Bottom currents,nepheloid layers and sedimentary features under the Gulf Stream near Cape Hatteras

The velocities of near-bottom currents were measured at six locations on a 180-km transect of the Gulf Stream adjacent to Cape Hatteras. The average velocities indicate a southwesterly flow - the Western Boundary Undercurrent. Maximum recorded velocities at each of the six locations ranged from 15 to 47 cm/sec. Depth distributions of suspended particulate matter over the transect indicated that near-bottom nepheloid layers were present and that relatively large amounts of suspended matter were being carried to the southwest. Bottom photographs taken over the same transect, however, showed no evidence that the sediment surface was being affected by the active bottom currents. These results indicate that swift bottom currents do not always leave a record of their work on deep ocean sediment.     

Comparison of flowpaths to a well and spring in a karst aquifer

The permeability of some karst aquifers consists of networks of poorly integrated conduits and dissolution-widened fractures. The flow includes conduit flow, especially during storm recharge, but lacks the focused recharge into single master conduits that occurs in more highly developed karst systems. The proportions of conduit and dispersed flow are difficult to quantify in such systems. This study examines the flowpaths in a small karst watershed, based on comparing the physical and chemical response to storm flow at both a spring and a well. By conducting continuous monitoring at both locations, a better understanding of the flowpaths in a poorly integrated network was obtained. A more permeable flowpath to the spring leads to faster storm response and lower ion concentrations. The flowpath to and from the well is more complicated. The higher ion content and slower storm response suggest slower, more dispersed flowpaths. However, the well has greater variation in ion chemistry. Periodic recharge may dilute well concentrations due to faster (conduit or fracture) flowpaths. Although karst systems such as this are difficult to characterize, applying a variety of geochemical and physical monitoring techniques at multiple locations illustrates that the flowpaths can vary in both space and time.     

Metal sources to the Baltic clam Macoma balthica (Mollusca: Bivalvia) in the southern Baltic Sea (the Gulf of Gdansk)

Metal concentrations of Cu, Fe, Mn, Ni, Pb and Zn in an infaunal facultative deposit-feeding bivalve, the Baltic clam Macoma balthica, in the Gulf of Gdansk (southern Baltic Sea) were assessed and compared to selected concentrations of metals in the environment. Between October 1996 and September 1997, dissolved and easy extractable (by 1M HCl) metal fractions of total suspended particulate matter (TPM) in the overlying water and of surficial sediments (<63 microm) were measured monthly at five sublittoral sites in the Gulf of Gdansk, and accumulated tissue metal concentrations in M. balthica were determined simultaneously. The study highlights the importance of sediment geochemistry as a factor modifying ambient trace metal bioavailabilities. Surficial sediments appeared to contribute most to the accumulation of Cu and Pb in M. balthica, reflecting the high metal availability in the Gulf. Assimilation of Cu from sediments is controlled by Mn components possibly through an inhibitory effect of Mn oxyhydroxides, while Pb accumulation from sediments depends on the organic content of the sediment. A dual metal uptake pathway, with a suspended particulate-bound fraction and surficial sediments, was apparent for Mn and Zn. Partitioning of Mn in sediments was related to the concentration of labile Fe, with increased levels of Fe tending to inhibit the accumulation of Mn by the clam. Tissue accumulated Zn might have been altered by the clam's internal regulation, making Zn tissue concentrations, to some degree, independent of its environmental level. The principal source of Ni accumulated by the clams exists in the soluble phase.     

Flora development in Northeastern Asia and Northern Alaska during the Cretaceous-Paleogene transitional epoch

Study of floral succession from the Cretaceous-Paleogene boundary interval in Russian Far East (Zeya-Bureya depression), Northeastern Russia (Koryak Upland), and Northern Alaska (Sagavanirktok River basin) is crucial for better understanding palaeoclimatic and palaeogeographic factors, which controlled events in vegetation evolution at that time. The succession of fossil floras in the Zeya-Bureya depression includes plant assemblages of the Santonian, Campanian, early Danian, Danian, and Danian-Selandian age. The early Danian Boguchan Flora keeps continuity in composition and dominating taxa with the Campanian Late Kundur Flora. The Koryak Flora of the Amaam Lagoon area (Northeastern Russia) is dated as late Maastrichtian based on correlation of plant-bearing beds with marine biostratigraphy, whereas the Early and Late Sagwon floras of Northern Alaska are dated back to the Danian-Selandian and early Paleocene based on palynological and macrofloristic data. The Early Sagwon Flora is most close to the late Maastrichtian Koryak Flora of the Amaam Lagoon area in composition and main dominants, while the Late Sagwon Flora is comparable with the Danian or Danian-(?) Selandian flora from the Upper Tsagayan Subformation of the Amur area. In a florogenic aspect, trans-Beringian plant migrations from northeastern Asia and southern palaeolatitudes of the Far East, which became possible due to Paleocene climate warming in Arctic, have played an important role in forming of the Paleocene floras of Northern Alaska. Floras of the Far East and high latitudes of Asia and North America show no evidence of catastrophic event at the Cretaceous-Paleogene boundary. Their development was most probably controlled by climate changes, plant evolution and migration.     

Timing of eclogite facies metamorphism in the southernmost Scandinavian Caledonides by Lu–Hf and Sm–Nd geochronology

The Scandinavian Caledonides contain several non-cogenetic eclogite-bearing terranes that were metamorphosed before the main orogenic stage in Scandian time (430–395 Ma). Although petrological and geochronological data from these terranes have provided essential information on the geodynamic history of the Caledonian orogenic cycle, the general picture is still patchy. To refine existing geodynamic models, we have dated the eclogite occurrence in the Jæren nappe, SW Norway, by Lu–Hf and Sm–Nd geochronology. Five out of the six studied samples provide a weighted mean Lu–Hf age of 469.9 ± 1.2 Ma (±2σ). One sample provided a significantly younger age of 457.9 ± 2.4 Ma. Garnet from the younger sample grew exclusively at eclogite facies conditions. In contrast, garnet from the other samples comprises prograde cores and peak metamorphic rims. Age estimates that take Lu-contributions of each zone into account provide an age of 471.0 ± 0.9 Ma for the cores and suggest a ca. 455 Ma age for the rims, which is identical to the bulk-garnet age of the younger sample. The same pattern is indicated by Sm–Nd ages, although these are relatively imprecise and reflect isotopic disturbance during thermal overprinting upon exhumation. The data define a new high-pressure age population for the Scandinavian Caledonides, which allows more detailed insight into the subduction history that affected the Baltoscandian margin before Scandian continental collision. Furthermore, this study highlights the potential complexities involved in garnet geochronology and shows the strength of Lu–Hf dating for unraveling the geochronological record of HP rocks.     

Modelling the Effect of Tree Foliage on Sprayer Airflow in Orchards

The effect of tree foliage on sprayer airflow through pear trees in a fruit orchard was studied and modelled in detail. A new three-dimensional (3-D) computational fluid dynamics model that integrates the 3-D canopy architecture with a local closure model to simulate the effect of the stem and branches and leaves of trees separately on airflow was developed. The model was validated with field observations made in an experimental orchard (pcfruit, Sint-Truiden, Belgium) in spring and summer 2008 and was used to investigate the airflow from three air-assisted orchard sprayers (Condor V, Duoprop and AirJet quatt). Velocity magnitudes were measured before and behind leafless and fully-leafed pear canopies across the row while the operating sprayers are passing along the row, and were compared with the simulations. The simulation results predicted the measured values well with all the local relative errors within 20%. The effect of foliar density on airflow from the three air assisted sprayers was manifested by changing the magnitude and direction of the sprayers’ air velocity behind the canopy, especially at the denser regions of the canopy and by changing the pattern of velocity decay horizontally along the jet. The developed methodology will also allow a thorough investigation of atmospheric airflow in canopy structures.     

Arman’ Flora of the magadan region and development of floras in the North Pacific during the Albian-Paleocene

The Arman’ Flora from volcanogenic-sedimentary deposits in the Arman’ River basin and Naraula Formation in the Nel’kandzha-Khasyn interfluve includes 82 species of fossil plants comprising liverworts, horsetails, ferns, caytonealeans, cycadaleans, ginkgoaleans, czekanowskialeans, conifers, gymnosperms incertae sedis, and angiosperms. The Arman’ Flora appears to be of Turonian-Coniacian age, as it is close to the reliably dated Penzhina and Kaivayam floras from the Northwest Kamchatka and to Tyl’pegyrgynai Flora of the Pekul’nei Ridge. The dating is consistent with isotopic dates (⁴⁰Ar/³⁹Ar and U-Pb SHRIMP) characterizing the age of plant-bearing sequences. Based on the considered position of the Arman’ Flora in the scheme of Cretaceous florogenesis, a leading role in that florogenesis was played by the gradual invasion of floras by new, angiosperm dominated, plant communities. These communities initially populated unstable habitats in the coastal lowlands of Northeast Asia and Alaska, gradually invading with time the Asiatic intracontinental areas. The peculiar combination of Early and Late Cretaceous plants characteristic of the Arman’ Flora is strong evidence that Cenophytic plant communities dominated by angiosperms colonized areas still populated in the Late Cretaceous by Mesophytic communities. Absence of Mesophytic and Cenophytic taxa mixing in the Arman’ Flora burials suggests a replacement of plant communities as whole rather than of separate plants by more advanced taxa.     

Orogenic Garnet Peridotite - Tools to Reconstruct Paleo-geodynamic Settings of Continental Collision Zones

<正>Orogenic garnet peridotites(metamorphic rocks containing the characteristic HP garnet-olivine mineral assemblage)exposed in ancient orogenic belts may contain quantitative data regarding formation of subcontinental/subcratonic lithosphere,evolution of a lithospheric mantle wedge,incorporation of garnet peridotite into subducted