Geochemistry of ODP Sites 121-758 and 121-757

Nd isotopes are useful tracers for paleoceanography due to the short Nd residence time in seawater and the large differences between the isotopic signatures of various geological reservoirs. Therefore, ?Nd variations reflect the geological history of individual oceanic basins. Using a differential dissolution technique, which extracts Nd isotopes of seawater trapped in MnO2 coatings and carbonates in marine sediment, we measured almost two hundred samples from ODP Sites 758 and 757 in the Northern Bay of Bengal covering the last 4 Ma. For the first time, we have shown a covariation between epsilon-Nd and d18O over at least the last 800 ka. We also show that from 4 Ma to 2.6 Ma, epsilon-Nd is almost constant and starts to fluctuate at 2.6 Ma when northern glaciations increased. From 2.6 Ma to 1 Ma the fluctuation period is close to 40 ka while from 1 Ma to present it is dominantly 100 ka. We attribute these findings to mixing between Himalayan river water (that ultimately originates as Indian summer monsoon rain) and normal Bay of Bengal seawater. Previous studies on seawater, using epsilon-Nd, d18O analyzed on planktonic foraminifera and sedimentary data, can be integrated into this model. A simple quantitative binary mixing model suggests that the summer monsoon rain was more intense during interglacial than glacial periods. During last glacial episode, the monsoon trajectory was deviated to the east. At a large scale, the Indian monsoon is fully controlled by the variations in Northern Hemisphere climate but with a complex response function to this forcing. Our study clearly establishes the large potential of Nd isotope data to evaluate the hydrological river regime during the Quaternary and its relationship with climate fluctuations, particularly when the sediment archive is sampled close to sediment sources.

Geochemistry of FeMn oxyhydroxides of IODP Site 303-U1302 and 303-1303

Regional weathering intensity must have changed dramatically at high latitudes during the Quaternary as a consequence of repeated continental glaciation. Investigation of these glacial/interglacial changes at high temporal resolution is possible with the recent development of Pb isotopes in FeMn oxyhydroxide phases as a proxy for region-specific weathering intensity, where increases in the radiogenic component are thought to correspond to increased continental weathering fluxes. Here we present a Pb isotope record sourced from the FeMn oxyhydroxide fraction in marine sediments from IODP Sites U1302/3 on Orphan Knoll (~3500 mbsl, NW Atlantic), spanning the last 37 ka. Located at the eastern edge of the Laurentide Ice Sheet (LIS), Site U1302/3 is well-placed to monitor changes in weathering intensity associated with LIS glacial history. Overall, the data show a close correspondence to local surface water d18O, with least radiogenic values during times of heavy d18O (glacial maximum) and most radiogenic values during times of light d18O (Holocene). This supports the prediction that weathering intensity in glaciated regions of the North Atlantic correlates with the exposure age of glacial debris. Superimposed on these background trends are extreme radiogenic excursions (e.g. variation in 206Pb/204Pb from ~19.2-21.0) contemporaneous with Heinrich events and the Younger Dryas. These data are substantially more radiogenic than existing records from the NW Atlantic, and most likely represent episodes of exceptionally high inputs of pre-formed FeMn oxyhydroxides during drainage of the LIS. Due to its extreme isotope composition, at least in the NW Atlantic region, Pb would appear to be a good proxy for the fluxes of weathered continental material and perhaps, by inference, nutrients to the surface ocean

Pollen and macrofossils profiles and age determination from three cores in Northeastern Kansas, U.S.A.

Two marshes near Muscotah and Arrington, Atchison County, northeastern Kansas, yielded a pollen sequence covering the last 25,000 yrs of vegetation development. The earliest pollen spectra are comparable with surface pollen spectra from southern Saskatchewan and southeastern Manitoba and might indicate a rather open vegetation but with some pine, spruce, and birch as the most important tree species, with local stands of alder and willow. This type of vegetation changed about 23,000 yrs ago to a spruce forest, which prevailed in the region until at least 15,000 yrs ago. Because of a hiatus, the vegetation changes resulting in the spread of a mixed deciduous forest and prairie, which was present in the region from 11,000 to 9,000 yrs ago, remain unknown. Prairie vegetation, with perhaps a few trees along the valleys, covered the region until about 5,000 yrs ago, when a re-expansion of deciduous trees began in the lowlands.

Pedogeomorphology, geochronology and paleobotany of soil profiles obtained in the Kyichu River catchment, sourthern Tibet

Results of pedogeomorphological, geochronological and paleobotanical investigations are presented covering the last ca. 4,000 years. The study sites are located in the heavily degraded Kyichu River catchment around Lhasa at 3,600-4,600 m a.s.l. Repeatedly, colluvial sediments have been recorded overlying paleosols. These deposits can be divided into i) coarse-grained sediments with a high proportion of stones and boulders originating from alluvial fans and debris flows, ii) matrix supported sediments with some stones and boulders originating from mudflows or combined colluvial processes such as hillwash plus rock fall, and iii) fine-grained sediments originating from hill wash. The IRSL multi-level dating of profile QUG 1 points to a short-time colluvial sedimentation between 1.0 ± 0.1 and 0.8 ± 0.1 ka. In contrast, dated paleosols of profile GAR 1 (7,908 ± 99 and 3,668 ± 57 BP) encompass a first colluvial episode. Here, the upper colluvial sedimentation took place during several periods between 2.6 ± 0.3 and 0.4 ± 0.1 ka. For the first time in Tibet, a systematic extraction, determination and dating of charcoals from buried paleosols was conducted. The charcoals confirm the Late Holocene presence of juniper forests or woodlands in a now treeless, barren environment. A pollen diagram from Lhasa shows a distinct decline of pollen of the Jumperus-type around 4,140 ± 50 BP, which is interpreted as indicating a clearing of forests on the adjacent slopes. It is assumed that the environmental changes from forests to desertic rangelands since ca. 4,000 BP have been at least reinforced by humans.

La producción discursiva en la traducción de textos pragmáticos francés/castellano : Estudio traductológico a través de los enunciados elípticos con anomalías

Esta tesis doctoral se inscribe dentro de la Traductología, interdisciplina que estudia tanto los procesos implicados en el complejo fenómeno de la traducción como los productos discursivos en la lengua hacia la cual se traduce. Su objetivo general consiste en contribuir a la investigación sobre el macroproceso de traducción en el par de lenguas francés/español, y en especial sobre la producción discursiva puesto que la literatura especializada coincide en destacar que ésta es la fase menos conocida [Lederer, 2005, 126; Toury, 2004, 244, 245]. Nuestro trabajo explora la producción discursiva, limitándola a traducciones absolutas [Gouadec, 1989: 21-30] de textos pragmáticos [Delisle, 1984: 22], cuya función esencial es el pasaje integral de la información. Dentro de dos corpora del campo de la Bioética constituidos por textos originales en francés y sus traducciones al castellano, hemos considerado como hipótesis general que los productos discursivos resultantes de la traducción absoluta de textos pragmáticos francés/castellano, presentan transferencias sintáctico-discursivas gobernadas por el universal de interferencia. Es decir que el planteo rector es que la memoria lingüístico-discursiva en la fase de reexpresión está atravesada por el mecanismo de interferencia. Las hipótesis específicas que se desgranan de la principal indican que la producción discursiva resultante de la traducción de textos pragmáticos francés/castellano exhibe enunciados elípticos anómalos gobernados por el universal de interferencia del discurso de partida [francés] o del sistema de la lengua materna del traductor [castellano]. Nuestra investigación parte entonces de la lectura del texto traducido [TT] y lo compara con el texto original [TO]; esta comparación es parcial puesto que indaga sobre las anomalías de producción; es indirecta pues observa la relación cohesión-coherencia-sentido en el discurso de llegada a través de las anomalías, especialmente de los enunciados elípticos; por último, analiza las anomalías dentro de la teoría de la interferencia y de la teoría de la elipsis [Toury, 2004: 121-124]. Sobre estas bases, hemos generado un instrumento que estudia los binomios textuales seleccionados según las siguientes aproximaciones: la sintaxis de la lengua meta [tipo de elipsis, elemento elidido, construcción de la elipsis, recuperabilidad]; la sintaxis del discurso meta [cohesión-coherencia], la comparación del binomio TT-TO [análisis de la producción del segmento problema en TO; el análisis de la producción del segmento solución en TT; posible extensión de las consecuencias de la anomalía microestructural; verificación del principio traducir toda la información]; los mecanismos de producción [elevación de la frecuencia de uso de recursos o elementos; control lingüístico de la lengua-cultura meta; control lingüístico-discursivo]; el resultado [visibilidad de interferencia; fenómeno sintáctico visible; alcance discursivo; producción palimpséstica; entropía informativa]. La elaboración de este andamiaje analítico aplicado a nuestros corpora nos ha permitido avanzar en el conocimiento de los mecanismos que participan en la producción discursiva en traducción y creemos que puede aplicarse, con las modificaciones de cada caso, para la descripción y quizás explicación de otros factores lingüístico-discursivos presentes en los textos traducidos