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1.
《International Geology Review》2012,54(4):313-334
The Jurassic through Oligocene stratigraphies of Trinidad and the Serrania del Interior of eastern Venezuela exhibit many similarities because of their proximity on the passive continental margin of northeastern South America. A slightly later subsidence in eastern Venezuela, and the generally deeper-water sedimentation in Trinidad, is interpreted to be the result of a serration of the original rift margin, producing an eastern Venezuelan promontory and Trinidadian reentrant. We interpret these serrations to be the result of oblique (NW-SE) spreading of North and South America during Middle and Late Jurassic time. The stratigraphies of northeastern Venezuela and Trinidad contrast in the Hauterivian-Albian interval, with dynamic shallow shelf environments prevailing in the Serrania del Interior and deeper marine submarine-fan deposition in Trinidad. Both areas develop middle to Upper Cretaceous source rocks during a time of eustatic sea level high and widespread oceanic anoxia. A slight lowering of eustatic sea level may have been responsible for the clastic influx represented by the sandstones of the Maastrichtian San Juan and Galera formations, disturbing the previous pelagic and hemipelagic sedimentation. The seaward transport of these sandstones may have been responsible for the localized erosion of the Maastrichtian section in central and southern Trinidad. Sedimentation stabilized with slope and outer-shelf turbiditic deposition during the Paleocene and Early Eocene, before diachronous, west-to-east shallowing occurred. Shallowing from the turbidites to shallow-water limestones and sandstones occurred in eastern Venezuela in the late Middle Eocene, and in the Late Eocene/Early Oligocene in Trinidad. Alhough eustasy and sediment progradation could have influenced the shallowing, its magnitude and rate requires that a tectonic uplift have occurred. Margin buckling, caused by the N-S relative convergence of North and South America, and forebulge uplift ahead of the Caribbean plate both are possible mechanisms. Following the shallowing, both areas subsided rapidly into laterally variable Oligocene to Recent flysch-like sedimentation. This is interpreted to represent the onset of direct interaction of the Caribbean plate with the South American depocenters of Trinidad and eastern Venezuela. Miocene to Recent sedimentation has been strongly influenced by these plate interactions. 相似文献
2.
Rethinking economy requires rethinking the relationship between economics and its object. The economy is a recent product of socio-technical practice, including the practice of academic economics. Previously, the term “economy” referred to ways of managing resources and exercising power. In the mid-twentieth century, it became an object of power and knowledge. Rival metrological projects brought the economy into being. The development of the modern electricity industry illustrates the kind of work involved. It required new technical processes, new forms of distribution, addressing, and monitoring, new forms of calculation that were simultaneously electrical, chemical, economic, and social. Analyses of how the economic is embedded in social ties or in cultural meanings cannot understand these intersecting projects. The projects that form the economy involve the work of economics. Economic knowledge does not represent the economy from some place outside. It participates in making sites where its facts can survive. The case of an economic research project on property rights in Peru illustrates how this happens. Economic facts were established in a world that was organized, through specific projects, such as the property titling programs of Hernando de Soto, to enable economic knowledge to be made. There is no simple divide between a virtual world of economic theory and a real world outside it. Every economic project involves multiple arrangements of the simulated and that to which it refers. 相似文献
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This paper presents a compilation of 16 present-day stress tensors along the southern Caribbean plate boundary zone (PBZ), and particularly in western and along northern Venezuela. As a trial, these new stress tensors along PBZ have been calculated from inversion of 125 focal mechanism solutions (FMS) by applying the Angelier & Mechler's dihedral method, which were originally gathered by the first author and published in 2005. These new tensors are compared to those 59 tensors inverted from fault-slip data measured only in Plio-Quaternary sedimentary rocks, compiled in Audemard et al. (2005), which were originally calculated by several researchers through the inversion methods developed by Angelier and Mechler or Etchecopar et al.The two sets of stress tensors, one derived from geological data and the other one from seismological data, compare very well throughout the PBZ in terms of both stress orientation and shape of the stress tensor. This region is characterized by a compressive strike-slip (transpressional senso lato), occasionally compressional, regime from the southern Mérida Andes on the southwest to the gulf of Paria in the east. Significant changes in direction of the maximum horizontal stress (σH = σ1) can be established along it though. The σ1 direction varies progressively from nearly east-west in the southern Andes (SW Venezuela) to between NW-SE and NNW-SSE in northwestern Venezuela; this direction remaining constant across northern Venezuela, from Colombia to Trinidad. In addition, the σV defined by inversion of focal mechanisms or by the shape of the stress ellipsoid derived from the Etchecopar et al.'s method better characterize whether the stress regime is transpressional or compressional, or even very rarely trantensional at local scale.The orientation and space variation of this regional stress field in western Venezuela results from the addition of the two major neighbouring interplate maximum horizontal stress orientations (σH): roughly east-west trending stress across the Nazca-South America type-B subduction along the pacific coast of Colombia and NNW-SSE oriented one across the southern Caribbean PBZ. Meanwhile, northern Venezuela, although dextral strike-slip (SS) is the dominant process, NW-SE to NNW-SSE compression is also taking place, which are both also supported by recent GPS results. 相似文献
5.
C. Schubert 《Tectonophysics》1979,52(1-4)
The El Pilar fault zone extends for about 700 km in an approximately E—W direction, from the Cariaco Trench to a point about 200 km northeast of Trinidad. It marks the southern boundary of the Araya—Paria peninsulas (eastern Caribbean Mts.) and of the Northern Range of Trinidad. It is characterized along its length by straight valleys, fault wedges, fumaroles, thermal springs, and sulfur deposits. The displacement along the El Pilar fault zone has been the subject of much controversy. Various authors recognize the following types of displacement: (1) southward thrust; (2) normal or graben faulting; (3) right-lateral strike-slip. The El Pilar fault zone probably represents a transform fault between the Caribbean and South America plates, and a hinge fault at its contact with the subduction zone east and south of the Lesser Antilles. It is planned to investigate the present-day movement along the El Pilar fault zone by high-precision geodetic methods, at the following localities: across the Gulf of Cariaco and at Casanay (central-southern Araya—Paria peninsulas). 相似文献
6.
Rural tourism in Spain: an analysis of recent evolution 总被引：6，自引：0，他引：6
The aim of this paper is to analyse the evolution of Rural Tourism1 (RT) in Spain within a European context. The first step is to examine the development of different “models” of RT and trace some experiences of the application of European policy. In order to set the scene and understand this evolution, the collective imagery on which RT is based is also analysed. This is followed by a study of the development of tourist products and services in rural Spain since the 1980s, as diversification of the traditional sun/sand/sea (3S) tourist economy is sought. The analysis underlines the importance of the role of women, and the consequences of the activity for the economy of rural areas. The purpose is to identify differences in the pattern of evolution with more northern European countries, understand their causes and formulate recommendations for future development. 相似文献
7.
Particulate trace metal speciation in stream sediments and relationships with grain size: Implications for geochemical exploration 总被引：1，自引：0，他引：1
Sediment samples were collected from streambeds in an undisturbed watershed in eastern Quebec (Gaspé Peninsula). Two sampling sites were located on a stream draining an area of known mineralization (Cu, Pb, Zn) and two on a control stream. The sediment samples were separated into 8 distinct size classes in the 850 μm to <1 μm size range by wet sieving, gravity sedimentation or centrifugation. Each sediment subsample was then subjected to a sequential extraction procedure designed to partition the particulate heavy metals into five fractions: (1) exchangeable; (2) specifically adsorbed or bound to carbonates; (3) bound to Fe-Mn oxides; (4) bound to organic matter; (5) residual. The following metals were analyzed in each extract: Cu, Pb, Zn; Fe, Mn.Comparison of samples from the mineralized area with control samples revealed the expected increase in total concentrations for Cu, Pb and Zn. Non-detrital metals were mainly associated with Fe oxides (specifically adsorbed; occluded) and with organic matter or resistant sulfides. For a given sample, variation of trace metal levels in fractions 2 and 3 with grain size reflected changes in the available quantities of the inorganic scavenging phase (FeOx/MnOx); normalization with respect to Fe and Mn content in fraction 3 greatly reduced the apparent dependency on grain size.The results of this study suggest that a single reducing extraction (NH2OH.HCl) could be used advantageously to detect anomalies in routine geochemical surveys. A second leaching step with acidified H2O2 could also be included, as the trace metal concentrations in fraction 4, normalized with respect to organic carbon content, also showed high {anomaly/background} ratios. 相似文献
8.
The problem of defining geochemical baselines. A case study of selected elements and geological materials in Finland 总被引：3，自引：0，他引：3
Although the term ‘geochemical baseline’ appears in the international geochemical mapping programmes IGCP 259 and 360, it has never been well defined. Several considerations relevant to such a definition are discussed. A geochemical baseline for an element refers to its natural variations in concentration in the surficial environment. Geochemical baselines were studied in Finland by comparing results from regional geochemical mapping programmes based on samples of till, clay and organic stream sediment. The geochemical background changes regionally with the basic geology and locally with the type and genesis of the overburden. Baseline concentrations depend on sample material collected, grain size and extraction method. In Finland, concentrations of potentially harmful elements tend to be higher in fine-grained marine and lacustrine sediments than in glacial till. Concentrations are also systematically higher in the < 0.06 mm fraction than in the < 2 mm size fraction of till samples. Only small proportions of the total heavy metal concentrations in Finnish marine clays are bioavailable. Geochemical baselines are needed for environmental legislation and political decision-making, especially in the assessment of contaminated soil. In many areas of Finland, natural concentrations of several heavy metals exceed the guide or limit values designated for contaminated soils. Thus baselines must always be verified in any assessment of sites for contamination. 相似文献
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The present research work deals with an expansive high plastic clayey soil with cement kiln dust (CKD) and stabilizer (RBI Grade 81). The physical and engineering properties of soil are plasticity, compaction, unconfined compressive strength (UCS), consolidation and California bearing ratio (CBR) of the clayey soil and clay treated with CKD and stabilizer were determined. Soil chemistry was examined before and after treatment using scanning electron microscope (SEM) and elemental dispersive spectrometer. The clay mixed with CKD, CKD and RBI Grade 81 was found that optimum contents are 10 % (CKD), 15 % CKD with 4 % RBI Grade 81, respectively. The result indicates that CKD alone will decrease maximum dry density and increase optimum moisture content. CKD with RBI Grade 81 slightly increases maximum dry density and decreases optimum moisture content. UCS increased with CKD alone and CKD with RBI Grade 81 from 88.3 to 976 kN/m2, respectively. CBR values were increased by the addition of CKD, CKD with RBI Grade 81 from 1.65 to 21.7 %. With the curing time of 3, 14 and 28 days, UCS and CBR values were increased due to pozzolanic reaction from cementations material. The treated soil has considerable reduction in compression index. SEM images clearly indicate the formation of CSH and CAH gel. 相似文献
11.
S. A. Punanova 《Geochemistry International》2014,52(1):57-67
Available data on the transformation of naphthides (oils and bitumens) in various petroleum basins (PB) during supergene processes were generalized to reveal their characteristic features for more accurate prediction of pool preservation and commercial quality of oils as hydrocarbon raw material enriched in economically significant toxic metals. Using petroleum basins of the United States, Canada, Brazil, Venezuela, Nigeria, Russia, Kazakhstan, and Turkmenia as examples, itwas demonstrated that trace-element concentrations and ratios as well as metalloporphyrin complexes (MPC), including vanadium (Vp) and nickel (Nip) ones, which are associated with heavy resinous-asphaltene components of oils, serve as geochemical criteria of supergene transformed fluids. During supergenesis, oils show differential enrichment in metals. Considerable enrichment in V, Ni, Co, Mo, Cr, and other trace elements as well as MPC were found in oils generated by sapropel organic matter (OM) and initially enriched in metals (deposits of the South Tatar arch of the Volga-Urals, Buzachi arch, Afghan-Tajik Basin, and Marakaibo petroleum province of Venezuela). Oils initially depleted in trace elements and usually generated by humic OM also show increase in trace elements, but their concentrations are 1–3 orders of magnitude lower than those in enriched oils (oil fields in the coastal basins of Nigeria and Brazil). It was shown that supergene transformed fluids are well deciphered on the basis of a complex use of hydrocarbon and trace element criteria. 相似文献
12.
Werner Skrotzki Roland Tamm Carl-Georg Oertel Jens Rseberg Heinz-Günter Brokmeier 《Journal of Structural Geology》2000,22(11-12)
Lead sulfide (galena) of different purity and grain size was extruded through a round and rectangular die at temperatures between 773 and 923 K. Global and local lattice preferred orientations (here referred to as textures) were measured by neutron and electron back-scattering diffraction. Tension leads to a <100> <111> double fibre texture. Pure shear deformation yields texture components near the ideal face-centered cubic metal brass, copper, Goss and cube positions. The intensity of the components depends on the purity and/or grain size. The microstructure is partially recrystallized. Electron back-scattering diffraction indicates that in tension the <100> and in pure shear the Goss and cube components are associated with dynamic recrystallization. The deformation texture can be qualitatively explained by the full and relaxed constraints Taylor model using slip on {100}<110>, {110}<110> and {111}<110> systems. The texture formation in lead sulfide compares well with that observed for other ionic crystals with the NaCl-structure as well as for face-centered cubic metals with a high stacking fault energy. 相似文献
13.
Crude oil is the world's leading fuel, and its prices have a big impact on the global environment, economy as well as oil exploration and exploitation activities. Oil price forecasts are very useful to industries, governments and individuals. Although many methods have been developed for predicting oil prices, it remains one of the most challenging forecasting problems due to the high volatility of oil prices. In this paper, we propose a novel approach for crude oil price prediction based on a new machine learning paradigm called stream learning. The main advantage of our stream learning approach is that the prediction model can capture the changing pattern of oil prices since the model is continuously updated whenever new oil price data are available, with very small constant overhead. To evaluate the forecasting ability of our stream learning model, we compare it with three other popular oil price prediction models. The experiment results show that our stream learning model achieves the highest accuracy in terms of both mean squared prediction error and directional accuracy ratio over a variety of forecast time horizons. 相似文献
14.
Privatization of rural industry and de facto urbanization from below in southern Jiangsu, China 总被引：4，自引：0，他引：4
At the heart of China’s economic transformation from plan to market is the institutional rearrangement of the ownership of property rights. Privatization of collectively owned township and village enterprises (TVEs) in recent years has significantly changed the rural economy and affected small town development in China. Located mainly in villages and small towns and producing 62% of the total industrial output in Jiangsu in 1994, TVEs played a crucial role in southern Jiangsu (Sunan)’s economic development and urbanization, giving rise to the well-known “Sunan model” of regional development during the 1980s. Since the mid-1990s, ownership transition (zhuanzhi) of the TVEs from collective to private in Sunan has altered the nature of the regional economy and the pattern of small town development. The privatization of TVEs in Sunan has been so pervasive that it can be seen as the “second industrial divide” in the region’s economy. This paper traces the evolution of ownership reform in Sunan’s rural industries leading to the current phase of privatization and analyzes the effects of privatization on de facto urbanization from below in Sunan. Given the importance of privatization, continuous scholarly monitoring of its relationship to regional economic development and urbanization from below is necessary. 相似文献
15.
Indian economy is vitally linked with the monsoon because of its water resources. A large part of the country gets more than 75% of the annual rainfall during the four months, June to September.The production of foodgrains depends fairly closely on the amount and distribution of monsoon rainfall over the country. Further the generation of hydro-electric power from monsoon rain water has been traced over the last 20 years. While hydro-electric power constitutes about 40% of power from all sources, with proper surveys and planning additional hydro-electric power projects this percentage could, perhaps, be further substantially increased. The distinct advantage of hydro-electric power over all other types of power is that its source, i.e. monsoon water, is perennial, although it shows some fluctuations from year to year. The power of the monsoon winds at four and two stations on the West coast and in the interior resp. has been assessed on the basis of five years hourly wind data. The wind at New Kandla on the West coast has a good potentiality for power. The wind power could be used for electricity, grinding corn and drawing water. On the debit side, Indian economy suffers heavy losses due to floods and droughts almost every year.The population of India is increasing at a much faster rate than the total foodgrains production and soon the country may be facing a serious economic crisis. A large part of the monsoon water which is currently unutilized should be held at suitable locations for irrigation and possible power generation. 相似文献
16.
Abhay Kumar Singh 《Environmental Earth Sciences》2011,62(7):1447-1459
Road dust collected from India’s richest and oldest coal mining belt of Dhanbad and Bokaro regions was analysed for particle
size characteristics and elemental composition. The particle size distribution pattern shows dominance of 500–250 μm and 250–125 μm
size fractions, constituting 45–58% of the mass size spectrum. Si is the most dominant element and its concentration varied
between 29.3 and 36.4% with the average value 34.3%. Fe, Ti and Mn are the dominant heavy metals followed by Zn, Cr, Pb, Cu,
Ni and Co. No significant differences concentration of metals between sampling sites was apparent; however, some sites tend
to accommodate relatively higher metals due to its proximity to industrial and mining sites. In general, finer fraction (<63 μm)
tend to contain 1–3 times higher metals as compared with the bulk composition. Except Pb and Mn all the measured metals are
generally lie below grade zero, suggesting that there is no pollution threat with respect to these metals in roadway dust
from the studied sites. Geochemical speciation study shows that the lithogenic phase is the major sink for heavy metals. Fe–Mn
oxide and organic are the major non-lithogenic phases and Pb and Zn are the major elements of the non-lithogenic phase. 相似文献
17.
This paper deals with second-generation, one-and-a-half generation and “prolonged sojourner” Trinidadian transnational migrants, who have decided to ‘return’ to the birthplace of their parents. Based on 40 in-depth interviews, the paper considers both the positive and critical things that these youthful transnational migrants report about returning to, and living in, this multi-ethnic plural society and the salience of racial and colour-class stratification as part of their return migration experiences. Our qualitative analysis is based on the narratives provided by these youthful returnees, as relayed “in their own words”, presenting critical reflections on racism, racial identities and experiences as transnational Trinidadians. It is clear that it is contexts such as contemporary working environments, family and community that act as the reference points for the adaptation “back home” of this strongly middle-class cohort. We accordingly encounter a diverse, sometimes contesting set of racial issues that emerge as salient concerns for these returnees. The consensus is that matters racial remain as formidable legacies in the hierarchical stratification of Trinidadian society for a sizeable number. Many of our respondents reported the positive aspects of racial affirmation on return. But for another sub-set, the fact that multi-ethnic and multi-cultural mixing are proudly embraced in Trinidad meant that it was felt that return experiences were not overly hindered, or blighted by obstacles of race and colour-class. For these returnees, Trinidad and Tobago is seen as representing a 21st century “Melting Pot”. But for others the continued existence of racial divisions within society - between ethnic groups and among those of different skin shades - was lamented. In the views of these respondents, too much racial power is still ascribed to ‘near-whiteness’. But for the most part, the returnees felt that where race played a part in their new lives, this generally served to advantage them. However, although the situation in Trinidad appears to have been moderated by assumptions that it remains a racial ‘Melting Pot’, the analysis strongly suggests that the colour-class system of stratification is still playing an essential role, along with racial stereotyping in society at large. 相似文献
18.
Suspended and bed sediments collected from the entire region of the Krishna River and its major tributaries were analyzed for heavy metals (V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Pb) by the thin-film energy dispersive x-ray fluorescence technique. There is considerable variation in the concentration of elements towards downstream, which may be due to the variation in the subbasin geology and various degrees of human impact. Suspended particles are enriched in heavy metals throughout the basin relative to bed sediments. The heavy metals are enriched in coarse size fractions (10–90 µm) throughout the Krishna River except its tributary Bhima, where finer fractions (2 µm) dominate. Transition elements correlate very well with each other. There is a striking similarity between the bed sediments of Krishna River and the Indian average. When the annual heavy metal flux carried by the Krishna River was estimated, and viewed in relation to the other major riverine transport, the Krishna is seen to be a minor contributor of heavy metals to the Bay of Bengal. 相似文献
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The Pirabas Formation of Early Miocene age represents the final stage of the central western Atlantic carbonate platform in northeastern South America, predating the emplacement of the Amazon delta system. The otolith-based fossil fish fauna is represented by 38 species typical of a shallow marine environment. A total of 18 species are described new to science from the families Congridae, Batrachoididae, Bythitidae, Sciaenidae and Paralichthyidae. The fish fauna was associated with high benthic and planktic primary productivity including seagrass meadows, calcareous algae and suspension-feeders. The break of todays shallow marine bioprovince at the Amazonas delta mouth is not evident from the fish fauna of the Pirabas Fm., which shows good correlation with the Gatunian/proto-Caribbean bioprovince known from an only slightly younger time window in Trinidad and Venezuela. Differences observed to those Early Miocene faunal associations are interpreted to be mainly due to stratigraphic and geographic and not environmental differences. We postulate that the emergence of the Amazonas river mouth close to its present day location has terminated the carbonate cycle of the Pirabas Fm. and pushed back northwards a certain proportion of the fish fauna here described. 相似文献