Strontium-isotope stratigraphy as a constraint on the age of condensed levels: examples from the Jurassic of the Subbetic Zone (southern Spain)   总被引：1，自引：0，他引：1  

LUIS M. NIETO  PEDRO A. RUIZ-ORTIZ  JAVIER REY†  Mª ISABEL BENITO‡ 《Sedimentology》2008,55(1):1-29

Condensed levels are often characterized by reworked fossils that may lead to incorrect age assessments. Strontium‐isotope stratigraphy is an important chronostratigraphic tool that can be used to verify the biostratigraphic information from condensed beds. This paper describes a study of the ⁸⁷Sr/⁸⁶Sr isotope ratios of 56 belemnite samples collected from 28 stratigraphic sections of the boundary between the Upper Member of the Gavilán Formation and the Zegrí Formation (Pliensbachian, Subbetic Zone). The petrographic and geochemical data (δ¹⁸O, δ¹³C, concentrations of Fe, Mn and Mg, and the Sr/Mn ratio) suggest that the belemnites have preserved their original marine geochemical composition. After plotting the samples in diagrams of ⁸⁷Sr/⁸⁶Sr values against time according to their biostratigraphic age, four different groups (A, B, C and D) were obtained with respect to the reference curve. In groups A and B, the age deduced from the Sr‐isotope ratio is in total or partial agreement, respectively, with the biostratigraphic age; therefore the ⁸⁷Sr/⁸⁶Sr ratio is a good method for the dating, correlation and assessment of biostratigraphic results. In groups C and D, the SIS age and the biostratigraphic age do not coincide. A graphic procedure is presented as a suitable methodology to constrain the age of the samples showing an SIS age that differs from the relative age deduced (by biostratigraphy or stratigraphic correlation) for the bed they were collected in. These situations are interpreted as being the result of reworking of the belemnites (group C) or ammonites (group D) that are included in condensed levels. These condensed levels formed during the maximum flooding event that led to the drowning of the Gavilán carbonate platform. The methodology supplied in this paper represents a valuable tool in identifying reworking processes, improving correlation and constraining biochronostratigraphic results. The values of ⁸⁷Sr/⁸⁶Sr represent a new contribution to the data set of ⁸⁷Sr/⁸⁶Sr ratios for the Pliensbachian.  相似文献   

INTÉERÉET D'ÉETUDES HYDROLOGIQUES APPROFONDIES SUR DES BASSINS EXPÉERIMENTAUX OCCUPANT PLUSIEURS MILLIERS DE KM2     

M. PARDÉE 《水文科学杂志》2013,58(4):13-19

Abstract

A relationship of hydrologic variables with stream salinity was determined statistically for two ephemeral streams located in western Oklahoma. The hydrologic variables employed in this study are measures of streamflow, precipitation, anteccedent conditions, and agricultural land use.

The best single estimate of stream salinity was achieved by use of those variables classed as direct measures of precipitation, with the greatest variability in stream salinity (51%) being predicted by maximum daily P, the maximum amount of precipitation received at any rain gage zone in the watershed during one month. Maximum daily P predicts nearly double the variability in stream salinity predicted by flow. Antecedent conditions did not correlate well with stream salinity, except for the variable describing the antecedent stream salinity. Similarly, the areal location of precipitation within the watershed and agricultural land use did not correlate significantly with stream salinity, except for a variable designating the distance between the stream gaging station and the rain gage zone receiving the most precipitation for the month.

The best overall estimate of salinity was given by a multiple regression equation chosen on the basis of a factor analysis. This equation accounted for 65 percent of the variability in salinity and emphasized the contribution of variables classed as direct measures of precipitation. In comparing the two streams, the watershed having the most intensive rain gage network produced the best prediction equation.  相似文献   

Mapping groundwater quality variables using PCA and geostatistics: a case study of Bajo Andarax,southeastern Spain     

FRANCISCO SÁNCHEZ-MARTOS  R. JIMÉNEZ-ESPINOSA  A. PULIDO-BOSCH 《水文科学杂志》2013,58(2):227-242

Abstract

A case study is presented for the application of statistical and geostatistical methods to the problem of estimating groundwater quality variables. This methodology has been applied to the investigation of the detrital aquifer of the Bajo Andarax (Almería, Spain). The use of principal components analysis is proposed, as a first step, for identifying relevant types of groundwater and the processes that bring about a change in their quality. As a result of this application, three factors were obtained, which were used as three new variables (VI: sulphate influence; V2: thermal influence; and V3: marine influence). Analysis of their spatial distribution was performed through the calculation of experimental and theoretical variograms, which served as input for geostatistical modelling using ordinary block kriging. This analysis has allowed a probabilistic representation of the data to be obtained by mapping the three variables throughout the aquifer for each sampling point. In this way, one can evaluate the spatial and temporal variation of the principal physico-chemical processes associated with the three variables VI, V2 and V3 implicated in the groundwater quality of the detrital aquifer.  相似文献   

Climate and landscape during Heinrich Event 3 in south‐western Europe: the small‐vertebrate association from Galls Carboners cave (Mont‐ral,Tarragona, north‐eastern Iberia)          下载免费PDF全文

JUAN MANUEL LÓPEZ‐GARCÍA  HUGUES‐ALEXANDRE BLAIN  MARIA BENNÀSAR  JOSEP ANTONI ALCOVER  SANDRA BAÑULS‐CARDONA  MÓNICA FERNÁNDEZ‐GARCÍA  MARTA FONTANALS  PATRICIA MARTÍN  JUAN IGNACIO MORALES  LAURA MUÑOZ  MIREIA PEDRO  JOSEP MARÍA VERGÉS 《第四纪科学杂志》2014,29(2):130-140

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Abrupt variability of the last 24 ka BP recorded by coccolithophore assemblages off the Iberian Margin (core MD03‐2699)     

ELIANA PALUMBO  JOSÉ A. FLORES  CARMEN PERUGIA  DARIO EMANUELE  ZACCARIA PETRILLO  TERESA RODRIGUES  ANTJE H. L. VOELKER  FILOMENA O. AMORE 《第四纪科学杂志》2013,28(3):320-328

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Long‐term dynamics of fire refuges in boreal mixedwood forests          下载免费PDF全文

SAMIRA OUARMIM  HUGO ASSELIN  CHRISTELLE HÉLY  YVES BERGERON  ADAM A. ALI 《第四纪科学杂志》2014,29(2):123-129

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Aeolian construction and alluvial dismantling of a fault‐bounded intracontinental aeolian dune field (Teruel Basin,Spain); a continental perspective on Late Pliocene climate change and variability     

JUAN PEDRO RODRÍGUEZ‐LÓPEZ  CARLOS L. LIESA  JAN VAN DAM  PALOMA LAFUENTE  LUIS ARLEGUI  LOPE EZQUERRO  POPPE L. DE BOER 《Sedimentology》2012,59(5):1536-1567

An aeolian dune field migrating to the east encroached on the toes of alluvial fans in the Teruel Basin (eastern Spain) during a short interval in the Late Pliocene (ca 2·9 to 2·6 Ma), when Northern Hemisphere glaciation and strong glacial–interglacial cycles began. Preservation of the dune field was controlled by syn‐sedimentary activity of a normal fault. Ephemeral water discharge eroded aeolian sands and formed V‐shaped channels in which aeolian sandstone blocks accumulated. The incorporation of loose aeolian sand in wadi waters modified the sediment/water ratio, changing the physical properties of the flows as they penetrated the aeolian dune field. The erosion and cover of aeolian dune foresets by sheetflood deposits suggest that dune‐damming caused the intermittent ponding of water behind the dunes and its flashy release. The arid climate in the Late Pliocene western Mediterranean realm favoured the transport of windblown sediments from northern Africa and western Mediterranean land masses into the Mediterranean. The formation of the studied aeolian dune field (2·9 to 2·6 Ma) and possibly others (for example, the Atacama, Namib and Sahara deserts) correlates with a strong increase of the influence of obliquity, which can be attributed to the combination of a regional expression related to the reduced effect of precession due to a minimum in the long‐period (2·3 Ma) eccentricity cycle and a remote expression of the onset of the Northern Hemisphere glaciation.  相似文献   

Swell impact on reef sedimentary processes: A case study of the La Reunion fringing reef     

EMMANUEL CORDIER  EMMANUEL POIZOT  YANN MÉAR 《Sedimentology》2012,59(7):2004-2023

Two surface‐sediment sampling campaigns were carried out in November and December 2003, before and after a strong swell event, in the back‐reef area of a microtidal fringing reef on the western coast of La Reunion, Indian Ocean. The spatial distributions of the mean grain size, sorting and skewness parameters are determined, and grain‐size trend analysis is performed to estimate the main sediment transport pathways in the reef. The results of this analysis are compared with hydrodynamic records obtained in the same reef area during fair weather conditions and during swell events. Sediment dynamics inferred from the hydrodynamic records show that significant sediment erosion and transport occur only during swell events and under strongly agitated sea states. Under normal wave conditions, there is a potential for onshore sediment transport from the reef‐flat to the back‐reef, but this transport is episodic and occurs principally during high‐tide stages. Sediment transport trends revealed by the grain‐size trend analysis method show onshore and alongshore low‐energy transport processes that are in agreement with the hydrodynamic records. The grain‐size trend analysis method also provides evidence of an offshore high‐energy transport trend that could be interpreted as a real physical process associated with return flow from the shore to the reef. The impact of swell on the reef sediment dynamics is clearly demonstrated by onshore and alongshore transport. Considering different combinations of the vector transport trends computed through the grain‐size trend analysis approach, more realistic and pertinent results can be obtained by applying an exclusive OR operation (XOR case) on the vectors. The main results presented here highlight a trend towards the accumulation of carbonate sands in the back‐reef area of the fringing reef. These sediments can only be resuspended during extreme events such as storms or tropical cyclones.  相似文献   

Treatment of an ECF bleaching effluent with white-rot fungi in an air-lift bioreactor     

Érica S. Souza  João V. B. Souza  Flávio T. Silva  Teresa C. B. Paiva 《Environmental Earth Sciences》2014,72(4):1289-1294

Pulp and paper mills utilise huge amount of natural resources, inorganic and organic materials along with large volume of water in different stages of paper manufacturing, resulting in a significant volume of effluents. The aim of this work was to investigate the treatment of a bleaching effluent [effluent chlorine free (ECF)] from the cellulose industry with white-rot fungi in an air-lift bioreactor. This effluent was submitted to the biological treatment with three white-rot fungi, and, every 24 h for 120 h, analytical tests were performed to analyse the quality parameters of treatment (COD, phenols, colour, pH). Before and after treatment, the effluent was analysed as its molecular mass distribution and absorptivity in the UV/VIS. Lentinus edodes, Trametes versicolor and Trametes villosa promoted similarly significant reductions in the following characteristics: (a) effluent colour (40–44 %), (b) total phenol (30–51 %) and (c) COD (37–43 %). The UV/visible spectrometry reading of the effluent after the fungi treatment showed a reduction in the absorbance of all wavelengths between 260 and 500 nm. The size exclusion HPLC profile of the effluent was modified, and the treatment promoted changes in the intensity of the peaks associated with compounds of high and low molecular weight. Phenoloxidases were produced during the treatment. T. versicolor produced the highest levels of laccase, and L. edodes was the only fungus that produced peroxidases.  相似文献   

Controls on the alluviation of oxbow lakes by bed‐material load along the Sacramento River,California     

JOSÉ ANTONIO CONSTANTINE  THOMAS DUNNE  HERVÉ PIÉGAY  G. MATHIAS KONDOLF 《Sedimentology》2010,57(2):389-407

Differences in the nature and quantity of sediment filling oxbow lakes have significant implications for the evolution of meandering rivers and the development of floodplains, influencing rates of meander migration and the valley width over which migration takes place. In an effort to identify the controls on the alluviation of oxbow lakes by coarse bed material, this study examined the sedimentary records stored within oxbow lakes of the Sacramento River of California, USA, and found that the volume of gravel in storage correlated negatively with the diversion angle separating flow between the river channel and the entrance into each lake. A method was devised for estimating the original channel bathymetry of the studied lakes and for modelling the hydraulic and sediment‐transport effects of the diversion angle within channels recently abandoned by meander cut‐off. The diversion angle determines the width of a flow separation within the abandoned‐channel entrance, reducing the discharge diverted from the river channel and thus limiting the ability of the abandoned channel to transport bed material. Aggradation rates are faster within entrances to abandoned channels with high diversion angles, resulting in the rapid isolation of lakes that store only a small volume of coarse‐grained sediment. Aggradation rates are slower within channel entrances where diversion angles are low, resulting in the slow transitioning of such channels into oxbow lakes with a larger and more extensive accumulation of coarse‐grained sediment. These findings compare well with observations in other natural settings and the mechanism which is described for the control of the diversion may explain why some oxbow lakes remain as open‐water environments for centuries, whereas others are filled completely within decades of cut‐off.  相似文献