885 resultados para Plowing the Dark
Resumo:
The mineralogy and chemistry of altered basalts and the stable isotopic compositions of secondary vein carbonates were studied in cores from Ocean Drilling Program Hole 843B, located in 95-Ma crust of the Hawaiian Arch. Millimeter- to centimeter-sized dark alteration halos around veins are 5%-15% altered to celadonite and Fe-oxyhydroxides, plus minor saponite and calcite. Adjacent gray host rocks are about 15% altered to saponite and calcite. The dark halos are enriched in H2O+, CO2, FeT, K2O, MnO, and Fe3+/FeT and depleted in SiO2, Al2O3, MgO, and TiO2 relative to gray host rocks. Brown alteration halos occur around veins where veins are more abundant, and are similar to dark halos, but contain more Fe-oxyhydroxides and exhibit greater Fe2O3T contents and higher Fe3+/FeT. Stable isotopic compositions of vein carbonates are consistent with their precipitation from seawater at temperatures of 5°-40°C. Crosscutting relationships of veins and zoned vein and vesicle fillings reveal a sequence of secondary mineral formation and alteration conditions. Celadonite and Fe-oxyhydroxides formed and dark alteration halos developed relatively early, under oxidizing conditions at low temperatures (<50°C). Saponite formed later at lower seawater/rock ratios and under more reducing conditions. Calcite and pyrite formed last in veins and vesicles from more evolved, seawaterderived fluids at temperatures of 5°-40°C. A second stage of celadonite, with compositions distinct from the early celadonite, also occurred relatively late (within the "calcite stage"), and may be related to refracturing of the crust and introduction of less-evolved seawater solutions into the rocks. Trends to higher K2O contents are attributed to alteration, but high K/Ti, Ba, and Zr contents indicate the presence of enriched or transitional MORB. CO2 contents of Pacific ODP cores exhibit a general increase with age suggesting progressive fixation of CO2 as calcite in the crust, but this could be complicated by local heterogeneities in fracturing and calcite formation in the crust.
Resumo:
La novela Tranvía a la Malvarrosa (1994), de Manuel Vicent, evoca una imagen nostálgica del pasado. Los olores, colores y sonidos de la Valencia de los años 50 hacen que el aprendizaje sentimental, profesional y moral del protagonista quede retratado de una manera profundamente atractiva. Sin embargo, el narrador de la novela critica el régimen franquista de aquellos días al mismo tiempo que los recuerda nostálgicamente. La combinación de un sentimiento crítico con uno nostálgico parece algo paradójica, pero se podría deducir que la crítica del pasado deja que la fuerza emocional de la nostalgia quede contenida y controlada. No obstante, en este caso sucede que la nostalgia termina por desestabilizar el tono crítico. Es más, la insistencia del narrador en los lados oscuros del pasado realzan su nostalgia, ya que sugiere una decadencia atractiva e intrigante
Resumo:
Los versos 990-1008 de Suplicantes de Eurípides constituyen un verdadero locus desperatus: allí Evadne se presenta sobre la escena y expresa en versos líricos los sentimientos previos a su suicidio final. Ni la métrica sin responsio del pasaje, ni el texto evidentemente corrupto, ni la gramática inadecuada ayudan a comprender el sentido del pasaje. Tan así es que la mayoría de los editores ha renunciado a tratar de comprender el sentido de sus palabras. Sin embargo, creemos que la adecuada interpretación de la metáfora utilizada por la esposa de Capaneo ayudará a la comprensión del pasaje: se trata de un priamel que se constituye en patético recordatorio del día de la boda por parte de una mujer que está a punto de suicidarse sobre la tumba de su esposo ya muerto. El fuego del rayo que mató a Capaneo, así como el fuego de la pira en donde arde ahora su cadáver (y en la que ella misma se arrojará muy pronto), le suscitan una serie de recuerdos de días mejores, vinculados todos ellos con el fuego y con la luz. La mención del carro del sol y de la luna, que constituye una metáfora casi cristalizada en la literatura griega, permite desarrollar de manera novedosa otra metáfora: las muchachas que, también ellas, cabalgan sobre la oscuridad portando sus antorchas. Evadne destaca la alegría que reinó el día de su boda, para que sea más agudo el contraste con el momento presente
Resumo:
Late Quaternary sediments of the Japan Sea are characterized by centimeter- to meter-scale alternations of dark and light layers which are synchronous basinwide. High-resolution analyses of the sediments from Ocean Drilling Program site 797 reveal that deposition of the meter-scale alternations reflect variations in paleoceanographic conditions which were closely associated with glacio-eustatic sea level changes through the modulation of the volume and character of the influx to the sea through the Tsushima Strait. The centimeter- to decimeter-scale alternations reflect millennial-scale variations which are possibly associated with Dansgaard-Oeschger (D-O) cycles, with each dark layer appearing to correspond to an interstadial. This variability is attributed to the development of a humid climate in central to eastern Asia and the consequent increase in discharge from the Huanghe and Changjiang Rivers during interstadials. This caused expansion of the East China Sea coastal water (ECSCW), which penetrated more strongly into the Japan Sea. The increased influence of the lower-salinity, nutrient-enriched ECSCW reduced deep water ventilation and enhanced the surface productivity, leading to the development of anoxic bottom waters and deposition of the dark layers. Thus the centimeter- to decimeter-scale alternations of the dark and light layers record wet and dry cycles in central to eastern Asia possibly associated with D-O cycles.
Resumo:
La novela Tranvía a la Malvarrosa (1994), de Manuel Vicent, evoca una imagen nostálgica del pasado. Los olores, colores y sonidos de la Valencia de los años 50 hacen que el aprendizaje sentimental, profesional y moral del protagonista quede retratado de una manera profundamente atractiva. Sin embargo, el narrador de la novela critica el régimen franquista de aquellos días al mismo tiempo que los recuerda nostálgicamente. La combinación de un sentimiento crítico con uno nostálgico parece algo paradójica, pero se podría deducir que la crítica del pasado deja que la fuerza emocional de la nostalgia quede contenida y controlada. No obstante, en este caso sucede que la nostalgia termina por desestabilizar el tono crítico. Es más, la insistencia del narrador en los lados oscuros del pasado realzan su nostalgia, ya que sugiere una decadencia atractiva e intrigante
Resumo:
Los versos 990-1008 de Suplicantes de Eurípides constituyen un verdadero locus desperatus: allí Evadne se presenta sobre la escena y expresa en versos líricos los sentimientos previos a su suicidio final. Ni la métrica sin responsio del pasaje, ni el texto evidentemente corrupto, ni la gramática inadecuada ayudan a comprender el sentido del pasaje. Tan así es que la mayoría de los editores ha renunciado a tratar de comprender el sentido de sus palabras. Sin embargo, creemos que la adecuada interpretación de la metáfora utilizada por la esposa de Capaneo ayudará a la comprensión del pasaje: se trata de un priamel que se constituye en patético recordatorio del día de la boda por parte de una mujer que está a punto de suicidarse sobre la tumba de su esposo ya muerto. El fuego del rayo que mató a Capaneo, así como el fuego de la pira en donde arde ahora su cadáver (y en la que ella misma se arrojará muy pronto), le suscitan una serie de recuerdos de días mejores, vinculados todos ellos con el fuego y con la luz. La mención del carro del sol y de la luna, que constituye una metáfora casi cristalizada en la literatura griega, permite desarrollar de manera novedosa otra metáfora: las muchachas que, también ellas, cabalgan sobre la oscuridad portando sus antorchas. Evadne destaca la alegría que reinó el día de su boda, para que sea más agudo el contraste con el momento presente
Resumo:
The Prydz Bay area is a key region for studying and understanding the history of the eastern Antarctic Continental Ice Sheet (O'Brien, Cooper, Richter, et al., 2001, doi:10.2973/odp.proc.ir.188.2001). Ocean Drilling Program (ODP) Site 1165 is situated in a water depth of 3357 m on the continental rise offshore from Prydz Bay and lies in front of the outlet for the Lambert Glacier-Amery Ice Shelf system that today drains 22% of East Antarctica. The site was drilled into mixed pelagic and hemipelagic sediments from the southwestern side of the Wild Drift. The drift is an elongate sediment body formed by the interaction of sediment supplied from continental shelf and slope with westward-flowing bottom currents. The sedimentary sequence is characterized by alternations between a generally gray to dark gray facies and a green to greenish gray facies. The greenish facies are structureless diatom-bearing clays with common bioturbation and larger amounts (>15%-20%) of biogenic silica, dispersed clasts, and lonestones than the dark gray facies, which are mostly less bioturbated clay with some silt laminations (Shipboard Scientific Party, 2001, doi:10.2973/odp.proc.ir.188.103.2001). High-quality advanced piston corer and extended core barrel cores containing nearly complete sections of middle Miocene to early Pliocene age allow a detailed characterization of sedimentary cycles and can provide indications for ice advances of the Lambert Glacier system into Prydz Bay, for the extent of sea ice, and for changes in oceanic circulation. The purpose of this work is to provide a data set of coarse-fraction mass percentage (>63, >125, and >250 µm) and biogenic silica content measured on sediments of late Miocene to early Pliocene age drilled at Site 1165. Additionally, high-resolution records of magnetic susceptibility (MS) and gamma ray attenuation (GRA) bulk density are presented. These shipboard data sets were edited postcruise. Furthermore, I provide a high-resolution dry bulk density record that is derived from GRA bulk density and can be used for the calculation of mass accumulation rates. These sedimentological and physical parameters will be used in future work to understand the depositional pattern of alternating biogenic and terrigenous sediments that was observed at Site 1165 (Shipboard Scientific Party, 2001, doi:10.2973/odp.proc.ir.188.103.2001).
Resumo:
The phytoplankton community composition and productivity in waters of the Amundsen Sea and surrounding sea ice zone were characterized with respect to iron (Fe) input from melting glaciers. High Fe input from glaciers such as the Pine Island Glacier, and the Dotson and Crosson ice shelves resulted in dense phytoplankton blooms in surface waters of Pine Island Bay, Pine Island Polynya, and Amundsen Polynya. Phytoplankton biomass distribution was the opposite of the distribution of dissolved Fe (DFe), confirming the uptake of glacial DFe in surface waters by phytoplankton. Phytoplankton biomass in the polynyas ranged from 0.6 to 14 µg Chl a / L, with lower biomass at glacier sites where strong upwelling of Modified Circumpolar Deep Water from beneath glacier tongues was observed. Phytoplankton blooms in the polynyas were dominated by the haptophyte Phaeocystis antarctica, whereas the phytoplankton community in the sea ice zone was a mix of P. antarctica and diatoms, resembling the species distribution in the Ross Sea. Water column productivity based on photosynthesis versus irradiance characteristics averaged 3.00 g C /m**2/d in polynya sites, which was approximately twice as high as in the sea ice zone. The highest water column productivity was observed in the Pine Island Polynya, where both thermally and salinity stratified waters resulted in a shallow surface mixed layer with high phytoplankton biomass. In contrast, new production based on NO3 uptake was similar between different polynya sites, where a deeper UML in the weakly, thermally stratified Pine Island Bay resulted in deeper NO3 removal, thereby offsetting the lower productivity at the surface. These are the first in situ observations that confirm satellite observations of high phytoplankton biomass and productivity in the Amundsen Sea. Moreover, the high phytoplankton productivity as a result of glacial input of DFe is the first evidence that melting glaciers have the potential to increase phytoplankton productivity and thereby CO2 uptake, resulting in a small negative feedback to anthropogenic CO2 emissions.
Resumo:
La novela Tranvía a la Malvarrosa (1994), de Manuel Vicent, evoca una imagen nostálgica del pasado. Los olores, colores y sonidos de la Valencia de los años 50 hacen que el aprendizaje sentimental, profesional y moral del protagonista quede retratado de una manera profundamente atractiva. Sin embargo, el narrador de la novela critica el régimen franquista de aquellos días al mismo tiempo que los recuerda nostálgicamente. La combinación de un sentimiento crítico con uno nostálgico parece algo paradójica, pero se podría deducir que la crítica del pasado deja que la fuerza emocional de la nostalgia quede contenida y controlada. No obstante, en este caso sucede que la nostalgia termina por desestabilizar el tono crítico. Es más, la insistencia del narrador en los lados oscuros del pasado realzan su nostalgia, ya que sugiere una decadencia atractiva e intrigante
Resumo:
Los versos 990-1008 de Suplicantes de Eurípides constituyen un verdadero locus desperatus: allí Evadne se presenta sobre la escena y expresa en versos líricos los sentimientos previos a su suicidio final. Ni la métrica sin responsio del pasaje, ni el texto evidentemente corrupto, ni la gramática inadecuada ayudan a comprender el sentido del pasaje. Tan así es que la mayoría de los editores ha renunciado a tratar de comprender el sentido de sus palabras. Sin embargo, creemos que la adecuada interpretación de la metáfora utilizada por la esposa de Capaneo ayudará a la comprensión del pasaje: se trata de un priamel que se constituye en patético recordatorio del día de la boda por parte de una mujer que está a punto de suicidarse sobre la tumba de su esposo ya muerto. El fuego del rayo que mató a Capaneo, así como el fuego de la pira en donde arde ahora su cadáver (y en la que ella misma se arrojará muy pronto), le suscitan una serie de recuerdos de días mejores, vinculados todos ellos con el fuego y con la luz. La mención del carro del sol y de la luna, que constituye una metáfora casi cristalizada en la literatura griega, permite desarrollar de manera novedosa otra metáfora: las muchachas que, también ellas, cabalgan sobre la oscuridad portando sus antorchas. Evadne destaca la alegría que reinó el día de su boda, para que sea más agudo el contraste con el momento presente
Resumo:
Pliocene and Pleistocene sediments of the Oman margin and Owen Ridge are characterized by continuous alternation of light and dark layers of nannofossil ooze and marly nannofossil ooze and cyclic variation of wet-bulk density. Origin of the wet-bulk density and color cycles was examined at Ocean Drilling Program Site 722 on the Owen Ridge and Site 728 on the Oman margin using 3.4-m.y.-long GRAPE (gamma ray attenuation) wet-bulk density records and records of sediment color represented as changes in gray level on black-and-white core photographs. At Sites 722 and 728 sediments display a weak correlation of decreasing wet-bulk density with increasing darkness of sediment color. Wet-bulk density is inversely related to organic carbon concentration and displays little relation to calcium carbonate concentration, which varies inversely with the abundance of terrigenous sediment components. Sediment color darkens with increasing terrigenous sediment abundance (decreasing carbonate content) and with increasing organic carbon concentration. Upper Pleistocene sediments at Site 722 display a regular pattern of dark colored intervals coinciding with glacial periods, whereas at Site 728 the pattern of color variation is more irregular. There is not a consistent relationship between the dark intervals and their relative wet-bulk density in the upper Pleistocene sections at Sites 722 and 728, suggesting that dominance of organic matter or terrigenous sediment as primary coloring agents varies. Spectra of wet-bulk density and optical density time series display concentration of variance at orbital periodicities of 100, 41, 23, and 19 k.y. A strong 41-k.y. periodicity characterizes wet-bulk density and optical density variation at both sites throughout most of the past 3.4 m.y. Cyclicity at the 41-k.y. periodicity is characterized by a lack of coherence between wet-bulk density and optical density suggesting that the bulk density and color cycles reflect the mixed influence of varying abundance of terrigenous sediments and organic matter. The 23-k.y. periodicity in wet-bulk density and sediment color cycles is generally characterized by significant coherence between wet-bulk density and optical density, which reflects an inverse relationship between these parameters. Varying organic matter abundance, associated with changes in productivity or preservation, is inferred to more strongly influence changes in wet-bulk density and sediment color at this periodicity.
Resumo:
Hole 504B, drilled into the 5.9 Ma crust of the southern flank of the Costa Rica Rift, tapped a hydrothermal system in its conductive stage. Three alteration zones were encountered along the 561.5 meters of basement drilled. The upper alteration zone, 274.5 to 584.5 meters below the seafloor (BSF), is characterized by the presence of color zonation in which red halos are located between dark gray inner rock portions and dark gray outer bands. The red halos are characterized by an abundance of iddingsite, and they have higher K2O contents and Fe3+/FeT ratios, but lower SiO2 contents, than the adjacent dark gray inner zones. The dark gray outer bands are characterized by the presence of celadonite-nontronite. Saponite is omnipresent in these three alteration bands. Phillipsite is the only zeolite that occurs in the upper alteration zone. The upper alteration zone is interpreted as being the result of low-temperature alteration, with large amounts of cold oxygenated seawater percolating through the upper ocean crust. In the upper alteration zone, the formation of red halos was both preceded and followed by formation of dark gray outer bands. Then followed formation of dark gray cores. The lower alteration zone (584.5-835.5 m BSF) is characterized by the absence of color zonation, the downward-increasing abundance of pyrite and saponite, and the presence of quartz, talc, and calcite. The chemical changes (downhole MgO enrichment and concomitant CaO depletion) observed in the basalts of the lower alteration zone are thought to result from reactions of oceanic basalts with evolved seawater (i.e., solutions derived from seawater that has already reacted with ocean crust), which is thus depleted in oxygen, potassium, and radiogenic strontium. This alteration process, which was responsible for saponite formation in both the upper and lower alteration zones, was rock dominated, and it took place under suboxic to anoxic conditions during a second stage of alteration. Reaction temperatures could have progressively increased with depth. There is also a zeolitic zone that essentially coincides with the lower part of the upper alteration zone (between 528.5 and 563 m BSF). The host rock adjacent to veins of zeolite exhibits a greenish discoloration due to the intensive replacement of the igneous minerals. The replacement minerals result in significant increases in the bulk rock K2O, MgO, CaO, CO2, and H2O+ contents. The solutions circulating along the newly opened fissures had high Ca activity, and minerals probably precipitated in these fissures at 60°C or 110°C. These hydrothermal solutions circulated later than those responsible for the formation of the minerals that characterize the upper and lower alteration zones.
Resumo:
Site 534 reflects a complex interplay of global, basinal, and local influences on sedimentation during the Callovian and Late Jurassic. Rifting and rapid subsidence of the continental margins of the North Atlantic-Tethys seaway occurred during the late Early Jurassic (Sinemurian-Pliensbachian), but rapid spreading between the North American margin (Blake Spur Ridge and magnetic lineation) and the northwest African margin did not commence until the Bathonian or earliest Callovian. Site 534, drilled on marine magnetic anomaly "M-28" of Bryan et al. (1980), was initially about 150 km from either continental margin. The ?middle Callovian basal sediments are dusky red silty marl. Callovian transgression led to active carbonate platforms on the margin, recorded at Site 534 as a rise in the CCD (carbonate compensation depth), then arrival of lime-rich turbidites from the Blake Plateau platform across the Blake Spur Ridge. The host pelagic sediment is greenish black, organic-rich, radiolarian-rich, silty claystone. Hydrothermal activity on the nearby spreading ridge enriched this lower unit in metals. In the Oxfordian, the input of terrestrial silt rapidly diminished; radiolarians or other bioclasts were not preserved. The dark variegated claystone has fine-grained marl and reddish claystone turbidite beds. The late Callovian-Oxfordian Western Tethys has radiolarian chert deposition, marine hiatuses, or organic-rich sediments. The Kimmeridgian and Tithonian had a stable or receding sea level. Near the end of the Jurassic many of the carbonate platforms of the margins were buried beneath prograding fan or alluvial deposits. Carbonate deposition shifted to the deep sea. Site 534 records the deepening of the CCD and ACD (aragonite compensation depth) during the Kimmeridgian and early Tithonian, then a rise of the ACD in the middle Tithonian. Similar trends occurred throughout the Western Tethys-Atlantic. High nannofossil productivity of the seaway led to deposition of very widespread white micritic limestone in the late Tithonian-Berriasian. The underlying sediment had a slower deposition rate of carbonate, therefore its higher clay and associated Fe content produced a red marl. A short sea-level incursion occurred on the Atlantic margins during the Kimmeridgian and is reflected in the Site 534 greenish gray marl unit by numerous turbidite beds of shallow-water carbonates.