17 resultados para the series Leuciscini

em Publishing Network for Geoscientific


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The MARECHIARA-mesozooplankton dataset contains mesozooplankton data collected in the ongoing time-series at Sation MC (40°48.5' N, 14°15' E) in the Gulf of Naples. This dataset spans over the period 1984-2006 and contains data of mesozooplankton abundance and species composition as well as biomass (as dry weight). Mesozooplankton was regularly sampled in 1984-1990 and 1995-2006, only a few samples were collected in 1991-1992 and no samples in 1993-1994. During the first period of the series sampling frequency was fortnightly, and weekly since 1995.

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Silicic Fe-Ti-oxide magmatic series was the first recognized in the Sierra Leone axial segment of the Mid-Atlantic Ridge near 6°N. The series consists of intrusive rocks (harzburgites, lherzolites, bronzitites, norites, gabbronorites, hornblende Fe-Ti-oxide gabbronorites and gabbronorite-diorites, quartz diorites, and trondhjemites) and their subvolcanic (ilmenite-hornblende dolerites) and, possibly, volcanic analogues (ilmenite-bearing basalts). Deficit of most incompatible elements in the rocks of the series suggests that parental melts derived from a source that had already been melted. Correspondingly, these melts could not be MORB derivatives. Origin of the series is thought to be related to melting of the hydrated oceanic lithosphere during emplacement of an asthenospheric plume (protuberance on the surface of large asthenospheric lens beneath MAR). Genesis of different melts was supposedly controlled by ascent of a chamber of hot mantle magmas thought this lithosphere in compliance with the zone melting mechanism. Melt acquired fluid components from heated rocks at peripheries of the plume and became enriched in Fe, Ti, Pb, Cu, Zn, and other components mobile in fluids.

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Late Miocene sediments from ODP Sites 652 and 654, drilled on the Sardinian margin in the Western Tyrrhenian Sea, are investigated through mineralogical, micromorphological, geochemical, and microgeochemical analyses. Clay associations appear to be little controlled by conditions of deposition, and largely depend on pre- and post-depositional conditions. The sedimentary series from Central Mediterranean gives very different geodynamic information, according to the sector considered. While relatively stable conditions, like those encountered in Caltanissetta Basin, Sicily, favor the mineralogical expression of warm-temperate and subarid Messinian climate, the Eastern Sardinia margin (Site 654) clay suites mainly reflect the transition from tectonically active to relaxed conditions. The series deposited at the foot of the same margin above a thinner crust (Site 652) experienced the effects of burial diagenesis, enhanced by strong geothermal gradient.

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The main characteristics of the Vernagtferner mass balance are sumarized in the table below. The mass balance years from 1964/65 to 2003/2004 are listed. The table includes the total area of the glacier (basis for the calculations), the equilibrium line altitude (ELA), percentage of the accumulation area in relation to the total area (AAR) and the specific net mass balance in mm w.e. (water equivalent) per year. It becomes clear that, after a rather minor growth period in the mid 1970's, the glacier continually lost mass since the beginning of the 1980's. Besides that, a clear increase of mass balance years with extreme mass losses could be observed in the last decade. The "glacier-friendly" summer with a well-balanced mass balance in 1999 could only interrupt the series of years with extreme mass losses, but this means no change in the trend. The minor mass loss in 1999 was caused by a winter snow cover above average, which prevented the glacier from becoming snow free over large areas and thus resulted in a lower ice melt. Although real summer conditions in 2000 were mainly restricted to August and produced a snow free area only slightly larger than in 1999, there have been further ice losses. This trend of negative mass balance continued also in the years 2001 and 2002. Nevertheless, the losses are moderate because a smaller part of the glacier became ice free until autumn (appr. 50 %). The summer 2003 caused a loss of ice in a dimension never seen since the beginning of the scientific investigations. This resulted from a combination of different factors: after only a moderate winter snowcover the glacier became snow free very early. For the first time the ablation area spanned over the entire glacier (blue fields in the mass balance tables!). Only one short snowfall event interrupted the ablation period, which lasted twice as long as in the years of large losses in the 1990's. The extreme mass loss in 2003 will also influence the mass balance in the following year 2004. The graphical representation of the elevation distribution of the specific mass balance together with the absolute mass balance can be found individually for each year by choosing one of the mass balance values from the table. These diagrams also include the area-height-distribution of the glacier and the ablation area. A tabular version of the numeric values in dependence of the elevation, provided separately for the accumulation area, the ablation area and the total glacier, can be found in colums "Persistent Identifier". The tables include the results for three different parts of the glacier and for the total glacier.

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Vertical distribution of common zooplankton species is examined on the base of two series of layer-by-layer net catches down to depth of 3400 m. Differences between the series are significant for most species only near the surface, whereas in deeper layers character of distribution remains the same. Great depths in the Sea of Japan are populated most actively by species performing intensive daily migrations, and less actively by species continuously confined to a definite depth range. Different character of nutrition of the animals apparently determines extent of utilization of deep layers, which are usual for the species.

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Using shells collected from a sediment trap series in the Madeira Basin, we investigate the effects of seasonal variation of temperature, productivity, and optimum growth conditions on calcification in three species of planktonic Foraminifera. The series covers an entire seasonal cycle and reflects conditions at the edge of the distribution of the studied species, manifesting more suitable growth conditions during different parts of the year. The seasonal variation in seawater carbonate saturation at the studied site is negligible compared to other oceanic regions, allowing us to assess the effect of parameters other than carbonate saturation. Shell calcification is quantified using weight and size of individual shells. The size-weight scaling within each species is robust against changes in environmental parameters, but differs among species. An analysis of the variation in calcification intensity (size-normalized weight) reveals species-specific response patterns. In Globigerinoides ruber (white) and Globigerinoides elongatus, calcification intensity is correlated with temperature (positive) and productivity (negative), whilst in Globigerina bulloides no environmental forcing is observed. The size-weight scaling, calcification intensity, and response of calcification intensity to environmental change differed between G. ruber (white) and G. elongatus, implying that patterns extracted from pooled analyses of these species may reflect their changing proportions in the samples. Using shell flux as a measure of optimum growth conditions, we observe significant positive correlation with calcification intensity in G. elongatus, but negative correlation in G. bulloides. The lack of a consistent response of calcification intensity to optimum growth conditions is mirrored by the results of shell size analyses. We conclude that calcification intensity in planktonic Foraminifera is affected by factors other than carbonate saturation. These factors include temperature, productivity, and optimum growth conditions, but the strength and sign of the relationships differ among species, potentially complicating interpretations of calcification data from the fossil record.

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A total of 51,074 archaeological sites from the early Neolithic to the early Iron Age (c. 8000-500 BC), with a spatial extent covering most regions of China (c. 73-131°E and c. 20-53°N), were analysed over space and time in this study. Site maps of 25 Chinese provinces, autonomous regions and municipalities, published in the series 'Atlas of Chinese Cultural Relics', were used to extract, digitalise and correlate its archaeological data. The data were, in turn, entered into a database using a self-developed mapping software that makes the data, in a dynamic way, analysable as a contribution to various scientific questions, such as population growth and migrations, spread of agriculture and changes in subsistence strategies. The results clearly show asynchronous patterns of changes between the northern and southern parts of China (i.e. north and south of the Yangtze River, respectively) but also within these macro-regions. In the northern part of China (i.e. along the Yellow River and its tributaries and in the Xiliao River basin), the first noticeable increase in the concentration of Neolithic sites occurred between c. 5000 and 4000 BC; however, highest site concentrations were reached between c. 2000 and 500 BC. Our analysis shows a radical north-eastern shift of high site-density clusters (over 50 sites per 100 * 100 km grid cell) from the Wei and middle/lower Yellow Rivers to the Liao River system sometime between 2350 BC and 1750 BC. This shift is hypothetically discussed in the context of the incorporation of West Asian domesticated animals and plants into the existing northern Chinese agricultural system. In the southern part of China, archaeological sites do not show a noticeable increase in the absolute number of sites until after c. 1500 BC, reaching a maximum around 1000 BC.

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Legs 59 and 60 of the International Phase of Oceanic Drilling (IPOD) were designed to study the nature and history of volcanism of the active Mariana arc, its currently spreading inter-arc basin (the Mariana Trough), and the series of inactive basins and intervening ridges that lie to the west. The older basins and ridges were drilled during Leg 59 as the first part of a transect of single-bit holes drilled in each major basin and ridge. The eastern part of the transect - the technically active region - was drilled during Leg 60. The evolution of island-arc volcanos and magma genesis associated with lithospheric subduction remain some of the most complex petrologic problems confronting us. Many types of source material (mantle, oceanic crust, continental crust) and an unusually wide range of possible physical conditions at the time of magma genesis must be identified even before the roles of partial melting and subsequent magma fractionation, mixing, and contamination can be assessed.

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Early instrumental pressure measurements from Gibraltar and the Reykjavik area of Iceland have been used to extend to 1821 the homogeneous pressure series at the two locations. In winter the two sites are located close to the centres of action that comprise the North Atlantic Oscillation (NAO). The extended 'winter half-year' record of the NAO enables recent changes in the record to be placed in the context of the period 1823-1996. The period since the early 1970s is the most prolonged positive phase of the oscillation and the late 1980s and early 1990s is the period with the highest values (strongest westerlies). The winter of 1995-1996 marked a dramatic switch in the index, with the change from 1994-1995 being the greatest change recorded from one year to the next since the series began in 1823. (The extended Gibraltar and Reykjavik monthly pressures and the NAO series can be found on the Climatic Research Unit home page, http://www.cru.uea.ac.uk/).

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Alternations between siliciclastic, carbonate and evaporitic sedimentary systems, as recorded in the Aptian mixed succession of southern Tunisia, reflect profound palaeoceanographic and palaeoclimatic changes in this area of the southern Tethyan margin. The evolution from Urgonian-type carbonates (Berrani Formation, lower Aptian) at the base of the series, to intervals dominated by gypsum or detrital deposits in the remainder of the Aptian is thought to result from the interplay between climate change and tectonic activity that affected North Africa. Based on the evolution of clay mineral assemblages, the early Aptian is interpreted as having been dominated by slightly humid conditions, since smectitic minerals are observed. Near the early to late Aptian boundary, the onset of a gypsiferous sedimentation is associated with the appearance of palygorskite and sepiolite, which supports the installation of arid conditions in this area of the southern Tethyan margin. The evaporitic sedimentation may have also been promoted by the peculiar tectonic setting of the Bir Oum Ali area during the Aptian, where local subsidence may have been tectonically enhanced linked to the opening of northern and central Atlantic. Stress associated with the west and central African rift systems may have triggered the development of NW-SE, hemi-graben structures. Uplifted areas may have constituted potential new sources for clastic material that has been subsequently deposited during the late Aptian. Chemostratigraphic (d13C) correlation of the Bir Oum Ali succession with other peri-Tethyan regions complements biostratigraphic findings, and indicates that a potential expression of the Oceanic Anoxic Event (OAE) 1a may be preserved in this area of Tunisia. Although the characteristic negative spike at the base of this event is not recognized in the present study, a subsequent, large positive excursion with d13C values is of similar amplitude and absolute values to that reported from other peri-Tethyan regions, thus supporting the identification of isotopic segments C4-C7 of the OAE1a. The absence of the negative spike may be linked to either non preservation or non deposition: the OAE1a occurred in a global transgressive context, and since the Bir Oum Ali region was located in the innermost part of the southern Tethyan margin during most of the Aptian, stratigraphic hiatuses may have been longer than in other regions of the Tethys. This emphasizes the importance of integrating several stratigraphic disciplines (bio-, chemo- and sequence stratigraphy) when performing long-distance correlation.

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Site 42 is one of the series of sites selected by the Pacific Advisory Panel along the 140th meridian to sample the longitudinal variation in sediment composition in the eastern Pacific. The site is located in an area of abyssal hills between the Clarion and Clipperton Fracture Zones, and is at the northern margin of the thick development of acoustically transparent sediment extending along the equator.

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A 21-year record is presented of surface mass balance measurements along the K-transect. The series covers the period 1990-2011. Data are available at 8 sites along a transect over an altitude range of 390 - 1850 m at approximately 67° N in West Greenland. The surface mass balance gradient is on average 3.8 x 10**-3 m w.e./m, and the mean equilibrium line altitude is 1553 m a.s.l. Only the lower 3 sites within 10 km of the margin experience a significant increasing trend in the ablation over the entire period.

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Janczyk-Kopikowa (1966): The series of the organic deposits, developed in the vicinity of Golkow near Warsaw as oil shales and peats, was laid down in a grough valley and now rests on the deposits of the Middle Polish Glaciation (Riss). The organic deposits are overlain by the fluviale deposits of the North Polish Glaciation (Würm). The locality Golkow occurs beyond the extent of the continental glacier of this glaciation. Polen analysis completed by microfloristic examinations allows to determine the age of the organic series that is thought to be Eemian. The pollen diagram from Golkow does not call in question the stratigraphical position of the deposits investigated mainly due to its characteristic features such as minimum content of coniferous trees in the climatic optimum - about 5%, high percentage of Corylus - 77.5% and well developed phase of hornbeam. It may be well compared with other Eemian diagrams from the area of Poland and reveals much similar features. The development of vegetation at Golkow has depended upon the prevailing climate. At first, the cool climate brings about the development of plants having small thermal requirements. Here belong thin, park-like forests with pine and birch (Pinus, Betula) accompanied by the heliophilic plants such as Hippohäe and Ephedra. Improvement of climate that becomes warm and humid provides for development of deciduous forests prevailing in the climatic optimum, of the interglacial. Decrease of temperature causes a repeated change in the type of forest. This latter changes into coniferous forest with prevailing spruce (Picea) and fir (Abies) at the beginning, and then with pine (Pinus) and birch (Betula). During the Eemian Interglacial, the development of plants at Golkow terminates with a new and long-lasting predominance of pine-birch forests. However, such a longevity may be apparent only. Apparent character of this phenomenon is proved by a fact that the pollen spectra of the warm climatic periods have found their reflex in the oil shale that increased considerably slower than the layers off feebly decomposed peat evidencing the existence of cool pine-birch forests from the decline of the Interglacial. The water basin, in which the polen grains were laid down from surrounding plants is characterized by a calm sedimentation as proved by the occurrence of the oil shale. An insignificant water flow left behind some thin sand laminae. The not too deep basin becomes shallower owing to the growing water vegetation, and marshy vegetation. The growing of the plants causes a complete shallowing of the basin and formation of peat bog in situ, as proved by the peat beds occurring in the section. ---- Gadomska (1966): In the vicinity of Golków a series of organic deposits occurs amounting to 6.5-9.3 m in thickness, and consisting of oil shales, lacustrine silts and sands, as well as peats and peaty silts. The organic deposits fill up an old, small, but fairly deep lake basin, probably of finger-lake origin. It may be seen to-day as a slight lowering of the relief, filled up with soaked ground, stretching from north to south. On the basis of palaeobotanical examinations the organic deposits considered are of Eemian Interglacial age (Z. Janczyk-Kopikowa, 1063). The lower part of the organic series consists of a compact oil shale horizon, the maximum thickness of which may attain up to 8 m. The oil shales contain particularly in their upper part, numerous intercalations of arenaceous silts, dark grey or black in colour, or of sands mainly of lacustrine provenance. At the top of the oil shales are found peats, up to 2.5 m in thickness, covered by black, humus silts with numerous plant remains. The Eemian Interglacial deposits are covered by a series of fluviatile sands belonging partly to the Baltic Glaciation (bottom part of the series), partly to the Holocene (top part of the series). The thickness of the sands is 0.5-3.7 m. Higher up, there are found the Holocene and present-day deposits developed as clayey alluvion, or arenaceous slide rocks, or arenaceous-silty soil.