Manifestations of the rim current,coccolithophore blooms,and continental runoff in the long-term monthly mean distributions of satellite reflectance coefficients of the Black Sea

Based on the archived data of the ocean color scanner MODIS-Aqua for 2003–2011, we constructed the long-term monthly mean distributions of the reflectance Rrs of the Black Sea for April, May, June, and September in order to visualize the contributions of seasonal factors to the long-term variability of the basin’s images. In April, the Rim Current’s branch west of 34° E is visualized by higher Rrs in different regions of the visible spectrum due to the transport of suspended matter caused by intensification of the Rim Current during the winter-spring period. During the June coccolithophore “blooms,” the long-term Rrs level is 2–3 times higher when compared to the previous and subsequent months. This excess is particularly considerable outside the shelf and coastal areas. The open sea Rrs distribution in June features horizontal inhomogeneity. The seasonal trend of the Rrs spectra on the Black Sea NW shelf is explicitly related to the annual cycle of the continental runoff effects.     

Microbial biomass response to different quantities and sources of organic matter in Brazilian coastal sediments

This study investigates the benthic microbial responses to organic matter (OM) variations in quantity and sources in two shallow water bays (Fortaleza and Ubatuba Bays) on the SE coast of Brazil on six occasions during the year. The pelagic and benthic compartments of the bays were evaluated by: (i) nutrients and chlorophyll a (Chl a) in the water column; (ii) quantity and sources of OM in the sediment (Chl a, total organic carbon and total nitrogen and lipid biomarker composition); and (iii) microbial biomass in sediments as an indicator of active benthic response. Although there were changes in water‐column nutrients during the year, Chl a was fairly constant, suggesting a regular supply of microalgae‐derived OM to the sea bottom. Based on the composition of lipid biomarkers in sediments, OM sources were classified as mostly marine and with high contributions of labile (microalgae‐derived) OM. Labile OM composition varied from diatoms in the summer to phytoflagellates in the winter and tended to accumulate in areas protected by physical disturbances in one of the bays. Microbial biomass followed this trend and was 160% higher in protected than in exposed areas. This study suggests that the coupling between labile OM and benthic microbial biomass occurs primarily in protected areas, irrespective of the time of the year. Since meio‐ and macrofaunal assemblages depend upon secondary microbial production within the sediments, this coupling may have an important role for the benthic food‐web.     

Sources of Zircons from Cretaceous and Lower Paleogene Terrigenous Sequences of the Southern Koryak Upland and Western Kamchatka

The mineral composition of sandstones from Cretaceous–Lower Paleocene terrigenous sequences of the western Kamchatka–Ukelayat zone (southern Koryak Upland, western Kamchatka) suggests that the Okhotsk–Chukot volcanogenic belt and fragments of the Uda–Murgal island arc served as the most probable provenance. Fission-track dating of zircon showed that sandstones from this zone contain detrital zircon of several different-age populations. Fission tracks in zircon grains were nor subjected to secondary ignition. The age of young zircon population coincides with the biostratigraphic age of host sequences. Thus, results of dating of detrital zircon grains from sandstones, which did not experience heating above 215–240°C, indicate that this method is appropriate for dating fossil-free terrigenous sequences. The young zircon population in the sandstones is related to erosion of plagiogranite and diorite intrusions of the Uda–Murgal arc and outer zone of the Okhotsk–Chukot volcanic belt exposed at the day surface owing to differential vertical movements and rapid exhumation of blocks.     

Heterogenity of planetesimal collisional plume probed by glass inclusions in metal globules of Sierra Gorda 013, an unusual CBa-like chondrite

Metal-rich carbonaceous CB chondrites are generally assumed to be materials accreted from the gas–dust plume formed in catastrophic collisions of planetesimals, at least one of which was differentiated into a metal core and silicate shell. Micron-sized inclusions of siliceous alkali-rich glasses associated with sulfides were found in the metal globules of the Sierra Gorda 013 (SG 013), a CBa-like chondrite. These inclusions are unusual carriers of volatile alkalis which are commonly depleted in CB chondrites. The inclusions are presented by two types: (1) Al-bearing Nb-poor glass associated with daubréelite and (2) Nb-bearing Ca,Al,Mg-poor glass associated with an unknown Na-bearing Cr-sulfide. The glass compositions do not correspond to equilibrium condensation, evaporation, or melting. The Nb-bearing glass has a superchondritic Nb/Ta ratio (31) most likely indicating the fractionation of Nb and Ta in the high-temperature gas–dust impact plume due to condensation from vapor or evaporation of precursor Nb-rich particles. The glasses are interpreted as reaction products between refractory plume condensate particles (or possibly planetary or chondritic solids) with relatively low-temperature K-Na-Si-rich gas in oxidized conditions, possibly in a common plume vapor reservoir. Compositional differences indicate that the glasses and sulfides originated from several different sources under different fO₂, fS₂, and T conditions and were likely combined together and transported to the metal globule formation region by material flows in the heterogeneous impact plume. The glass–sulfide particles were enclosed in the globules aggregated from smaller solid or molten metal grains. The metal globules were further melted during transport to the high-temperature plume region or by plume shockwave heating. Thus, the composition of the glasses, the host metal, and the main mass of SG 013 shows dynamic heterogeneity of physical conditions and impact plume composition after a large-scale planetesimal collision.     

Concentration–discharge relationships in the coal mined region of the New River basin and Indian Fork sub‐basin,Tennessee, USA

For many basins, identifying changes to water quality over time and understanding current hydrologic processes are hindered by fragmented and discontinuous water‐quality and hydrology data. In the coal mined region of the New River basin and Indian Fork sub‐basin, muted and pronounced changes, respectively, to concentration–discharge (C–Q) relationships were identified using linear regression on log‐transformed historical (1970s–1980s) and recent (2000s) water‐quality and streamflow data. Changes to C–Q relationships were related to coal mining histories and shifts in land use. Hysteresis plots of individual storms from 2007 (New River) and the fall of 2009 (Indian Fork) were used to understand current hydrologic processes in the basins. In the New River, storm magnitude was found to be closely related to the reversal of loop rotation in hysteresis plots; a peak‐flow threshold of 25 cubic meters per second (m³/s) segregates hysteresis patterns into clockwise and counterclockwise rotational groups. Small storms with peak flow less than 25 m³/s often resulted in dilution of constituent concentrations in headwater tributaries like Indian Fork and concentration of constituents downstream in the mainstem of the New River. Conceptual two or three component mixing models for the basins were used to infer the influence of water derived from spoil material on water quality. Copyright © 2012 John Wiley & Sons, Ltd.     

Geochemical surveillance of active volcanoes: data on the fumaroles of Vulcano (Aeolian Islands,Italy)

Temperature and chemical composition of condensates of higher temperature fumaroles, located on the rim of the crater of Vulcano, were studied over a period of one year. Maximum temperature changed from 216°C (June 1977) to 291°C (May 1978). HCl is the main constituent of condensates which, in comparison with data from fumaroles of other volcanoes, contain also noteworthy quantities of boron and bromine. Since these chemical characteristics suggested the possible inflow of water of marine origin into the volcanic conduit, experimental data on seawater-rock reactions at high temperatures and pressures were taken into account. A model is drafted for the volcanic system, in which the occurrence of an aquifer interposed between the magma chamber and the surface is considered. The vaporization of this aquifer would feed the fumaroles giving rise, through different mixing processes with surface waters, to the observed differences in temperature and chemical composition. However, data available at present are not sufficient to support the proposed model, which must be mainly considered as a working hypothesis.     

Nonlinear dynamics of gravity flows in sloping channels

Doklady Earth Sciences -