Dissolved oxygen dynamics in a eutrophic estuary,Upper Newport Bay,California

Eutrophication often causes hypoxia in estuarine and coastal systems, but the mechanisms that control hypoxic events vary among estuaries and are often difficult to discern. We monitored surface and bottom dissolved oxygen (DO) in the Upper Newport Bay (UNB), a tidally mixed estuary in southern California subject to anthropogenic nutrient loading, eutrophication and hypoxia. Our goal was to identify the environmental factors regulating DO dynamics. Six hypoxic events occurred between June and November and were associated with a combination of low solar radiation, increased freshwater discharge following precipitation, and enhanced haline stratification during reduced tidal range periods. At the head of the estuary, high macroalgal biomass and pronounced haline stratification resulted in high DO in the surface layer and low DO in the bottom layer. Oxygen-rich and oxygen-poor waters were transported down-estuary by ebb tides, resulting in DO heterogeneity throughout the UNB. Cross-wavelet analysis illustrated the down-estuary propagation of high/low DO signal correlated with the phases of diurnal photosynthetic and semi-diurnal tidal cycles.     

Precision of the ephemerides of outer planetary satellites

Ephemerides of planetary satellites are needed to address many problems. These ephemerides are used for subsequent observations. A comparison of the available ephemerides with new observations allows the accuracy of the former to be assessed. However, the precision of the ephemerides must be known a priori when solving the tasks. In this paper we formulate and solve the problem of estimating the precision of the ephemerides of outer planetary satellites derived from observations when applied up to the future moments.The methods of assessing the precision of ephemerides involve producing a set of samples of the same ephemeris inferred from observations with different samples of Monte Carlo generated random errors (RO) superimposed onto it. The statistical parameters of simulated observational errors are based on the results of the reduction of real satellite observations. We compute the deviations of the samples of the ephemeris from the standard ephemeris inferred from real observations and adopt the root-mean-square deviation of the apparent coordinates as the precision of the ephemeris. We also use alternative methods: one based on the matrix of covariances of parameter errors (RP), and another one based on bootstrap samples of observations (BS).We use three methods (RO, RP, and BS) to estimate the precision of the ephemerides of all the 107 outer planetary satellites over the 2010-2020 time interval. The precision of the ephemerides of different satellites varies from 0.05 to 4.0 arcsec. For a number of satellites new observations are of vital importance for maintaining the precision of the ephemerides at a level that would allow identification of satellites during the reduction of observations. For some satellites the precision of their ephemerides is of the order of the sizes of their orbits and such satellites can be considered to have been lost. We show that the method of bootstrap samples (BS) can give doubtful results in the cases where there are few observations, which covered a time interval that is shorter than the orbital period of the satellite.Our results suggest obtaining more precise ephemeris making new observations at the times of maximum estimated errors of the ephemeris.All the inferred estimates of the precision of ephemerides are available from the MULTI-SAT ephemeris server: www.imcce.fr/sat (IMCCE), www.sai.msu.ru/neb/nss/index.htm (SAI).     

Analysis of effects of operating parameters on rate of penetration in drilling process with air down-the-hole hammer

Air down-the-hole(DTH)hammer drilling has long been recognized to have the potential of drilling faster than conventional rotary drill,especially in some hard rocks such as granite,sandstone,limestone,dolomite,etc.with the same weight on bit(WOB)and rotations per minute(RPM).So,it has been widely used in many drilling fields including mineral resource exploration drilling,oil and gas drilling and geothermal drilling.In order to reduce drilling cost by selecting optimal drilling parameters,rate of penetration(ROP)should be estimated accurately and the effects of different factors on ROP should be analyzed.In this research,ANN model with several multi-layer perception back propagation(BP)networks for predicting ROP of air DTH hammer drilling was developed using controllable parameters such as impact energy,impact frequency,WOB,RPM and bit operating time for the formations with a certain drillability index of rock.Several BP neural networks with the different neurons in hidden layers were developed and compared for selecting optimal architecture of ANN.The effects of the drilling parameters such as impact energy,impacting frequency,WOB,RPM and bit operating time on the ROP of air DTH hammer drilling were investigated by trained ANN.From the analyses,the optimum range of drilling parameters for providing high ROP were determined and analyzed for a formation with a certain drillability index of rock.The methodology proposed in this study can be used in many mathematical problems for optimization of drilling process with air DTH hammer.     

Seasonal variations in methane concentrations and diffusive fluxes in the Curonian and Vistula lagoons,Baltic Sea

Expected seasonal variations in methane concentrations and diffusive fluxes from surficial sediments into near-bottom waters were investigated in autumn 2012 and winter 2013 in the Curonian and Vistula lagoons of the Baltic Sea, expanding on earlier findings for summer 2011. Methane concentrations in bottom sediments (upper ca. 2 cm) generally ranged from ca. 1 to 1,000 μmol/dm³, and in near-bottom waters from ca. 0 to 1 μmol/l. Highest concentrations were found in the Curonian Lagoon, plausibly explained by the influence of freshwater conditions and finer-grained, organic-rich sediments. Vistula Lagoon methane concentrations and fluxes are dampened by periodic saline water inflow from the open sea, intensifying sulphate reduction. Calculated diffusive methane fluxes from the upper sediment layer (usually 0–5 cm, i.e. excluding any fluffy layer) into near-bottom waters were highest—2.48 mmol/(m² day)—in clayey silts of the Curonian Lagoon in autumn (September) 2012, contrasting strongly with the minimum value of 0.002 mmol/(m² day) observed there in February 2013 under ice-covered conditions. Seasonal and even weekly variations in methane dynamics can be largely explained by two main drivers, i.e. wind and temperature, operating at various spatiotemporal scales via, for example, wind wave-induced resuspension of bottom sediments, and involving regional weather patterns including autumnal low-pressure zones over the Gulf of Gdansk.     

Semiparametric regression models for spatial prediction and uncertainty quantification of soil attributes

In many studies, the distribution of soil attributes depends on both spatial location and environmental factors, and prediction and process identification are performed using existing methods such as kriging. However, it is often too restrictive to model soil attributes as dependent on a known, parametric function of environmental factors, which kriging typically assumes. This paper investigates a semiparametric approach for identifying and modeling the nonlinear relationships of spatially dependent soil constituent levels with environmental variables and obtaining point and interval predictions over a spatial region. Frequentist and Bayesian versions of the proposed method are applied to measured soil nitrogen levels throughout Florida, USA and are compared to competing models, including frequentist and Bayesian kriging, based an array of point and interval measures of out-of-sample forecast quality. The semiparametric models outperformed competing models in all cases. Bayesian semiparametric models yielded the best predictive results and provided empirical coverage probability nearly equal to nominal.     

Transgressive Eocene clastic–carbonate sediments from the Circum‐Rhodope belt,northeastern Greece: implications for a rocky shore palaeoenvironment

Locally exposed Middle to Upper Eocene conglomerates in the western part of the Cenozoic Thrace Basin are interpreted as products of continuous marine erosion of a rocky coast (consisting of Lower Cretaceous carbonates) and subsequent redeposition of the land‐derived limestone material in a wave‐dominated nearshore setting during a prolonged transgression. Contemporaneous biological activity in the warm‐temperate marine environment contributed to the accumulation of mixed coarse‐grained clastic–carbonate sediments on the upper shoreface. The formation of a relatively thick sedimentary succession was favoured by the interplay of several controlling factors as only shoreface deposits were preserved in the rock record. The results may help to elucidate the evolution of the hydrocarbon‐bearing Thrace Basin and to assist with the regional correlation of its basal deposits. Copyright © 2014 John Wiley & Sons, Ltd.     

Enigmatic sedimentary–volcanic successions in the central European Variscides: a Cambrian/Early Ordovician age for the Wojcieszów Limestone (Kaczawa Mountains,SW Poland) indicated by SHRIMP dating of volcanic zircons

Metamorphosed volcanic and sedimentary successions in the central European Variscides are, in many areas, poorly biostratigraphically constrained, making palaeotectonic interpretations uncertain. In such instances, geochronological data are crucial. Sensitive high resolution ion microprobe (SHRIMP) dating of volcanic zircons from a quartz–white mica schist (interpreted as deformed metavolcaniclastic/epiclastic rock) within the stratigraphically controversial Wojcieszów Limestone of the Kaczawa Mountains (Sudetes, SW Poland), near to the eastern termination of the European Variscides, has yielded an age of 498 ± 5 Ma (2σ error), corresponding to late Cambrian to early Ordovician magmatism in that area and constraining the depositional age of the limestones. The new SHRIMP data are not consistent with the recent revision of the age of the Wojcieszów Limestone based on Foraminifera findings that ascribed them to a Late Ordovician—Silurian or even younger interval. They are though, consistent with sparse macrofossil data and strongly support earlier interpretations of the lower part of the Kaczawa Mountains succession as a Cambrian–Early Ordovician extensional basin‐fill with associated initial rift volcanic rocks, likely emplaced during the breakup of Gondwana. Copyright © 2008 John Wiley & Sons, Ltd.     

Terrane analysis and accretion in North-East Asia

Abstract A terrane map of North-East Asia at 1:5 000 000 scale has been compiled. The map shows terranes of different types and ages accreted to the North-Asian craton in the Mesozoic–Cenozoic, sub-and superterranes, together with post-amalgamation and post-accretion assemblages. The great Kolyma-Omolon superterrane adjoins the north-east craton margin. It is composed of large angular terranes of continental affinity: craton fragments and fragments of the passive continental margin of Siberia, and island arc, oceanic and turbidite terranes that are unconformably overlain by shallow marine Middle-Upper Jurassic deposits. The superterrane resulted from a long subduction of the Paleo-Pacific oceanic crust beneath the Alazeya arc. Its south-west boundary is defined by the Late Jurassic Uyandina-Yasachnaya marginal volcanic arc which was brought about by subduction of the oceanic crust that separated the superterrane from Siberia. According to paleomagnetic evidence the width of the basin is estimated to be 1500–2000 km. Accretion of the superterrane to Siberia is dated to the late Late Jurassic-Neocomian. The north-east superterrane boundary is defined by the Lyakhov-South Anyui suture which extends across southern Chukotka up to Alaska. Collision of the superterrane with the Chukotka shelf terrane is dated to the middle of the Cretaceous. The Okhotsk-Chukotka belt, composed of Albian-Late Cretaceous undeformed continental volcan-ites, defines the Cretaceous margin of North Asia. Terranes eastward of the belt are mainly of oceanic affinity: island arc upon oceanic crust, accretion wedge and turbidite terranes, as well as cratonic terranes and fragments of magmatic arcs on the continental crust and metamorphic terranes of unclear origin and age. The time of their accretion is constrained by post-accretionary volcanic belts that extend parallel to the Okhotsk-Chukotka belt but are displaced to the east: the Maastrichtian-Miocene Kamchatka-Koryak belt and the Eocene-Quaternary Central Kamchatka belt which mark active margins of the continent of corresponding ages.     

Collision of the Kronotskiy arc at the NE Eurasia margin and structural evolution of the Kamchatka–Aleutian junction

Structural evolution of the Kamchatka–Aleutian junction area in late Mesozoic and Tertiary was generally controlled by (1) the processes of subduction in Kronotskiy and Proto-Kamchatka subduction zones and (2) collision of the Kronotskiy arc against NE Eurasia margin. Two structural zones of the pre-Pliocene age and six structural assemblages are recognized in studied region. 1: Eastern ranges zone comprises SE-vergent thrust folded belt, which evolved in accretionary and collisional setting. Two structural assemblages (ER1 and ER2), developed there, document shortening in the NW–SE direction and in the N–S direction, respectively. 2: Eastern Peninsulas zone generally corresponds to Kronotskiy arc terrane. Four structural assemblages are recognized in this zone. They characterize (1) precollisional deformations in the accretionary wedge (EP1) and in the fore-arc basin and volcanic belt (EP2), and (2) syn-collisional deformation of the entire Kronotskiy terrane in plunging folds (EP3) and deformations in the foreland basin (EP4). Analysis of paleomagnetic declinations versus present day structural strike in the Kronotskiy arc terrane shows that originally the arc was trending from west to east. Relative position of the accretionary wedge, fore-arc basin and volcanic belt, as well as northward dipping thrusts in accretionary wedge indicate, that a northward dipping subduction zone was located south of the arc. The accretionary wedge developed from the Late Cretaceous through the Eocene, and it implies that the subduction zone maintained its direction and position during this time. It implies that Kronotskiy arc was neither a part of the Pacific nor Kula plates and was located on an individual smaller plate, which included the arc and Vetlovka back-arc basin. Motion of the Kronotskiy arc towards Eurasia was connected only with NW-directed subduction at Kamchatka margin since Middle Eocene (42–44 Ma). Emplacement of the Kronotskiy arc at the Kamchatka margin occurred between Late Eocene and Early Miocene. This is based on the age of syn-collisional plunging folds in Kronotskiy terrane, and provenance data for the Upper Eocene to Middle Miocene Tyushevka basin, which indicate in situ evolution of the basin with respect to Kamchatka. Collision was controlled by the common motion of the Kronotskiy arc with Pacific plate towards the northwest, and by the motion of the Eurasian margin towards the south. The latter motion was responsible for the southward deflection of the western part of the Kronotskiy arc (EP3 structures), and for oblique transpressional structures in the collisional belt (ER2 structures).