Corg, CaCO3, bulk densities, accumulation rates and ages of ODP Leg 167 sites and three piston cores, California margin

Sediments from five Leg 167 drill sites and three piston cores were analyzed for Corg and CaCO3. Oxygen isotope stratigraphy on benthic foraminifers was used to assign age models to these sedimentary records. We find that the northern and central California margin is characterized by k.y.-scale events that can be found in both the CaCO3 and Corg time series. We show that the CaCO3 events are caused by changes in CaCO3 production by plankton, not by dissolution. We also show that these CaCO3 events occur in marine isotope Stages (MIS) 2, 3, and 4 during Dansgaard/Oeschger interstadials. They occur most strongly, however, on the MIS 5/4 glaciation and MIS 2/1 deglaciation. We believe that the link between the northeastern Pacific Ocean and North Atlantic is primarily transmitted by the atmosphere, not the ocean. Highest CaCO3 production and burial occurs when the surface ocean is somewhat cooler than the modern ocean, and the surface mixed layer is somewhat more stable.

Percepción de la relación con los padres y autoconcepto de los niños con Trastorno por Déficit de Atención con Hiperactividad (TDAH)

La forma en que los individuos se perciben y valoran a sí mismos cumple una función muy importante en su adaptación psicológica y social. Los niños con Trastorno por Déficit de Atención con Hiperactividad (TDAH) enfrentan múltiples situaciones de fracaso, por lo que sería esperable que tuvieran una percepción pobre de sí mismos. Sin embargo, los hallazgos en esta área han sido inconsistentes. Por otra parte, la familia es el principal contexto implicado en la constitución del autoconcepto, pero las variables familiares prácticamente no han sido tenidas en cuenta. Objetivo general: Conocer las características del autoconcepto de niños con TDAH y su vinculación con la percepción de la relación con los padres. Método: Muestra: Niños de ambos sexos con diagnóstico de TDAH según los criterios del DSM-IV-TR (n = 35). Grupos control: Niños que concurren a psicoterapia por motivos distintos del TDAH (n = 26)(Grupo Control Clínico, GCC) y niños que no reciben asistencia psicoterapéutica o psiquiátrica (n = 44) (Grupo Control Sano, GCS) de entre 7 y 13 años. Al menos uno de sus padres y un docente de estos niños. Las tres muestras presentan características sociodemográficas equiparables. Instrumentos: Para los niños: Escala Argentina de Percepción de la relación con los padres; Perfil de autopercepción para niños. Para los padres: Cuestionario sociodemográfico; SNAP-IV; Escala de evaluación del comportamiento del niño. Versión para padres. Para los docentes: SNAP-IV; Escala de evaluación del comportamiento del niño. Versión para docentes. Procedimiento: se realizó un estudio descriptivo correlacional de tipo transversal. Se pidió consentimiento informado a los padres de los niños evaluados. La participación fue voluntaria y confidencial. Los niños con TDAH y del GCC fueron contactados en centros de salud. Los niños del GCS fueron contactados en instituciones educativas. Procesamiento de la información: Se utilizó la prueba de Kruskal Wallis y U Mann-Whitney para la comparación entre grupos. Para estudiar la asociación entre variables se utilizó el coeficiente Rho de Spearman y la prueba Ji cuadrado. Se realizaron regresiones logísticas simples para estudiar el poder predictivo de unas variables sobre las otras. Se estudió el tamaño del efecto en todos los análisis realizados. Resultados: Los niños con TDAH presentan un autoconcepto más negativo y un mayor sesgo positivo ilusorio (SPI) comparados con los niños del GCS. Sin embargo, su autoconcepto no difiere del de los niños del GCC. Estos niños tienen un autoconcepto más negativo que los niños del GCS. En cuanto al SPI, el GCC forma un grupo intermedio que no difiere de los otros dos. En cuanto a la percepción de la relación con los padres, se encontró que el TDAH afecta principalmente la relación con la madre. Estos niños perciben un mayor control patológico por parte de ella que los niños que no padecen el trastorno y una menor autonomía que los niños del GCS. Asimismo, cuanto mayor es el nivel de síntomas combinados que se expresan en la escuela, mayor es el control patológico percibido por el niño en esta relación. Si bien no se encontraron diferencias en la percepción de aceptación por parte de los padres respecto de los otros grupos estudiados, los síntomas de hiperactividad/impulsividad se asociaron positivamente con la percepción de aceptación materna. El estudio de la vinculación entre el autoconcepto y la percepción de la relación con los padres reveló que, también en este caso, la relación con la madre es la que tiene la mayor influencia. En el grupo con TDAH, la percepción de un bajo control patológico en esta relación predijo autopercepciones más negativas en el dominio de las competencias académicas y el comportamiento. Asimismo, un alto control patológico predijo un alto SPI en el dominio de las competencias académicas. En el GCC y el GCS, un bajo control patológico percibido en la relación con la madre predijo autopercepciones positivas. Se discuten las implicancias

Percepción de la relación con los padres y autoconcepto de los niños con Trastorno por Déficit de Atención con Hiperactividad (TDAH)

La forma en que los individuos se perciben y valoran a sí mismos cumple una función muy importante en su adaptación psicológica y social. Los niños con Trastorno por Déficit de Atención con Hiperactividad (TDAH) enfrentan múltiples situaciones de fracaso, por lo que sería esperable que tuvieran una percepción pobre de sí mismos. Sin embargo, los hallazgos en esta área han sido inconsistentes. Por otra parte, la familia es el principal contexto implicado en la constitución del autoconcepto, pero las variables familiares prácticamente no han sido tenidas en cuenta. Objetivo general: Conocer las características del autoconcepto de niños con TDAH y su vinculación con la percepción de la relación con los padres. Método: Muestra: Niños de ambos sexos con diagnóstico de TDAH según los criterios del DSM-IV-TR (n = 35). Grupos control: Niños que concurren a psicoterapia por motivos distintos del TDAH (n = 26)(Grupo Control Clínico, GCC) y niños que no reciben asistencia psicoterapéutica o psiquiátrica (n = 44) (Grupo Control Sano, GCS) de entre 7 y 13 años. Al menos uno de sus padres y un docente de estos niños. Las tres muestras presentan características sociodemográficas equiparables. Instrumentos: Para los niños: Escala Argentina de Percepción de la relación con los padres; Perfil de autopercepción para niños. Para los padres: Cuestionario sociodemográfico; SNAP-IV; Escala de evaluación del comportamiento del niño. Versión para padres. Para los docentes: SNAP-IV; Escala de evaluación del comportamiento del niño. Versión para docentes. Procedimiento: se realizó un estudio descriptivo correlacional de tipo transversal. Se pidió consentimiento informado a los padres de los niños evaluados. La participación fue voluntaria y confidencial. Los niños con TDAH y del GCC fueron contactados en centros de salud. Los niños del GCS fueron contactados en instituciones educativas. Procesamiento de la información: Se utilizó la prueba de Kruskal Wallis y U Mann-Whitney para la comparación entre grupos. Para estudiar la asociación entre variables se utilizó el coeficiente Rho de Spearman y la prueba Ji cuadrado. Se realizaron regresiones logísticas simples para estudiar el poder predictivo de unas variables sobre las otras. Se estudió el tamaño del efecto en todos los análisis realizados. Resultados: Los niños con TDAH presentan un autoconcepto más negativo y un mayor sesgo positivo ilusorio (SPI) comparados con los niños del GCS. Sin embargo, su autoconcepto no difiere del de los niños del GCC. Estos niños tienen un autoconcepto más negativo que los niños del GCS. En cuanto al SPI, el GCC forma un grupo intermedio que no difiere de los otros dos. En cuanto a la percepción de la relación con los padres, se encontró que el TDAH afecta principalmente la relación con la madre. Estos niños perciben un mayor control patológico por parte de ella que los niños que no padecen el trastorno y una menor autonomía que los niños del GCS. Asimismo, cuanto mayor es el nivel de síntomas combinados que se expresan en la escuela, mayor es el control patológico percibido por el niño en esta relación. Si bien no se encontraron diferencias en la percepción de aceptación por parte de los padres respecto de los otros grupos estudiados, los síntomas de hiperactividad/impulsividad se asociaron positivamente con la percepción de aceptación materna. El estudio de la vinculación entre el autoconcepto y la percepción de la relación con los padres reveló que, también en este caso, la relación con la madre es la que tiene la mayor influencia. En el grupo con TDAH, la percepción de un bajo control patológico en esta relación predijo autopercepciones más negativas en el dominio de las competencias académicas y el comportamiento. Asimismo, un alto control patológico predijo un alto SPI en el dominio de las competencias académicas. En el GCC y el GCS, un bajo control patológico percibido en la relación con la madre predijo autopercepciones positivas. Se discuten las implicancias

Palynology on sediment profile Tso Kar in Ladakh

Palynological investigation of a 410 cm long core section from Tso Kar (33°10'N, 78°E, 4527 m a.s.l.), an alpine lake situated in the arid Ladakh area of NW India at the limit of the present-day Indian summer monsoon, was performed in order to reconstruct post-glacial regional vegetation and climate dynamics. The area was covered with alpine desert vegetation from ca. 15.2 to 14 kyr BP (1 kyr=1000 cal. years), reflecting dry and cold conditions. High influx values of long-distance transported Pinus sylvestris type pollen suggest prevailing air flow from the west and northwest. The spread of alpine meadow communities and local aquatic vegetation is a weak sign of climate amelioration after ca. 14 kyr BP. Pollen data (e.g. influx values of Pinus roxburghii type and Quercus) suggest that this was due to a strengthening of the summer monsoon and the reduced activity of westerly winds. The further spread of Artemisia and species-rich meadows occurred in response to improved moisture conditions between ca. 12.9 and 12.5 kyr BP. The subsequent change towards drier desert-steppe vegetation likely indicates more frequent westerly disturbances and associated snowfalls, which favoured the persistence of alpine meadows on edaphically moist sites. The spread of Chenopodiaceae-dominated vegetation associated with an extremely weak monsoon occurred at ca. 12.2-11.8 kyr BP during the Younger Dryas interstadial. A major increase in humidity is inferred from the development of Artemisia-dominated steppe and wet alpine meadows with Gentianaceae after the late glacial/early Holocene transition in response to the strengthening of the summer monsoon. Monsoonal influence reached maximum activity in the Tso Kar region between ca. 10.9 and 9.2 kyr BP. The subsequent development of the alpine meadow, steppe and desert-steppe vegetation points to a moderate reduction in the moisture supply, which can be linked to the weaker summer monsoon and the accompanying enhancement of the winter westerly flow from ca. 9.2 to 4.8 kyr BP. The highest water levels of Tso Kar around 8 kyr BP probably reflect combined effect of both monsoonal and westerly influence in the region. An abrupt shift towards aridity in the Tso Kar region occurred after ca. 4.8 kyr BP, as evidenced by an expansion of Chenopodiaceae-dominated desert-steppe. Low pollen influx values registered ca. 2.8-1.3 kyr BP suggest scarce vegetation cover and unfavourable growing conditions likely associated with a further weakening of the Indian Monsoon.

Chemial and isotope compositions of rocks from the West Antarctic

The paper is devoted to a marine geophysical-geological research in the West Antarctic. This researche contributed to establishing the base geodesic network of the West Antarctic and supplemented geokinematic monitoring based on this network with geophysical and geologic information on structure and features of geomorphological and tectonic development of the South Ocean floor. Collected materials allow to conclude about the inhomogeneity of the Scotia Sea floor and about combination of fragments of a continental massif with young rift structures in conditions of the upwelling mantle. The ancient continental bridge, faunal connections between the South America and the West Antarctic has been destroyed by processes of destruction, taphrogeny and sea floor spreading. Structures of the Scotia and Caribbean Seas, North Fiji and Arctic Basins are similar.

Fission track age determinations of rocks from north Greenland

Apatite fission track (FT) ages and length characteristics of samples obtained from Cambrian to Paleocene-aged sandstones collected along the margin of Nares Strait in Ellesmere Island in the Canadian Arctic Archipelago are dominated by a thermal history related to Paleogene relative plate movements between Greenland and Ellesmere Island. A preliminary inverse FT thermal model for a Cambrian (Archer Fiord Formation) sandstone in the hanging wall of the Rawlings Bay thrust at Cape Lawrence is consistent with Paleocene exhumational cooling, likely as a result of erosion of the thrust. This suggests that thrusting at Cape Lawrence occurred prior to the onset of Eocene compression, likely due to transpression during earlier strikeslip along the strait. Models for samples from volcaniclastic sandstones of the Late Paleocene Pavy Formation (from Cape Back and near Pavy River), and a sandstone from the Late Paleocene Mount Lawson Formation (at Split Lake, near Makinson Inlet) are also consistent with minor burial heating following known periods of basaltic volcanism in Baffin Bay and Davis Strait (c. 61-59 Ma), or related tholeiitic volcanism and intrusive activity (c. 55-54 Ma). Thermal models for samples from sea level dykes from around Smith Sound suggest a period of Late Cretaceous - Paleocene heating prior to final cooling during Paleocene time. These model results imply that Paleocene tectonic movements along Nares Strait were significant, and provide limited support for the former existence of the Wegener Fault. Apatite FT data from central Ellesmere Island suggest however, that cooling there occurred during Early Eocene time (c. 50 Ma), which was likely a result of erosion of thrusts during Eurekan compression. This diachronous cooling suggests that Eurekan deformation was partitioned at discrete intervals across Ellesmere Island, and thus it is likely that displacements along the strait were much less than the 150 km that has been previously suggested for the Wegener Fault.

Physical oceanography during five ECOMARGE cruises

The first experiment of the ECOMARGE programme (ECOsystèmes de MARGE continentale) was initiated in 1983-1984, in the Gulf of Lions (northwestern Mediterranean Sea). The objectives of the ECOMARGE-I experiment were: to quantify the transfer of particulate matter, in general, and of organic carbon, in particular, from its introduction to and formation in the waters of the continental shelf-to its consumption or sedimentation on the shelf or its transfer to the slope and deep sea; and to understand the processes involved in that transfer, consumption and sedimentation together with their variability in space and time. The results of that experiment, from 1983 to 1988, are presented in this Special Issue. The highlights of the results are summarised in this paper. These results indicate that, of the particles formed in the waters of the continental shelf and those introduced by rivers, some are deposited as sediments on the shelf. A portion is transported offshore, however, to the slope and deep sea. The Rho^ne River, in the northeastern part of the study area, is the major source of continental material; this is transported to sea in a benthic nepheloid layer and, mostly, alongshore to the southwest. Here, it largely leaves the shelf through the canyons, especially the Lacaze-Duthiers Canyon. In the offshore waters, particle concentrations and distributions show surficial, intermediate and benthic nepheloid layers. These turbid structures increase towards the southwest, corresponding to the seaward shift of the front between the coastal waters and the Liguro-Provençal cyclonic gyre, a major forcing function in the Gulf of Lions. Considering the source and fate of particles (largely biogenic from the euphotic zone and abiogenic from deeper waters) a layered system is described, which is emphasized by the concentrations of natural and artificial elements and compounds. Of the flux of particles to the Lacaze-Duthiers Canyon, on a decadal scale, about 30% (as a minimum) is estimated to be stored as sediment; the remainder is transported down-canyon, towards the deep sea. The temporal variability of processes affecting this net seaward transport, of both biogenic and abiogenic material, is from hours, days to seasonal, and probably interannual, time scales. The response of the system to these variations is rapid, with pulses of increased discharge of particles from the adjacent shelf being detected in sediment traps in the Lacaze-Duthiers Canyon in less than 16 days (the temporal resolution of the traps). Based upon the study of tracers of particulate matter and environmental factors (i.e. river discharge and climatic conditions), it appears that the contribution from the Rho^ne River and its adjacent area is maximal during the winter; at this time, the flow of the Liguro-Provençal Current also increases. In contrast, the maximum relative contribution of the adjacent southwesterly area to the flux in the Lacaze-Duthiers Canyon occurs in summer, during storm events.

U-Pb, trace element, and Hf isotope analysis for Macquarie Island detrital zircon

Oceanic zircon trace element and Hf-isotope geochemistry offers a means to assess the magmatic evolution of a dying spreading ridge and provides an independent evaluation of the reliability of oceanic zircon as an indicator of mantle melting conditions. The Macquarie Island ophiolite in the Southern Ocean provides a unique testing ground for this approach due to its formation within a mid-ocean ridge that gradually changed into a transform plate boundary. Detrital zircon recovered from the island records this change through a progressive enrichment in incompatible trace elements. Oligocene age (33-27 Ma) paleo-detrital zircon in ophiolitic sandstones and breccias interbedded with pillow basalt have trace element compositions akin to a MORB crustal source, whereas Late Miocene age (8.5 Ma) modern-detrital zircon collected from gabbroic colluvium on the island have highly enriched compositions unlike typical oceanic zircon. This compositional disparity between age populations is not complimented by analytically equivalent eHf data that primarily ranges from 14 to 13 for sandstone and modern-detrital populations. A wider compositional range for the sandstone population reflects a multiple pluton source provenance and is augmented by a single cobble clast with eHf equivalent to the maximum observed composition in the sandstone (~17). Similar sandstone and colluvium Hf-isotope signatures indicate inheritance from a similar mantle reservoir that was enriched from the depleted MORB mantle average. The continuity in Hf-isotope signature relative to trace element enrichment in Macquarie Island zircon populations, suggests the latter formed by reduced partial melting linked to spreading-segment shortening and transform lengthening along the dying spreading ridge.

(Table 1) Lead, thorium and uranium isotopic concentration and ages of zircons from Yenisey Ridge metapelites

Reconstruction of the geologic history of the Yenisey Ridge, which developed as an accretionary collision orogen on the western margin of the Siberian craton is essential to understanding the evolution of mobile belts surrounding older cratons, as well as to resolving the recently much debated problem of whether Siberia was part of the supercontinent Rodinia. Available paleotectonic models suggest that this supercontinent was assembled at the Middle-Late Riphean boundary (1100-900 Ma) as a result of the Grenville orogeny, the first long-lived mountain building event which occurred in geosynclinal areas during the Neogaea. However, the character of crustal evolution at that stage is still speculative due to the lack of reliable and conclusive isotope data. In many current geodynamic models, a common underlying assumption is that the Yenisey Ridge showed very little endogenic activity for 1 Gyr, from the time of Tarak granite emplacement (1900-1840 Ma) to the Middle Neoproterozoic (~750 Ma). On the basis of this assumption, several recent studies suggested the absence of Grenvillian collisional events within the Yenisey Ridge. The results of the SHRIMP II U-Pb analysis of rift-related plagiogranites of the Nemtikha Complex, Yenisey Ridge (1380-1360 Ma) suggest an increase in magmatic activity in the Mesoproterozoic. Interpretation of these results in terms of a supercontinent cycle may help find evidence for possible occurrence of the Grenville orogeny on the western margin of the Siberian craton. With this in mind, we attempted to reconstruct using recent geochronological constraints the evolution of metapelitic rocks from the Teya polymetamorphic complex (TPMC), which is a good example of superimposed zoning of low and medium-pressure facies series. High precision age determinations from rock complexes formed in different geodynamic settings under different thermodynamic conditions and geothermal gradients were used to distinguish several major metamorphic events and unravel their time relations with tectonic and magmatic activity in the region.

Abundance and biomass of planktonic diatom Proboscia alata and associated species, chlorophyll a, organic carbon and nitrogen concentrations in waters over the Bering Sea middle shelf in August 2001

During most of the vegetation season from late May to early September large-sized diatom alga Proboscia alata forms local patches with high abundances and biomasses in different oceanographic domains of the eastern Bering Sea shelf. For 0-25 m layer average abundance and biomass of species in these patches are 700000 cells/l and 5 g/m**3 (wet weight), while corresponding estimates for the layer of maximal species concentrations are 40000000 cells/l and 38 g/m**3 (wet weight) or 1.6 g C/m**3. These levels of abundance and biomass are typical for the spring diatom bloom in the region. Outbursts of P. alata mass development are important for the carbon cycle in the pelagic zone of the shelf area in the summer season. The paradox of P. alata summertime blooms over the middle shelf lies in their occurrences against the background of the sharp seasonal pycnocline and deficiency in nutrients in the upper mixed layer. Duration of the outbursts in P. alata development is about two weeks and size of patches with high abundances can be as large as 200 km across. Degradation of the P. alata summertime outbursts may occur during 4-5 days. Rapid sinking of cells through the seasonal pycnocline results in intense transport of organic matter to bottom sediments. One of possible factors responsible for rapid degradation of the blooms is affect on the population by ectoparasitic flagellates. At terminal stages of the P. alata blooms percentage of infected cells can reach 70-99%.

Palynology on profile Rotmoss at Obergurgl in Austria

Die pollenanalytische Untersuchung des Rotmooses in Verbindung mit C-14 Daten hat ergeben, daß die organogenen Sedimente nachwärmezeitliche Bildungen sind. Ein Gletschervorstoß um 2500 v. Chr. konnte mit Hilfe der C-14 Daten eingegrenzt und mit anderen Fundstellen parallelisiert werden. Weitere pollenanalytisch festgestellte Gletscher und auch Waldgrenzschwankungen konnten festgestellt, müssen aber noch genau datiert und parallelisiert werden.

Geochemical composition of bentonite layers and U-Pb ages of detrital zircons from the Paleogene Basilika Formation (Svalbard) and Mount Lawson Formation (Ellesmere Island)

Major and trace element composition as well as Sm-Nd isotopes of whole-rock samples and clay fractions (<2 µm) of bentonite layers and U-Pb ages of detrital zircons from the Paleogene Basilika Formation (Svalbard) and Mount Lawson Formation (Ellesmere Island).