Lake Maracaibo Research Articles

La dimensión social del actor local en el talento territorial

Esta investigación parte de la definición del actor local en los planteamientos expuestos por García (2007), Fernández (2008) y Arocena (2002). Los actores locales con su capacidad asociativa ligada a decisiones y acciones, a influencias de poder o de experticia para el desarrollo territorial. Este artículo estudia la dimensión social, - el capital social -, del actor local, dentro del talento territorial. Esta dimensión está vinculada con la exigencia a los actores locales involucrados en el desarrollo territorial de contar con altos niveles de organización social para la producción, participación social protagónica, auto dependencia, confianza en los sistemas e instituciones de la participación, capacidad de articulación con otros actores organizados o en comunidades, así como, con otros territorios y con redes territoriales del desarrollo. Metodológicamente es una investigación exploratoria, de análisis de un territorio como laboratorio vivencial a partir de un enfoque sistémico procesal, desde la metodología sistémica interpretativa, sustentada en referencias bibliográficas y electrónicas dando apoyo a las reflexiones y experiencias del autor sobre el tema abordado de manera inductiva y constructivista. Como resultado se presentan la conceptualización de la dimensión social del actor local y su rol en el desarrollo territorial a partir de un territorio referencial bajo investigación (Zona Sur del Lago de Maracaibo. Concluyendo con laidentificación de tres escenarios de actuación del actor local dentro dela dimensión social del talento territorial.

Rapid ecological assessment of mammals from a locality of middle basin at Palmar River, Zulia state, Venezuela

Here we present the results from a rapid ecological assessment of mammals within Campo Boscán, located in the middle basin of the Palmar River in Zulia state, Venezuela. Records for species inventories were obtained from mist-nets and traps surveys and direct observation across three-vegetation types; we also include data from surveys to local communities. We identified 47 mammal species–representing 24 families and nine orders–, including the first record of the Hairy Big-eared Bat (Micronycteris hirsuta) for the Maracaibo Lake Depression region. Orders Chiroptera, Rodentia and Carnivora represented the most diverse and abundant taxa. Insectivores and carnivores were the most diverse trophic groups. Approximately 13% of the species are included within some threat category. Our results can be used for developing future monitoring programs in order to increase the knowledge on terrestrial vertebrates and biodiversity in general within the region. Key words: Ecology, species richness, mammals, Maracaibo Lake Depression, Zulia state

HEMIBRYCON GUEJARENSIS, A NEW SPECIES FROM THE GÜEJAR RIVER, ORINOCO BASIN, COLOMBIA (CHARACIFORMES: CHARACIDAE) WITH A REVIEW THE POPULATIONS IDENTIFIED AS HEMIBRYCON METAE

Hemibrycon guejarensis, new species, is described from the Güejar River, La Macarena mountain range, upper Guaviare River drainage, Colombia. The new species is distinguished from most cis-Andean congeners (H. jabonero Lake Maracaibo and adjacent Caribbean drainages, H. metae which is found in the Guavio River, some Orinoco and Caribbean River drainages in Venezuela, and H. taeniurus from Trinidad and adjacent mainland drainages in Venezuela) in having ii, 7, i dorsal-fin rays (vs. ii, 8). H. guejarensis is further distinguished from H. taeniurus and H. jabonero, in having a wider second pigment layer in the humeral spot (covering 3 vs. 2 scale widths). H. guejarensis is very similar to H. metae (an allopatric species also present in streams of the Orinoco River Basin in Venezuela and Colombia and some Venezuelan Caribbean drainages). Hemibrycon guejarensis is distinguishedby the orientation of the dorsal lateral-line canal which crosses the ventral part of the humeral spot transversely vs. horizontally across dorsal part of spot in the holotype of H. metae and Orinoco and Caribbean populations. H. guejarensis differs from H. metae in having the tip of the pectoral fin passing the pelvic-fin insertions (vs. pectoral fin tip not reaching pelvic-fin insertions). We identify populations previously considered as Hemibrycon metae from Venezuelan Orinoco River Basin piedmont streams and Caribbean drainages to be instead H. jabonero and H. taeniurus. Careful analysis of these populations indicated that all of them differ from the H. metae holotype and topotypic specimens in pelvic fin and postorbital lengths.

English

Except for the professional work conducted by a few adventurous anthropologists such as Roth (1970) and Johannes (1963), little is actually known about the great impact that the Warao of north eastern Venezuela and the Guajiro of Zulia State near to Lake Maracaibo, Venezuela, have made on both allopathic and traditional medicine in the modern world. During my undergraduate years at the University of the West Indies in St Augustine, Trinidad and Tobago, I ventured out to Venezuela in search of 'food' for my 'hungry' Caribbean Studies paper. Years later, during my postgraduate years in the United States of America (USA), I found similar 'food' to whet the appetite of my research paper on the incidence and management of diabetes mellitus among the Guajiro Indians and I discovered that in spite of the geographical and topographical differences in the physical locations of these two ethnic groups, there still exist remarkable similarities in their food intake, lifestyle, traditional beliefs, family ties and customs. In my sojourns through relatively remote parts of Venezuela and during the course of my social interludes with these great people, I discovered that they were almost totally non-dependent on modern medical personnel and modern medicine within their immediate environment. The Warao, also known as the 'Boat people', survive on the fauna of the tributaries of the vast Orinoco River and the flora of the dense jungle that yield fresh vegetation and other foods that are loaded with a myriad of botanical and nutritional cures.

Lightning over Three Large Tropical Lakes and the Strait of Malacca: Exploratory Analyses

Lightning stroke density measured by the Global Lightning Dataset (GLD360) has shown several strong maxima around the globe. Several of these extremes are located over large tropical water bodies surrounded by terrain features. Four prominent maxima are examined and compared in this study: Lake Maracaibo in South America, the Strait of Malacca in equatorial Asia, Lake Victoria in East Africa, and Lake Titicaca in South America. Specifically, the authors observe that all four water bodies exhibit sustained maxima in lightning occurrence all night, the peak lightning frequency occurs very late at night or the following morning at three of the four sites, and the nocturnal maxima are out of phase at the four locations even though the afternoon maxima over the surrounding terrain all occur between 1500 and 1700 local solar time. The meteorological factors affecting the diurnal cycle of lightning occurrence over these four water bodies, which are all adjacent to mountains, are explored in this study.

Consorcio microbiano autóctono para el tratamiento de aguas contaminadas con gasoil del puerto de Isla de Toas (Venezuela)

El tratamiento biológico de aguas contaminadas mediante consorcios microbianos autóctonos, aprovecha las potencialidades metabólicas de grupos distintos de microorganismos para degradar y/o remover una amplia variedad de compuestos. Adicionalmente, las técnicas de bioestimulación y bioaumentación contribuyen a potenciar las capacidades de estos procesos de biodegradación. El objetivo de este trabajo consistió en evaluar la utilización de un consorcio microbiano autóctono (Chlorella spp.-bacterias) para el tratamiento de aguas del puerto de Isla de Toas (Lago de Maracaibo, Venezuela), contaminadas con 1% v/v de gasoil. Para ello, se usaron dos tratamientos (T1: bioestimulado y T2: bioaumentado) y un control por 70 días, a escala de 20 L y condiciones ambientales controladas. Durante los ensayos se monitorearon: temperatura, pH, demanda química de oxígeno (DQO), nitrito, nitrato, nitrógeno total Kjeldahl, nitrógeno total (N-total), ortofosfato, fósforo total (P-total), hidrocarburos totales del petróleo (HTP), fracciones de hidrocarburos (SARA), densidad microalgal y bacteriana, y pigmentos fotosintéticos, de acuerdo con los métodos estandarizados. Los valores medios para la remoción de materia orgánica (DQO), N-total y P-total, fueron: 23,3±2,3; 35,2±4,5 y 64,6±4,8%, de 27,6±1,64; 79,8±2,05 y 87,7±1,95%, y de <0,1; 16,1±0,38 y 44,7±1,18%, para el control, T1 y T2, respectivamente. Las concentraciones finales de HTP estuvieron por encima del límite permisible de la normativa venezolana para descarga a cuerpos de aguas naturales, no obstante, se obtuvieron altas tasas de remoción de hidrocarburos saturados y aromáticos (>70%), particularmente en el tratamiento bioaumentado (T2). Los consorcios microbianos autóctonos poseen gran potencial para la biorrecuperación del agua del puerto de Isla de Toas, contaminada con hidrocarburos del petróleo, por lo cual se recomienda continuar investigando sobre esta tecnología de tratamiento.

Taxonomic review of Trans-Andean species of Pimelodus (Siluriformes: Pimelodidae), with the descriptions of two new species

We review the trans-Andean species of Pimelodus from Colombia, Panamá, and Venezuela. Based on meristic and morphometric data of preserved specimens, four of five species reported from this region are considered valid and two new Colombian species are described. Here we review Pimelodus coprophagus Schultz, 1944 from Lake Maracaibo Basin of Venezuela and Colombia; Pimelodus grosskopfii Steindachner, 1879 from Magdalena River Basin; Pimelodus navarroi Schultz, 1944 from Lake Maracaibo Basin of Venezuela and Colombia; and Pimelodus punctatus (Meek & Hildebrand, 1913) from Atrato, Baudó, and Tuyra River Basins of Colombia and Panamá. Pimelodus crypticus new species is described from the upper Cauca river drainage. Pimelodus yuma new species is described from the Cauca, Magdalena, and Sinú river drainages. A key for species identification and geographical ranges is provided. We also reidentify trans-Andean specimens previously reported as Pimelodus blochii Valenciennes, 1840, a widespread cis-Andean species, or species complex, that ranges across the coastal rivers of the Guianas and Brazil and the Orinoco and Amazon Basins.

On the outflow of Lake Maracaibo, Venezuela

Lake Maracaibo, an important wet coastal area located in the Caribbean Sea, is connected to the Gulf of Venezuela by a narrow, shallow channel known as Barra de Maracaibo. The water quality of this is poor owing to the very low water rate exchange with the Gulf. The authors make use of sea surface temperature (SST) satellite imagery and numerical modelling to study the conditions of the outflow of Lake Maracaibo. The lake is found to be fully driven by the circulation out of the lake. Three different situations are considered: upwelling, no upwelling, and the transient state between them. The authors propose conceptual and numerical models to explain the conditions for outflow. Moreover, it is found that outflow is possible only when the tradewinds stop and before the warmer waters of the Caribbean have reached the Colombian coasts.

Systematic evaluation of asphaltene formation damage of black oil reservoir fluid from Lake Maracaibo, Venezuela

One of the most concerning areas for asphaltene deposition is the near-wellbore region, where such deposition may cause formation damage. The reservoir fluid of the Lake Maracaibo region is known to cause operational problems such as production losses due to asphaltene deposition. In this paper, we focus on the systematic evaluation of the asphaltene formation damage using stacked composite core samples and live oil samples from Lake Maracaibo area and study the formation damage due to asphaltene deposition inside the composite core stack.A special coreflood system was designed for an asphaltene formation damage study using reservoir core samples and sour–live reservoir fluid samples. The phenomenon of asphaltene precipitation and deposition in porous media and subsequent permeability impairment was evaluated while the fluid pressure decreased below the asphaltene onset pressure (AOP). Live fluid samples were collected and flooded through the stacked composite core plugs under reservoir conditions. Progressive pressure reductions were performed to induce asphaltene precipitation and deposition in the composite core. Changes in the absolute permeability of the composite core assembly due to asphaltene precipitation and deposition were calculated in the context of the pressure depletion process. Significant permeability impairment occurred from the depressurization of the reservoir fluid below the AOP. The upstream inlet pressure of the composite core stack was maintained just above the AOP while the outlet pressure was regulated approximately 50 psig above the saturation pressure throughout the coreflood experiment so that the onset of asphaltene precipitation occurred along the length of the composite core.Following the coreflood experiment, the core stack was depressurized and the remaining fluid was extracted from individual core plugs. Various analytical techniques such as asphaltene content measurement, simulated distillation and optical density were used to perform detailed post-trial analyses of the residual fluids extracted from each individual core plugs. Analyses of the thin sections extracted from various core plugs were also performed to investigate the microstructure of the residual hydrocarbon as well as the distribution of the flow pathways plugged with asphaltene aggregates in the pore structures. The results associated with these post-trial analyses confirmed that the observed permeability impairment was indeed due to the plugging of the flow pathways of the core plugs by asphaltene aggregates, and that the asphaltene-induced permeability loss was somewhat more extensive in the tighter plugs associated with the stacked core assembly. We present the systematic approach to perform asphaltene formation damage study using composite core and live reservoir fluid samples above the saturation pressure.

From Wetland to Saltland: Natural Obstacles and Socioecological Consequences in the Production of Solar Salt in Venezuela

ABSTRACTThis article provides a critical analysis of the process involved in transforming small-scale artisanal production of solar salt into large-scale industrial production by Produsal in Los Olivitos Wildlife Refuge and Fishing Reserve in Lake Maracaibo, Venezuela. In doing so, it highlights the socioecological impacts resulting from this process in the wetland and the fishing community of Ancón de Iturre. Using political economy of nature as a theoretical framework, especially notions of the formal subsumption of nature, materiality of natural resources, and the commodification of nature, this article explores how the biophysical characteristic of salt and the ecosystem where it is contained present a specific set of natural obstacles for its production; the different strategies used by Produsal to overcome these obstacles; and the social and ecological contradictions embedded in the process.

Characterization of tar-like material and producible oil in Misoa C2 and C3 reservoir sands of the Area 2 South (Ceuta Field, Venezuela)

Here we characterized asphaltic oil occurrences in the Misoa C2 and C3 reservoirs within Area 2 South of the Ceuta Field (Lake Maracaibo Basin, NW Venezuela). To perform the geochemical and petrological characterization of the C2 and C3 sub-units, which cover an interval in which tar-like material was detected, we analyzed core (18) and cutting (123) samples using the Rock-Eval 6 technique in reservoir mode. Samples were studied under fluorescence light and scanning electron microscopy (SEM), showing the presence of two charges of oils and the relationships within silica cements and clay minerals. To evaluate vertical inter-reservoir communication and lateral intra-reservoir continuity, we also studied 12 oil samples from wells in Area 2 South. Biomarkers and isotopic signatures were examined using gas chromatography-mass spectrometry (GC-MS) and isotope ratio mass spectrometry (IRMS). The results suggest that oil and core extracts belongs to a single family derived from two pulses of hydrocarbon generation from the La Luna source rock, which was deposited in a marine reducing environment. The oil samples are a mixture of a paleobiodegraded oil charge and a later fresh, more mature oil recharge. The geochemical analyses also evidence that the formation of heavy oil tar zones can be related to biodegradation and in-reservoir oil mixing, though other formation mechanisms for the tar are also feasible. Finally, the GC fingerprints of the oils are indicative of lateral reservoir continuities across the F-1 and F-2 faults and vertical communication between the Misoa C2 and C3 sub-units in Area 2 South, suggesting that tar occurrences do not act as permeability barriers within the two reservoirs studied.

A new species of Hoplomyzon (Siluriformes: Aspredinidae) from Maracaibo Basin, Venezuela: osteological description using high-resolution computed microtomography of a miniature species

ABSTRACT A new miniature species of banjo catfish of the genus Hoplomyzon is described from the Lake Maracaibo Basin in Venezuela. The new species is distinguished from all its congeners by the straight anterior margin of the mesethmoid (vs. a medial notch); a smooth and straight ventral surface of the premaxilla (vs. presence of bony knobs on the ventral surface of premaxilla); absence of teeth on dentary (vs. teeth present on dentary); configuration of ventral vertebral processes anterior to anal fin, which are composed of single processes anterior to anal-fin pterygiophore (vs. paired process); presence of several filamentous barbel-like structures on the ventral surface of head of adults (vs. small papillous structures in the ventral surface of head of adults); and 8 anal-fin rays (vs. 6 or 7). An extensive osteological description is made of the holotype using high-resolution x-ray computed microtomography (HRXCT).

Implantation System Brine Recover from Some Chemical Treatment Tanks in a Plant Chlor - Alkali

Objectives: This study establishes aimed at recovering the brine flowing with sewage sludge to decrease the concentration of chlorides and reduce salt intake. Methods/Statistical Analysis: A piping system taking into account the characteristics of the sludge, which served as the basis for determining the loss of brine in the effluent, make the necessary calculations for the piping systems to develop and to transport the sludge from the point was raised unloading to the recovery site. considered the issue sis sizing based on the measurement of levels, distance the pipe section to place, make the hydraulic study and plans isometric system was developed. Findings: With the recovery of brine, it manages to reduce consumption of 7.11 tons of salt daily at the plant, leading to savings of 35,539.6 bolivars per year for salt intake. Application/Improvements: When recovering the drained brine the impact this causes for chlorine soda plant, the central plant effluent and receiving water body (Lake Maracaibo) is decreased.

Identification of the Volatile Compounds in the roasting Venezuela Criollo cocoa beans by Gas Chromatography-Spectrometry Mass

An identification of the volatile compounds from the fermented dried and toasted (at 20 °C, 25 minutes) cocoa beans from a population of selected cocoa, were studied. The selected material “Criollo” (205 trees) was gathered from the plantation “El Pedregal” located at the south of Maracaibo Lake, Rio Frio “ Merida state, Venezuela. The volatile fraction was extracted and analyzed by gas chromatography coupled to a mass spectrometer (SPME/MS). The goal of the researching was the quantification of the content of organic volatile compounds developed by effect of the cocoa roasting. Volatile identification was performed comparing the retention indices and mass spectra obtained with those of the compounds existing as reference in the bank of the “Wiley Mass Spectral Data”. Sixty-nine volatile compounds that were grouped into 12 chemical families were identified. Aldehydes, alcohols, acids, hydrocarbons, pyrazines and diverse compounds, were the compounds prevalent in the volatile fraction of roasted cocoa. As conclusion this research permits the establishment of the identification and sensory quality of the Venezuelan creole cocoa, is of consensus that the volatile profile of the Venezuelan cocoa, which is highly appreciated by the chocolatiers of the world, has been fewer studied. It is also observed that there is an effect of post-harvest treatment (fermentation, drying) and roasted on the formation of flavor compounds in the fraction of roasted cacao. The results of these studies also show that SPME has a significant advantage over more traditional methods for analysis of volatile compounds in the cocoa beans post-harvest process: no fermented, fermented, dried and roasted.

Curie point depth in the SW Caribbean using the radially averaged spectra of magnetic anomalies

We have estimated the Curie Point Depth (CPD) using the average radial power spectrum in a tectonically complex area located in the SW Caribbean basin. Data analyzed came from the World Digital Magnetic Anomaly Map, and three methods have been used to compare results and evaluate uncertainties: Centroid, Spectral Peak, and Forward Modeling. Results show a match along the three methods, suggesting that the CPD values in the area ranging between 6km and 50km. The results share the following characteristics: A) High values (>30km) are in continental regions; B) There is a trend of maximum CPD values along the SW-NE direction, starting from the Central Cordillera in Colombia to the Maracaibo Lake in Venezuela; C) There is a maximum CPD at the Sierra Nevada de Santa Marta (Colombia) as well as between Costa Rica - Nicaragua and Nicaragua - Honduras borders. The lowest CPD values (<20km) are associated with the coastal regions and offshore. We also tested results by estimating the geothermal gradient and comparing measured observations of the study area. Our results suggest at least five thermal terrains in the SW Caribbean Basin: A) The area that is comprising the Venezuela Basin, the Beata Ridge and the Colombia Basin up to longitude parallel to the Providencia Throat. B) The area that includes zones to the north of the Cocos Ridge and Panam Basin up to the trench. C) The orogenic region of the northern Andes and including areas of the Santa Marta Massif. D) The continental sector that encompasses Nicaragua, northern Costa Rica and eastern of Honduras. E) Corresponds to areas of the northern Venezuela and Colombia, NW of Colombia, the Panamanian territory and the transition zones between the Upper and Lower Nicaragua Rise.

Where Are the Lightning Hotspots on Earth?

Abstract Previous total lightning climatology studies using Tropical Rainfall Measuring Mission (TRMM) Lightning Imaging Sensor (LIS) observations were reported at coarse resolution (0.5°) and employed significant spatial and temporal smoothing to account for sampling limitations of TRMM’s tropical to subtropical low-Earth-orbit coverage. The analysis reported here uses a 16-yr reprocessed dataset to create a very high-resolution (0.1°) climatology with no further spatial averaging. This analysis reveals that Earth’s principal lightning hotspot occurs over Lake Maracaibo in Venezuela, while the highest flash rate density hotspot previously found at the lower 0.5°-resolution sampling was found in the Congo basin in Africa. Lake Maracaibo’s pattern of convergent windflow (mountain–valley, lake, and sea breezes) occurs over the warm lake waters nearly year-round and contributes to nocturnal thunderstorm development 297 days per year on average. These thunderstorms are very localized, and their persistent development anchored in one location accounts for the high flash rate density. Several other inland lakes with similar conditions, that is, deep nocturnal convection driven by locally forced convergent flow over a warm lake surface, are also revealed. Africa is the continent with the most lightning hotspots, followed by Asia, South America, North America, and Australia. A climatological map of the local hour of maximum flash rate density reveals that most oceanic total lightning maxima are related to nocturnal thunderstorms, while continental lightning tends to occur during the afternoon. Most of the principal continental maxima are located near major mountain ranges, revealing the importance of local topography in thunderstorm development.

Source-rock potential of the lowest coal seams of the Marcelina Formation at the Paso Diablo mine in the Venezuelan Guasare Basin: Evidence for the correlation of Amana oils with these Paleocene coals

The aims of this work were to carry out a combined petrographic, palynofacies, and organic geochemical study of twelve drill-core samples collected from the lowest coal seams in the Paleocene Marcelina Formation (Paso Diablo mine, Guasare Basin, northwestern Venezuela), to characterize crude oil samples from three wells in the nearby Amana Field and to evaluate oil-source correlations of these crude oils with the Paso Diablo coal extracts. The coals under study were classified as high volatile bituminous A or at the B-A boundary, and showed vitrinite contents between 50.0 and 89.4vol.%, liptinites ranging from 1.4 to 24.2vol.%, and inertinites in the 6.2–30.8vol.% range. Results from organic geochemical investigations indicate that the Guasare coals were generated in a limno-telmatic to telmatic zone under fluctuating oxygen conditions. A Type III kerogen with relatively high hydrogen content and a thermal maturity corresponding to the early oil window are proposed for these coals as supported by Rock-Eval and petrographic data, as well as biomarker interpretations. Oil generation potential from Marcelina Formation coals is probably due to the perhydrous nature of the vitrinite, high bitumen contents, and considerable liptinite concentrations, mainly oil-prone resinites and exsudatinites. Palynofacies observations denote a dominance of psilate pollen grains related to angiosperm plants and, as expected, Type III kerogens or humic coals in the studied seams, the parent material of which contained a significant contribution of algae. The non-detection of 18α(H)-oleanane does not preclude the fact that angiosperms are the dominant plants in the Guasare paleomire. On the other hand, the characterization of the Amana oils suggests that they all fall into a unique oil family; the presence of 25-norhopanes in them could indicate paleobiodegradation and mixing from various hydrocarbon charges in the reservoir. Thus, the crude oils from the Amana Field seem to be a mixture of one or more oil charges from the early mature marine carbonate source rocks of the La Luna Formation, deposited under anoxic reducing conditions, and a later pulse of hydrocarbon generation which originated from an unknown – so far – nonmarine source rock. In this regard, hydrocarbon liquid derived from the lowest Marcelina coal seams may be tentatively identified as the latter oil charge. Also, this work delineates some components of a currently subcommercial and hypothetical Tertiary petroleum system – identified and named as Marcelina/Misoa C5(.) – in the Lake Maracaibo region. Finally, the coalbed gas contents of sampled coals were determined.

Levels of Trace Metals in the Clam, Polymesoda solida (Philippi, 1846) (Bivalvia: Cyrenidae), from the Strait of Lake Maracaibo and Bahía El Tablazo, Venezuela

This study determined concentrations of arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), selenium (Se), vanadium (V), and zinc (Zn) in the clam Polymesoda solida, collected in nine different sites in the Strait of Lake Maracaibo and Bahia El Tablazo, to assess the spatial distribution of metals, and the safety of clam consumption by humans. Overall average concentrations ± standard deviations in µg/g dw were 8.34 ± 1.51 for As, 0.59 ± 0.28 for Cd, 13.80 ± 6.13 for Cu, 1.22 ± 0.51 for Pb, 2.29 ± 0.62 for Se, 2.59 ± 1.55 for V, and 24.70 ± 4.98 for Zn. No distinct trend in the spatial distribution of metals was observed, and levels in clams were below maximum permissible values for seafood consumption. Positive correlations of V with Pb, and Cd suggest common pollution sources, and their levels were comparable to other bivalve species from contaminated aquatic systems.

Hydrogeochemical characterization of oilfield waters from southeast Maracaibo Basin (Venezuela): Diagenetic effects on chemical and isotopic composition

Free water and water in emulsion with oil from hydrocarbon wells onshore–offshore Lake Maracaibo were extracted and analyzed. The use of classical and new chemical diagrams evidenced that Na–HCO3 and Na–Cl are the main chemical facies, whereas Na–SO4 facies was rare and revealed only in faulted areas in which shallow groundwater was involved in deep circulation. Cretaceous Ca–Cl waters were not revealed, but their imprint on some samples was traced and evidenced by Langelier–Ludwig, Brine-Differentiation and Caexcess vs. Nadeficit diagrams. These square plots, allowing a discrimination between the water contributions from the different source rocks, should be more exploited as hydrogeochemical tools in hydrocarbon exploration. Original data on monocarboxylic anions showed acetate concentration higher than ten times that of formate at sampling conditions, but speciation under deep conditions indicated a reversed activity dominance. Calculation of saturation indexes and kinetic modeling showed an active precipitation of chalcedony, kaolinite and clays, especially where the temperature was lower (T < 100 °C). Formation waters and lake water showed quite similar chloride concentration and hydrogen isotope composition. However, thermodynamic calculations at the oilfield P-T conditions revealed chlorite and illite, produced during previous diagenetic stages of Misoa sandstones, recrystallization to smectite and vermiculite in present-day stage. The diagenetic water produced in these reactions could have enriched the δ18O isotopic composition of approximately +2‰. This isotope diagenetic effect was more evident in Na–HCO3 waters, which also showed a decrease in chloride at constant boron concentration as a consequence of clay dewatering. In this regard, a new boron geothermometer useful for formation waters is also proposed:T°C=[5.1364×ln(1/B)mg/1]+5.728(±0.180)−0.164(±0.012)

Alianzas de poder en una región histórica: el caso de la élite pamplonesa en el Virreinato de la Nueva Granada, 1795-1808

&lt;p&gt;Las dinámicas sociales en Pamplona de Indias, provincia del Virreinato de Nueva Granada, a finales del siglo XVIII y comienzos del XIX, muestran el ascenso y consolidación del grupo conformado por hacendados-comerciantes insertos en el circuito agroexportador que tenía salida al exterior por el lago de Maracaibo. Ponemos en diálogo el concepto &lt;em&gt;región histórica&lt;/em&gt; con el de &lt;em&gt;redes sociales,&lt;/em&gt; a través del análisis de las alianzas de poder establecidas por la &lt;em&gt;élite&lt;/em&gt; pamplonesa durante los años 1795 y 1808. Nos interesa profundizar en los vínculos, en esta ocasión basados en el parentesco, que lograron tejer los miembros de la mencionada élite, los cuales le permitieron ampliar su red local alcanzando la inserción en diversos circuitos regionales tanto económicos como políticos.&lt;/p&gt;