“Cretaceous black flysch” in the Pieniny Klippen Belt, West Carpathians: a case of geological misinterpretation     

Krzysztof Birkenmajer  Przemys&#x;aw Gedl  Ryszard Myczy&#x;ski  Jaros&#x;aw Tyszka 《Cretaceous Research》2008,29(3):535-549

This is a critical assessment of the paper by Oszczypko et al. (2004: Cretaceous Research 25, 89–113), in which they tried to prove a mid-Cretaceous age for the Szlachtowa (“black flysch”) and Opaleniec Formations, in the Pieniny Klippen Belt, West Carpathians, both of which had previously been shown to be of Jurassic age. We argue that the mid-Cretaceous age assignment is a misinterpretation, primarily resulting from their field samples having been collected from some Cretaceous lithostratigraphic units, tectonically associated with the Jurassic formations, and/or from tectonic contact-breccias involving Jurassic and Cretaceous strata. In addition, we suggest that they have overlooked a number of significant palaeontological papers, published since 1962, which record the presence of in situ ammonites, aptychi, belemnites, thin-shelled bivalves (Bositra), gryphaeids, foraminifera, and ostracod assemblages, all indicating a Jurassic (mainly Aalenian), and not a Cretaceous, age for the Szlachtowa Formation, and also the in situ Jurassic (Bajocian) ammonites and thin-shelled bivalves (Bositra), Bositra-microfacies, and age-diagnostic foraminiferal assemblages of the Opaleniec Formation.Our presentation here of recently published dinocyst data from well-preserved assemblages further supports the Jurassic ages for the Szlachtowa (“black flysch”) and Opaleniec Formations.  相似文献   

Nutrient dynamics and seasonal succession of phytoplankton assemblages in a Southern European Estuary: Ria de Aveiro, Portugal   总被引：2，自引：1，他引：2  

C.B. Lopes  A.I. Lilleb  J.M. Dias  E. Pereira  C. Vale  A.C. Duarte 《Estuarine, Coastal and Shelf Science》2007,71(3-4):480-490

The spatial and temporal dynamics of dissolved inorganic nitrogen, dissolved phosphate, dissolved silica and chlorophyll a were measured seasonally at eight stations in the Ria de Aveiro. Between December 2000 and September 2001, the seasonal succession of phytoplankton assemblages, inferred after the spatial and seasonal variation of silica and of chlorophyll a concentrations, showed that diatoms (μmol Si L⁻¹) dominated from late autumn until early spring, while chlorophytes (μg Chl a L⁻¹) bloomed during late spring and summer. The Si:N:P ratios and Si concentrations indicated no seasonal depletion in dissolved silica, as in other temperate systems, possibly because of abnormal precipitation and flood events prolonging the supply of dissolved Si to the system. The Si:N:P ratios suggested P limitation at the system level. Despite the relative proportions of available nutrients, the mean phosphorus concentration (5.3 μmol L⁻¹) was above the reported half-saturation constants for P uptake by phytoplankton. Thus, in Ria de Aveiro, the seasonal succession of phytoplankton assemblages may also be dependent on the grazing capacity of the pelagic community through top-down regulation.  相似文献   

Zircon M257 ‐ a Homogeneous Natural Reference Material for the Ion Microprobe U‐Pb Analysis of Zircon     

Lutz Nasdala  Wolfgang Hofmeister  Nicholas Norberg  James M. Martinson  Fernando Corfu  Wolfgang Dörr  Sandra L. Kamo  Allen K. Kennedy  Andreas Kronz  Peter W. Reiners  Dirk Frei  Jan Kosler  Yusheng Wan  Jens Götze  Tobias Häger  Alfred Kröner  John W. Valley 《Geostandards and Geoanalytical Research》2008,32(3):247-265

We introduce and propose zircon M257 as a future reference material for the determination of zircon U‐Pb ages by means of secondary ion mass spectrometry. This light brownish, flawless, cut gemstone specimen from Sri Lanka weighed 5.14 g (25.7 carats). Zircon M257 has TIMS‐determined, mean isotopic ratios (2s uncertainties) of 0.09100 ± 0.00003 for ²⁰⁶pb/²³⁸U and 0.7392 ± 0.0003 for ²⁰⁷pb/²³⁵U. Its ²⁰⁶pb/²³⁸U age is 561.3 ± 0.3 Ma (unweighted mean, uncertainty quoted at the 95% confidence level); the U‐Pb system is concordant within uncertainty of decay constants. Zircon M257 contains ～ 840 μg g^?1 U (Th/U ～ 0.27). The material exhibits remarkably low heterogeneity, with a virtual absence of any internal textures even in cathodoluminescence images. The uniform, moderate degree of radiation damage (estimated from the expansion of unit‐cell parameters, broadening of Raman spectral parameters and density) corresponds well, within the “Sri Lankan trends”, with actinide concentrations, U‐Pb age, and the calculated alpha fluence of 1.66 × 10¹⁸ g^?1. This, and a (U+Th)/He age of 419 ± 9 Ma (2s), enables us to exclude any unusual thermal history or heat treatment, which could potentially have affected the retention of radiogenic Pb. The oxygen isotope ratio of this zircon is 13.9%o VSMOW suggesting a metamorphic genesis in a marble or calc‐silicate skarn.  相似文献   

A spectrophotometric measurement of soil cation exchange capacity based on cobaltihexamine chloride absorbance     

Delphine Aran  Armand Maul  Jean-Franois Masfaraud 《Comptes Rendus Geoscience》2008,340(12):865-871

Among numerous methods for cation exchange capacity (CEC) determination for soils and sediments, the cobaltihexamine chloride method is frequently used due to its ability to measure CEC at soil pH. After exchange with Co(NH₃)₆³⁺ ions, CEC is estimated via the measurement of the Co remaining in solution. The modified method proposed allows a more rapid determination of CEC based on the measurement of the absorbance at 472 nm of the cobaltihexamine chloride solution before and after exchange. This method has been applied to various soil's horizons from four sites, selected to cover a wide range of CEC and pH values. The model obtained allows one to calculate CEC from absorbance at 472 nm with 95% confidence intervals. As CEC is of relevant meaning in agronomical and environmental purposes, and more recently in ecotoxicological studies, this modified method can be proposed as a rapid test for CEC evaluation.  相似文献   

Mais comment s'écoule donc un glacier ? Aperçu historique     

Frédérique Rémy  Laurent Testut 《Comptes Rendus Geoscience》2006,338(5):368-385

Ice and snow have often helped physicists understand the world. On the contrary it has taken them a very long time to understand the flow of the glaciers. Naturalists only began to take an interest in glaciers at the beginning of the 19th century during the last phase of glacier advances. When the glacier flow from the upslope direction became obvious, it was then necessary to understand how it flowed. It was only in 1840, the year of the Antarctica ice sheet discovery by Dumont d'Urville, that two books laid the basis for the future field of glaciology: one by Agassiz on the ice age and glaciers, the other one by canon Rendu on glacier theory. During the 19th century, ice flow theories, adopted by most of the leading scientists, were based on melting/refreezing processes. Even though the word ‘fluid’ was first used in 1773 to describe ice, more the 130 years would have to go by before the laws of fluid mechanics were applied to ice. Even now, the parameter of Glen's law, which is used by glaciologists to model ice deformation, can take a very wide range of values, so that no unique ice flow law has yet been defined. To cite this article: F. Rémy, L. Testut, C. R. Geoscience 338 (2006).  相似文献   

Water temperature behaviour in the River Loire since 1976 and 1881     

Florentina Moatar  Joël Gailhard 《Comptes Rendus Geoscience》2006,338(5):319-328

Analysis of monthly mean river temperatures, recorded on an hourly basis in the middle reaches of the Loire since 1976, allows reconstruction by multiple linear regression of the annual, spring and summer water temperatures from equivalent information on air temperatures and river discharge. Since 1881, the average annual and summer temperatures of the Loire have risen by approximately 0.8?°C, this increase accelerating since the late 1980s due to the rise in air temperature and also to lower discharge rates. In addition, the thermal regime in the Orleans to Blois reach is considerably affected by the inflow of groundwater from the Calcaires de Beauce aquifer, as shown by the summer energy balance. To cite this article: F. Moatar, J. Gailhard, C. R. Geoscience 338 (2006).  相似文献   

Sur les anomalies structurales de l'anticlinal de l'oued Bahloul de Tunisie : héritage tectonique et plissement cisaillant de couverture     

Ahmed Saadi  Noureddine Boukadi  Ali Gaaya 《Comptes Rendus Geoscience》2006,338(9):650-657

The Oued Bahloul structure exists in the central Atlas of Tunisia. This structure is oriented N70 and it shows a very particular geometry characterized by: (i) an important disharmony between the northern and the southern flanks; (ii) a dissymmetry between the east and the west parts of the structure; (iii) several gaps and progressive unconformities present in the Cretaceous and Eocene series.Three major tectonic directions characterize this structure: (i) the N120 appears in the western part of the anticline; (ii) some north–south faults distinguish the oriental part; (iii) the strike fault, which is confirmed by seismic data, affects the central part of this anticline. To cite this article: A. Saadi et al., C. R. Geoscience 338 (2006).  相似文献   

Les failles récentes des Grands-Moulins (Savoie) : un Sackung (tassement gravitaire) majeur dans les Alpes françaises     

Jean-Claude Hippolyte  Marc Tardy  Gérard Nicoud 《Comptes Rendus Geoscience》2006,338(10):734-741

In Savoy, the Grands-Moulins recent fault scarps, previously interpreted as seismic fault ruptures, are in fact part of a major Sackung (deep seated gravitational spreading) of the French Alps (9 km long). We mapped more than 60 sackung scarps, some of them reaching 1330 m long and 30 m high. These antislope scarps stop the active screes and offset relict Dryassic rock glaciers by 16 m. We present geomorphologic observations attesting for their gravitational origin. This Sackung is primarily due to glacial debuttressing, while seismic shaking could be a triggering mechanism. To cite this article: J.-C. Hippolyte et al., C. R. Geoscience 338 (2006).  相似文献   

低聚合羟基铁离子-蒙脱石复合体吸附砷的实验研究   总被引：15，自引：2，他引：15  

姜浩  廖立兵  王素萍 《地球化学》2002,31(6):593-601

将提纯的钙蒙脱石与羟基铁离子溶液作用，制备了低聚合羟基铁－蒙脱石复合体，用化学分析，电子探针分析，粉晶X射线衍射分析，差热分析和穆斯堡尔谱分析等手段。对蒙脱石原样，低聚合羟基铁－蒙脱石复合体和相同条件下制备的铁的含水氧化物进行了表征。在实际土壤的酸度（pH=4-7)和温度（18－40℃）条件下，进行了低聚合羟基铁－蒙脱石复合体吸附有害元素砷的实验，探讨了复合体的砷吸附能力与pH值，温度，吸附时间，砷初始浓度，离子强度间的关系，并与蒙脱石和铁的含水氧化物的砷吸附行为进行了对比，研究表明，在实验条件下，低聚合羟基铁－蒙脱石复合体对砷具有明显的亲合力，低聚合羟基铁－蒙脱石复合体吸附砷的过程有可能是地表岩石和土壤中重要的地球化学过程，是影响砷地地表，特别是土壤中迁移，富集的重要因素。  相似文献   

Une méthode de quantification de la dégradation d'un escarpement de faille au cours des cycles climatiques du Quaternaire : la faille de Jobourg (Nord Cotentin,France)Quantification of a fault-scarp degradation through Quaternary: the Jobourg fault (North Cotentin,France)     

Marianne Font  Jean-Louis Lagarde  Daniel Amorese  Jean-Pierre Coutard  Jean-Claude Ozouf 《Comptes Rendus Geoscience》2002,334(3):171-178

The degradation of the Jobourg fault-scarp occurred by cryoclastic processes in a periglacial environment during a part of Quaternary time. An attempt of quantification indicates a bulk scarp erosion of about 39 m³ m^?2, while the head accumulated at the bottom of the fault scarp only represents 4.6 m³ m^?2. To cite this article: M. Font et al., C. R. Geoscience 334 (2002) 171–178.  相似文献