Fluctuations in productivity and denitrification in the Southeastern Arabian Sea during the Late Quaternary

Sedimentological and stable isotopic characteristics of sediments have been studied in a core from the southeastern Arabian Sea containing records of the past 70 ka. Palaeoproductivity proxies such as organic carbon (Corg), total nitrogen (TN) and calcium carbonate (CaCO3) contents, show high values at the core top and during the Last Glacial Maximum (LGM) and marine isotope stage (MIS) 4, suggesting high productivity, whereas low Corg and CaCO3 contents are associated with the MIS ½ and mid-MIS 3, indicating reduced productivity. The δ18O values in planktonic foraminifera range between - 2.7% and - 0.1%, with a large glacial-interglacial amplitude Δδ18O of ∼2.6%, suggesting changes related to monsoonal precipitation/ runoff. The δ15N values fluctuate between 5.4% and 7.3%, signifying variation in denitrification intensity. The δ15N indicates an overall increase in denitrification intensity during MIS 1 and MIS 3 and, reduced intensity during MIS ½, LGM and mid-MIS 3. Higher primary productivity and reduced denitrification intensity during LGM and MIS 4 might be due to convective winter mixing and more oxygenated subsurface waters. Reduced primary productivity during MIS ½ and mid-MIS 3 might be the effect of enhanced precipitation associated with the intensified southwest monsoon fortifying near-surface stratification

Uso de múltiples indicadores geoquímicos como herramienta de estudio en yesos (Golfo de Carpentaria, Australia, -70ka)

Los cambios en el nivel del mar y las asociadas fluctuaciones climáticas provocaron cambios cíclicos y extremos en los ambientes deposicionales en la región del Golfo de Carpentaria (N, Australia). La desconexión con el mar dio lugar al «Lago Carpentaria». En este ambiente, las condiciones evaporíticas alrededor de los 70 ka originaron una alternancia repetitiva de laminas evaporíticas y micríticas de espesores mm a mm con una apariencia de varvas. Estas láminas son interpretadas como precipitados primarios, depositadas en un lago somero que retuvo una cantidad limitada de agua en su centro (sondeo MD-32). Los datos de geoquímica elemental e isotópica de las láminas de yeso y micrita sugieren un ambiente evaporítico complejo donde las aguas marinas iniciales se evaporaron y la entrada de aguas continentales compensaron las pérdidas por evaporación. El contenido en estroncio del yeso varía entre 691 y 1353 ppm, el valor del d34S y del d18O del yeso varía entre +21.8 y +22.5 ‰ y entre +14.1 y +16.5 ‰; la relación 87Sr/86Sr oscila entre 0.7093 y 0.7098. Mientras que los contenidos en Sr y los valores de isótopos de azufre indican una contribución esencialmente marina, los valores isotópicos de estroncio y los de oxígeno en los sulfatos sugieren aportes continentales y otros procesos tales como el reciclado de evaporitas precipitadas anteriormente, la sulfatoreducción y efecto reservorio. Se analizaron elementos menores y traza, REE (<0.45 mm filtrado) en yesos con el objetivo de establecer la procedencia de las aguas continentales que llegan al Lago Carpentaria y se compararon con los valores de ríos actuales del área. Las tendencias normalizadas en elementos REE para muestras de yesos son comparables a las de los ríos del área norte de Cape York, lo que restringe los potenciales aportes continentales a un área geográfica limitada. La aproximación realizada en este estudio evidencia la importancia del uso de múltiples indicadores geoquímicos en las reconstrucciones paleoambientales de medios complejos, tales como las cuencas evaporítica

Clinical Course of acute-on-chronic liver failure syndrome and effects on prognosis

Cellular mechanisms in basic and clinical gastroenterology and hepatolog

Climate change and freshwater zooplankton: what does it boil down to?

Recently, major advances in the climate–zooplankton interface have been made some of which appeared to receive much attention in a broader audience of ecologists as well. In contrast to the marine realm, however, we still lack a more holistic summary of recent knowledge in freshwater. We discuss climate change-related variation in physical and biological attributes of lakes and running waters, high-order ecological functions, and subsequent alteration in zooplankton abundance, phenology, distribution, body size, community structure, life history parameters, and behavior by focusing on community level responses. The adequacy of large-scale climatic indices in ecology has received considerable support and provided a framework for the interpretation of community and species level responses in freshwater zooplankton. Modeling perspectives deserve particular consideration, since this promising stream of ecology is of particular applicability in climate change research owing to the inherently predictive nature of this field. In the future, ecologists should expand their research on species beyond daphnids, should address questions as to how different intrinsic and extrinsic drivers interact, should move beyond correlative approaches toward more mechanistic explanations, and last but not least, should facilitate transfer of biological data both across space and time

Maryland medicine : MM ; a publ. of MedChi, the Maryland State Medical Society

Southern Mendoza, Argentina, is characterised by abundant Pleistocene to Holocene volcanism associated with back-arc magmatism, influenced by the subducting Nazca plate. Age determinations in this volcanic area have been improved during the last 5 years

The Mallee Dunefield: development and sand provenance

Sands of the Mallee Dunefield, south-eastern Australia, are divided into two groups on the basis of physical and chemical characteristics. The first group is called the Lowan Sand, the second the Woorinen Formation. Evidence suggests derivation of sands from local bedrock, with very little aeolian transport. Ultimate protosources for the Lowan Sand lie dominantly to the west, while those for the Woorinen Formation lie to the north-east. Sands also include an additional 'exotic' component, probably derived mainly from Antarctica. Sediment transport from protosources to the sedimentary basins was dominantly by fluvial, not aeolian, means. Post-Tertiary aeolian transport has been minimal, serving only to form dunes by vertical corrasion of underlying sedimentary rocks

Journal of the Institute of Nuclear Materials Management : JNMM

The Payenia Basaltic Province (PBP) is located 450. km east of the Chile-Peru trench in central west Argentina, behind the Andean arc front, constituting the back-arc. In order to evaluate the influence of the subducting slab as well as the magmatic source of this region, two volcanic fields located at comparable distance to the trench, having abundant basaltic products and similar eruptive timeframes were chosen. The Llancanelo (LLVF) and the Payún Matrú (PMVF) volcanic fields are part of the PBP and exhibit abundant basaltic activity during the Pleistocene. The geochemical data suggest that the LLVF has some arc signatures which have been described as weak as they are not as pronounced as in the Andean arc. The weak arc signature is not derived from slab dehydration as high Th enrichment relative to U cannot be explained by this process. We relate the Th enrichment as well as the lack of large residual garnet signatures, to slab sediments in the source. In the case of the PMVF, no arc signature has been inferred despite being only 30. km south of the LLVF. However the PMVF has a composition similar to that of the local intraplate end member, represented by the Rio Colorado volcanic field. The two volcanic fields, LLVF and PMVF, show indications of lower crustal assimilation as they trend towards the lower continental crust end member in Nb/U vs Ce/Pb and Nb/Yb vs Th/Yb diagrams.The geochemical differences between the LLVF and the PMVF as well as between several volcanic fields are illustrated using spatial distribution maps of geochemical ratios. Using this new approach, the decrease in arc signature can be traced in the back-arc and the higher enrichment in high field strength elements (HFSE) relative to large ion lithophile elements (LILE) in the PMVF compared to the LLVF is explicitly shown. These geospatial maps provide a graphical manner to illustrate the presence of two distinct types of volcanism (OIB-like and arc-like) occurring in the same Quaternary basaltic province