929 resultados para wavefront rise


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We report relative paleointensity proxy records from four piston cores collected near the Agulhas Ridge and Meteor Rise (South Atlantic). The mean sedimentation rate of the cores varies from 24 cm/kyr to 11 cm/kyr. The two cores with mean sedimentation rates over 20 cm/kyr record positive remanence inclinations at 40-41 ka coeval with the Laschamp Event. Age models are based on oxygen isotope data from three of the cores, augmented by radiocarbon ages from nearby Core RC11-83, and by correlation of paleointensity records for the one core with no oxygen isotope data. The relative paleointensity proxy records are the first from the South Atlantic and from the high to mid-latitude southern hemisphere. Prominent paleointensity lows at ?40 ka and ?65 ka, as well as many other features, can be correlated to paleointensity records of comparable resolution from the northern hemisphere. The records are attributable, in large part, to the global-scale field, and therefore have potential for inter-hemispheric correlation at a resolution difficult to achieve with isotope data alone.

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Sedimentation of pelagic biogenic coccolithic-foraminiferal sediments predominates in the section of the South Atlantic ridge between 20° and 30°S. Sedimentation rate and thickness of Late Quaternary sediments differ in the rift valley, the crestal section of the ridge, its flanks and transform faults. Holocene and layers representing the most recent and pen¬ultimate continental glaciations and the last interglacial are distinguishable in the late Quaternary profile. During their development, changes in the mean annual sea surface temperature in the tropical zone of the South Atlantic were minimal, i.e. 1-2°C.

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General note: Title and date provided by Bettye Lane.

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Sex sells. A lot. But who exactly is on the market?

What kinds of bodies are calibrated for traffic and consumption, and how exactly do they get there? When it comes to “sex” trafficking—which comprises a minority percentage of human trafficking, yet dominates the moral imagination as an “especially heinous” crime—the rise in predominantly white, evangelical Christian American interest in the trafficked subject galvanizes an ethical outrage that rarely observes critiques of race, ethnicity, sexuality or class as conditions of possibility. Though a nuanced mandate to fight trafficking is all but cemented in the contemporary American political and moral conscience, Virgin Territory accounts for the ways Christian ideas of purity annex both gender and sexuality inside the legacies of racialized colonial encounter, and foreground the market expansion of the global sex trade as it exists today.

In Part I, I argue that the narratives of virginity tied to Mary’s body simultaneously foregrounded the gendered, sexed Other as sparked disdain for the religious Other, for the Jewish body and for Mary’s Jewish identity. Through this analysis I explore the connections of racial identity to the Christian theological elision of Jewish election. I demonstrate how the questions of sexual ethics materialized at the site of the Virgin Mary, and align the moral attachments of sex and purity in the production of whiteness. These machinations, tied to the emerging European identity of empire, irrupt horrifically into the narrative ontology of dark flesh in Africa, Asia, and the Americas.

In Part II, I highlight the function of these narratives inside of the moments of colonial encounter, demonstrating how the logics of purity and virginity were directly applied to manage dark female flesh. I map the visual iconography of the Black Madonna first through a Dutch painting entitled The Rape of the Negress. I read this image through the social theological imagination instantiating the idea of the reprobate body and white imperial gaze. This analysis foregrounds a theological reading of Sarah Baartman, the “Hottentot Venus,” as the center of a complex sex trafficking investigation, outlining the genealogy of race, as well as the ideologies of the racial, ethnic and national Other, as mitigating factors in the conditions of possibility of a global sex trade. By restoring these narratives and their theological undertones, I reiterate the ways Christian thought is imbricated in the global sex trade, and propose theological strategies for rethinking humanitarian responses to sex trafficking.

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Radiocarbon-age measurements on single species of foraminifera from a core on the Ceara Rise demonstrate the importance of the joint effect of bioturbation and variable rain abundance of foraminifera. The relatively high mixed layer ages for Pulleniatina obliquiloculata reflect, at least in part, an early Holocene peak in its abundance while the relatively young ages for Globorotalia menardii reflect the delay until mid Holocene of its reappearance in the Atlantic Ocean. These results clearly demonstrate that core-top sediment samples need not be representative foraminifera falling from today's surface ocean. Rather, at least on the Ceara Rise, such samples consist of a composite of changing species groupings. These results also reconfirm the pitfalls associated with attempts to reconstruct the radiocarbon age of deep ocean water on the basis of benthic-planktonic foraminiferal age differences.

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Oxygen and carbon isotope analyses show that the biserial forarniniferal genus Streptochilus, which was originally described from pelagic sediments on the Eauripik Rise and Ontong Java Plateau, lived deep in the upper water column within the oxygen minimum layer. The species of Streptochilus average from 4 to 19% of the foraminiferal assemblages in which benthic forms compose less than 1 or 2%. Specimens of Streptochilus are selectively dissolved when in contact with the bottom water mass. Their rapid evolutionary turnover of less than a few million years and their wide areal distribution in the equatorial Indo-Pacific are indicative of planktonic foraminifera. Aside from usefulness of the species of Streptochilus as stratigraphic indices, these Neogene biserial planktonic foraminifera are potential indices of paleoceanographic stratification.

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We present new isotopic and micropaleontological data from a depth transect on Shatsky Rise that record the response of the tropical Pacific to global biotic and oceanographic shifts during the mid-Maastrichtian. Results reveal a coupling between the upper ocean, characterized by a weak thermocline and low to intermediate productivity, and intermediate waters. During the earliest Maastrichtian, oxygen and neodymium isotope data suggest a significant contribution of relatively warm intermediate water from the North Pacific. Isotopic shifts through the early Maastrichtian suggest that this warmer water mass was gradually replaced by cooler waters originating in the Southern Ocean. Although the cooler water mass remained dominant through the remainder of the Maastrichtian, it was displaced intermittently at shallow intermediate depths by North Pacific intermediate water. The globally recognized "mid-Maastrichtian event" ~69 Ma, manifested by the brief appearance of abundant inoceramid bivalves over shallow portions of Shatsky Rise, is characterized by an abrupt increase (~2°-3°C) in sea surface temperatures, a greater flux of organic matter out of the surface ocean, and warmer (~4°C) intermediate waters. Results implicate simultaneous changes in surface waters and the sources/distribution patterns of intermediate water masses as an underlying cause for widespread biotic and oceanographic changes during mid-Maastrichtian time.

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The magnetic microparticle and nanoparticle inventories of marine sediments from equatorial Atlantic sites were investigated by scanning and transmission electron microscopy to classify all present detrital and authigenic magnetic mineral species and to investigate their regional distribution, origin, transport, and preservation. This information is used to establish source-to-sink relations and to constrain environmental magnetic proxy interpretations for this area. Magnetic extracts were prepared from sediments of three supralysoclinal open ocean gravity cores located at the Ceará Rise (GeoB 1523-1; 3°49.9'N/41°37.3'W), the Mid-Atlantic Ridge (GeoB 4313-2; 4°02.8'N/33°26.3'W), and the Sierra Leone Rise (GeoB 2910-1; 4°50.7'N/21°03.2'W). Sediments from two depths corresponding to marine isotope stages 4 and 5.5 were processed. This selection represents glacial and interglacial conditions of sedimentation for the western, central, and eastern equatorial Atlantic and avoids interferences from subsurface and anoxic processes. Crystallographic, elemental, morphological, and granulometric data of more than 2000 magnetic particles were collected by scanning and transmission electron microscopy. On basis of these properties, nine particle classes could be defined: detrital magnetite, titanomagnetite (fragmental and euhedral), titanomagnetite-hemoilmentite intergrowths, silicates with magnetic inclusions, microcrystalline hematite, magnetite spherules, bacterial magnetite, goethite needles, and nanoparticle clusters. Each class can be associated with fluvial, eolian, subaeric, and submarine volcanic, biogenic, or chemogenic sources. Large-scale sedimentation patterns are delineated as well: detrital magnetite is typical of Amazon discharge, fragmental titanomagnetite is a submarine weathering product of mid-ocean ridge basalts, and titanomagnetite-hemoilmenite intergrowths are common magnetic particles in West African dust. This clear regionalization underlines that magnetic petrology is an excellent indicator of source-to-sink relations. Hematite encrustations, magnetic spherules, and nanoparticle clusters were found at all investigated sites, while bacterial magnetite and authigenic hematite were only detected at the more oxic western site. At the eastern site, surface pits and crevices were seen on the crystal faces indicating subtle early diagenetic reductive dissolution. It was observed that paleoclimatic signatures of magnetogranulometric parameters such as the ratio of anhysteretic and isothermal remanent magnetizations can be formed either by mixing of multiple sources with separate, relatively narrow grain size ranges (western site) or by variable sorting of a single source with a broad grain size distribution (eastern site). Hematite, goethite, and possibly ferrihydrite nanoparticles occur in all sediment cores studied and have either high-coercive or superparamagnetic properties depending on their partly ultrafine grain sizes. These two magnetic fractions are generally discussed as separate fractions, but we suggest that they could actually be genetically linked.

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X-ray computed tomography (CT) provides an insight into the progression of dissolution in the tests of planktonic foraminifera. Four species of foraminifera (G. ruber [white], G. sacculifer, N. dutertrei and P. obliquiloculata) from Pacific, Atlantic and Indian Ocean core-top samples were examined by CT and SEM. Inner chamber walls began to dissolve at Delta[CO3**2-] values of 12-14 µmol/kg. Close to the calcite saturation horizon, dissolution and precipitation of calcite may occur simultaneously. Inner calcite of G. sacculifer, N. dutertrei and P. obliquiloculata from such sites appeared altered or replaced, whereas outer crust calcite was dense with no pores. Unlike the other species, there was no distinction between inner and outer calcite in CT scans of G. ruber. Empty calcite crusts of N. dutertrei and P. obliquiloculata were most resistant to dissolution and were present in samples where Delta[CO3**2-] ~ -20 µmol/kg. Five stages of preservation were identified in CT scans, and an empirical dissolution index, XDX, was established. XDX appears to be insensitive to initial test mass. Mass loss in response to dissolution was similar between species and sites at ~ 0.4 µg/µmol/kg. We provide calibrations to estimate Delta[CO3**2-] and initial test mass from XDX.

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From humble beginnings less than twenty years ago, the economic relationship between Canada and the Chinese has flourished so that China is now Canada’s second most important trading partner after the United States. The Chinese demand for Canada’s exports, in particular in the natural resource sectors, has been a clear win for Canada, especially during the recent Great Recession where demand from other countries dropped sharply. But other aspects of the relationship have led to suggestions of costs. Canada’s large trade deficit with China at least looks superficially as a drag on the Canadian economy. It has been suggested the greater exposure to a low cost producer has displaced Canadian production and jobs and lowered wages. We find that each argument for costs to the relationship ignores important factors. On balance we conclude the relationship has been good for Canada, and it could be even better in the future.