A study of three massive star-forming regions in CS lines

We have mapped three star-forming regions (G265.14+1.45, G269.16?1.14, G291.27?0.71) in the CS(3–2) and C³⁴S(2–1) lines using the 15 m SEST telescope (Chile), and analyzed the relative positions of methanol and H₂O masers, IRAS sources, and emission maxima in the CS lines. In most cases, the maser positions are close to those of the IRAS sources. We compared the radial velocities of the maser sources and high-density CS cores, and estimated the CS column densities assuming LTE. The sizes, densities, and masses of the dense core are estimated; the masses obtained in the LTE approximation agree with the virial masses.     

Textural-structural,mineralogical, isotopic,and age characteristics of Jurassic terrigenous rocks of the northwestern Caucasus (the Belaya River section)

Results of the comprehensive study of structural, lithological, mineralogical, and isotopic characteristics of Lower Jurassic rocks exposed in the Belaya River valley (Adygeya) in meganticlinorium of the Greater Caucasus are presented. Deformation microstructures were studied. Lithological and textural-structural changes in sequences related to intense secondary transformations should affect the state of isotopic systems of rocks. To reveal basic trends in the evolution of isotopic systems, investigation using the K-Ar method was carried out. Clay fraction (less than 1 μm) separated from rocks and bulk samples were analyzed. Cleavage development, approximate value of rock contraction, and isotopic characteristics are compared with the available data on alteration of clay mineral assemblages. Relationship between the degree of rock deformation at the microlevel and calculated K-Ar ages has been established. K-Ar systems of clayey rocks indicate the age of cleavage formation and correspond to the Bajocian-Bathonian contraction period.     

Sedimentary and faunal events revealed by a revised correlation of post‐glacial Hirnantian (Late Ordovician) strata in the Welsh Basin,UK

The discovery of a previously unrecognized unconformity and of new faunas in the type Llandovery area underpins a revised correlation of Hirnantian strata in mid Wales. This has revealed the sedimentary and faunal events which affected the Lower Palaeozoic Welsh Basin during the global rise in sea level that followed the end‐Ordovician glacial maximum and has allowed their interpretation in the context of local and global influences. In peri‐basinal shelfal settings the onset of post‐glacial deepening is recorded by an unfossiliferous, transgressive shoreface sequence (Cwm Clyd Sandstone and Garth House formations) which rests unconformably on Rawtheyan rocks, deformed during an episode of pre‐Hirnantian tectonism. In the deep water facies of the basin centre, this same sequence boundary is now recognized as the contact between fine‐grained, re‐sedimented mudstones and an underlying regressive sequence of turbidite sandstones and conglomerates; it is at a level lower than previously cited and calls into question the established lithostratigraphy. In younger Hirnantian strata, graptolites associated with the newly recognized Ystradwalter Member (Chwefri Formation) demonstrate that this distal shelf unit correlates with the persculptus graptolite‐bearing Mottled Mudstone Member of the basinal succession. Together these members record an important macrofaunal recolonization of the Welsh Basin and mark a key event in the post‐glacial transgression. Further deepening saw the establishment of a stratified water column and the imposition of anoxic bottom water conditions across the basin floor. These post‐glacial Hirnantian events are consistent with the re‐establishment of connections between a silled Welsh Basin and the open Iapetus Ocean. However, a comparison with other areas suggests that each event records a separate deepening episode within a pulsed glacio‐eustatic transgression, while also reflecting changes in post‐glacial climate and patterns of oceanic circulation and associated biotic flux. British Geological Survey © NERC 2009. All rights reserved.     

Effects of historical and projected land use/cover change on runoff and sediment yield in the Netravati river basin,Western Ghats,India

In this study, the effects of changes in historical and projected land use land cover (LULC) on monthly streamflow and sediment yield for the Netravati river basin in the Western Ghats of India are explored using land use maps from six time periods (1972, 1979, 1991, 2000, 2012, and 2030) and the soil and water assessment tool (SWAT). The LULC for 2030 is projected using the land change modeller with the assumption of normal growth. The sensitivity analysis, model calibration, and validation indicated that the SWAT model could reasonably simulate streamflow and sediment yield in the river basin. The results showed that the spatial extent of the LULC classes of urban (1.80–9.96%), agriculture (31.38–55.75%), and water bodies (1.48–2.66%) increased, whereas that of forest (53.04–27.03%), grassland (11.17–4.41%), and bare land (1.09–0.16%) decreased from 1972 to 2030. The streamflow increased steadily (7.88%) with changes in LULC, whereas the average annual sediment yield decreased (0.028%) between 1972 and 1991 and increased later (0.029%) until 2012. However, it may increase by 0.43% from 2012 to 2030. The results indicate that LULC changes in urbanization and agricultural intensification have contributed to the increase in runoff, amounting to 428.65 and 58.67 mm, respectively, and sediment yield, amounting to 348 and 43 ton/km², respectively, in the catchment area from 1972 to 2030. The proposed methodology can be applied to other river basins for which temporal digital LULC maps are available for better water resource management plans.     

Provenance of Precambrian Fe- and Al-rich Metapelites in the Yenisey Ridge and Kuznetsk Alatau, Siberia： Geochemical Signatures

Major, trace and rare earth element contents of Fe- and Al-rich metapelites from the Korda （Yenisey Ridge） and Amar （Kuznetsk Alatau） formations were determined to examine the nature, origin and evolution of their protoliths. Results indicate that these rocks are the redeposited and metamorphosed products of Precambrian kaolinitic weathering crusts, while the geochemical distinctions between the studied metapelites are determined by different weathering conditions in the source area and tectonic settings. The protolith of the Korda Formation metapelites was produced by erosion products of the post-Archean granitoid rocks, which accumulated under humid climate conditions in shallow-water basins along the continental margin. The geochemical characteristics of the deeper primary deposits of the Amar Formation suggest that volcanogenic material of mafic composition derived from an island-arc environment had a major role in supplying the erosion zone. These results agree with lithofacies data and with the geodynamic reconstruction of the evolution of the Yenisey Ridge and Kuznetsk Alatau during the Mesoproterozoic and Neoproterozoic, respectively. It was shown that REEs had limited mobility during contact metamorphism. The coherent mobility of REEs during collisional metamorphism may be attributed both to mineral reactions responsible for modal changes and to local chemical heterogeneity inherited from the initial protolith.     

Hydration shell structures in a LiI solution at elevated temperature and pressure: a molecular dynamics study

Molecular dynamics simulations of a 0.55 molal aqueous LiI solution have been performed at 508 K and 308 K and a density of 1.05 g/cm³. The structural changes resulting from increased temperature and pressure are discussed.     

Effects of cold eddy on phytoplankton production and assemblages in Luzon strait bordering the South China Sea

The biochemical effects of a cold-core eddy that was shed from the Kuroshio Current at the Luzon Strait bordering the South China Sea (SCS) were studied in late spring, a relatively unproductive season in the SCS. The extent of the eddy was determined by time-series images of SeaWiFS ocean color, AVHRR sea surface temperature, and TOPEX/Jason-1 sea surface height anomaly. Nutrient budgets, nitrate-based new production, primary production, and phytoplankton assemblages were compared between the eddy and its surrounding Kuroshio and SCS waters. The enhanced productivity in the eddy was comparable to wintertime productivity in the SCS basin, which is supported by upwelled subsurface nitrate under the prevailing Northeastern Monsoon. There were more Synechococcus, pico-eucaryotes, and diatoms, but less Trichodesmium in the surface water inside the eddy than outside. Prochlorococcus and Richelia intracellularis showed no spatial differences. Water column-integrated primary production (IPP) inside the eddy was 2–3 times that outside the eddy in the SCS (1.09 vs. 0.59 g C m⁻²d⁻¹), as was nitrate-based new production (INP) (0.67 vs. 0.25 g C m⁻²d⁻¹). INP in the eddy was 6 times that in the Kuroshio (0.12 g C m⁻²d⁻¹). IPP and INP in the eddy were higher than the maximum production values ever measured in the SCS basin. Surface chlorophyll a concentration (0.40 mg m⁻³) in the eddy equaled the maximum concentration registered for the SCS basin and was higher than the wintertime average (0.29 ± 0.04 mg m⁻³). INP was 3.5 times as great and IPP was doubled in the eddy compared to the wintertime SCS basin. As cold core eddies form intermittently all year round as the Kuroshio invades the SCS, their effects on phytoplankton productivity and assemblages are likely to have important influences on the biogeochemical cycle of the region.     

Soilscape and land‐use evolution related to drift sand movements since the bronze age in Eastern Jutland,Denmark

Quarry faces several kilometers long in the Glesborg area in Denmark show that Bronze Age farmers used a sustainable land‐use system. Despite nutrient‐poor soils, the Glesborg area was under a rotation system in which cropland alternated with grassland. Soil fertility was improved by the addition of household waste and probably also by locally obtained inorganic fertilizer. The soil surface was very stable, and local drift sand movement was limited. Toward the end of the Bronze Age, the landscape changed dramatically with the arrival of overwhelming amounts of drift sand, and farmsteads were abandoned. Subsequent land use on these poor fine sandy soils was no longer capable of maintaining a stable soil surface, and frequent erosion/sedimentation events of more local importance took place. The post‐Bronze Age landscape may have been mainly a shifting mosaic of heathland with some temporary arable fields and deflation/accumulation areas. This landscape persisted up to about 200 years ago, when afforestation programs started. © 2007 Wiley Periodicals, Inc.