Статті в журналах: "COx claystone"

1

Zeng, Zhixiong, Yu-Jun Cui, Nathalie Conil, and Jean Talandier. "Investigating the contribution of claystone to the swelling pressure of its mixture with bentonite." E3S Web of Conferences 195 (2020): 03043. http://dx.doi.org/10.1051/e3sconf/202019503043.

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Compacted MX80 bentonite/Callovo-Oxfordian (COx) claystone mixture has been considered as a possible sealing/backfilling material in the French deep geological radioactive waste disposal. The swelling pressure of such mixture is an important factor in the design and long-term safety assessment of deep geological repositories. In this study, constant-volume swelling pressure tests were performed on the mixtures with different claystone fractions and dry densities. The test results show that the swelling pressure of the mixtures decreased with the increasing claystone fraction and decreasing dry density. According to the experimental results, the contribution of claystone to the global swelling pressure was further investigated. It was found that the deformation of claystone and its contribution to swelling pressure was highly dependent on the claystone fraction. As the claystone fraction was larger than 30%, the claystone in the mixture swelled, contributing to the global swelling pressure; On the contrary, as the claystone fraction was less than 30%, the swelling of claystone was inhibited by the bentonite and it worked an inert material without any contribution to the swelling pressure.

2

Song, Yang, C. A. Davy, P. Bertier, F. Skoczylas, and J. Talandier. "On the porosity of COx claystone by gas injection." Microporous and Mesoporous Materials 239 (February 2017): 272–86. http://dx.doi.org/10.1016/j.micromeso.2016.10.017.

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3

Harrington, J. F., R. de la Vaissière, D. J. Noy, R. J. Cuss, and J. Talandier. "Gas flow in Callovo-Oxfordian claystone (COx): results from laboratory and field-scale measurements." Mineralogical Magazine 76, no. 8 (December 2012): 3303–18. http://dx.doi.org/10.1180/minmag.2012.076.8.43.

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AbstractTo understand the fate and impact of gas produced within a repository for radioactive waste, a series of laboratory and field scale experiments have been performed on the Callovo-Oxfordian claystone (COx), the proposed host rock for the French repository. Results show the movement of gas is through a localized network of pathways, whose properties vary temporarily and spatially within the claystone. Significant evidence exists from detailed laboratory studies for the movement of gas along highly unstable pathways, whose aperture and geometry vary as a function of local stress, gas and porewater pressures. The coupling of these parameters results in the development of significant time-dependent effects, impacting on all aspects of COx behaviour, from gas breakthrough time, to the control of deformation processes. Variations in gas entry, breakthrough and steady-state pressures are indicative of microstructural heterogeneity which exerts an important control on the movement of gas. The localization of gas flow is also evident in preliminary results from the large scale gas injection test (PGZ) where gas flow is initially focussed within the excavation damaged zone (EDZ), which acts as a preferential pathway for gas. Numerical models based on conventional two-phase flow theory are unable to adequately describe the detailed observations from laboratory tests.

4

Xu, Hao, Jonny Rutqvist, Carlos Plúa, Gilles Armand, and Jens Birkholzer. "Modeling of thermal pressurization in tight claystone using sequential THM coupling: Benchmarking and validation against in-situ heating experiments in COx claystone." Tunnelling and Underground Space Technology 103 (September 2020): 103428. http://dx.doi.org/10.1016/j.tust.2020.103428.

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5

Song, Yang, C. A. Davy, D. Troadec, A. M. Blanchenet, F. Skoczylas, J. Talandier, and J. C. Robinet. "Multi-scale pore structure of COx claystone: Towards the prediction of fluid transport." Marine and Petroleum Geology 65 (August 2015): 63–82. http://dx.doi.org/10.1016/j.marpetgeo.2015.04.004.

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6

Yuan, Haifeng, Franck Agostini, Frédéric Skoczylas, and Jean Talandier. "About adsorption effects on the poroelastic properties and gas permeability of COx claystone." European Journal of Environmental and Civil Engineering 24, no. 2 (September 20, 2017): 267–82. http://dx.doi.org/10.1080/19648189.2017.1379444.

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7

Wang, Chuanrui, Nicolas Gay, Jean Talandier, and Frédéric Skoczylas. "Poroelastic experiments on COx claystone: Insight from the Biot's coefficient measurement with water." Engineering Geology 300 (April 2022): 106580. http://dx.doi.org/10.1016/j.enggeo.2022.106580.

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8

Bluthé, Joffrey, Benoît Bary, and Eric Lemarchand. "Micromechanical modeling of the Compression of the Damaged Zone experiment in the Callovo-Oxfordian formation." Advances in Geosciences 45 (July 24, 2018): 25–33. http://dx.doi.org/10.5194/adgeo-45-25-2018.

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Abstract. A theoretical model of the Compression of the Damaged Zone experiment is proposed. The tools of micromechanics are used to represent the fractured zone. Assuming an elastic behavior of the sound COx claystone and a simplified geometry of the drift, an analytical solution is presented and the crack closure is determined as a function of distance from the drift wall for two loading cases: a prescribed 4 MPa pressure and a stress-free strain with 1 % average value to describe the swelling due to resaturation. The results are in agreement with experimental observations and give insights into the heterogeneous character of self-sealing in the damaged zone.

9

Zeng, Zhixiong, Yu-Jun Cui, Feng Zhang, Nathalie Conil, and Jean Talandier. "Effect of technological voids on swelling behaviour of compacted bentonite–claystone mixture." Canadian Geotechnical Journal 57, no. 12 (December 2020): 1881–92. http://dx.doi.org/10.1139/cgj-2019-0339.

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The effect of technological voids on the swelling pressure of compacted MX80 bentonite–Callovo-Oxfordian (COx) claystone mixture was investigated by simulating the technological voids with a pre-defined space between the compacted disks of the mixture. Both axial and radial swelling pressures were monitored. After the tests, the microstructure of samples at different positions was investigated using mercury intrusion porosimetry (MIP), together with the determination of dry density and water content. Results showed that two main processes, filling and homogenization, occurred during soil hydration. In the filling process, the initial technological voids were gradually filled and the axial swelling pressure tended to increase. In the homogenization process, the samples had a sealing zone and a swelling zone. The sealing zone was characterized by a lower dry density than the expected final dry density while the swelling zone was characterized by a larger one. From the MIP results, the sealing zone showed larger inaccessible-pore, medium-pore, and large-pore void ratios and a lower small-pore void ratio than the swelling zone. Over time, the medium and large pores in the sealing zone were compressed, while the small pores in the swelling zone decreased. The stabilized axial swelling pressure followed a unique relationship with the expected final dry density. Moreover, the swelling pressure anisotropy was found to decrease as the technological voids increased.

10

Necib, Sophia, Fréderic Bumbieler, Claude Duret-Thual, Nicolas Bulidon, Didier Crusset, and Pierre Combrade. "Assessment of the resistance to environmentally assisted cracking (EAC) of C-steel casing and overpack in the COx claystone." Corrosion Engineering, Science and Technology 52, sup1 (April 28, 2017): 95–100. http://dx.doi.org/10.1080/1478422x.2017.1336003.

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11

Djizanne, Hippolyte, Jad Zghondi, Gilles Armand, Nathalie Conil, and Rémi de La Vaissière. "Some aspects of the hydro-mechanical behaviour of Callovo-Oxfordian (COx) claystone around a gallery parallel to the principal horizontal minor stress." Geomechanics for Energy and the Environment 17 (March 2019): 3–15. http://dx.doi.org/10.1016/j.gete.2018.11.003.

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12

Sweet, A. R., D. R. Braman, and J. F. Lerbekmo. "Sequential palynological changes across the composite Cretaceous-Tertiary (K-T) boundary claystone and contiguous strata, western Canada and Montana, U.S.A." Canadian Journal of Earth Sciences 36, no. 5 (May 1, 1999): 743–68. http://dx.doi.org/10.1139/e98-061.

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The boundary claystone in the western Canada Basin is composed of three intimately associated layers with a regional distribution: a basal brownish-grey hackly claystone, a middle brownish-black satiny claystone, and an upper brown laminated shale. These layers appear to represent a graded succession in terms of grain size and depositional rate. An abrupt reduction in the relative abundance of gymnospermous pollen, representing canopy vegetation, immediately precedes the hackly layer. The hackly claystone is accepted as being originally formed of microtektites from a ballistically transported ejecta blanket deposited within minutes or hours of the bolide's impact and associated with a heat pulse. The variable miospore content of the hackly layer is considered to be from local, reproductively active understorey vegetation. The shocked-quartz-rich satiny claystone is interpreted as being formed by fine debris deposited over days, weeks, or months. Its homogeneous texture suggests a short depositional event, but must have involved enough time for a residual Cyathidites-Ulmoideipites survival flora to release miospores. Further, the presence of this flora requires the continuation of light levels required for photosynthesis and temperatures generally above freezing. A settling time of several years for very fine debris and aerosols would fit with the apparent seasonal interlayering of the organic tissue in the laminated shale. The abruptly overlying Laevigatosporites-Kurtzipites recovery flora initiates the succession leading to the return of a canopied swamp, and its presence may signal the clearing of the atmosphere of all impact-generated debris, except for postulated elevated CO2 abundances.

13

Berthe, G., S. Savoye, C. Wittebroodt, and J. L. Michelot. "Changes in containment properties of claystone caprocks induced by dissolved CO2 seepage." Energy Procedia 4 (2011): 5314–19. http://dx.doi.org/10.1016/j.egypro.2011.02.512.

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14

Hadian, Pooya, and Reza Rezaee. "The Effect of Supercritical CO2 on Shaly Caprocks." Energies 13, no. 1 (December 27, 2019): 149. http://dx.doi.org/10.3390/en13010149.

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The effect of supercritical CO2 on the shaly caprocks is one of the critical issues to be considered in CO2 sequestration programs. Shale-scCO2 interactions can alter the seal integrity, leading to environmental problems and bringing into question the effectiveness of the program altogether. Several analytical studies were conducted on samples from Jurassic Eneabba Basal Shale and claystone rich facies of the Triassic Yalgorup Member (725–1417 m) in the Harvey CO2 sequestration site, Western Australia, to address the shale-scCO2 interactions and their effect on the petrophysical properties of the caprock. Shale samples saturated with NaCl brine were exposed to scCO2 under the reservoir condition (T = 60 °C, P = 2000 psi) for nine months and then tested to determine their altered mineralogical, petrophysical and geochemical properties. The experimental study examined changes to the mineralogical composition, capillary threshold pressure, and pore size distribution (PSD) of samples. The X-ray diffraction (XRD) results showed several changes in mineralogy because of rock-brine-CO2 reactions. Quartz, feldspars, kaolinite, and goethite were dissolved in most samples and muscovite, and halite were precipitated in general. Nuclear magnetic resonance (NMR), low-pressure nitrogen adsorption (LPNA), and mercury injection capillary pressure (MICP) tests indicate an increase in pore volume, except for relatively tighter, clay-rich samples. A reduction in capillary threshold pressures of samples after exposure to scCO2 is observed.

15

Weibel, R., C. Kjøller, K. Bateman, T. Laier, L. H. Nielsen, and G. Purser. "Carbonate dissolution in Mesozoic sand- and claystones as a response to CO2 exposure at 70°C and 20MPa." Applied Geochemistry 42 (March 2014): 1–15. http://dx.doi.org/10.1016/j.apgeochem.2013.12.006.

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16

Łączny, Marian Jacek, Sebastian Iwaszenko, and Adam Smoliński. "Process Kinetics of the Carbonation of Fly Ashes: A Research Study." Materials 14, no. 2 (January 6, 2021): 253. http://dx.doi.org/10.3390/ma14020253.

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The aim of the paper is to present the results of research on the carbonation process kinetics of coal combustion ashes originating from fluidized bed boilers used in power plants. Based on the thermogravimetric analysis (TGA), the hypothesis that carbon dioxide is bounded by the mineral substances (calcium compounds) in the fly ashes was confirmed. Determining the kinetic parameters of the carbonation of fly ashes requires simultaneously taking into consideration the kinetics of the drying process of the sample. The drying process of the sample masks the effect of the reaction of CO2 with calcium compound. Unlike the ashes generated in pulverized fuel boilers, fly ashes contain irregular amorphic mineral components or poorly crystalized products of complete or partial dehydroxylation of claystone substance present in shale formations constituting the gangue as well as anhydrite (CaSO4), a desulfurization product. The content of free calcium oxide (CaO) in such ashes ranges from a few to several percent, which is a significant obstacle considering their use in cement and concrete production as type II admixtures understood to be inorganic grained materials of pozzolanic or latent hydraulic properties. The paper presents effective mechanisms which reduce the content of free CaO in ashes from Fluidized Bed Combustion (FBC) boilers to a level that allows their commercial utilization in the cement industry.

17

Goldie Divko, Louise, Geoffrey O'Brien, Michael Harrison, and Joseph Hamilton. "Evaluation of the regional top seal in the Gippsland Basin: implications for geological carbon storage and hydrocarbon prospectivity." APPEA Journal 50, no. 1 (2010): 463. http://dx.doi.org/10.1071/aj09028.

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GeoScience Victoria and partners have undertaken the first detailed basin-wide study of the regional top seal in the Gippsland Basin. The Gippsland Basin is an attractive site for geological carbon storage (GCS) because of the close proximity to emission sources and the potential for large-scale storage projects. This top seal assessment involved the analysis of seal attributes (geometry, capacity and mineralogy) and empirical evidence for seal failure (soil gas geochemical anomalies, gas chimneys, hydrocarbon seepage and oil slicks). These datasets have been integrated to produce a qualitative evaluation of the containment potential for GCS, and also hydrocarbons, across the basin. Mineralogical analysis of the top seal has revealed that the Lakes Entrance Formation is principally a smectite-rich claystone. The geometry of the top seal is consistent with deposition in an early post-rift setting where marine sediments filled palaeo-topographic lows. The seal thickness and depth to seal base are greatest in the Central Deep and decrease toward the margins. There is a strong positive relationship between seal capacity column heights, seal thickness, depth to seal base and smectite content. At greater burial depths (below 700 m) and where smectite content is greater than 70%, seal capacity is increased (supportable column heights above 150 m). Natural hydrocarbon leakage and seepage onshore and offshore is correlated with fault distribution and areas of poor seal capacity. This study provides a framework for qualitatively evaluating seal potential at a basin scale. It has shown that the potential of the regional top seal over the Central Deep, Southern Terrace, central eastern Lake Wellington Depression and the southern to central near shore areas in the Seaspray Depression are most suitable for the containment of supercritical CO2. Further toward the margin of the regional seal in both onshore and offshore areas, containment of supercritical CO2 is less likely.

18

MacDonald, Justin, Rosalind King, Richard Hillis, and Guillaume Backé. "Structural style of the White Pointer and Hammerhead Delta—deepwater fold-thrust belts, Bight Basin, Australia." APPEA Journal 50, no. 1 (2010): 487. http://dx.doi.org/10.1071/aj09029.

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GeoScience Victoria and partners have undertaken the first detailed basin-wide study of the regional top seal in the Gippsland Basin. The Gippsland Basin is an attractive site for geological carbon storage (GCS) because of the close proximity to emission sources and the potential for large-scale storage projects. This top seal assessment involved the analysis of seal attributes (geometry, capacity and mineralogy) and empirical evidence for seal failure (soil gas geochemical anomalies, gas chimneys, hydrocarbon seepage and oil slicks). These datasets have been integrated to produce a qualitative evaluation of the containment potential for GCS, and also hydrocarbons, across the basin. Mineralogical analysis of the top seal has revealed that the Lakes Entrance Formation is principally a smectite-rich claystone. The geometry of the top seal is consistent with deposition in an early post-rift setting where marine sediments filled palaeo-topographic lows. The seal thickness and depth to seal base are greatest in the Central Deep and decrease toward the margins. There is a strong positive relationship between seal capacity column heights, seal thickness, depth to seal base and smectite content. At greater burial depths (below 700 m) and where smectite content is greater than 70%, seal capacity is increased (supportable column heights above 150 m). Natural hydrocarbon leakage and seepage onshore and offshore is correlated with fault distribution and areas of poor seal capacity. This study provides a framework for qualitatively evaluating seal potential at a basin scale. It has shown that the potential of the regional top seal over the Central Deep, Southern Terrace, central eastern Lake Wellington Depression and the southern to central near shore areas in the Seaspray Depression are most suitable for the containment of supercritical CO2. Further toward the margin of the regional seal in both onshore and offshore areas, containment of supercritical CO2 is less likely.

19

Luxton, C. W., S. T. Horan, D. L. Pickavance, and M. S. Durham. "THE LA BELLA AND MINERVA GAS DISCOVERIES, OFFSHORE OTWAY BASIN." APPEA Journal 35, no. 1 (1995): 405. http://dx.doi.org/10.1071/aj94026.

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In the past 100 years of hydrocarbon exploration in the Otway Basin more than 170 exploration wells have been drilled. Prior to 1993, success was limited to small onshore gas fields. In early 1993, the La Bella-1 and Minerva-1 wells discovered significant volumes of gas in Late Cretaceous sandstones within permits VIC/P30 and VIC/P31 in the offshore Otway Basin. They are the largest discoveries to date in the basin and have enabled new markets to be considered for Otway Basin gas. These discoveries were the culmination of a regional evaluation of the Otway Basin by BHP Petroleum which highlighted the prospectivity of VIC/P30 and VIC/P31. Key factors in this evaluation were:geochemical studies that indicated the presence of source rocks with the potential to generate both oil and gas;the development of a new reservoir/seal model; andimproved seismic data quality through reprocessing and new acquisition.La Bella-1 tested the southern fault block of a faulted anticlinal structure in the southeast corner of VIC/P30. Gas was discovered in two Late Cretaceous sandstone intervals of the Shipwreck Group (informal BHP Petroleum nomenclature). Reservoirs are of moderate to good quality and are sealed vertically, and by cross-fault seal, by Late Cretaceous claystones of the Sherbrook Group. The gas is believed to have been sourced from coals and shales of the Early Cretaceous Eumeralla Formation and the structure appears to be filled to spill as currently mapped. RFT samples recovered dry gas with 13 moI-% CO2 and minor amounts of condensate.Minerva-1 tested the northern fault block of a faulted anticline in the northwest corner of VIC/ P31. Gas was discovered in three excellent quality reservoir horizons within the Shipwreck Group. Late Cretaceous Shipwreck Group silty claystones provide vertical and cross-fault seal. The hydrocarbon source is similar to that for the La Bella accumulation and the structure appears to be filled to spill. A production test was carried out in the lower sand unit and flowed at a rig limited rate of 28.8 MMCFGD (0.81 Mm3/D) through a one-inch choke. The gas is composed mainly of methane, with minor amounts of condensate and 1.9 mol-% C02. Minerva-2A was drilled later in 1993 as an appraisal well to test the southern fault block of the structure to prove up sufficient reserves to pursue entry into developing gas markets. It encountered a similar reservoir unit of excellent quality, with a gas-water contact common with that of the northern block of the structure.The La Bella and Minerva gas discoveries have greatly enhanced the prospectivity of the offshore portion of the Otway Basin. The extension of known hydrocarbon accumulations from the onshore Port Campbell embayment to the La Bella-1 well location, 55 km offshore, demonstrates the potential of this portion of the basin.

20

Lisk, M., S. C. George, R. E. Summons, R. A. Quezada, and G. W. O'Brien. "MAPPING HYDROCARBON CHARGE HISTORIES: DETAILED CHARACTERISATION OF THE SOUTH PEPPER OIL FIELD, CARNARVON BASIN." APPEA Journal 36, no. 1 (1996): 445. http://dx.doi.org/10.1071/aj95024.

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The South Pepper Field is a small hydrocarbon accumulation located in the Barrow Sub-basin, North West Shelf. In this study, an integrated approach has been adopted which uses new analytical approaches, and combines fluid inclusion, micro and conventional GC-MS, stable isotope, mineralogical and petrological data, to allow the accurate reconstruction of the charge history of this field. The micro GC-MS work on oil-bearing fluid inclusions in the reservoir section allows, for the first time, a comparison to be made between the geochemical characteristics of the presently reservoired oil with samples of the palaeo-r eservoired oils, as preserved within the fluid inclusions.Oil inclusion abundances (OIA) recorded within the reservoir section in South Pepper-1 show two distinct abundance peaks, which are interpreted to correspond to zones of high oil saturation. The first occurs near the top of the reservoir, in sands that are presently gas saturated and represents a palaeo-oil column. The oil inclusions occur primarily within pre-existing ankerite cement that crystallised from highly saline fluids, probably derived from Palaeozoic evaporites. Carbon isotope compositions measured on the ankerite are isotopically depleted, consistent with the derivation of CO2 from the maturation of organic matter. Geochemical characterisation of the oil contained within these inclusions shows the presence of biomarkers such as 30-norhopanes and methylhopanes which are indicative of a calcareous source rock. This excludes the Jurassic Dingo Claystone as a source for this early oil charge and migration of oil from a pre-Jurassic source rock is inferred. Subsequent uplift and sub-aerial exposure of the basin margin during the Middle Miocene allowed fresh waters to dilute formation waters in the Barrow Group and biodegrade this early oil charge. However, the abundance of highly water-soluble compounds in the fluid inclusion oil suggests that biodegradation occurred subsequent to initial oil emplacement.The second oil inclusion abundance peak corresponds to the present-day oil zone and, although absolute oil inclusion abundances are similar to those recorded in the upper zone, the fluorescence colours are significantly different, suggesting a different source for the second oil charge. Geochemical characterisation of oil recovered by DST confirms this later oil charge was derived from a more clay-rich oxic source and has previously been typed to the Upper Dingo Claystone. The low abundance of this type of oil inclusion in samples from above the present GOC indicates that this later oil charge failed to accumulate at the top of the reservoir and so it cannot have been displaced by a later gas charge. Rather, the oil inclusion data suggest the emplacement of gas, probably derived from Triassic source rocks, occurred either prior to, or coincident with, the second oil charge.High OIA in the presently water bearing reservoir of South Pepper-3 suggests that high oil saturation originally extended beyond the present OWC. However, the absence of stratigraphically equivalent high OIA samples in wells from the east of the field suggests that late stage westerly tilting of the structure resulted in a reduction in closure and loss of oil across the eastern spill point. The presence of high gas readings and associated amplitude anomalies in the Windalia Radiolarite suggests that hydrocarbons are continuing to leak up the bounding fault. However, the absence of significant residual oil zones in other wells suggests that liquids were largely retained and that leakage involved the progressive bleeding of gas across a soft seal.

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PIEŃKOWSKI, GRZEGORZ, GRZEGORZ NIEDŹWIEDZKI, and MARTA WAKSMUNDZKA. "Sedimentological, palynological and geochemical studies of the terrestrial Triassic–Jurassic boundary in northwestern Poland." Geological Magazine 149, no. 2 (September 12, 2011): 308–32. http://dx.doi.org/10.1017/s0016756811000914.

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AbstractThe Kamień Pomorski IG-1 borehole (Pomerania, NW Poland) yields a profile through the Triassic–Jurassic (T–J) transition in continental deposits. An integrated study of the sedimentology, sequence stratigraphy, palynology, biostratigraphy and geochemistry of these deposits has been carried out on the boundary interval, which represents a time of major environmental change. Two lithological units within the transitional section are distinguished: the Lower–Middle Rhaetian Wielichowo Beds of alluvial plain facies, which shows evidence of a semi-arid climate, and the Upper Rhaetian to Lower Hettangian Zagaje Formation, lying above a marked erosional sequence boundary, composed of mudstone-claystone and sandstone deposited in a fluvial-lacustrine environment. Carbon isotope values obtained from palynomaceral separates, and thus reflecting isotopic changes in atmospheric CO2, show significant fluctuations through the Rhaetian; the most conspicuous negative δ13Corgexcursion is correlated with the Rhaetian ‘initial’ excursion and shows two sub-peaks, pointing to short-term carbon-cycle disturbances of lesser magnitude. Above the ‘initial’ negative excursion, there is a positive excursion followed again by more negative values, representing subordinate fluctuation within a positive excursion and is correlated with the T–J boundary. Seventy-two miospore taxa have been determined from the studied T–J transitional section. Two major palynological assemblages have been distinguished: the lower one, typically Rhaetian, named theCingulizonates rhaeticus–Limbosporites lundblandiiassociation, which corresponds to theRhaetipollis–Ricciisporites(=Rhaetipollis–Limbosporites) Zone; and the upper one, typically Hettangian, named theConbaculatisporites mesozoicus– Dictyophyllidites mortoni–Cerebropollenites thiergartiiassociation (with the age-diagnostic pollenC.thiergartii), which corresponds to thePinuspollenites–Trachysporites(= Trachysporites–Heliosporites) Zone. The T–J palynofloral turnover occurred in a humid period and is more conspicuous then palynofloral changes observed in Greenland, the Tethyan domain or other parts of NE Europe. The osmium isotope system is studied herein for the first time from T–J continental deposits and shows marked disturbances similar to those measured in marine deposits and attributed to volcanic fallout. Carbon and osmium isotope correlation and coeval increase in polycyclic aromatic hydrocarbon (PAH) content and darkening of miospores confirm that eruptions of the Central Atlantic Magmatic Province (CAMP) contributed to the perturbances in climate and crisis in the terrestrial biosphere. A series of periodical atmospheric loading by CO2, CH4or alternatively by SO2, sulphate aerosols and toxic compounds is inferred to have caused a series of rapid climatic reversals, directly influencing the ecosystem and causing the Triassic floral crisis. A floral turnover period commenced at the ‘initial’ δ13C excursion, with the onset of CAMP volcanism. Obtained values of initial187Os/186Os between 2.905 and 4.873 and very low iridium content (about 5 ppt) lend no support to a role for an extraterrestrial impact at the T–J boundary event. The position of the ‘initial’ negative carbon isotope excursion about 12 m below the T–J boundary, position of sequence boundaries (emergence surfaces) and other isotope excursions allow reliable correlation with marine profiles, including St Audrie's Bay (UK), Csövár (Hungary) and the GSSP profile at Kuhjoch (Austria).

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Debure, Mathieu, Yannick Linard, Christelle Martin, and Francis Claret. "In situ nuclear-glass corrosion under geological repository conditions." npj Materials Degradation 3, no. 1 (October 31, 2019). http://dx.doi.org/10.1038/s41529-019-0100-7.

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Abstract Silicate glasses are durable materials but laboratory experiments reveal that elements that derive from their environment may induce high corrosion rates and reduce their capacity to confine high-level radioactive waste. This study investigates nuclear-glass corrosion in geological media using an in situ diffusion experiment and multi-component diffusion modelling. The model highlights that the pH imposed by the Callovo–Oxfordian (COx) claystone host rock supports secondary-phase precipitation and increases glass corrosion compared with pure water. Elements from the COx rock (mainly Mg and Fe) form secondary phases with Si provided by the glass, which delay the establishment of a passivating interface. The presence of elements (Mg and Fe) that sustain glass alteration does not prevent a significant decrease in the glass-alteration rate, mainly due to the limited species transport that drives system reactivity. These improvements in the understanding of glass corrosion in its environment provide further insights for predictive modelling over larger timescales and space.

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