Paleomagnetic of DSDP Leg 90

Sediments recovered during Leg 90 (Sites 587-594, plus Site 586 cored during Leg 89) are, in general, extremely weakly magnetized carbonate oozes and chalks with NRM intensities seldom greater than 0.05 µG. The quality of the paleomagnetic records deteriorates with increasing depth caused by the combined effects of removal of primary magnetic oxides by sulfate reduction processes and the dispersal of magnetic grains during compaction. Magnetic reversal sequences are generally recognizable back to the Gilbert, 3.4 to 5.35 m.y., except at equatorial Site 586 where only the Brunhes/Matuyama boundary could be identified. Longer reversal records were obtained at Site 588 (to Chron 13, about 13 m.y.) and Site 594 (base of Chron 5, about 5.9 m.y.). Sediments are characterized by extremely high calcium carbonate contents (90-100%) with almost no biosiliceous components. Blebs and streaks of pyrite are common, and the presence of iron sulfides with poor magnetic stabilities is suspected, although not yet positively identified. Viscous components of magnetization are common, sometimes to the extent of dominating the primary remanence, and there is evidence to suggest that a magnetic remanence is imparted during core recovery. Siliceous carbonate oozes provide better paleomagnetic records than pure carbonate oozes.

Geochemistry on smectites in sediment cores CRP-1 and CRP-2 from the Ross Sea, Antarctica

TEM (transmission electron microscopy) observations and microanalyses on smectite microparticles in the sediments of the CRP-2A core were carried out to determine their origin (authigenic or detrital) and the source rocks. Smectites are dioctahedral and are Fe-rich members of the nontronite-beidellite series. They generally display both flaky and hairy shapes, but no large compositional difference between the two forms was observed. Flaky smectites are detrital while hairy smectites probably formed in situ through the reorganisation of previous flaky particles. The source rocks for smectites are probably represented by the McMurdo Volcanic Group to the south, but also by the Ferrar Dolerites and Kirkpatrick Basalts in the Transantarctic Mountains. CRP-2A smectites are Fe and Mg richer than those of the coeval or not coeval levels of the CIROS-I, DSDP 270 and 274 cores. The average compositions of smectite in CRP-1 and CRP-2A cores show a downcore trend toward more alluminiferous terms, which might reflect the increase of the chemical weathering processes on the continent.

El cajón de Herminio finalmente fue para el Partido Justicialista

En las elecciones presidenciales de abril de 2003 tres históricos dirigentes del Partido Justicialista (Carlos Menem, Adolfo Rodriguez Saa y Néstor Kirchner) se presentaron como candidatos a ocupar la presidencia de la Nación; sin embargo, la candidatura oficial del tradicional partido quedó vacante y los distintos candidatos crearon para la ocasión etiquetas partidarias nuevas (Frente por la Lealtad, Alianza Frente Movimiento Popular, Frente para la Victoria). El trabajo de tesis presentado procura reconstruir los factores tanto de largo plazo como coyunturales que condujeron a la fragmentación del PJ en distintas unidades partidarias. Consideraremos para ello, en un primer momento, procesos relacionados con la desindicalización partidaria, el vaciamiento de la burocracia del partido y la reconversión ideológica; en un segundo momento, nos centraremos en la reconstrucción del proceso político específico operado entre 1999 y 2003, año en que se efectiviza la ruptura del PJ. La fractura del Partido Justicialista constituye un hecho de gran relevancia puesto que significó una inflexión histórica en la organización partidaria del peronismo y marcó un cambio en el sistema partidario argentino que dejó de estructurarse en torno a partidos políticos sólidos

Age determination, planktic foraminifera and stable istopes of sediment core MSM05/5_712-2

A sediment core from the West Spitsbergen continental margin was studied to reconstruct climate and paleoceanographic variability during the last ~9 ka in the eastern Fram Strait. Our multiproxy evidence suggests that the establishment of the modern oceanographic configuration in the eastern Fram Strait occurred stepwise, in response to the postglacial sea-level rise and the related onset of modern sea-ice production on the shallow Siberian shelves. The late Early and Mid Holocene interval (9 to 5 ka) was generally characterized by relatively unstable conditions. High abundance of the subpolar planktic foraminifer species Turborotalita quinqueloba implies strong intensity of Atlantic Water (AW) inflow with high productivity and/or high AW temperatures, resulting in a strong heat flux to the Arctic. A series of short-lived cooling events (8.2, 6.9. and 6.1 ka) occurred superimposed on the warm late Early and Mid Holocene conditions. Our proxy data imply that simultaneous to the complete postglacial flooding of Arctic shallow shelves and the initiation of modern sea-ice production, strong advance of polar waters initiated modern oceanographic conditions in the eastern Fram Strait at ~5.2 ka. The Late Holocene was marked by the dominance of the polar planktic foraminifer species Neogloboquadrina pachyderma, a significant expansion of sea ice/icebergs, and strong stratification of the water column. Although planktic foraminiferal assemblages as well as sea surface and subsurface temperatures suggest a return of slightly strengthened advection of subsurface Atlantic Water after 3 ka, a relatively stable cold-water layer prevailed at the sea surface and the study site was probably located within the seasonally fluctuating marginal ice zone during the Neoglacial period.

El cajón de Herminio finalmente fue para el Partido Justicialista

En las elecciones presidenciales de abril de 2003 tres históricos dirigentes del Partido Justicialista (Carlos Menem, Adolfo Rodriguez Saa y Néstor Kirchner) se presentaron como candidatos a ocupar la presidencia de la Nación; sin embargo, la candidatura oficial del tradicional partido quedó vacante y los distintos candidatos crearon para la ocasión etiquetas partidarias nuevas (Frente por la Lealtad, Alianza Frente Movimiento Popular, Frente para la Victoria). El trabajo de tesis presentado procura reconstruir los factores tanto de largo plazo como coyunturales que condujeron a la fragmentación del PJ en distintas unidades partidarias. Consideraremos para ello, en un primer momento, procesos relacionados con la desindicalización partidaria, el vaciamiento de la burocracia del partido y la reconversión ideológica; en un segundo momento, nos centraremos en la reconstrucción del proceso político específico operado entre 1999 y 2003, año en que se efectiviza la ruptura del PJ. La fractura del Partido Justicialista constituye un hecho de gran relevancia puesto que significó una inflexión histórica en la organización partidaria del peronismo y marcó un cambio en el sistema partidario argentino que dejó de estructurarse en torno a partidos políticos sólidos

Age-depth correlations for Ontong Java Plateau sites

We used well logs, in some cases combined with shipboard physical properties measurements to make more complete profiles and to correlate between sites on the Ontong Java Plateau. By comparing sediment bulk density, velocity, and resistivity logs from adjacent holes at the same site, we showed that even subtle features of the well logs are reproducible and are caused by variations in sedimentation. With only minor amounts of biostratigraphic information, we could readily correlate these sedimentary features across the entire top of the Ontong Java Plateau, demonstrating that for most of the Neogene the top of the plateau is a single sedimentary province. We found it more difficult, but still possible, to correlate in detail sites from the top of the plateau to those drilled on the flanks. The pattern of sedimentation rate variation down the flank of the plateau cannot be interpreted as simply controlled by dissolution. Site 805, in particular, oscillates between accumulating sediment at roughly the same rate as cores on top of the Ontong Java Plateau, and accumulating sediment as slowly as Site 803, 200 m deeper in the water column. These oscillations do not match earlier reconstructions of central Pacific carbonate compensation depth variations.