Nature and origin of magnetic minerals within the Middle Jurassic shallow-water carbonate rocks of the Paris Basin, France: implications for magnetostratigraphic dating     

Nadia K. Belkaaloul  Djafar M. Aïssaoui 《Geophysical Journal International》1997,130(2):411-421

The Middle and Upper Jurassic Bathonian-Oxfordian shallow-water carbonate rocks from the Paris Basin, France, consist mainly of oolitic and bioclastic limestones that are hydrocarbon reservoirs in the subsurface. Despite a preliminary positive study, these deposits have been considered to be largely remagnetized (Rochette, private communication), and hence not amenable to palaeomagnetic dating. To establish their magnetic mineralogy and test this remagnetization hypothesis, we have used an integrated investigation combining petrographic, geochemical, rock-magnetic and palaeomagnetic measurements on samples extracted from five cores from the Paris Basin and from outcrops in Burgundy. Magnetic minerals in the Bathonian-Oxfordian carbonates include: (1) primary biogenic single-domain magnetite and detrital multi-domain Ti-magnetite and their oxidized form, maghemite; (2) authigenic spheres of magnetite probably related to hydrocarbons; and (3) goethite, either restricted to ferruginous ooid layers or resulting from surficial alteration, notably replacement of pyrite framboids. Rock-magnetic experiments carried out on 68 samples reveal H _cr/ H _c and M _rs/ M _s ratios ranging from 1.88 to 5.58 and 0.017 to 0.314, respectively. These values are clearly distinct from diagnostic values for a chemical remagnetization. Pyrrhotite was not identified within these sediments. Moreover, the average H _cr/ H _c ratio of 3.14 is significantly different from the value of 1.333 for natural pyrrhotite (Dekkers 1988). These results have a direct implication for the preservation of the primary magnetization; consequently, these deposits are selectively amenable for magnetostratigraphic dating and possible regional correlations.  相似文献   

A transversely isotropic thermo-poroelastic model for claystone: parameter identification and application to a 3D underground structure     

Richard Giot  Sylvie Granet  Maxime Faivre  Nadia Massoussi  Julie Huang 《Geomechanics and Geoengineering》2018,13(4):246-263

A transversely isotropic thermo-poroelastic constitutive law is developed and implemented in the finite element code Code_Aster (EDF, France). It is then validated using an analytic solution for an inclined borehole in a transversely isotropic medium. A strategy for identifying the parameters of the transversely isotropic thermo-poroelastic model based on an inverse method is proposed on the basis of different laboratory tests. To demonstrate the efficiency and applicability of the model, it is then applied in a three-dimensional numerical model of an underground structure in a parameter sensitivity study. The results of the modelling highlight the importance of accounting for anisotropic phenomena when determining the dimensions of underground facilities. The whole approach is presented in the paper, from model development to application to 3D numerical modelling to an engineering case study.  相似文献   

Sedimentology of a Late Quaternary lacustrine record from the south-eastern Carpathian Basin     

Christian Zeeden  Ulrich Hambach  Nicole Klasen  Peter Fischer  Philipp Schulte  Janina J. Nett  Daniel Veres  Igor Obreht  Wei Chu  Maria Papadopoulou  Finn Viehberg  Frank SchÄBitz  Milivoj B. Gavrilov  Slobodan B. MarkoviĆ  Andreas VÖTT  Frank Lehmkuhl 《第四纪科学杂志》2021,36(8):1414-1425

The Upper Pleistocene geoarchives in the south-eastern Carpathian Basin are represented predominantly by loess–palaeosol records. In 2015, a 10 m sediment core composed of clay-rich lacustrine sediments was recovered by vibracoring a dry lake basin located between the Vršac Mountains (Serbia) and the Banat Sands in the south-eastern Carpathian Basin; a location relevant for placing regional archaeological results in a palaeoenvironmental context. Here, we present results from geoelectrical prospection and a lithostratigraphic interpretation of this sequence supported by a detailed granulometric study supplemented by ostracod analysis. An age model based on luminescence dating is discussed against sedimentological proxy data and its implication for palaeoenvironmental change. The cores show a stratigraphy of lighter ochre-coloured and darker greyish sediment, related to the deposition of clay and silt trapped in an aquatic environment. Geophysical measurements show ~20 m thick lacustrine sediments. The grain-size distributions including the variability in fine clay are indicative of a lacustrine environment. Fine particles were brought into the depositional environments by aquatic input and settled from suspension; also, direct dust input is constrained by grain-size results. Riverine input and aeolian dust input interplayed at the locality.  相似文献   

Water retention and compression behavior of MX80 bentonite pellet     

Zhang  Zhao  Cui  Yu-Jun  Yang  Jinwen  Mokni  Nadia  Ye  Wei-Min  He  Yong 《Acta Geotechnica》2022,17(6):2435-2447

Acta Geotechnica - Bentonite pellet/powder mixture has been considered as a possible sealing material in deep geological disposal of radioactive waste. As the hydro-mechanical behavior of such...  相似文献   

Effect of salt solution on the optimum lime contents of bentonite and silt     

Ying  Zi  Cui  Yu-Jun  Duc  Myriam  Benahmed  Nadia 《Acta Geotechnica》2022,17(9):3731-3745

Acta Geotechnica - In practice, prior to treating a soil with lime, the optimum lime content required for the cation exchange and for providing sufficient Ca2+ and high pH for pozzolanic reaction...  相似文献   

Changes in microstructure and water retention property of a lime-treated saline soil during curing     

Ying  Zi  Cui  Yu-Jun  Benahmed  Nadia  Duc  Myriam 《Acta Geotechnica》2022,17(1):319-326

Acta Geotechnica - This study aims at investigating the lime treatment effect on the changes in microstructure and water retention property of compacted saline soil, with consideration of the...  相似文献   

Nature, distribution and origin of polycyclic aromatic hydrocarbons (PAHs) in the sediments of Olbia harbor (Northern Sardinia, Italy)   总被引：1，自引：0，他引：1  

De Luca G  Furesi A  Micera G  Panzanelli A  Piu PC  Pilo MI  Spano N  Sanna G 《Marine pollution bulletin》2005,50(11):1223-1232

The nature, origin and distribution of US EPA polycyclic aromatic hydrocarbons (PAHs) in the sediments of Olbia harbor (North Sardinia, Italy) were investigated by gas-chromatography/mass spectrometry (GCMS). PAH concentrations in the sediments (SigmaPAHs) ranged from 0.16 to 0.77 microg g(-1), indicating a homogeneously low level of pollution. A rather exceptional prevalence of low molecular weight PAHs was substantiated: nearly 80% of SigmaPAHs include naphthalene (15.19%) and phenanthrene (64.47%). Carcinogenic compounds were present in very low (BaP, BkF, BaA and DBA) or negligible (BbF and Inp) concentrations. As indicated by the Phen/Ant molar ratio, the main source of PAHs is petrogenic, probably due to oil spills from shipping. The low/high molecular weight ratio (ranging between 1.2 and 26) distinguishes the sediments of the tourist harbor from those of the commercial/industrial harbor. Moreover, a slight but meaningful pyrolytic contribution to pollution was found in the tourist harbor, which has the most polluted sediments in the whole harbor. Finally, good linear correlations were found between a selected PAH (Phen and Naph) and selected sums of PAHs (i.e. the total amount of the other 15 US EPA and the sum of low molecular weight PAHs).  相似文献   

Factors Affecting the Distribution and Diversity of Polychaetes in Amivrakikos Bay, Greece     

Artemis Nicolaidou  K.-Nantia Papadopoulou 《Marine Ecology》1989,10(3):193-204

Abstract. The polychaetc fauna was studied in 18 soft-bottom stations in Amvrakikos Bay of the Ionian Sea. Of the 146 species found many had single occurrences, which caused low similarity between stations. Mixing and renewal of water influenced the distribution of species and feeding types of polychaetes, while their diversity correlated with sedimentary structure. Water depth was the factor which accounted for the greatest variability in the data, whereas salinity had no discernible effect on the polychaetc fauna.  相似文献   

Improving the quantitative estimation of trawling impacts from sidescan-sonar and underwater-video imagery     

Smith  C. J.; Banks  A. C.; Papadopoulou  K-N. 《ICES Journal of Marine Science》2007,64(9):1692-1701

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Changes in wild fish assemblages after the establishment of a fish farming zone in an oligotrophic marine ecosystem     

A. Machias  I. Karakassis  M. Labropoulou  S. Somarakis  K. N. Papadopoulou  C. Papaconstantinou 《Estuarine, Coastal and Shelf Science》2004,60(4):771-779

The species composition, abundance and diversity of demersal fish assemblages has been investigated in an oligotrophic coastal bay in the Aegean Sea which is a designated zone for the development of aquaculture. Samples were collected using experimental trawling, before the establishment of fish cages in the area during early June 1987 and after attaining the maximal production of the aquaculture zone in late May 2001. The overall abundance of the fish assemblage increased by a factor of 4 and the average trophic level of the fish community increased from 3.59 to 3.79. Traditional diversity indices showed an increase in dominance but the distinctness measures of biodiversity showed that the overall structure obtained after the establishment of fish farming was not phylogenetically impoverished. Multivariate analysis showed that the community differences between the two periods are quantitative rather than qualitative. Comparisons in length frequencies between the two periods indicated that specimens of the species compared were either similar or larger in the second period. The species favoured by the presence of aquaculture were not the ones normally feeding on the food pellets under the cages but those normally occurring in the fishing grounds of the study. It is concluded that the release of nutrients from fish farming in nutrient-poor systems can have a positive effect on local fisheries with no visible negative change in species composition or biodiversity.  相似文献