Stratigraphy of the tectonically imbricated lithological succession of the Neves Corvo mine area,Iberian Pyrite Belt,Portugal     

J.?Tomás?Oliveira  Zélia?PereiraEmail author  Pedro?Carvalho  Nelson?Pacheco  Dieter?Korn 《Mineralium Deposita》2004,39(4):422-436

Biostratigraphic research, based on palynomorphs and ammonoids, of the tectonically imbricated lithological succession of the Neves Corvo mine, in the Portuguese part of the Iberian Pyrite Belt, has yielded ages for all formerly recognised lithostratigraphic units. These can be assembled in three main lithological sequences: (1) detrital sandy/shale substrate (Phyllite-Quartzite Formation) of late Famennian age; (2) Volcano-Sedimentary Complex, divided into a lower and an upper suite, in which one basic, three dolerite sills and four felsic volcanic units and a mineralised package of massive sulphides are identified with ages which range from the late Famennian to the late Visean; (3) flysch succession (Mértola Formation) composed of shale and greywacke dated as late Visean to early Serpukhovian. Precise biostratigraphic dating of the sedimentrary host rocks of massive sulphide mineralisation constrains the age of the latter to the late Strunian (354.8–354.0 Ma). Three stratigraphic hiatuses, corresponding to early/middle Strunian, Tournaisian and early Visean respectively and a south-westward progressive unconformity were also recognised. Sequences 1 and 2 are related to extensional episodes while sequence 3 marks the beginning of compressive tectonic inversion which gave rise to south-westward flysch progradation in close relation to a foreland basin development. Our results lead to the reinterpretation of the tectonic structure of the Neves Corvo mine, with implications for the interpretation of the regional basin dynamics and metal exploration.Editorial handling: F. Tornos  相似文献   

Calibration and validation of a model of forest disturbance in the Western Ghats,India 1920–1990     

Robert?Gilmore PontiusJr.Email author  Pablo?Pacheco 《GeoJournal》2004,61(4):325-334

This paper introduces a new statistical method that we recommend should become standard procedure to quantify the goodness-of-fit of calibration and validation for land-use change models. We present a multiple-resolution Relative Operating Characteristic (ROC) that measures the goodness-of-fit between a reference map, which is considered reality, and a simulated map, which is a model’s output. This proposed ROC is based on: (1) multiple-resolutions, (2) soft classification, (3) sampling without replacement, and 4) explicit separation of factors of quantity versus location of land-use change. We illustrate the method with a case study in India’s Western Ghats, a biodiversity hotspot, where we have maps of cumulative forest disturbance for 1920 and 1990. We use a predictive modeling approach similar to GEOMOD in which we calibrate the model with the map of 1920, then predict the map of 1990, at which point we subject the model to validation. We show that the fit of calibration tends to be much larger than the fit of validation. Thus if a modeler assess a model by goodness-of-fit of calibration only, then the modeler will likely be over confident in the model’s predictive ability.  相似文献   

Minor improvement for intertidal seaweeds and invertebrates after acid mine drainage diversion at Britannia Beach, Pacific Canada     

Zis T  Ronningen V  Scrosati R 《Marine pollution bulletin》2004,48(11-12):1040-1047

In December 2001, acid mine drainage (AMD) from an abandoned copper mine at Britannia Beach (British Columbia, Canada) was diverted to flow from Britannia Creek into an outfall at 30 m depth in Howe Sound. Britannia Beach was studied in early 2003 to determine whether AMD diversion resulted in improved conditions for intertidal organisms. Species number and abundance have increased at the intertidal zone since AMD diversion, although they were still lower than at an unpolluted control site nearby (Furry Creek). Survivorship and growth rates of transplanted Mytilus trossulus (mussel) have increased since AMD diversion, although they were still significantly lower than at the control site. Transplanted Fucus gardneri (seaweed) performed better than before the AMD diversion; at Britannia Beach the chlorophyll a concentration in tissues was not significantly different from that at the control site, although the concentration of chlorophyll c in tissues and the chlorophyll c to a ratio was lower than at the control site six weeks after transplantation. Britannia Beach is still subject to leaching of metals from surrounding soils, low levels of AMD coming down the creek, and AMD discharge from the deep outfall. Although there has been an improvement, the intertidal environment at Britannia Beach still seems unable to support normal growth and survival of organisms.  相似文献   

Element-Enrichment Factors in Lichens from Terceira, Santa Maria and Madeira Islands (Azores and Madeira Archipelagoes)     

B. J. Vieira  M. C. Freitas  A. F. Rodrigues  A. M. G. Pacheco  P. M. Soares  N. Correia 《Journal of Atmospheric Chemistry》2004,49(1-3):231-249

In this study, more than 20 minor and trace elements have been determined by INAA (instrumental neutron activation analysis), in different species of lichens in three Portuguese islands of the Central North Atlantic (Santa Maria, Terceira, and Madeira Islands). The foliose species Parmotrema bangii, Parmotrema robustum, Parmotrema crinitum, Flavoparmelia caperata, Platismatia glauca, and the fruiticose species Ramalina canariensis, Ramalina farinacea, Ramalina implectens, Ramalina pusilla, Cladonia furcata, Cladonia coniocraea, Usnea dasaea, Usnea esperantiana, were the collected species. Samples of superficial soils were also collected and the fraction below 64 m was analysed. The enrichment factors relative to this fraction using Al as the normalising element were calculated. Fruiticose and foliose lichens displayed different EF values concerning bromine and potassium. The first was more enriched in the foliose species while the latter was more enriched in the fruiticose species and was assigned to the physiological response. Enrichment was found for Mg, Cs, As, Hg, Na, Zn, and Cl, in all the species. Lichen-based concentration patterns were shown for Na, Al, Cl, Br, Sb, Ce, and Hg and compared to similar patterns in Portugal mainland. In general, the patterns compared well except for Cl, Na, and Br. Background levels of the epiphytic lichens collected in the islands were obtained.  相似文献   

A participatory approach to integrated aquifer management: The case of Guanajuato State,Mexico     

Ricardo?SandovalEmail author 《Hydrogeology Journal》2004,12(1):6-13

Guanajuato State, located in central Mexico, with less than 2% of the countrys area, has almost 17,000 deep water wells, from which nearly 4,000 cubic hectometers (hm³) per year are being extracted, more than 1,000 hm³ over the estimated renewable yield. Since, in Mexico, water is administered under federal jurisdiction by the National Water Commission (CNA, for its Spanish acronym), the state government faces the challenge of ensuring its populations economic development without formal means of intervention. Being thus limited to apply mandatory policies and measures, the state water program has focused on the implementation of a two-sided strategy. First, basic hydrogeological studies and mathematical groundwater hydrodynamic models were developed upon a comprehensive survey of existing wells and a general revision of the states geological framework. Second, a structure for water users participation in water management actions was promoted (from the dissemination of information to the implementation of pilot efficient water use projects) with financial, technical and political support from the state. Simultaneously, a coordinated effort towards the completion of the water users registry was performed with the federal authority along with other supporting measures such as training and monitoring programs. In this paper, a general overview of the projects achievements and challenges is presented.To make direct contact with the water-user associations mentioned in this paper, please write to Eng. Aurelio Navarrete of the State Water Council at: cehgto@prodigy.net.mx.  相似文献   

Some comments on Dr. Ramón Llamas’ remarks on the paper “A participatory approach to integrated aquifer management—the case of Guanajuato State, Mexico”     

M. S. Ricardo Sandoval-Minero 《Hydrogeology Journal》2006,14(1-2):265-266

  相似文献   

Geology and tectonics of the basin of Mexico and their relationship with the damage caused by the earthquakes of September 1985     

Ricardo Jose Padilla Y Sanchez 《Geotechnical and Geological Engineering》1989,7(1):17-28

Summary The earthquakes of 19 September 1985 (18.2° N, 102.7° W and a magnitude of 8.1 Richter scale) and of 20 (17.6° N, 101.8° W and a magnitude of 7.5 Richter scale) September 1985, caused the total or partial destruction of more than 2000 structures in Mexico City. The most affected areas are located along the fringes of and bordering old roadways, earthworks (dikes), aquaducts and pre-hispanic population centres. Ancient construction artificially modified the sedimentation in the basin of the Mexico Valley Lakes making the sub-soil of Mexico City more rigid near to the surface, and producing deviations of the surface seismic waves (Rayleigh waves and Love waves). Also, when earthquakes occur on the Pacific coast, seismic waves travel quickly through plutonic, metamorphics and continental and marine rocks of different ages, having high seismic velocities. When the seismic waves enter the poorly consolidated lake sediments having low seismic velocities in the Mexico City Basin, they produce an energy buildup that causes the phenomenon called magnification.There exists a direct relation between the amplification mentioned above and the presence of rigid bodies that are buried in the sub-soil. The length of these bodies is of the order of tens of kilometres horizontally with thicknesses less than 50 metres. These Rigid Barriers produce reflections and refractions of the surface waves along their borders with destructive consequences for the buildings. A correlation between the buildings and the houses damaged and destroyed and the location of the prehispanic construction on the sub-soil has been made which shows that the most damage happened in the borders of old roadways (i.e. Tlalpan road), perimeter walls (i.e. San Lazaro), aqueducts (i.e. Chapultepec Avenue), pyramids (i.e. Templo Mayor) and population centres (i.e. Tlaltelolco).  相似文献   

The spectrum of Cyg X-1 — A theoretical model     

J. A. De Freitas Pacheco  J. E. Steiner 《Astrophysics and Space Science》1976,39(2):487-494

We have calculated the spectrum of Cyg X-1 under the assumption that the radiation orginates in a disk around a 11M black-hole. Supersonic turbulence prevails in the outer parts of the disk and electron-electron bremsstrahlung appears to be resonsible for the maintenance of the temperature at a level less than 10¹⁰ K near the inner edge of the disk. The theoretical spectrum gives the best fit with the observations if the Reynolds number is about 1200.  相似文献   

Single Particle Characterisation of the Aerosol in the Marine Boundary Layer and Free Troposphere over Tenerife, NE Atlantic, during ACE-2     

Stefaan Hoornaert  Ricardo Henrique Moreton Godoi  René Van Grieken 《Journal of Atmospheric Chemistry》2003,46(3):271-293

In the framework of the 2nd Aerosol Characterization Experiment (ACE-2), in June and July 1997, size segregated samples were collected for single particle analysis on the island of Tenerife, in both the marine boundary layer (MBL) and the free troposphere (FT), to study the characteristics of the North Atlantic aerosol. A systematic assessment was made of the aerosol under background conditions and when the environment was perturbed by European emissions and/or Saharan dust. The aerosol particles were analysed by automated and manual SEM-EDX, followed by cluster analysis to identify the different particle types and their abundance. Basing on back trajectory calculations, particle numbers and volume concentrations, different periods can be identified regarding the origin of the sampled air masses. In the FT, the air masses were classified as clean Atlantic, Saharan dust from Africa or pollution from Europe. In the MBL, air masses were classified as clean, polluted or perturbed by emissions from Europe. For both the FT and MBL samples, the main changes in chemical composition were observed between the fine and coarse mode aerosol. The FT fine mode aerosol is dominated by S-poor aluminosilicates (62%) in the event of the dust samples or sulphates, carbonaceous particles (20%) and S-rich aluminosilicates (46%) in the polluted samples. For the larger fractions, a strong decreasing trend was observed for the sulphates (less than 20%) and carbonaceous particles (10%) in the polluted samples. The MBL fine mode was completely dominated by S-rich particles (polluted 55% and perturbed 59%), and to a lesser extent, carbonaceous and aged sea salt particles. In the coarse mode, the polluted air mass is dominated by sea salt particles (62%). Contrary to the fine fraction, the polluted air mass in the coarse fraction contained 5.3% of S-rich particles. The combined interpretation of the data from the analysis of size-fractioned particles and the calculated backward trajectories for air masses coming from Europe, Africa and the Atlantic, results in better insights on aerosol chemistry, especially for the comparison of the particle composition in the FT and the MBL.  相似文献   

Large Scale Rockfall Reach Susceptibility Maps in La Cabrera Sierra (Madrid) performed with GIS and Dynamic Analysis at 1:5,000   总被引：1，自引：0，他引：1  

Ayala-Carcedo  Francisco J.  Cubillo-Nielsen  Silvia  Alvarez  Ana  Domínguez  María J.  Laín  Luis  Laín  Ricardo  Ortiz  Guillermo 《Natural Hazards》2003,29(3):325-340

For the testing of the effect on the tsunami prevention facilities, a simplified methodfor tsunami risk assessment was suggested without wave run-up analysis. This methodis proposed using calculated offshore tsunami waveform and field reconnaissance suchas the seawall height, time necessary for residents' evacuation and tsunami warninginsurance. Then, two normalized values are evaluated; one is the ratio of calculatedmaximum tsunami height to seawall height, the other is the ratio of time betweentsunami over-topping and evacuation completion to total time required for evacuation.These two values are used to qualitatively estimate the safety of residents and the effectof tsunami prevention facilities, eliminating the necessity to compute complicatedtsunami run-up onshore.  相似文献