Turonian Radiolarians from Karnezeika,Argolis Peninsula,Peloponnesus (Greece)     

Alexandre N. Bandini  Peter O. Baumgartner  Michéle Caron 《Swiss Journal of Geoscience》2006,99(1):S1-S20

Near Karnezeika a roughly 140 m thick Upper Cretaceous section consists of interbedded pelagic limestones, cherts and coarse polymict breccias including ophiolites and shallow water limestones. At the base, pink pelagic limestones rest on deeply altered and fractured Lower Jurassic Pantokrator Limestone. This first pelagic facies is dated as middle Turonian, based on planktonic Foraminifera. Over 100 m of coarse ophiolite-carbonate breccias, interpreted as a channel or canyon fill in a pelagic environment, document the erosion of the Late Jurassic nappe edifice along the Cretaceous Pelagonian margin. Above these breccias, we mesured 16 m of principally pink and red pelagic limestones and radiolarian cherts, in which we recovered well-preserved radiolarians discussed here. In this interval, the presence of planktonic Foraminfera allows to state a late Turonian to Coniacian age. More than 40 radiolarian species are described and figured in this work. The radiolarian chronostratigraphy established by 10 different authors in 11 publications was compared for this study and used to establish radiolarian ranges. This exercise shows major discrepancies between authors for the radiolarian ranges of the studied assemblage. Nevertheless, a Turonian age can be stated based on a synthesis of cited radiolarian ranges. This age is consistent with the age based on planktonic foraminifera. In combining the ages of both Radiolaria and planktonic Foraminifera, the studied samples can be restricted to the late Turonian. However, the discrepancies of published radiolarian ranges call for an urgent, major revision of the Late Cretaceous radiolarian biochronology. The integration of planktonic foraminifera with radiolarians may greatly enhance biochronologic resolution in sections where both groups occur.  相似文献   

Process–form relationships in Southern Italian badlands: erosion rates and implications for landform evolution     

Michle L. Clarke  Helen M. Rendell 《地球表面变化过程与地形》2006,31(1):15-29

Characteristic badlands are incised into Plio‐Pleistocene clays in Basilicata, southern Italy, creating steep, scarp slopes with knife‐edge ridges (calanchi) and small dome‐shaped forms (biancane). Erosion pin data for the period 1997–2003 give mean annual erosion rates for dome‐shaped biancane in the range 9–19 mm a^?1, while rates for the calanchi scarps are lower, at 7–10 mm a^?1. The erosion pin data also show a non‐linear relationship with slope angle. Maximum erosion rates coincide with a slope angle of 35°, within an envelope defined by combining the theoretical effects of both rainsplash and surface weathering. Monitoring of surface changes and erosion rates for two 0·5 m² cleared swathes on biancane forms reveals a complex relationship between weathering and erosion. Characteristic forms can develop from large blocks of intact clay bedrock over a time period of less than 30 a. The implications of the measured erosion rates for the landform association of mountain front/pediment/domed inselberg are explored. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Large scale patterns of chemical recovery in lakes in Norway and Sweden: Importance of seasalt episodes and changes in dissolved organic carbon     

Brit Lisa Skjelkvåle  Hans Borg  Atle Hindar  Anders Wilander 《Applied Geochemistry》2007

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The oxygen isotope composition of Karoo and Etendeka picrites: High δ18O mantle or crustal contamination?     

Chris Harris  Petrus le Roux  Ryan Cochrane  Laure Martin  Andrew R. Duncan  Julian S. Marsh  Anton P. le Roex  Cornelia Class 《Contributions to Mineralogy and Petrology》2015,170(1):1-24

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Spatial and temporal variations of nutrient concentration in the groundwater of a floodplain: effect of hydrology,vegetation and substrate     

Naima Takatert  Jos Miguel Sanchez‐Prez  Michle Trmolires 《水文研究》1999,13(10):1511-1526

Spatio‐temporal variations in nitrogen and phosphorus concentrations in groundwater were analysed and related to the variations in hydrological conditions, vegetation type and substrate in an alluvial ecosystem. This study was conducted in the Illwald forest in the Rhine Plain (eastern France) to assess the removal of nutrients from groundwater in a regularly flooded area. We compared both forest and meadow ecosystems on clayey‐silty soils with an anoxic horizon (pseudogley) at 1·5–2 m depth (eutric gley soil) and a forest ecosystem on a clayey‐silty fluviosoil rich in organic matter with a gley at 0·5 m depth (calcaric gley soil). Piezometers were used to measure the nutrient concentrations in the groundwater at 2 m depth in the root layer and at 4·5 m depth, below the root layer. Lower concentrations of nitrate and phosphate in groundwater were observed under forest than under meadow, which could be explained by more efficient plant uptake by woody species than herbaceous plants. Thus NO₃‐N inputs by river floods were reduced by 73% in the shallow groundwater of the forested ecosystem, and only by 37% in the meadow. Compared with the superficial groundwater layer, the lowest level of nitrate nitrogen (NO₃‐N) and the highest level of ammonium nitrogen (NH₄‐N) were measured in the deep layer (under the gley horizon at 2·5 m depth), which suggests that the reducing potential of the anoxic horizon in the gley soils contributes to the reduction of nitrate. Nitrate concentrations were higher in the groundwater of the parcel rich in organic matter than in the one poorer in organic matter. Phosphate (PO₄‐P) concentrations in both shallow and deep groundwater are less than 62 to 76% of those found in surface water which can be related to the retention capacity of the clay colloids of these soils. Moreover, the temporal variations in nutrient concentrations in groundwater are directly related to variations in groundwater level during an annual hydrological cycle. Our results suggest that variations in groundwater level regulate spatio‐temporal variations in nutrient concentrations in groundwater as a result of the oxidation–reduction status of soil, which creates favourable or unfavourable conditions for nutrient bioavailability. The hydrological variations are much more important than those concerning substrate and type of vegetation. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Real-time gas monitoring at the Tekke Hamam geothermal field (Western Anatolia,Turkey): an assessment in relation to local seismicity     

Süer  Selin  Wiersberg  Thomas  Güleç  Nilgün  Erzinger  Jörg  Parlaktuna  Mahmut 《Natural Hazards》2020,104(2):1655-1678

Natural Hazards - This study presents the results of a real-time gas monitoring experiment conducted, via the use of a quadrupole mass spectrometer, in a mofette field within the Tekke Hamam...  相似文献   

Metabolism and organ distribution of nonylphenol in Atlantic salmon (Salmo salar).     

A Arukwe  A Goks?yr  R Thibaut  J P Cravedi 《Marine environmental research》2000,50(1-5):141-145

Nonylphenol (NP) is a breakdown product of alkylphenol polyethoxylates (APEs), an important class of non-ionic surfactants that are widely used in many detergent formulations and plastic products for industrial and domestic use. A complex microbial degradation pattern, characterized by the formation of several metabolic products that are more toxic than the parent compound, has been established for APEs. We have studied the in vivo metabolism and organ distribution of NP in juvenile salmon. Fish were exposed to a single oral dose of [3H]-4-n-NP (1295 KBq, 25 micrograms) and sampled at 24, 48 and 72 h after exposure. Metabolites were separated by radio-high-performance liquid chromatography and tentatively identified by cochromatography with standards characterized by mass spectrometry. Our results show that 4-n-NP was mainly metabolized in vivo to its corresponding glucuronide conjugate and to a lesser extent to various hydroxylated and oxidated compounds. Biliary excretion at 72 h after dosing amounted to 2.83 +/- 0.75% of the administered radioactivity. Kinetic analysis shows that NP-glucuronide accounted for 83, 95 and 81% of total radioactivity in the HPLC-injected bile sample at 24, 48 and 72 h, respectively, after exposure. The half-life of residues in carcass and muscle was between 24 and 48 h after exposure.  相似文献   

Oil well produced water discharges to the North Sea. Part I: comparison of deployed mussels (Mytilus edulis), semi-permeable membrane devices, and the DREAM model predictions to estimate the dispersion of polycyclic aromatic hydrocarbons     

Durell G  Utvik TR  Johnsen S  Frost T  Neff J 《Marine environmental research》2006,62(3):194-223

The oil companies operating in the Norwegian sector of the North Sea have conducted field studies since the mid-1990s to monitor produced water discharges to the ocean. These studies have been used to refine monitoring methods, and to develop and validate a dispersion and impact assessment model. This paper summarizes monitoring data from surveys conducted in two major oil and gas production areas, and compares the results to concentrations of polycyclic aromatic hydrocarbons (PAH) in surface waters predicted by the dose-related risk and effect assessment model (DREAM). Blue mussels and semi-permeable membrane devices (SPMDs) were deployed in the Ekofisk and Tampen Regions and analyzed for more than 50 PAH. PAH concentrations in ambient seawater were estimated based on the mussels and SPMD concentrations, and compared to model predictions. Surface water total PAH concentrations ranged from 25 to 350 ng/L within 1 km of the platform discharges and reached background levels of 4-8 ng/L within 5-10 km of the discharge; a 100,000-fold dilution of the PAH in the discharge water. The PAH concentrations in surface water, predicted by three methods, compared well for the Ekofisk Region. The model predicted higher concentrations than the field-based methods for parts of the Tampen Region; particularly the most tidally influenced areas. Tidally-mediated fluctuations in PAH concentrations in surface water must be considered because they affect the estimation of PAH concentrations from mussel and SPMD residue data, and the predictions by the DREAM model. Predictions using mussels, SPMDs, and modeling support and complement each other; all are valuable tools for estimating the fate and impact of chemical contaminants in produced water that are discharged to the ocean.  相似文献   

Oil well produced water discharges to the North Sea. Part II: comparison of deployed mussels (Mytilus edulis) and the DREAM model to predict ecological risk     

Neff JM  Johnsen S  Frost TK  Utvik TI  Durell GS 《Marine environmental research》2006,62(3):224-246

Large volumes of water often are produced with oil and gas from offshore platforms. The produced water is separated from the oil and gas and either reinjected into a deep formation or discharged to the ocean. The Norwegian oil and gas industry advocates ecological risk assessment as the basis for managing produced water discharges to the North Sea. In this paper, we compare estimates of ecological risks to water-column communities based on data on hydrocarbon residues in soft tissues of blue mussels deployed for a month near offshore platforms and based on predictions of the Dose related Risk and Effect Assessment Model (DREAM). The study was performed near produced water discharges to the Tampen and Ekofisk Regions of the Norwegian Sector of the North Sea. Because polycyclic aromatic hydrocarbons (PAH) are considered the most important contributors to the ecological hazard posed by produced water discharges, comparisons made here focus on this group of compounds. The mussel approach is based on predicted environmental concentrations (PECs) of individual PAH, estimated from PAH residues in mussels following deployment for a month near several produced water discharges, and predicted no effects concentrations (PNECs) based on a K(ow) regression model. In the DREAM method, PECs for three PAH fractions are estimated in the three-dimensional area around produced water discharge with the DREAM model. PNECs for each fraction are based on the chronic toxicity of a representative PAH from each fraction divided by an assessment factor to account for uncertainty in the chronic value. The mussel method gives much lower estimates of ecological risk than the DREAM method. The differences are caused by the much lower PNECs used in DREAM than derived from the regression model, and by the lower concentrations of aqueous PAH predicted by DREAM than estimated from PAH residues in mussel tissues. However, the two methods rank stations at different distances from produced water discharges in the same order and both identify 2- and 3-ring PAHs as the main contributors to the ecological risk of produced water discharges. Neither method identifies a significant ecological risk of PAH in the upper water column of the oil fields. The DREAM model may produce an overly conservative estimate of ecological risk of produced water discharges to the North Sea.  相似文献   

Ce anomalies in Gough Island lavas — Trace element characteristics of a recycled sediment component     

Cornelia Class  Anton P. le Roex 《Earth and Planetary Science Letters》2008,265(3-4):475-486

High precision trace element data obtained by inductively coupled plasma mass spectrometry and Sr–Nd isotope analyses are presented for mafic volcanic rocks from Gough Island, South Atlantic. The new data reveal negative Ce anomalies, with Ce/Ce^? values in Gough lavas extending down to ～ 0.92. Ce is only fractionated from other rare earth elements (REE) due to formation of Ce⁴⁺ under oxidizing conditions of near-surface environments while other REE remain trivalent. Ce anomalies in convergent margin magmas have been shown to indicate a contribution of a subducted sediment component. In contrast, Ce anomalies in intra-plate basalts have been attributed to weathering processes, but can be excluded here based on element–element systematics indicating magmatic trends rather than weathering-induced element mobility. Shallow-level contamination by local marine sediments with negative Ce anomaly inherited from seawater can be excluded because Gough lavas with increasingly negative Ce anomalies do not trend towards low Ce/Pb ratios characterizing such sediments. Rather, it is argued that the negative Ce anomalies in Gough Island lavas are consistent with variable amounts of a sediment component in the mantle plume source. Mixtures between estimates of subducting sediment columns with negative Ce anomaly and mantle capable of giving rise to Gough Island magmas without Ce anomalies reproduce the Gough compositional array with the exception of highly fluid-mobile elements. The calculated trace element composition of the deeply recycled sediment in the Gough plume source is depleted in fluid-mobile elements such as Ba and Pb relative to the composition of some present-day subducting sediments. This loss is attributed to the dehydration or flushing of sediment in the subduction factory, consistent with constraints from arc magmas.  相似文献