-Orosei canyon system, NE Sardinia-terrestrial and oceanic significance

The narrow shelf and upper slope immediately above the Gonone canyon head off NE Sardinia represent areas of very low sedimentation rates. Along the sides of the canyon head (1,600 m water depth), the sediment deposits are homogeneous but show alternating light-grey intervals rich in carbonate and dark-grey ones rich in organic matter, possibly related to distal turbidite processes. Deposits older than 50,000 years are already encountered at core depths of 2.50 m, the sedimentation rates varying from 6–21 cm/103 years in the lower parts of two cores and from 1.5–3 cm/103 years in the upper parts. At about 35,000 years BP, both cores show a simultaneous drop in sedimentation rate by a factor of 3, probably in response to local mechanisms of channel avulsion. Lithological, mineralogical and geochemical properties reveal the environmental factors which are responsible for the extremely slow sediment accumulation. The southernmost sector of the coast, and partly also of the shelf, consists of Jurassic limestones which supply only small amounts of fine-grained material transported in suspension. During the last sea-level highstand, the accumulation of the Cedrino River pro-delta remained restricted to the coast, the low siliciclastic sediment yields resulting in poor shelf sediment trapping. The present morphology of the canyon head prevented the occurrence of gravity processes in the deeper part of the canyon system, including the coring sites. Accordingly, deposition was mainly fed by hemipelagic material of planktonic origin, together with only moderate terrigenous inputs. On a wider late Pleistocene timescale, seismic data indicate the occurrence of a coarse-grained, layered turbidite facies, implying a very different architecture of the canyon drainage system probably prior to 60,000 years BP

Observations sur la lenteur de la sédimentation sur la pente orientale de la Sardaigne (versant du Canyon d'Orosei).

Deux carottes KS02 et KS07 ont été prélevées à des profondeurs assez proches (1602 m et 1648 m) sur les versants du canyon d'Orosei, le long de la marge est-sarde, lors de la campagne "METYSS 2" (avril 2010, N/O " Téthys II "). Elles présentent des logs lithologiques assez comparables. Sur la base de 8 premières datations AMS du 14C, on constate des rythmes d'accumulation particulièrement faibles puisque les deux verticales de 2,50 m de longueur permettent d'enregistrer environ les 52 derniers milliers d'années, c'est-à-dire une vitesse à peu près trois fois plus faible que celle la plus lente enregistrée sur la marge algérienne. Les rythmes d'accumulation des deux carottes sont compris entre 6 à 21 cm /103 ans entre 50 et 30 000 BP, puis s'affaiblissent fortement après (1,5 à 3 cm /103 ans). Ces faibles accumulations sont attestées par l'épaisseur des couches oxydées au sommet de chaque colonne sédimentaire (15 cm en KS07 et 7 cm en KS02). Elles correspondent à une sédimentation hémipélagique où la faible fraction sableuse (4 à 12 % du sédiment entier) est principalement constituée par les tests de la microfaune surtout pélagique. Si les minima des teneurs en CaCO3 sont, dans les deux cas, de l'ordre de 15 %, les maxima s'approchent de 50 % dans le cas de KS02, mais ne dépassent pas 40 % dans le cas de KS07, différence pouvant être analysée en fonction de fluctuation des flux silicoclastiques. Il est à souligner que ces teneurs en CaCO3 de l'ordre de 50 % se situent parmi les concentrations les plus élevées enregistrées à ce jour, dans les sédiments hémipélagiques des pentes méditerranéennes. Si les rythmes de l'accumulation s'avèrent comparables à l'échelle globale des 52 derniers millénaires, il n'en est de pas de même à l'échelle des épisodes paléoclimatiques successifs. Ainsi en KS07, la sédimentation holocène (stade 1) se limite aux 15 cm supérieurs (en fait, les niveaux ocre au-dessus de la rédoxcline) alors qu'en KS02, ces dépôts holocènes atteignent 35 cm. Un constat inverse serait fait à hauteur de l'épaisseur du stade 2. Enfin, pour le stade 3, les rythmes seraient à peu près équivalents dans les deux carottes. Ces différences laissent supposer que les deux sites, malgré leur proximité, réceptionnent des flux terrigènes légèrement différents en fonction du temps et de l'espace. La distribution verticale de plusieurs bio et géo-marqueurs souligne ces différences. Aujourd'hui, la modestie des flux terrigènes sur la plateforme se traduit par la transparence des eaux et une forte accumulation photosynthétique (notamment posidonies et lithotamniées)

Back-arc extension dated from natural time markers across the Western Tyrrhenian Basin

International audienceThe rifting of the Eastern Sardinian margin is considered to have occurred during the Neogene, by back-arc extension related to the eastward migration of the Apennine subduction system, leading to the development of the Tyrrhenian Basin, Western Mediterranean Sea. The locus of the extension during the rifting is interpreted to have occurred first in the East-Sardinia Basin (proximal margin), and then in the Cornaglia Terrace (distal margin). However, the dynamics of the Western Tyrrhenian Basin during the rifting is still largely undated, and the kinematics of the development of the different domains of the Eastern Sardinian margin remains poorly understood. This is due to the sparsity of dated rock samples within the basin, mainly recovered locally during ODP Leg 103, and because the timing of activity of the structures of the basin has been addressed so far using regional data, whose resolution is insufficient to observe the timing of the extension at the scale of a fault plane.</p><p>In this study, we use a 2400 km-long high-resolution seismic-reflection dataset acquired along the Eastern Sardinian margin during the “METYSS” research cruises in 2009 and 2011, and specifically designed to observe the block-bounding faults and the syn-rift and post-rift units. We interpret the syn-tectonic markers of the crustal deformation across the Eastern Sardinian margin, and we use the seismic markers of the Messinian Salinity Crisis (MSC) that provide exceptional and accurate natural time markers, to estimate the age of faults development and understand their evolution within the Western Tyrrhenian Basin.</p><p>Our observations demonstrate that the rifting was polyphased across the Western Tyrrhenian Basin, and that syn-rift extension was active on the proximal margin long before the MSC, whereas the distal Cornaglia Terrace developed only a short time before the MSC. Surprisingly, our interpretations also evidence significant post-rift reactivation of some structures of the Eastern Sardinian margin. These reactivations, formerly considered to be very minor or absent in the Western Tyrrhenian Basin, started in the Pliocene and occurred up to very-recent times along local fault-planes, as shown by the deformation of the shallowest Pleistocene layers and the seafloor.</p><p>Our results permit to precise the timing of the syn-rift and post-rift evolution of the Eastern Sardinian margin. Given the rarity of natural time makers in offshore sedimentary basins to address the dynamics of basins development, we expect our results to provide useful comparisons to study the kinematics of extension at other back-arc basins worldwide.</p&gt

From proximal to distal margin in a backarc setting: the hyper-extended Eastern Sardinian Margin

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