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The Ordovician of North and West Africa comprises three main transgressive–regressive sequences understood as ‘second-order’ cycles of 10–15 myr duration. Tide- to wave-dominated shallow-marine clastic successions, preserving incidental bryozoan carbonates to the north, include fluvial deposits over the most proximal southern stretches of the platform. The boundary with Cambrian strata remains unclear but the latter are progressively less represented to the south in the undifferentiated ‘Cambro-Ordovician’. To the north, graptolites, brachiopods and trilobites combined with palynomorphs provide a robust biostratigraphic frame. Maximum flooding intervals occurred in the early to middle Tremadocian, middle Darriwilian and middle to late Katian. Two events interfered with an overall long-term transgressive trend. The ‘intra-Arenig’ (late Floian?) tectonic event highlighted palaeohighs coinciding with Paleoproterozoic basements. Gondwanan drainage basins were reorganized, which had an impact on sediment sourcing and distribution of detrital material (e.g. zircons) feeding the pre-Variscan Europe. The second event is the end-Ordovician glaciation. The domain supported the greatest part of the Hirnantian glaciers and may also have preserved pre-Hirnantian glacial archives. It is not until the very latest Ordovician that offshore conditions developed far inland; it is however suspected that this inundation benefited from a transient postglacial isostatic flexure.

The Late Cretaceous period records a pronounced decrease in marine temperatures at a global scale initiating the last greenhouse-icehouse transition, whose origin still remains enigmatic. Continental weathering represents a major sink of atmospheric CO2 through silicate weathering reactions yet the importance of this process in the Late Cretaceous cooling has only been scarcely explored.In this study we explore the impact of the eastern South American margin uplift, concomitant to the long-term Late Cretaceous cooling, on the evolution of chemical weathering of the Brazilian margin, using a new proxy of silicate weathering based on the coupled Lu-Hf and Sm-Nd isotope systems in clays. This proxy, expressed as ΔεHf, has been recently calibrated in modern environments (Bayon et al., 2016) but has only been scarcely applied to deep-time environments. This proxy, applied on sediments from DSDP site 356 on the São Paulo Plateau, highlights a marked increase in silicate chemical weathering of the southeastern Brazilian margin from the Santonian to the Maastrichtian, also supported by the evolution of the chemical index of alteration (CIA) and clay mineralogy.This increase follows an episode of enhanced mechanical erosion of the margin revealed in the Turonian to Santonian by an increase of primary clay mineral (illite, chlorite) and Ti/Al ratio, linked to the tectonic uplift of the margin. Clay mineral assemblages additionally point to an evolution of local climatic conditions from arid to a more hydrolysing climate following this episode, that we link to a “rain shadow effect” affecting the eastern side of the newly formed relief that would have enhanced chemical weathering of the margin.Importantly the temporal coincidence of the increase in chemical weathering depicted here with the marked acceleration of the global cooling recorded worldwide during the Campanian points to a potentially important role of this process on the overall climate decline initiating the descent into our icehouse climate mode. Although records from additional sites are needed to establish the spatial extent of the margin affected by this process, our new dataset brings new insights about the impact of tectonic forcing on climate.Bayon et al. (2016) EPSL 438, p. 25-36.

Over million-year timescale the carbon cycle evolution is driven by mantle CO2 degassing (source) and by continental weathering that drawdowns atmospheric CO2 through silicate weathering reactions (sink). Based on a novel geochemical proxy of chemical weathering intensity (i.e. using measurements of Hf and Nd isotope ratios in clay-size fractions of sediments) and clay mineralogy, we discuss the links between tectonic, continental weathering and climate evolution during the late Cretaceous. That period records the very first step of the last greenhouse to icehouse transition and is concomitant to major uplift phases affecting the African and South-American margins.Two sites along the South American Atlantic margin (ODP 356 and 1259) were targeted based on their relatively complete record of upper Cretaceous sediments. At Site 356, our results indicate the occurrence of enhanced chemical weathering during the Campanian and Maastrichtian following the uplift of the Southeastern Brazilian margin that promoted the establishment of more hydrolysing conditions.At Demerara Rise (Site 1259), our data suggest a coupling between physical erosion and chemical weathering, which may be explained in this area by the presence of persistent hydrolysing conditions typical of equatorial climate and reduced tectonic activity. From the Turonian to the early Campanian, i.e. a period of relative tectonic quiescence, our data suggest that climate was likely the main driver controlling the evolution of chemical weathering intensity. By contrast, from the middle Campanian to Maastrichtian, we propose that mountain uplift, although moderate, induced a marked increase in chemical weathering intensity.Together, this new data acquired at two 2 sites that encountered different regional climatic, geologic and tectonic conditions suggest that chemical weathering markedly intensified during the late Cretaceous and likely acted as a major sink for atmospheric CO2. While the onset of weathering increase at both sites appear to postdate the initiation of global temperature decrease, we suggest here that this process could have participated to accelerating or maintaining colder climate conditions at that time. Key Words: late Cretaceous – paleoclimate – weathering – uplift - clay mineralogy – Hf-Nd isotope

Continental weathering is a major sink of atmospheric CO2 over long time scale (> 1Ma) through CO2 consumption during chemical weathering of silicate minerals. Yet the importance of this process in climate evolution remains debated. The Late Cretaceous period records a pronounced decrease in temperatures at a global scale between 90 and 65 million years, that marks the first step of the progressive climatic decline leading to our modern climate. This cooling is concomitant to a major tectonic uplift of the African and South American continents (Friedrich et al., 2012; Gallagher et al., 1999).The main objective of this work is to bring new constraints on the links between tectonic, weathering and climate processes, in order to explore the potentially determinant impact of this tectonic uplift on the late Cretaceous long-term cooling. We use here a new proxy of silicate weathering, based on the coupled Lu-Hf and Sm-Nd isotope systems in clays. This proxy has been recently calibrated in modern environments (Bayon et al., 2016) but has only been scarcely applied to deep-time environments. This approach was coupled to clay mineralogy, assessing the evolution of the intensity of physical erosion linked to the uplift. In this study, these coupled weathering and erosion proxies have been applied on clays recovered from DSDP site 356 (Brazil margin).A change in detrital clay material is recorded at the Santonian-Campanian transition (83.6 Ma), characterized by a decrease in primary clay minerals (illite, chlorite) proportions and an increase of smectite. We interpret this change as reflecting an increase in chemical weathering forming pedogenic smectites, which would have followed an episode of intense mechanical erosion from the Turonian to the Santonian. Enhanced chemical weathering, lasting until the Maastrichtian, was likely associated to locally increased hydrolysing conditions, that would be consistent with the observed decrease in palygorskite proportions, a clay mineral commonly formed in arid conditions.We interpret the ɛNd decrease observed (at 87 Ma) as reflecting a change of sources with a possibly decreasing contribution of basalts from the Parana-Etendeka traps associated to an increasing contribution of old crustal material. ΔɛHf values, which represents the deviation of the sample’s ɛHf compared to the clay array (Bayon et al., 2016), highlight a marked increase in the intensity of chemical weathering at the transition between the Santonian and the Campanian, that is coherent with the concomitant evolution of clay mineral assemblages.Our new results point to the existence of a relatively arid local climate in the Turonian to Santonian interval, which would have favoured the physical disaggregation of rocks during the uplift of the Brazilian margin. The new relief would thereafter have favoured, from the Campanian onward, locally enhanced precipitations and more hydrolysing conditions, and thus intensified chemical weathering. In the context of the Brazilian margin, the observed chemical weathering increase would then represent the consequence of the active uplift.Bayon et al. (2016) EPSL 438, p. 25-36.Friedrich et al. (2012) GSA 40(2), p. 107-110.Gallagher and Brown (1999) Geol. Soc. Londond Sepc. Pub 153(1), p.41-53

Paola Movalli et al., European Raptor Biomonitoring Facility COST Action (CA16224) is supported by COST (European Cooperation in Science and Technology) and funded by the Horizon 2020 Framework Programme of the European Union. Life APEX is financed by the European Union through the program LIFE17ENV/SK/000355‘Systematic use ofcontaminant data from apex predators and their prey in chemicals management’.

25 pages; International audience; The Franceville Basin (2100–2000 Ma) has been widely studied for its uranium deposits most of which are located close to the major faults at the transition from the FA to FB (FB1, FB2a and FB2b) Formations. These formations deposited during the Paleoproterozoic and represents volcano-sedimentary series. Well-preserved outcrops may be found in quarries (i.e. Oklo, Mikouloungou and Socoba) and along roads and railways’ track (i.e. M’vengue). Our study identifies footwall anticlines and hangingwall forced synsedimentary synclines (i.e. progressive unconformities) associated with a NW–SE trending longitudinal normal faults. It also contributes to the identification of main (MPB) and secondary permeability barriers (SPB) promoting fluid-pressure at the FA–FB1 and FB2a–FB2b stratigraphic transitions. Multiscale and multidisciplinary approaches of outcrop studies allowed to describe synlithification and postlithification fluid-pressure related structures. Synlithification faults in Oklo quarry and sand injectites at M’vengue underlined the former structuration, while quartz veins and stylolites observed in Socoba quarry are associated with a postlithification stage. The observation from outcrop to centimeter scales of intraformational breccia reworked during postlithification extensional episodes (i.e. quartz veins and stylolites) close to synsedimentary faults at Oklo and Mikouloungou suggest a near-surface postlithification deformation model (i.e. chemical compaction). We propose a possible reconstruction model of fluid-pressure structuration at the basin scale. Solid bitumen and associated uranium ores are restricted to fluid-pressure structures related to hydraulic fracturing induced by oil migration. They are spatially restricted by permeability barriers within footwall forced anticlines.

Sediments deposited from the Permian–Triassic boundary (~252 Ma) until the end-Smithian (Early Triassic;c.250.7 Ma) in the Sonoma Foreland Basin show marked thickness variations between its southern (up toc.250 m thick) and northern (up toc.550 m thick) parts. This basin formed as a flexural response to the emplacement of the Golconda Allochthon during the Sonoma orogeny. Using a high-resolution backstripping approach, a numerical model and sediment thickness to obtain a quantitative subsidence analysis, we discuss the controlling factor(s) responsible for spatial variations in thickness. We show that sedimentary overload is not sufficient to explain the significant discrepancy observed in the sedimentary record of the basin. We argue that the inherited rheological properties of the basement terranes and spatial heterogeneity of the allochthon are of paramount importance in controlling the subsidence and thickness spatial distribution across the Sonoma Foreland Basin.

The Paleozoic intracratonic North African Platform is characterized by an association of arches (ridges, domes, swells or paleo-highs) and low subsidence rate syncline basins of different wavelengths (75–620 km). The structural framework of the platform results from the accretion of Archean and Proterozoic terranes during the Pan-African orogeny (750–580 Ma). The Ahnet and Mouydir basins are successively delimited from east to west by the Amguid El Biod, Arak-Foum Belrem, and Azzel Matti arches, bounded by inherited Precambrian sub-vertical fault systems which were repeatedly reactivated or inverted during the Paleozoic. Major unconformities are related to several tectonic events such as the Cambrian–Ordovician extension, Ordovician–Silurian glacial rebound, Silurian–Devonian “Caledonian” extension/compression, late Devonian extension/compression, and “Hercynian” compression. The deposits associated with these arches and syncline basins exhibit thickness variations and facies changes ranging from continental to marine environments. The arches are characterized by thin amalgamated deposits with condensed and erosional surfaces, whereas the syncline basins exhibit thicker and well-preserved successions. In addition, the vertical facies succession evolves from thin Silurian to Givetian deposits into thick Upper Devonian sediments. Synsedimentary deformations are evidenced by wedges, truncations, and divergent onlaps. Locally, deformation is characterized by near-vertical planar normal faults responsible for horst and graben structuring associated with folding during the Cambrian–Ordovician–Silurian period. These structures may have been inverted or activated during the Devonian compression and the Carboniferous. The sedimentary infilling pattern and the nature of deformation result from the slow Paleozoic reactivation of Precambrian terranes bounded by vertical lithospheric fault zones. Alternating periods of tectonic quiescence and low-rate subsidence acceleration associated with extension and local inversion tectonics correspond to a succession of Paleozoic geodynamic events (i.e. far-field orogenic belt, glaciation).

21 pages; International audience; New clay mineralogical analyses have been performed on Campanian sediments from the Tethyan and Boreal realms along a palaeolatitudinal transect from 45° to 20°N (Danish Basin, North Sea, Paris Basin, Mons Basin, Aquitaine Basin, Umbria-Marche Basin and Tunisian Atlas). Significant terrigenous inputs are evidenced by increasing proportions of detrital clay minerals such as illite, kaolinite and chlorite at various levels in the mid- to upper Campanian, while smectitic minerals predominate and represented the background of the Late Cretaceous clay sedimentation. Our new results highlight a distinct latitudinal distribution of clay minerals, with the occurrence of kaolinite in southern sections and an almost total absence of this mineral in northern areas. This latitudinal trend points to an at least partial climatic control on clay mineral sedimentation, with a humid zone developed between 20° and 35°N. The association and co-evolution of illite, chlorite and kaolinite in most sections suggest a reworking of these minerals from basement rocks weathered by hydrolysis, which we link to the formation of relief around the Tethys due to compression associated with incipient Tethyan closure. Diachronism in the occurrence of detrital minerals between sections, with detrital input starting earlier during the Santonian in the south than in the north, highlights the northward progression of the deformation related to the anticlockwise rotation of Africa. Increasing continental weathering and erosion, evidenced by our clay mineralogical data through the Campanian, may have resulted in enhanced CO2 consumption by silicate weathering, thereby contributing to Late Cretaceous climatic cooling.

The chapter is focused on ex situ geoheritage, i.e., to say on collections, and more specifically those hosted by museums. These objects have different status. They were collected for different purposes (e.g., scientific value, aesthetic appearance, archive significance) and therefore their use varies accordingly. Geoheritage collections disseminate knowledge, both for students and the general public. Acquisition policy is therefore guided by the preservation of a current state of nature, culture or mankind. Regarding acquisition, a new concern has arisen in the last years since science has been confronted by issues of land rights and rightful ownership. Acquisition policy has to conform with international conventions and the International Council of Museums Code of Ethics and needs to address two issues: the commercial value of geological samples and the political interest of governments.

25 pages; International audience; In the eastern part of the Moroccan Anti-Atlas Mountains, the Alnif area exposes a buried Ordovician glacial tunnel valley (5 km wide, 180 m deep) cut into preglacial marine sediments. The preglacial sedimentary sequence, deposited in a marine environment, is characterized by a typical "layer-cake" configuration of permeable (sand) and impermeable (clays and early-cemented sandstones) layers. At the base of the tunnel valley, a discontinuous and fan-shaped glacial conglomeratic unit 10 to 15 m thick occurs, erosively deposited over preglacial marine sediments. The conglomeratic unit is composed of preglacial intraclasts embedded within a sandy matrix. Both preglacial and glacial sediments display soft-sediment deformation structures related to fluctuating porewater pressure and strain rates, including ball structures, clastic dykes, fluted surfaces, turbate structures, folds and radial extensional normal faults. Kinematics and relative chronology of these deformation structures allow the role of porewater pressure in the process of tunnel valley genesis on soft beds to be understood. The tunnel valley formed through multi-phased episodes of intense hydrofracturing of the preglacial bed due to overpressure development promoted by ice sheet growth over the study area, and configuration of the substratum. Transport of the resulting conglomerate composed of preglacial intraclasts and fluidized sand occurred through subglacial pipes. The brecciated material is deposited in subglacial cavities, forming fans of massive sandy conglomerate infilling the base of the tunnel valley. The conglomeratic unit is partially reworked by meltwater and exhibits intense softsediment deformations, due to episodes of ice-bed coupling and decoupling.

A pit located near Ballyhorsey, 28 km south of Dublin (eastern Ireland), displays subglacially deposited glaciofluvial sediments passing upwards into proglacial subaqueous ice-contact fan deposits. The coexistence of these two different depositional environments at the same location will help with differentiation between two very similar and easily confused glacial lithofacies. The lowermost sediments show aggrading subglacial deposits indicating a constrained accommodation space, mainly controlled by the position of an overlying ice roof during ice-bed decoupling. These sediments are characterized by vertically stacked tills with large lenses of tabular to channelized sorted sediments. The sorted sediments consist of fine-grained laminated facies, cross-laminated sand and channelized gravels, and are interpreted as subglaciofluvial sediments deposited within a subglacial de-coupled space. The subglaciofluvial sequence is characterized by glaciotectonic deformation structures within discrete beds, triggered by fluid overpressure and shear stress during episodes of ice/bed recoupling (clastic dykes and folds). The upper deposits correspond to the deposition of successive hyperpycnal flows in a proximal proglacial lake, forming a thick sedimentary wedge erosively overlying the subglacial deposits. Gravel facies and large-scale trough bedding sand are observed within this proximal wedge, while normally graded sand beds with developed bedforms are observed further downflow. The building of the prograding ice-contact subaqueous fan implies an unrestricted accommodation space and is associated with deformation structures related to gravity destabilization during fan spreading (normal faults). This study facilitates the recognition of subglacial/submarginal depositional environments formed, in part, during localized ice/bed coupling episodes in the sedimentary record. The sedimentary sequence exposed in Ballyhorsey permits characterization of the temporal framework of meltwater production during deglaciation, the impact on the subglacial drainage system and the consequences on the Irish Sea Ice Stream flow mechanisms.

This paper presents the sedimentary analysis of an exceptional Ordovician glacial tunnel valley in the eastern part of the Anti-Atlas. The valley infill comprises two major glacial erosion surfaces (striated pavements) each overlain by a fining-upward glacial unit. These units are composed of five distinct facies associations, recording the evolution from subglacial to proglacial environments, and an additional sixth facies association, overtopping the tunnel valley infill, and associated with post-glacial environments. The tunnel valley infill also records a transitional environment between the subglacial and proglacial settings, which is compared with the Antarctic ice-sheet margin. These three environments are defined by the position of the grounding line and the coupling line. The new proposed depositional model also differs from usual Ordovician depositional models in which the main tunnel valley infill is interpreted as essentially proglacial outwash deposits, in a range of glaciomarine to glaciofluvial environments. Overall, a substantial part of the valley infill (~ 50% of volume) was deposited in a subglacial setting. The sedimentary bodies could form potentially thick and laterally extended, although these were limited by the shape and extent of the subglacial accommodation space. Finally, the sedimentary record, when compared with regional analogues, also provides information for the palaeogeographic reconstruction of the Ordovician ice-sheet in this region.

International audience; The Sonoma Foreland Basin was formed as a flexural response to the emplacement of the Golconda Allochthon during the Sonoma Orogeny around the Permian/Triassic boundary (~252 Ma), and it includes an excellent fossil and sedimentary record of the Early Triassic. However, sediments deposited from the Permian/Triassic boundary until the end-Smithian (~250.7 Ma) shows marked thickness variations between its southern (up to ~200 m thick) and northern (up to ~550 m thick) parts. Differences in dominant lithologies can also be noticed throughout the basin, with mostly terrigenous sandstones and microbial limestones in the southern part while the northern part is dominantly composed of fine siltstones and carbonates. Based on an integrated study within a high-resolution timeframe and using georeferenced data from sedimentological, paleontological, structural and cartographic approaches, we propose to discuss the controlling factor(s) responsible for spatial variations in sedimentary thickness. Regional palinspastic reconstruction and high time-resolution subsidence analyses are thus conducted to obtain an accurate image of the basin by the time of the deposition. We notably show that sedimentary overload in the basin and heterogeneity of the topographic load exerted by the Golconda Allochthon, when emplaced, are not sufficient to explain the significant discrepancy observed within the Early Triassic sedimentary record. We therefore argue that the age and thus, the rheological properties of the terranes that compose the basin basement are of paramount importance in controlling both the subsidence and thickness spatial distribution across the Sonoma Foreland Basin.

20 pages; International audience; Neodymium isotopic compositions (εNd) have been largely used for the last fifty years as a tracer of past ocean circulation, and more intensively during the last decade to investigate ocean circulation during the Cretaceous period. Despite a growing set of data, circulation patterns still remain unclear during this period. In particular, the identification of the deep-water masses and their spatial extension within the different oceanic basins are poorly constrained. In this study we present new deep-water εNd data inferred from the Nd isotope composition of fish remains and Fe–Mn oxyhydroxide coatings on foraminifera tests, along with new εNd data of residual (partly detrital) fraction recovered from DSDP Sites 152 (Nicaraguan Rise), 258 (Naturaliste Plateau), 323 (Bellinghausen Abyssal Plain), and ODP Sites 690 (Maud Rise) and 700 (East Georgia Basin, South Atlantic). The presence of abundant authigenic minerals in the sediments at Sites 152 and 690 detected by XRD analyses may explain both middle rare earth element enrichments in the spectra of the residual fraction and the evolution of residual fraction εNd that mirror that of the bottom waters at the two sites. The results point towards a close correspondence between the bottom water εNd values of Sites 258 and 700 from the late Turonian to the Santonian. Since the deep-water Nd isotope values at these two sites are also similar to those at other proto-Indian sites, we propose the existence of a common intermediate to deep-water mass as early as the mid-Cretaceous. The water mass would have extended from the central part of the South Atlantic to the eastern part of proto-Indian ocean sites, beyond the Kerguelen Plateau. Furthermore, data from south and north of the Rio Grande Rise–Walvis Ridge complex (Sites 700 and 530) are indistinguishable from the Turonian to Campanian, suggesting a common water mass since the Turonian at least. This view is supported by a reconstruction of the Rio Grande Rise–Walvis Ridge complex during the Turonian, highlighting the likely existence of a deep breach between the Rio Grande Rise and the proto-Walvis Ridge at that time. Thus deep-water circulation may have been possible between the different austral basins as early as the Turonian, despite the presence of potential oceanic barriers. Comparison of new seawater and residue εNd data on Nicaraguan Rise suggests a westward circulation of intermediate waters through the Caribbean Seaway during the Maastrichtian and Palaeocene from the North Atlantic to the Pacific. This westward circulation reduced the Pacific water influence in the Atlantic, and was likely responsible for more uniform, less radiogenic εNd values in the North Atlantic after 80 Ma. Additionally, our data document an increasing trend observed in several oceanic basins during the Maastrichtian and the Palaeocene, which is more pronounced in the North Pacific. Although the origin of this increase still remains unclear, it might be explained by an increase in the contribution of radiogenic material to upper ocean waters in the northern Pacific. By sinking to depth, these waters may have redistributed to some extent more radiogenic signatures to other ocean basins through deep-water exchanges.

Subglacial meltwater drainage and sedimentary processes play a major role in ice-sheet dynamic but there is a lack of study of subglacial environment because modern ice-sheet beds remain inaccessible. Previous authors already intended to provide diagnostic criterion and recent investigations suggest that fluid pressure variations are a key factor in subglacial environment. This paper investigated the late Devensian sedimentary record in order to describe subglacial sedimentological facies associations and deformation features related to fluid overpressures. We used an integrated approach, based on stratigraphy, sedimentology and deformations styles to demonstrate a subglacial depositional model. The studied interval is composed of stratified gravel and sand interbedded with diamicton and boulder pavement, deposited in depressions formed by irregularity of the upper surface of diamicton. Deformation structures include convolutes, dykes and normal micro-faulting. Dykes show different dip directions from vertical, oblique to subhorizontal from which both directions of shortening and extension can be determined. Vertical dykes are formed under pure shear strain related to ice weight only. Oblique dykes imply both ice-bed coupling and simple shear strain between ice and substrate induced by flowing ice related to progressively increasing meltwater drainage intensity. Horizontal dykes are formed when minimum strain is vertical and therefore the overpressure exceeds the weight of overburden. They are associated with high meltwater drainage intensity and ice-bed uncoupling and refer to hydrofracturing. Overall, depositional and deformation sequence also illustrates the increasing intensity of meltwater drainage in small cavity as high energy channelised deposits, and in large cavities where subaqueous fan are deposited under hydraulic jump conditions. Moreover, large cavities represent lee-side cavities formed by fast-flowing ice over an obstacle. Hydrofracturing is likely to occur when a dense fluid, potentially associated with catastrophic drainage of an upstream cavity enters the low-pressure confined environment of a downstream cavity and is injected under pressure in the soft substrate. The studied glacial sequence represents a regional pattern probably related to an allocyclic control on sedimentation linked to long-term glacial dynamics rather than local depositional conditions. Based on these results, we provided a synthetic model linking depositional and deformation processes during ice-sheet growth and decay, but also valid at different timescales from annual to seasonal scale.

The Djado Basin (Niger) was located beneath the inner part of the Late Ordovician ice sheet. The Felar-Felar Formation consists mainly of glaciomarine deposits, associated with the major ice sheet recession within the glaciation, and is bounded by two glacial unconformities. Structures corresponding to sandstone ridges are found within the Felar-Felar Formation. Sandstone ridges are several metres high, about 10 m wide and hundreds of metres long. These structures are organized in extensive anastomosed to subpolygonal networks. The association of sandstone ridge networks with the later glacial unconformity and with other glacial evidence suggests sub-glacial conditions for their origin. Sandstone ridge sedimentological characteristics indicate that sandstone ridges result from the scouring of the Felar-Felar Formation by sub-glacial, turbulent and pressurized meltwater; then subglacial cavities were infilled with sand derived from glacial abrasion. Sandstone ridge networks are comparable with tunnel channels and document unusual drainage structures of the inner part of the palaeo-ice sheet.

18 pages; International audience; Soft-sediment deformation structures are being increasingly used as a tool for reconstructing palaeoenvironments and porewater pressure conditions in glacial settings. However, the potential of hydrofractures and clastic injections in the reconstruction of ice dynamics remains poorly constrained. This paper presents the results of a detailed study of a clastic injection network outcropping in the Sólheimajökull forefield (South Iceland). Sedimentological descriptions are combined with microscopic to macroscopic analyses of clastic injection geometries, sediment-fills, and cross-cutting relationships. The 250 m long and 20 m high exposure observed along the east flank of the proglacial braid plain displays alternating glaciofluvial sediments and subglacial tills, illustrating oscillations of the ice margins. These sediments are cross-cut by a dense network of injection composed of dykes propagating upward or downward, sills, and stepped sills. These clastic injections result from processes of hydrofracturing and the sediment-fills in these hydrofractures are generally laminated with an increase of grain-size towards the centre of the injections. These fracture-fill characteristics suggest multiple injection phases within the hydrofractures and an increase of porewater pressure over time. Five main generations of clastic injections showing different senses of propagation and dip directions are determined and are interpreted as forming in different environments. Per descensum clastic dykes dipping down ice demonstrate subglacial hydrofracturing underneath flowing-ice, while sills and per ascensum clastic dykes form in submarginal to marginal environments due to the decrease of ice overburden pressure. The integration of these results with the sedimentological characteristics allows the Holocene ice front oscillations of the Sólheimajökull to be reconstructed. This study demonstrates the importance of hydrofracture systems and their sediment-fills in the reconstruction of palaeo-ice dynamics.

27 pages; International audience; This study discusses the characteristics of two Lower Cretaceous injectite networks in the Vocontian Basin (SE France) using combined structural, sedimentary, diagenetic, and petrophysical analyses. Internal structures, at both the macro- and micro-scale, and diagenetic phases characterising these injectite networks have been described. Simultaneously, precementation porosity values were estimated and parameters controlling the geographical distributions of these values were analysed and statistically tested. All of the data were integrated so as to reconstruct the spatial evolution of the porosity from the time of injection to modern times through five major phases. (1) The injection of fluidised sand into hydrofractures combined with high porewater pressure results in high porosity (up to 53%) where injectite thickness and distance to the parent beds exert a primary control. (2) Early deformational imprints, including elutriation structures and cataclastic deformation bands, cause a reduction in the localised porosity. (3) At low burial depths, the intruded sand becomes pervasively cemented by carbonate and is associated with a drastic decrease in porosity (

A re-interpretation of the deep structure of the High Atlas is presented through integration of geophysical and geological data, highlighting the architectural significance of the southern Tethys palaeomargin. Previous crustal models suggest the occurrence of a flat intra-crustal detachment at a depth of � 20 km, a zone where surface thrusts merge and below which the lower High Atlas crust appears continuous. However, within this study seismic refraction data, electrical resistivity surveys and gravity modelling all appear to detect a jump in crustal thickness between the High Atlas and the northern plains. We interpret these data as penetration by thrusts within the ‘‘South-Atlasic fault’’ zone through the lower crust to offset the Moho in accordance with a ‘‘deep-rooted thick skinned tectonic model’’. The ‘‘South-Atlasic fault’’ zone corresponds to a series of crustal-scale structures inherited from a series earlier orogenic events (Pan-African, Hercynian and Atlasic) and thus is sufficiently weak to create separate crustal blocks in the northern part of the stable African plate. This structural configuration was achieved during Cenozoic plate collision between Africa and Europe culminating in tectonic inversion of Mesozoic extensional basins, linked to the development of Tethys and opening of the Atlantic. The inherited structures typically comprise normal faults and tilted blocks affecting the upper crust, and crustal-scale detachments affecting the lower crust. 2006 Elsevier Ltd. All rights reserved.

When a mineral is included in another, the pressure on the two is the same. As pressure and temperature then change, the pressure on the inclusion is likely to become increasingly different to the pressure on its host as a consequence of the two minerals having different equations of state (i.e. pressure–volume–temperature P – V – T relationships). Under some limiting assumptions, including that the host behaves elastically, it is simple to calculate the under- or overpressure experienced by an inclusion along the PT path the host follows. By focussing diagrammatically on V , the natural variable, rather than the normally used conjugate variable, P , we represent the consequences of inclusion for arbitrary PT paths, giving the under- or overpressure as well as the equilibrium reaction progress if reaction in the inclusion is involved.

In the Pointe Geologie area (66°40 S; 140°00 E; Terre Adelie, East Antarctica), the Paleoproterozoic basement consists in a migmatitic complex of metasedimentary origin. Metasediments underwent a thermal event, leading to the high-grade amphibolite facies assemblages biotite–cordierite–sillimanite and to dehydration melting reactions at 4–6 kbar and 700±50 °C, followed by retrogression in greenschist facies. In most of the archipelago, K-feldspar gneisses (KFG) are characterized by a Sil+Crd+Kfs+Bt assemblage and many K-feldspar-rich leucosomes. Locally, a spectacular rock type occurs as North dipping bands of about 10 m thick and consists in nodular gneisses (NG) that display less abundant, K-feldspar-poor leucosomes. Commonly, the retrograde imprint facies is quite weak in KFG and only expressed by sporadic Bt–Ms±And equilibrium assemblage, whereas it developed more extensively in NG. A pseudosection calculated at constant P=4 kbar shows that the differences between NG and KFG assemblages can be considered to be mainly driven by difference in H2O proportions and much less by differences in FeO/MgO or K2O/MgO ratios. The hydrated assemblage (Bt–Ms nodules) in NG requires at least 10–20% more H2O than the Crd+Kfs+Sil/And assemblage does in KFG. Parageneses and mineral compositions indicate that this difference in H2O occurred early in the history, at least as early as the anatectic stage. Therefore, differences between NG and KFG are related to the variation in partial melting features (water distribution, proportion of melt extraction), which appears to be spatially controlled by cryptic tectonic structures. The particular shape and orientation of NG bands are interpreted as a complex history of melt extraction in the Pointe Geologie area which could involve a two stage melting process.

Dans l'utilisation des equilibres calcules impliquant les mineraux necessaires pour comprendre les processus metamorphiques, il y a des choix naturels des axes a utiliser pour construire les diagrammes de phases, dependant des suppositions faites a propos des processus importants dans les roches. Les variables thermodynamiques se presentent en paires conjuguees, l'un etant intensif, et l'autre, extensif, et le choix naturel a faire depend de quelle paire mene a un trace evolutif des processus metamorphiques qui soit le plus facile a visualiser. Un choix non naturel mene a un diagramme pour lequel les traces ne sont pas evidents de facon intuitive, et un tel diagramme doit en general etre calcule. Nous illustrons les concepts liant les paires conjuguees en utilisant les equilibres portant sur les mineraux typiques du facies amphibolite a granulite, calcules pour une composition representative d'une pelite alumineuse en termes du systeme Na 2 O-CaO-K 2 O-FeO-MgO-Al 2 O 3 -SiO 2 -H 2 O (NCKFMASH). Nous examinons tout particulierement les paires conjuguees pression-volume et teneur en H 2 O-aH 2 O (i.e., la paire H 2 O-μ H 2 O ). Les diagrammes P-T versus V-T et T-M H 2 O versus T-a H 2 O servent a evaluer les processus metamorphiques. Nous montrons que la variable la moins evidente, par exemple V plutot que P, peut etre plus utile dans certaines situations, generalement transitoires.

Many thermodynamic calculations relating to metamorphic rocks hinge on the thermodynamic parameters of garnet. Though some models are widely used, it is not clear whether their underlying premise is correct: that a single set of equations can be written for the activities of the end-members of garnet covering the whole compositional range. A voluminous body of data can be used to constrain the thermodynamics of garnet, namely Fe–Mg exchange experimental data involving garnet and another mineral, particularly clinopyroxene, orthopyroxene and olivine. However, examination of these data reveals inconsistencies, apparently stemming from differences between the thermodynamics of low-Ca and high-Ca garnets, with a boundary of about XgCa= 0.15. In the two regions, for the high P–T of the experimental data, the thermodynamics follow the regular model, with values for the interaction parameters in the low Ca region of about wgFeMg= 50R and waFe–wgMgCa=– 1300R, in which R is the gas constant, and in the high Ca region of about wgFeMg= 1100R and wgCaFe–wgMgCa=– 2200R. Using the subregular, rather than the regular, model does not remove the discrepancy. The cause of the discrepancy needs to be identified if reliable calculations on rocks are to be made.

In the Hlinsko region (Variscan Bohemian Massif, Czech Republic) a major extensional shear zone separates low-grade metasedimentary series (Hlinsko schists) and high-grade rocks of the Moldanubian terrane (Svratka Crystalline Unit). During late-Variscan extension, a tonalite intruded syntectonically into the normal ductile shear zone, and caused contact metamorphism of the overlying schists. Concurrent syntectonic sedimentation of a flysch series took place at the top of the hangingwall schists. In order to decipher the detailed petrological evolution of the Hlinsko unit situated in the hangingwall of this tectonic contact, a phase diagram approach and pctrogenetic grids, calculated with the thermocalc computer program, were used. The crystallization/deformation relationships and the paragenetic analysis of the Hlinsko schists define a P-T path with an initial minor increase in pressure followed by cooling. Calculated pseudosections constrain this anticlockwise P-T evolution to the upper part of the andalusite field between 0.36 and 0.40 GPa for temperatures ranging from 570 to 530 -C. A low uHZ0 is required to explain the presence of andalusite-biotite-bearing assemblages, and could be related to the presence of abundant graphite. In contrast, the footwall rocks of the Svratka Crystalline Unit record decompression from around 0.8 GPa at a relatively constant temperature, followed by cooling. Thus, the footwall and the hangingwall units display opposite, but convergent P-Thistories. Decompression in the footwall rocks is related to a rapid exhumation. We propose that the inverse, anticlockwise P-T path recorded in the hangingwall pelites is related to the rapid, extension-controlled sedimentation of the overlying flysch series.

Three historical ‘asteriated’ diamond slices present mixed-habit growth with contemporaneous lobe-shaped cuboid sectors and octahedral sectors. The lobe shape is explained by continuous variation of the relative growth rates. Nitrogen concentration in octahedral sectors is higher than in cuboid sectors, whereas hydrogen is incorporated mostly in cuboid sectors. The H-related IR peak at 3236 cm−1 peak, and the two peaks at 3050 and 3154 cm−1 (which may be completely absent from the spectra) are independent from the well-known 1405–3107 cm−1 system. Nitrogen aggregation during thermal history seems partially inhibited in cuboid sectors by the large amount of hydrogen, as platelets and N3 centres are present in octahedral sectors but not in cuboid sectors. Cuboid, H-rich growth sectors are thought to appear when the amount of hydrogen in the medium is too high to be incorporated in the octahedral sectors only. The definition of ‘H-rich diamonds’ is revisited. The first-order Raman peak at 1332 cm−1 is slightly growth-sector dependent; cuboid sectors show a sharper and more Lorentzian peak than octahedral sectors.

Corundum + quartz as an assemblage has been reported in a limited number of high to ultra-high grade metamorphic terrains. It is worth noting that rocks hosting this unusual assemblage have common features with respect to mineral assemblages, textures, metamorphic conditions and geological environments. In addition to corundum and quartz, these rocks are characterised by variable amounts of magnetite, spinel, ilmenite together with rutile and sillimanite/kyanite in Fe-rich rocks; and sapphirine, orthopyroxene, garnet and cordierite in more Mg-rich rocks. These rocks are characterised in general by (i) coarse-grained texture with inclusions of corundum and spinel in magnetite, (ii) sharp contact between corundum and quartz and/or separated by a thin rim of sillimanite or kyanite between these two minerals, (iii) presence of spinel + quartz, sapphirine + quartz in equilibrium as well as osumilite. Although there has been some discussions in the past concerning whether “corundum + quartz” assemblage represents a “thermodynamic” stable or metastable assemblage, it is clear that this assemblage observed mainly in the magnetite-ilmenite-spinel bearing rocks is “texturally” stable. On the basis of the available experimental and thermodynamic data as well as natural occurrences, we conclude that this assemblage is consistent with ultra-high temperature metamorphic environments (up to 1100°C at pressure of 7 to 12 kbars). Therefore, its presence in natural rocks should draw close attention from field metamorphic petrologists working on deep crustal processes.

Displacement rates of normal faults deduced from stratigraphic data are often unreliable. Here we calculate the velocity of motion on a normal fault from the variations in accommodation potential on both sides of the fault within a highresolution time-frame established by biostratigraphy and physical stratigraphy. Our example is the Ornon normal fault bounding the Early Jurassic Bourg-d’Oisans Basin formed during Tethyan rifting. We show that motion on the fault was discontinuous when examined at high resolution and over a long time interval. During a first interval (Hettangian to Sinemurian Arietites bucklandi zone) a low rate of displacement (= 202–423 m Myr -1 ) coeval with diffused extensional deformation throughout the sedimentary basin is observed. A second interval of localized deformation (Early Sinemurian Caenisites turneri zone) is characterized by higher rates of displacement on the fault (1846 m Myr -1 ). Our results concur with recent numerical models identifying the main stages of extensional deformation.

Historically, the Tuareg shield is divided into three parts bordered by mega-shear zones with the centre, the Central Polycyclic Hoggar, characterized byArchaean and Palaeoproterozoic lithologies. Nearly10 y ears ago, the Tuareg shield was shown to be composed of 23 displaced terranes (Geology22 (1994) 641) whose relationships were deciphered in A € i to the SE (Precambr. Res. 67 (1994) 59). The Polycyclic Central Hoggar terranes were characterized by the presence of well preserved Archaean/Palaeoproterozoic and Neoproterozoic lithologies. We show here that the terranes from Central Hoggar (Laouni, Azrou-n-Fad, Tefedest, Eg��e belonged to a single old passive margin, to which we gave the acronym name LATEA, which behaved as a craton during the Mesoproterozoic and the Early- Middle Neoproterozoic but was partlydestabilized and dissected during the Late Neoproterozoic as a consequence of its involvement as a passive margin in the Pan-African orogen. An earlyPan-African phase consisted of thrust sheets including garnet-bearing lithologies (eclogite, amphibolite, gneiss) that can be mapped and correlated in three LATEA terranes. In the Tin Begane area, P -T -t paths have been established from >15 kbar--790 � C (eclogite) to 4 kbar--500 � C (greenschist retrogression) through 12 kbar--830 � C (garnet amphibolite) and 8 kbar--700 � C (garnet gneiss), corresponding to the retrograde path of a Franciscan-type loop. Sm-Nd geochronology on minerals and laser ablation ICP-MS on garnet show the mobilityof REE, particularlyLREE, during the retrograde greenschist facies that affects, although slightly, some of these rocks. The amphibolite-facies metamorphism has been dated at 685 ± 19 Ma and the greenschist facies at 522 ± 27 Ma. During the thrust phase, the Archaean-Palaeoproterozoic basement was onlylocallyaffected bythe Pan- African tectonics. LATEA behaved as a craton. Other juvenile terranes were also thrust earlyonto LATEA: the Iskel island arc at � 850 Ma to the west of LATEA, the Serouenout terrane in the 700-620 Ma age range to the east. No subduction-related magmas have intruded LATEA during this epoch, which behaved as a passive margin. During the main Pan-African phase (625-580 Ma), LATEA was dissected bymega-shear zones that induced several hundreds km of relative displacement and allowed the emplacement of high-K calc-alkaline batholiths. Smaller movements continued till 525 Ma, accompanied bythe emplacement of subcircular plutons with alkaline affinity. Here is dated the Ounane granodiorite (624 ± 15 Ma; 87 Sr/ 86 Sri ¼ 0.70839 ± 0.00016; 6WR, MSWD ¼ 0.87) and the Tisselliline granite (552 ± 15 Ma; 87 Sr/ 86 Sri ¼ 0.7074 ± 0.0001; 5WR, MSWD ¼ 1.4). Nd isotopes indicate a preponderant Palaeoproterozoic crustal source for these two plutons: eNd ¼� 14 to )21 at 624 Ma and TDM ¼ 1650-2320 Ma for Ounane and eNd ¼� 13 to )15 at 555 Ma and TDM ¼ 1550-1720 Ma for Tisselliline. Our model links these intrusions to a linear lithospheric delamination along mega-shear zones, allowing the hot asthenosphere to rise, melt by adiabatic pressure release and inducing the melting of the Palaeoproterozoic and Archaean lower crust.

The Lower Paleozoic detrital succession of the half-graben Kandi Basin in West Africa (Niger-Benin) is about 600 m thick and rests unconformably on the Pan-African basement. Along the western edge of the basin, the base of the succession locally features large glacial fault-bounded paleovalleys. These valleys are filled by the lowermost continental deposits of the Were Formation characterized by massive diamictites with dropstones, and coarse to conglomeratic sandstones associated with large-scale channel structures and internal erosional truncations. The uppermost braided-river deposits of the Were Formation deposited across the entire basin are overlain by the Late Ordovician–Early Silurian storm and tidal sediments of the Kandi Formation, made up of hummocky cross-stratified sandstones and siltstones. Computer-aided analysis of the populations of synsedimentary to synlithification microfaults observed in the Late Ordovician to Early Silurian sediments shows evidence of extensional paleostress tensors with a N90°E to N100°E horizontal σ3 stress responsible for normal displacement along the Kandi Fault. The synsedimentary normal activation of this major fault, inherited from the Precambrian, controls the spatial arrangement of the glacial, braided-stream, storm to tidal, and offshore deposits as well as the deformation of the basin-fill into an asymmetric synsedimentary syncline associated with progressive unconformities. The characterization of glacial features and Late Ordovician deposits from the biostratigraphic distribution of traces of trilobites strongly supports the idea that the deposits of the Kandi Basin are contemporaneous with the melting of the wide ice sheet which overlay the Afro-Arabian Shield during Late Ordovician times. The successive deposits of the Were and Kandi Formations reflect a gradual change from tillites, through glaciofluvial outwash conglomerates (Wa Member), braided-stream sediments (Wb Member), and shoreface barrier sands (Ka Member), to offshore clays and sands (Kb Member). They correspond to reworked, glaciofluvial to marine facies laid down by the Late Ordovician glacial retreat. The Kandi Basin is therefore defined as a staging-post between the Late Ordovician––Early Silurian basins of the Sahara and those of South Africa.

The detailed 3D geometry of normal fault planes is described and analysed using datasets from outcrop studies (2D), seismic surveys (3D) and analogue models (4D). Different geometric configurations of simple isolated normal faults are studied by reference to processes of normal fault propagation. When a normal fault propagates without interacting with other fault zones, the entire border of the principal plane displays characteristic connected secondary structures. These secondary structures cause bifurcations of the principal fault terminations. The along-strike terminations of the principal plane display typical bifurcation configurations (‘ear geometry‘). The orientation of the bifurcations depends on the vertical direction of propagation (downwards and/or upwards). The along-dip terminations display en echelon secondary fault planes linked to the principal plane and are described as ‘lobate geometry’. A 3D genetic model of isolated normal fault geometry is proposed with a new general terminology for the secondary structures. When two isolated normal faults propagate towards each other and overlap, the two principal planes connect up via a relay fault. The resulting geometry is a longer fault exhibiting a characteristic undulation with two inactive branches.

18 pages; International audience; Several Ordovician tunnel valleys are exposed in the Moroccan Anti-Atlas Mountains, including the Alnif and the Foum Larjamme tunnel valleys, located 150 km away from each other. Sedimentological and deformational analyses of these two glacial troughs reveal that differing processes lead to their formations.The Alnif tunnel valley contains numerous deformation structures within sediments both below and above the main glacial erosion contact surface. Ball-structures and clastic dykes occur within preglacial sediments down to 35 m below glacial incisions while overlying glacial sediments contain fluted surfaces, clastic dykes, dewatering structures, folds and radial step normal faults. The characteristics of the Alnif tunnel valley can be explained by a porewater pressure-driven model of formation where the localized increase of basal shear stress and porewater pressure underneath subglacial deforming zones lead to the development of a dense hydrofracture network in the preglacial bed. These processes of hydraulic brecciation promoted subglacial remobilization of the preglacial material and contributed to the formation of the tunnel valley.The Foum Larjamme tunnel valley displays undisturbed preglacial sediments and few dewatering structures at the base of the glacial sedimentary infill which suggests relatively low porewater pressures within the tunnel valley during formation. This second type of tunnel valley where porewater pressure remained relatively low appears to have been formed by meltwater erosion. The undulating base of the Foum Larjamme tunnel valley implies progressive erosion by a stable subglacial braided network of Nye-channels, or alternatively by channels migrating laterally during episodic minor subglacial outbursts.These two tunnel valleys highlight the regional variability of processes involved in the formation of tunnel valleys. The distribution of palaeo-ice streams in North Africa illustrate that morphologies and processes involved in the formation of tunnel valleys vary between ice stream and inter-ice stream zones due to variations in meltwater availability, the topography and bed lithological properties.

Recent studies combining field data (facies and paleocurrent analyses, structural surveys), sub-surface data (core analyses, well logs, seismic sections) and palynological data provide insight into the sedimentary dynamics of pre-rift deposits of the interior basin of Gabon and their structural and paleoclimatic setting. These sedimentary deposits belong to the Noya, Agoula and M’vone series of Late Precambrian to Jurassic age. Although these deposits are potential sources of petroleum, they are partly known because of poor outcrop in a wet equatorial climate, low density and uneven distribution of exploration wells and poor seismic survey coverage. The pre-rift deposits reflect fluvial-lacustrine and glacial continental sedimentation, punctuated by many sedimentary gaps and episodes of erosion, and were affected by Late Precambrian extensional faulting indicated by NNE-SSW oriented tilted blocks. This Precambrian extensional faulting was reactivated during subsequent tectonic episodes, and most notably during the Early Cretaceous rifting phase.

The Ivory Coast-Ghana margin is a typical transform margin along which large-scale tectonism has been well documented. The Cretaceous sediments of the Ivory Coast-Ghana transform margin were subjected to numerous tectonic, gravitational, and hydrothermal forces during lithification. In this paper, we infer the order of occurrence of deformation regimes from characteristic deformations observed in samples of Ocean Drilling Program (ODP) Leg 159. Three main types of minor scale deformation are identified and characterized in terms of geometry, rheology, and kinematics: (1) extensional structures such as normal faults and irregular veins with angular, indented walls that are widely recorded at all ODP sites; (2) compressional structures that are confined to the marginal ridge of the Ivory Coast-Ghana transform margin and include reverse faults, folds, and vertical crenulation cleavage and (3) various types of shear zone at low angles with respect to bedding, which are continuous throughout the Cretaceous succession of the ridge. Structural analysis combined with thin section observation shows that most of these deformations occurred in water-rich sediments. The extensional, minor-scale structures are related to the Early Cretaceous rifting stage of the margin as characterized at regional scale by half-grabens and tilted blocks. The compressional structures observed in the samples are attributed to Turonian-Santonian positive inversion tectonics and related to the occurrence of large-scale flower structures and inverted extensional blocks. In contrast, the shear zones at low angles with respect to bedding observed throughout the Cretaceous series are linked to local gravity-induced tectonics.

The metamorphic series of Filali and the Beni Bousera massif represent the most metamorphic unit in the inner part of the Moroccan Rif. The Filali series is composed of micaschists, gneisses, migmatites and granulites wrapped around the ultramafic body of the Beni Bousera. The foliation is broadly coherent all over the massif although differences in lineation and fold axis have been found between the granulites and the micaschists-gneisses. Metamorphic grade increases continuously towards the ultramafic body; however, seven metamorphic zones which account for this increase can be defined: - chlorite zone: muscovite and chlorite underline the S1 schistosity refolded by S2. Small garnet is wrapped by or cut across S2; - chloritoid zone: chloritoid displays the same textures as chlorite and muscovite, underlining S1 and S2 schistosity. Chlorite reacts out to biotite; - staurolite+andalusite zone: staurolite, andalusite, cordierite and garnet have pre-, syn- and post- kinematic features with respect to S2. Garnet reacts out to muscovite, biotite and plagioclase; - staurolite+andalusite+kyanite zone: same textural relationships as in the previous zone. Kyanite is an additional phase, often displaying epitaxial textures with staurolite and andalusite; - andalusite+kyanite+sillimanite zone: fibrolitic sillimanite generally associated with biotite crystallizes from staurolite. However, sillimanite is also directly formed from andalusite and kyanite. As in the previous zone garnet reacts out to biotite, muscovite and plagioclase; - sillimanite+k-feldspar zone: muscovite reacts out to k-feldspar. Modes of biotite and sillimanite increase; - migmatites zone are composed by biotite, sillimanite, garnet, cordierite quartz and feldspars. Garnets do not display the reaction textures seen in the previous zones; - granulites are composed of a primary paragenesis with kyanite+k-feldspar+garnet+ or -biotite+plagioclase+rutile, partially obliterated by a secondary paragenesis with cordierite, sillimanite and spinel.

Novel palaeoenvironmental interpretations and high-resolution correlations in Oxfordian reefal formations (fig. 1, 2) are provided by genetic stratigraphy. The main objectives of this study are: (1) to determine environmental conditions and the zonation of depositional environments; (2) to propose a genetic sequence framework and correlations of the outcrop sections; (3) to evaluate a possible tectonic control on coral buildup settlement and growth both at local scale.

Structural analysis of extensional faults in the Mâconnais Hills shows that low-intensity extensional phenomena occurred back from the passive margin of the Ligurian Tethys, the axis of which lay some 400 km southeast of the study area in Mid-Jurassic times. Storm-induced rip current directions and coral lens positions suggest that the palaeotopography was maintained by early faulting.

In the Variscan Bohemian Massif (Czech Republic), no agreement has been reached on the nature of the relationship between the Tepla-Barrandian and the Moldanubian terranes. However, the Tepla-Barrandian is interpreted as a central segment separating the Moldanubian and Saxothuringian terranes and its position is therefore essential for any reconstruction of this part of the Variscan belt. Our petrological and structural study in the Domazlice-Klatovy region spans the boundary between the Tepla-Barrandian and Moldanubian terranes. There is no conformity of ductile structures in both domains near their interface and their P–T evolution is separate in time. The development of major structures and associated metamorphism in the southwestern part of the Barrandian was accompanied by syntectonic intrusions of granitoid and diorite bodies, dated at about 520 Ma. The Moldanubian migmatites are characterized by a LP-HT metamorphism that possibly took place at about 320 Ma. The metamorphic record of the Barrandian rocks shows no influence of the Moldanubian partial melting. The contacts are marked by semi-brittle to brittle structures: sinistral strike-slip faulting developed in the Central Bohemian Shear Zone, whereas the West Bohemian Shear Zone acted as a semi-brittle normal fault with a dextral component. Both shear zones may be nearly contemporaneous, accommodating a bulk N-S compression. The Central Bohemian Shear Zone was later reactivated in a dextral regime. Although timing is uncertain, the juxtaposition of both terranes took place probably in the waning stages of the Variscan orogeny, earlier than the late Stephanian. We argue that the late-orogenic (semi)brittle strike-slip tectonics modified considerably the face of the Bohemian Massif and the geodynamic models of the Bohemian Massif have to be reviewed with reference to this essential point.

Forty patients, scheduled for abdominal surgery, were randomized to receive postoperatively either a structured or a physical mixture of long-chain triacylglycerols/medium-chain triacylglycerols (LCT/MCT) emulsions to assess the tolerance and the effectiveness of the structured triacylglycerol emulsion. Total parenteral nutrition started the day after surgery and covered 100% of measured energy expenditure with nitrogen (0.2 g N · kg−1 · d−1) and non-protein calories: glucose (50%) and lipids (50%). Blood samples for liver function tests, albumin, transthyretin, and triacylglycerols were checked at 0800 h on the day before surgery and on day 1, day 3, and day 6 after surgery. Urine samples were taken each day from day 1 to day 7 for 3-methylhistidine (3 Me His) and total nitrogen measurements. Aspartate transaminase (ASAT), alanine transaminase (ALAT), and triacylglycerol plasma levels in routine clinical biochemistry increased significantly in the physical mixture group. Nitrogen balance and 3 Me His excretion were not significantly different between groups. Structured triacylglycerol (STG) lipid emulsions are as efficacious as the physical mixture on nitrogen balance in postoperative patients. They could have some advantages: no disturbances were found to occur in liver function tests or plasma triacylglycerol levels.

Tectonic analysis in conjunction with the microtectonic study of Mesozoic–Cenozoic series of the Central Constantinois of Algeria are used to reconstruct the sequence of tectonic phases since Cretaceous times. The retrotectonic method used to marshal the microtectonic data makes it possible to distinguish deformations related to Mesozoic tectonic phases from those associated with Cenozoic pre- and post-thrust sheet phases. A N120°E extensional and a N180°E compressional phase are highlighted in Albian–Cenomanian and latest Maastrichtian times, respectively. The Cenozoic era is marked by a series of three compressional phases oriented N90°–120°E in the Late Eocene, and N20°–30°E and N170°E in the Late Miocene. The first Late Miocene compressional phase related to the emplacement of Numidian flysch thrust sheets was followed by N–S compression affecting the overriding thrust sheets and their substratum. During latest Miocene–Pliocene and Quaternary times the tectonic pattern changed with NE–SW regional extension giving way in Quaternary and present-day times to a N130°–150°E compressional episode. The characteristics of the palaeostress fields and the regional structures are specified for the different phases defined.

During the Equanaute survey (June 1992), fourteen submersible dives were performed between 4950 and 2250 m water depths across the southern slope of the Cote d'Ivoire-Ghana Marginal Ridge (CIGMR), in the eastern Equatorial Atlantic. The CIGMR, a high-standing topographic marginal ridge along the Cote d'Ivoire-Ghana transform margin, is believed to result from a complex structural evolution due to the specific wrench-related rifting between Western Equatorial Africa and Northeastern Brazil, in Early Cretaceous times. In this paper we report and discuss geological observations made during dives, and sample analyses to resolve the lithology, paleoenvironmental conditions, age and origin of the CIGMR. The data help in better characterizing the different sedimentary and tectonic regimes which successively prevailed during the CIGMR formation and assessing the thermal regime operative during the fabrication and subsequent evolution of the margin. The thick sedimentary pile exposed along the southern CIGMR slope is made up of a repetitive clastic sequence indicative of a deltaic-to-prodeltaic environment. This sedimentary pile, of Early Cretaceous age, has recorded different stages of the transform margin structural evolution. 1. (1)|Syn- to post-lithification deformations first record extensional deformations related to the rifting of the adjacent northern divergent margin segment (the Deep Ivorian Basin). 2. (2)|Wrench tectonics has, at a later stage, produced intense fracturing and participated in local folding, chiefly detected upslope. The integrated studies of geological samples and in situ observations obtained during the Equanaute survey support models for transform margin evolution proposed mainly from geophysical data.

During the Equanaute cruise (June 1992), 14 submersible deep dives were conducted along the steep southern slope of the Cote d’Ivoire–Ghana marginal ridge. In situ diving observations and sample analysis were done to specify the clastic lithology of a sedimentary sequence about 2200 m thick. Most of the rocks collected consist of dark shales, greenish lenticular- to wavy-bedded siltstones and large-scale trough cross-bedded sandstones. Lithofacies analysis favors a deltaic origin for this sedimentary synrift succession, which is probably of Early Cretaceous age.