ABSTRACT. Thriving benthic communities were observed in the oxygen minimum zones along the southwestern African margin. On the Namibian margin, fossil cold-water coral mounds were overgrown by sponges and bryozoans, while the Angolan margin was characterized by cold-water coral mounds covered by a living coral reef. To explore why benthic communities differ in both areas, present-day environmental conditions were assessed, using conductivity–temperature–depth (CTD) transects and bottom landers to investigate spatial and temporal variations of environmental properties. Near-bottom measurements recorded low dissolved oxygen concentrations on the Namibian margin of 0–0.15 mL L−1 (≜0 %–9 % saturation) and on the Angolan margin of 0.5–1.5 mL L−1 (≜7 %–18 % saturation), which were associated with relatively high temperatures (11.8–13.2 ∘C and 6.4–12.6 ∘C, respectively). Semidiurnal barotropic tides were found to interact with the margin topography producing internal waves. These tidal movements deliver water with more suitable characteristics to the benthic communities from below and above the zone of low oxygen. Concurrently, the delivery of a high quantity and quality of organic matter was observed, being an important food source for the benthic fauna. On the Namibian margin, organic matter originated directly from the surface productive zone, whereas on the Angolan margin the geochemical signature of organic matter suggested an additional mechanism of food supply. A nepheloid layer observed above the cold-water corals may constitute a reservoir of organic matter, facilitating a constant supply of food particles by tidal mixing. Our data suggest that the benthic fauna on the Namibian margin, as well as the cold-water coral communities on the Angolan margin, may compensate for unfavorable conditions of low oxygen levels and high temperatures with enhanced availability of food, while anoxic conditions on the Namibian margin are at present a limiting factor for cold-water coral growth. This study provides an example of ...
The eastern boundary region off Angola encompasses a highly productive ecosystem important for the food security of the coastal population. The fish-stock distribution, however, undergoes large variability on intraseasonal, interannual, and longer time scales. These fluctuations are partly associated with large-scale warm anomalies that are often forced remotely from the equatorial Atlantic and propagate southward, reaching the Benguela upwelling off Namibia. Such warm events, named Benguela Niños, occurred in 1995 and in 2011. Here we present results from an underexplored extensive in situ dataset that was analyzed in the framework of a capacity-strengthening effort. The dataset was acquired within the Nansen Programme executed by the Food and Agriculture Organization of the United Nations and funded by the Norwegian government. It consists of hydrographic and velocity data from the Angolan continental margin acquired biannually during the main downwelling and upwelling seasons over more than 20 years. The mean seasonal changes of the Angola Current from 6° to 17°S are presented. During austral summer the southward Angola Current is concentrated in the upper 150 m. It strengthens from north to south, reaching a velocity maximum just north of the Angola Benguela Front. During austral winter the Angola Current is weaker, but deeper reaching. While the southward strengthening of the Angola Current can be related to the wind forcing, its seasonal variability is most likely explained by coastally trapped waves. On interannual time scales, the hydrographic data reveal remarkable variability in subsurface upper-ocean heat content. In particular, the 2011 Benguela Niño was preceded by a strong subsurface warming of about 2 years' duration.
The eastern boundary region off Angola encompasses a highly productive ecosystem important for the food security of the coastal population. The fish-stock distribution, however, undergoes large variability on intraseasonal, interannual, and longer time scales. These fluctuations are partly associated with large-scale warm anomalies that are often forced remotely from the equatorial Atlantic and propagate southward, reaching the Benguela upwelling off Namibia. Such warm events, named Benguela Niños, occurred in 1995 and in 2011. Here we present results from an underexplored extensive in situ dataset that was analyzed in the framework of a capacity-strengthening effort. The dataset was acquired within the Nansen Programme executed by the Food and Agriculture Organization of the United Nations and funded by the Norwegian government. It consists of hydrographic and velocity data from the Angolan continental margin acquired biannually during the main downwelling and upwelling seasons over more than 20 years. The mean seasonal changes of the Angola Current from 6° to 17°S are presented. During austral summer the southward Angola Current is concentrated in the upper 150 m. It strengthens from north to south, reaching a velocity maximum just north of the Angola Benguela Front. During austral winter the Angola Current is weaker, but deeper reaching. While the southward strengthening of the Angola Current can be related to the wind forcing, its seasonal variability is most likely explained by coastally trapped waves. On interannual time scales, the hydrographic data reveal remarkable variability in subsurface upper-ocean heat content. In particular, the 2011 Benguela Niño was preceded by a strong subsurface warming of about 2 years' duration. ; publishedVersion
This article highlights aspects concerning the background, electoral system, election contenders and campaigns, as well as results from the 2008 Angolan parliamentary elections. As the author notes Angola's political history since independence in 1975, factions and parties such as UNITA and MPLA are in place as representatives of the Angolan people. However, the election was not without incident, including physical confrontation between the larger parties, and denial of members of the Portuguese press entry into Angola to cover the election, because of political leanings. The article also looks at the statistical overcome of the election, providing gains and loss margins by party (see table within article); examines the overall administration and international observation of the election process; and provides some insight re the election, its effect on Angola as a whole, and the author's assessment on the new government. M. Diem
This article highlights aspects concerning the background, electoral system, election contenders and campaigns, as well as results from the 2008 Angolan parliamentary elections. As the author notes Angola's political history since independence in 1975, factions and parties such as UNITA and MPLA are in place as representatives of the Angolan people. However, the election was not without incident, including physical confrontation between the larger parties, and denial of members of the Portuguese press entry into Angola to cover the election, because of political leanings. The article also looks at the statistical overcome of the election, providing gains and loss margins by party (see table within article); examines the overall administration and international observation of the election process; and provides some insight re the election, its effect on Angola as a whole, and the author's assessment on the new government. M. Diem
Intro -- Acknowledgements -- Contents -- Notes on Contributors -- List of Figures -- List of Tables -- Chapter 1: Introduction -- Introduction -- The Transnational Public Domain: What Does It Mean? Where Does It Lead Us? -- New Nationalism and Globalism: Reconciling Dialectics -- The Scope of the Book -- References -- Chapter 2: The BRI in a Multipolar World: A Normative Tool for Cooperation or Nationalism? -- Introduction -- Flexible Selectivity of the BRI Participant States and Its Strengths -- The BRI Project as a Hindrance of Normative Transfer -- Conclusion -- References -- Chapter 3: Margins of Autonomy in the Chinese Belt and Road Initiative: Negotiating Growth in Rural Angola -- Introduction -- The Context of China's Role in Angola-Global Influences Wax and Wane -- Building Preferred Partnerships -- Angolan Mode of Business Meets China's BRI -- The BRI's Transformations of Angola's Rural Economy-Mechanization -- Irrigation -- Agro-Industrial Farms -- Conclusion -- References -- Chapter 4: China's Belt and Road Initiative in Three Diverse African Countries: A Comparative Approach -- Introduction -- The DRC: Natural Resources -- Kenya: Building Infrastructure -- Djibouti: Strategic Waterways and Extended Military Footprint -- Conclusion -- References -- Chapter 5: A Challenging Nation-State in the Middle East in Transition -- Introduction -- Geopolitics of the "Arab Spring" -- The Regional Flow of "Arab Spring" -- The Global Flow of "Arab Spring" -- Challenging Nation-States in the Middle East: Formation of Geopolitical Sub-regions -- Conclusion -- References -- Chapter 6: "New Silk Roads" in the Service of a "Great Power"? The Influence of Xi Jinping's Operational Code in the Strategic Orientations of the People's Republic of China -- Introduction -- The NSR Project Strategic Framework -- Operational Code and Methodology.
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This article reflects on Histórias do Kakwaku, a documentary film about social activism in the urban margins of Luanda, produced as part of a partnership between myself, an academic working on urban citizenship, and an Angolan political youth organisation, Projecto AGIR. The article details the whole process of collective film-making and questions the impact of this method on the film-makers, both individually and collectively. From our initial brainstorming sessions to our final editing decisions on the computer, I show how we slowly drifted away from the initial political objectives dictated by the organisers of Projecto Agir and opened unexpected spaces for engagement that allowed us 'to see together without claiming to be another' (Haraway 1991).
Following the chronological steps of collective film-making, we used practice as a point of departure from which to approach storytelling more broadly. Although I provide practical details about our logistics, our equipment and our working documents, this is not a one-size-fits-all recipe for collective documentary film-making. Rather, the focus is on what can be described as an exercise in intersubjective writing, neither entirely under control nor totally serendipitous.
I argue that telling a story in images, words and sounds is a dynamic process, open to constant reinterpretation. Combining the unpredictability of collective writing with the somewhat narrow imperatives of audiovisual storytelling creates an opportunity to question participatory research beyond the binary of the researcher and the researched.
[spa] Las carbonatitas volcánicas de Catanda son las únicas descritas hasta el momento de carácter extrusivo en Angola. Esta localidad es, además, significativamente interesante por la presencia de lavas carbonatíticas, las cuales se han descrito en tan solo 14 lugares a nivel mundial. Sin embargo, la información publicada referente a Catanda se reducía, hasta ahora, a unos pocos trabajos elaborados por investigadores portugueses en la década de los años 1960 y 1970, en los cuales se aportaban datos sobre geología regional y se describían características de las carbonatitas, aunque estos resultados eran muy limitados. La falta de información geológica que hasta ahora había sobre la zona de estudio se debe, principalmente, a la inestabilidad política y social reinante en Angola por los conflictos bélicos que asolaron su territorio durante más de cuarenta años y que imposibilitaron el acceso y el estudio de la región de Catanda, así como de otras muchas áreas en el conjunto del país. Bajo este contexto general se planteó el presente proyecto de tesis doctoral, con el objetivo de aportar nueva información y conocimientos referentes al vulcanismo carbonatítico de la región de Catanda y, en particular, a las características litológicas, mineralógicas, petrológicas, geoquímicas, petrogenéticas y de emplazamiento de las carbonatitas volcánicas. A partir de las observaciones realizadas se ha podido constatar que las carbonatitas de Catanda están formadas por un conjunto de hasta siete edificios volcánicos con morfologías de anillos de tobas y maares que afloran en un graben de unos 50 km2 de extensión. Además, asociado a este conjunto principal, se ha descrito un octavo centro eruptivo, con morfología de maar, localizado a unos cinco kilómetros al este del graben de Catanda, en la zona conocida como laguna de Chiva. Los afloramientos de rocas piroclásticas y lávicas de la región forman series de materiales vulcano-sedimentarios que alcanzan 100 metros de potencia, hallándose dispuestos sobre un basamento de granitos de edad Arcaica que, a su vez, se encuentran recubiertos por sedimentos aluviales y coluviales de edad reciente. Se ha podido determinar que las carbonatitas de Catanda se formaron a partir de procesos volcánicos eminentemente explosivos y que la actividad efusiva que dio lugar a las lavas carbonatíticas fue escasa y está concentrada en las zonas externas del graben, asociadas a importantes fracturas regionales. El estudio petrográfico de las rocas de Catanda ha permitido diferenciar hasta cinco facies distintas de rocas piroclásticas y tres tipologías distintas de lavas carbonatíticas. Estas lavas pueden clasificarse como calciocarbonatitas (con un contenido de calcita superior al 70% modal), aillikitas (con contenidos de calcita inferiores al 35% y 5102 por encima del 14 % en peso) y natrocarbonatitas alteradas (formadas por cristales tabulares de calcita pseudomórficos de carbonatos alcalinos). La caracterización geoquímica de las lavas ha permitido constatar que a pesar de sus diferencias texturales y composicionales, todas ellas se formaron a partir de un mismo magma parental carbonatítico que, tras el estudio de las inclusiones fundidas incluidas en magnetita, se ha podido determinar que tenía una composición eminentemente alcalina. Los estudios realizados en Catanda por Silva y Pereira (1973) afirmaban que las carbonatitas de la región se formaron en el Cretácico superior (92 Ma), dato que obtuvieron a partir de la datación de un dique de rocas alcalinas (tinguaíta) que consideraron contemporáneo con las carbonatitas. Sin embargo, durante la realización del presente proyecto de tesis, se han llevado a cabo dataciones de minerales presentes en las carbonatitas de Catanda, utilizando los métodos de Rb/Sr en flogopita y U-Th-He en apatito. La edad obtenida ha sido de 0,65-0,66 Ma (Pleistoceno medio), variando sustancialmente la edad establecida en primera instancia por esos autores y obligando a replantear el contexto geodinámico y volcanológico del graben de Catanda y, en general, del margen Atlántico de Angola. ; [eng] The volcanic carbonatitic region of Catanda is the only extrusive carbonatite locality reported in Angola. The Catanda area is also significant due to the occurrence of carbonatitic lavas; those have been only reported in 14 localities worldwide. However, the available information about these carbonatites was restricted to a few works developed in the 60's and the 70's, in which the reported data about the geological setting and main features of the carbonatites were strongly limited. The information gap about Catanda was especially generated by the politic and social instability caused by the Angolan civil war, which made impossible the access to the Catanda region and entire Angola, for more than forty years. According to this general approach, the aim of the present Ph.D. project was to obtain new information and knowledge about the carbonatitic volcanism of the Catanda region and, especially, in relation to its lithological features, mineralogy, petrology geochemistry, genetic and emplacement processes related to the formation of the extrusive carbonatites. Coupled analyses of satellital images and field data demonstrated thatCatanda carbonatites are formed by a group of seven small volcanic edifices with maar and tuff ring morphologies, outcropping in a graben of 50 km2 in extension. In addition, we also discovered and maar at 5 km east from the main volcanic area, in the region known as Chiva lagoon. The pyroclastic rocks from the Catanda region may achieve up to 100 metres in thickness deposited over Archaean granites and broadly covered by recent alluvial and colluvial sediments. We have determined that Catanda carbonatites were especially formed by explosive events, while carbonatitic lavas were very minor and restricted to the external parts of the graben, associated to the most important fractures. The petrographic study of the Catanda rocks allowed us to distinguish 5 different facies of pyroclastic rocks and 3 typologies of carbonatitic lavas. These lavas can be classified as calciocarbonatites (containing more than 70% of modal calcite), silicocarbonatites-aillikites (with less than 35% of modal calcite and more than 14 wt.% of SiO2) and altered natrocarbonatites (formed by tabular calcite crystals pseudomorphs of primary alkaline carbonates). Geochemical data also permits to confirm that, even their compositional and textural differences, all Catanda lavas were formed from the same parental melt. The study of melt inclusions hosted in magnetite grains also indicates that the parental melt composition was broadly alkaline. The studies carried in Catanda by Silva & Pereira (1973) argued for the late Cretaceous age of the carbonatites (92 Ma). This age was obtained from the dating of a tinguaite dyke that the authors considered contemporaneous to the carbonatitic rocks. However, in the present Ph.D. project we carried out the first direct dating of the Catanda lavas, using Rb/Sr and U-Th-He methods in fluorapatite and phlogopite, respectively. The age obtained from these dating has been approximately 0.65-0.66 Ma. This new dating changes the general view of the volcanic and geodynamic setting of the Catanda graben and, in general, the entire Angolan Atlantic margin.
