982 resultados para Bivalves, Fossil.
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Fossil bones and teeth of Late Pleistocene terrestrial mammals from Rhine River gravels (RS) and the North Sea (NS), that have been exposed to chemically and isotopically distinct diagenetic fluids (fresh water versus seawater), were investigated to study the effects of early diagenesis on biogenic apatite. Changes in phosphate oxygen isotopic composition (delta O-18(PO4)), nitrogen content (wt.% N) and rare earth element (REE) concentrations were measured along profiles within bones that have not been completely fossilized, and in skeletal tissues (bone, dentine, enamel) with different susceptibilities to diagenetic alteration. Early diagenetic changes of elemental and isotopic compositions of apatite in fossil bone are related to the loss of the stabilizing collagen matrix. The REE concentration is negatively correlated with the nitrogen content, and therefore the amount of collagen provides a sensitive proxy for early diagenetic alteration. REE patterns of RS and NS bones indicate initial fossilization in a fresh water fluid with similar REE compositions. Bones from both settings have nearly collagen-free, REE-, U-, F- and Sr-enriched altered outer rims, while the collagen-bearing bone compacta in the central part often display early diagenetic pyrite void-fillings. However, NS bones exposed to Holocene seawater have outer rim delta O-18(PO4) values that are 1.1 to 2.6 parts per thousand higher compared to the central part of the same bones (delta O-18(PO4) = 18.2 +/- 0.9 parts per thousand, n = 19). Surprisingly, even the collagen-rich bone compacta with low REE contents and apatite crystallinity seems altered, as NS tooth enamel (delta O-18(PO4) =15.0 +/- 0.3 parts per thousand, n=4) has about 3%. lower delta O-18(PO4) values, values that are also similar to those of enamel from RS teeth. Therefore, REE concentration, N content and apatite crystallinity are in this case only poor proxies for the alteration of delta O-18(PO4) values. Seawater exposure of a few years up to 8 kyr can change the delta O-18(PO4) values of the bone apatite by > 3 parts per thousand. Therefore, bones fossilized in marine settings must be treated with caution for palaeoclimatic reconstructions. However, enamel seems to preserve pristine delta O-18(PO4) values on this time scale. Using species-specific calibrations for modern mammals, a mean delta O-18(H2O) value can be reconstructed for Late Pleistocene mammalian drinking water of around -9.2 +/- 0.5 parts per thousand, which is similar to that of Late Pleistocene groundwater from central Europe. (c) 2008 Elsevier B.V. All rights reserved.
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The end-Permian mass extinction removed more than 80% of marine genera. Ammonoid cephalopods were among the organisms most affected by this crisis. The analysis of a global diversity data set of ammonoid genera covering about 106 million years centered on the Permian-Triassic boundary (PTB) shows that Triassic ammonoids actually reached levels of diversity higher than in the Permian less than 2 million years after the PTB. The data favor a hierarchical rather than logistic model of diversification coupled with a niche incumbency hypothesis. This explosive and nondelayed diversification contrasts with the slow and delayed character of the Triassic biotic recovery as currently illustrated for other, mainly benthic groups such as bivalves and gastropods.
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Over the last decades, there has been an increasing interest on the chronology, distribution and mammal taxonomy (including hominins) related with the faunal turnovers that took place around the Pliocene-Pleistocene transition [ca. 1.8 mega-annum (Ma)] in Europe. However, these turnovers are not fully understood due to: the precarious nature of the period's fossil record; the"non-coexistence" in this record of many of the species involved; and the enormous geographical area encompassed. This palaeontological information gap can now be in part bridged with data from the Fonelas P-1 site (Granada, Spain), whose faunal composition and late Upper Pliocene date shed light on some of the problems concerning the timing and geography of the dispersals.
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This paper analyses the international inequalities in CO2 emissions intensity for the period 1971–2009 and assesses explanatory factors. Multiplicative, group and additive methodologies of inequality decomposition are employed. The first allows us to clarify the separated role of the carbonisation index and the energy intensity in the pattern observed for inequalities in CO2 intensities; the second allows us to understand the role of regional groups; and the third allows us to investigate the role of different fossil energy sources (coal, oil and gas). The results show that, first, the reduction in global emissions intensity has coincided with a significant reduction in international inequality. Second, the bulk of this inequality and its reduction are attributed to differences between the groups of countries considered. Third, coal is the main energy source explaining these inequalities, although the growth in the relative contribution of gas is also remarkable. Fourth, the bulk of inequalities between countries and its decline are explained by differences in energy intensities, although there are significant differences in the patterns demonstrated by different groups of countries. JEL codes: D39; Q43; Q56. Key words: CO2 international distribution, inequality decomposition, CO2 emissions intensity
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This paper describes petrologic and morphologic characteristics of fossil beaches submerged in the sector of the Costa Brava located between the Pals Beach and Blanes (Girona). These submerged beaches are composed of large-grain sandstone andconglomerate platforms, situated at a depth between 0.5 and 2.5 meters. These platforms are slightly inclinated towards the open sea. These deposits have been formed very recently, and date from Holocene, as noted by the presence of fragments of roman ceramics inside sandstone
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En aquest article es pretén explicar breument la viabilitat de la futura gestió i utilització de la biomassa forestal de Bellver de Cerdanya mitjançant un district heating al futur barri del Pla de Tomet. Les particularitats per les quals aquest poble és ideal per a aquest projecte són que l'ajuntament és propietari de gairebé un 90% dels boscos situats en aquest municipi; i que alhora ja ha realitzat diverses instal·lacions que utilitzen la biomassa forestal per a calefacció i ACS. La situació econòmica de la comarca és bastant complicada, ja que s'ha basat en el sector turístic i la construcció, però ambdós no passen pel millor moment. El projecte serviria per donar un valor a la biomassa forestal que fins ara no s'ha donat, i alhora s'intenta buscar nous inputs econòmics per a la Cerdanya. En aquest treball també s'analitza quins haurien de ser els futurs tractaments que s'haurien d'aplicar a la forest, tenint en compte les activitats que es realitzen actualment, i evitant en tot moment possibles efectes negatius, com podria ser la sobreexplotació. També es dedica una part del projecte a explicar els sistemes per obtenir i gestionar de forma correcta la biomassa. A continuació es tracta la part més tècnica, realitzant una estimació del possible futur consum energètic del barri del Pla de Tomet, encara no construït; i decidint quins sistema de calderes seria el més adequat, el tipus d’emmagatzematge més apropiat i els passos a seguir per millorar el rendiment del procés de la gestió i extracció de la biomassa. Seguint tots aquests passos s'arriba a la conclusió que aprofitar la biomassa forestal és millor solució que utilitzar combustibles fòssils. A part dels obvis beneficis medi ambientals, també és millor a nivell econòmic, tant pels futurs veïns com per l'ajuntament.
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Aim Species distribution models (SDMs) based on current species ranges underestimate the potential distribution when projected in time and/or space. A multi-temporal model calibration approach has been suggested as an alternative, and we evaluate this using 13,000 years of data. Location Europe. Methods We used fossil-based records of presence for Picea abies, Abies alba and Fagus sylvatica and six climatic variables for the period 13,000 to 1000yr bp. To measure the contribution of each 1000-year time step to the total niche of each species (the niche measured by pooling all the data), we employed a principal components analysis (PCA) calibrated with data over the entire range of possible climates. Then we projected both the total niche and the partial niches from single time frames into the PCA space, and tested if the partial niches were more similar to the total niche than random. Using an ensemble forecasting approach, we calibrated SDMs for each time frame and for the pooled database. We projected each model to current climate and evaluated the results against current pollen data. We also projected all models into the future. Results Niche similarity between the partial and the total-SDMs was almost always statistically significant and increased through time. SDMs calibrated from single time frames gave different results when projected to current climate, providing evidence of a change in the species realized niches through time. Moreover, they predicted limited climate suitability when compared with the total-SDMs. The same results were obtained when projected to future climates. Main conclusions The realized climatic niche of species differed for current and future climates when SDMs were calibrated considering different past climates. Building the niche as an ensemble through time represents a way forward to a better understanding of a species' range and its ecology in a changing climate.
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Most bituminous adhesives or binders that are used for pavement materials are derived primarily from fossil fuels. With petroleum oil reserves becoming depleted and the drive to establish a bio-based economy, there is a push to produce binders from alternative sources, particularly from biorenewable resources. However, until now, no research has studied the applicability of utilizing bio-oils as a bitumen replacement (100% replacement) in the pavement industry. The main objective of this research was to test various properties of bio-oils in order to determine the applicability of using bio-oils as binders in the pavement industry. The overall conclusions about the applicability of using bio-oils as bio-binders in the pavement industry can be summarized as follows: 1. Bio-oils cannot be used as bio-binders/pavement materials without any heat pre-treatment/upgrading procedure. 2. Current testing standards and specifications, especially Superpave procedures, should be modified to comply with the properties of bio-binders. 3. The temperature range of the viscous behavior for bio-oils may be lower than that of bitumen binders by about 30°–40° C. 4. The rheological properties of the unmodified bio-binders vary in comparison to bitumen binders, but the rheological properties of these modified bio-binders change significantly upon adding polymer modifiers. 5. The high-temperature performance grade for the developed bio-binders may not vary significantly from that of the bitumen binders, but the low-temperature performance grade may vary significantly
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Nota sobre les conseqüències de la invasió del mol·lusc d'aigua dolça, Anodonta woodiana, a la Península Ibèrica
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The fossiliferous beds of the 'Cementerio de Ciurana (Gerona) ', have been studied from Taphonomy and Paleoeco.. logy viewpoints. The mode of formation of the fossil assem.. blages hardly implicates transport and the vertical successiori seems to represent a regressive sequence from former normal marine conditions.
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En base a los moluscos fósiles y a criterios sedimentológicos, se realiza una reconstrucción paleoambiental del sector de Sant Pau d'Ordal y de La Pedrera de Sant Llorenq d'Hortons y se deduce la equivalencia lateral de ambas localidades, a las que se atribuye una edad Langhiense-Serravaliense inferior. La presencia del pterópodo Vaginella austriaca, KITTL citado por primera vez en diversos yacimientos del Penedis, permite afirmar que durante este periodo existió una buena comunicación entre el golfo del Penedes y el mar abierto.
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En la presente nota se da una lista ampliada de la fauna malacológica del yacimiento pliocénico de la Plaça de les Bruixes (Molis de Rei, Barcelona). Los fenómenos de coacción que se describen nos muestran su utilidad a la hora de definir las condiciones ambientales y paleogeográficas del lugar donde habita la fauna.
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New stratigraphic data along a profile from the Helvetic Gotthard massif to the remnants of the North Penninic basin in eastern Ticino and Graubunden are presented. The stratigraphic record together with existing geochemical and structural data, motivate a new interpretation of the fossil European distal margin. We introduce a new group of Triassic facies, the North-Penninic-Triassic (NPT), which is characterised by the Ladinian ``dolomie bicolori''. The NPT was located in-between the Brianconnais carbonate platform and the Helvetic lands. The observed horizontal transition, coupled with the stratigraphic superposition of a Helvetic Liassic on a Briaconnais Triassic in the Luzzone-Terri nappe, links, prior to Jurassic rifting, the Brianconnais paleogeographic domain at the Helvetic margin, south of the Gotthard. Our observations suggest that the Jurassic rifting separated the Brianconnais domain from the Helvetic margin by complex and protracted extension. The syn-rift stratigraphic record in the Adula nappe and surroundings suggests the presence of a diffuse rising area with only moderately subsiding basins above a thinned continental and proto-oceanic crust. Strong subsidence occurred in a second phase following protracted extension and the resulting delamination of the rising area. The stratigraphic coherency in the Adula's Mesozoic questions the idea of a lithospheric m lange in the eclogitic Adula nappe, which is more likely to be a coherent alpine tectonic unit. The structural and stratigraphic observations in the Piz Terri-Lunschania zone suggest the activity of syn-rift detachments. During the alpine collision these faults are reactivated (and inverted) and played a major role in allowing the Adula subduction, the ``Penninic Thrust'' above it and in creating the structural complexity of the Central Alps. (C) 2012 Elsevier B.V. All rights reserved.
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This paper addresses the surprising lack of quality control on the analysis and selection on energy policies observable in the last decades. As an example, we discuss the delusional idea that it is possible to replace fossil energy with large scale ethanol production from agricultural crops. But if large scale ethanol production is not practical in energetic terms, why huge amount of money has been invested in it and is it still being invested? In order to answer this question we introduce two concepts useful to frame, in general terms, the predicament of quality control in science: (i) the concept of “granfalloons” proposed by K. Vonnegut (1963) flagging the danger of the formation of “crusades to save the world” void of real meaning. These granfalloons are often used by powerful lobbies to distort policy decisions; and (ii) the concept of Post-Normal science by S. Funtowicz and J. Ravetz (1990) indicating a standard predicament faced by science when producing information for governance. When mixing together uncertainty, multiple-scale and legitimate but contrasting views it becomes impossible to deal with complex issue using the conventional scientific approach based on reductionism. We finally discuss the implications of a different approach to the assessment of alternative energy sources by introducing the concept of Promethean technology.
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Many questions in evolutionary biology require an estimate of divergence times but, for groups with a sparse fossil record, such estimates rely heavily on molecular dating methods. The accuracy of these methods depends on both an adequate underlying model and the appropriate implementation of fossil evidence as calibration points. We explore the effect of these in Poaceae (grasses), a diverse plant lineage with a very limited fossil record, focusing particularly on dating the early divergences in the group. We show that molecular dating based on a data set of plastid markers is strongly dependent on the model assumptions. In particular, an acceleration of evolutionary rates at the base of Poaceae followed by a deceleration in the descendants strongly biases methods that assume an autocorrelation of rates. This problem can be circumvented by using markers that have lower rate variation, and we show that phylogenetic markers extracted from complete nuclear genomes can be a useful complement to the more commonly used plastid markers. However, estimates of divergence times remain strongly affected by different implementations of fossil calibration points. Analyses calibrated with only macrofossils lead to estimates for the age of core Poaceae ∼51-55 Ma, but the inclusion of microfossil evidence pushes this age to 74-82 Ma and leads to lower estimated evolutionary rates in grasses. These results emphasize the importance of considering markers from multiple genomes and alternative fossil placements when addressing evolutionary issues that depend on ages estimated for important groups.