Search results for "Fossil"
showing 10 items of 412 documents
Non-marine invertebrate trace fossils from the Tertiary Calatayud- Teruel Basin, NE Spain. Reply
2021
We thank the comments of Dr Calzada. We think that this kind of discussions is very healthy to the Paleontology and it would be necessary to do it more frequently, so that thanks again for your example. It is true that some of the descriptions of ichnofossils in our work need further discussion and comments, but when we analysed several poorly-preserved specimens (such as the so-called Spongeliomorpha isp.) we preferred to make a quick introduction and describe them in open nomenclature. It was beyond the scope of our paper to make a revision of the ichnogenus with this kind of material, but we hope that Calzada's comments and our reply will improve some ideas concerning the ichnogenus Spon…
Concept of Biogenic Ferromanganese Crust Formation: Coccoliths as Bio-seeds in Crusts from Central Atlantic Ocean (Senghor Seamount/Cape Verde)
2011
At depths of 2,000 to 3,000 m, seamounts from the Cape Verde archipelago (Central Atlantic Ocean) are largely covered with ferromanganese crusts. Here we studied 60 to 150 mm thick crusts from the Senghor Seamount (depth: 2257.4 m). The crusts have a non lamellated texture and are covered with spherical nodules. The chemical composition shows a dominance of MnO2 (26.1%) and Fe2O3 (38.8%) with considerable amounts of Co (0.74%) and TiO2 (2.1%). Analysis by scanning electron probe microanalyzer (EPMA) revealed a well defined compositional zonation of micro-layers; the distribution pattern of Mn does not match that of Fe. Analysis by high resolution scanning electron microscopy (SEM) revealed…
Comment on "Lethally hot temperatures during the Early Triassic greenhouse".
2013
Sun et al . (Reports, 19 October 2012, p. 366) reconstructed Permian to Middle Triassic equatorial seawater temperatures. After correct temporal positioning of their data points, their presumed trends of temperature changes, and hence their assumption of a one-to-one relationship between putative "lethally hot" seawater temperatures and a disputable equatorial "eclipse" of some organisms, are no longer supported by their data.
Cytochrome b sequences of ancient cattle and wild ox support phylogenetic complexity in the ancient and modern bovine populations.
2009
Mitochondrial DNA has been the traditional marker for the study of animal domestication, as its high mutation rate allows for the accumulation of molecular diversity within the time frame of domestic history. Additionally, it is exclusively maternally inherited and haplotypes become part of the domestic gene pool via actual capture of a female animal rather than by interbreeding with wild populations. Initial studies of British aurochs identified a haplogroup, designated P, which was found to be highly divergent from all known domestic haplotypes over the most variable portion of the D-loop. Additional analysis of a large and geographically representative sample of aurochs from northern and…
Correction: Phylogeny of the Eurasian Wren Nannus troglodytes (Aves: Passeriformes: Troglodytidae) reveals deep and complex diversification patterns …
2020
The Mediterranean Basin represents a Global Biodiversity Hotspot where many organisms show high inter- and intraspecific differentiation. Extant phylogeographic patterns of terrestrial circum-Mediterranean faunas were mainly shaped through Pleistocene range shifts and range fragmentations due to retreat into different glacial refugia. Thus, several extant Mediterranean bird species have diversified by surviving glaciations in different hospitable refugia and subsequently expanded their distribution ranges during the Holocene. Such a scenario was also suggested for the Eurasian Wren (Nannus troglodytes) despite the lack of genetic data for most Mediterranean subspecies. Our phylogenetic mult…
Improving geoconservation of the palaeontological heritage through a semiotic vision
2019
The panoply of reasons that may attract people to fossils, which result from the meaning they attribute to these palaeontological objects, may contribute to endangering of the integrity of the fossil record. Semiotics can be of great help to assist geoconservation actions, usually based only on expertise statements, and are of particular relevance in palaeontological heritage inventory, evaluation, conservation, valuation and monitoring procedures. This work argues that fossils can be envisaged as signs displaying different meanings among experts and non-specialists. Such meanings support the heritage contents and values attributable to any palaeontological object and are affected by the re…
New chronology for Ksâr ‘Akil (Lebanon) supports Levantine route of modern human dispersal into Europe
2015
Modern human dispersal into Europe is thought to have occurred with the start of the Upper Paleolithic around 50,000-40,000 y ago. The Levantine corridor hypothesis suggests that modern humans from Africa spread into Europe via the Levant. Ksâr 'Akil (Lebanon), with its deeply stratified Initial (IUP) and Early (EUP) Upper Paleolithic sequence containing modern human remains, has played an important part in the debate. The latest chronology for the site, based on AMS radiocarbon dates of shell ornaments, suggests that the appearance of the Levantine IUP is later than the start of the first Upper Paleolithic in Europe, thus questioning the Levantine corridor hypothesis. Here we report a seri…
The Acheulian Site of Gesher Benot Ya‘aqov
2011
Gesher Benot Ya‘aqov (GBY) is located in the southern Hula Valley, which, in turn, is located in the northernmost segment of the Dead Sea Rift, part of the Great African Rift System. This region is an integral part of the “Levantine Corridor,” a land bridge connecting Africa and Europe, through which the diffusion and biotic exchange of many organisms took place in prehistoric times. The Hula Valley has preserved data of a phenomenon of great importance in human history: archaeological evidence recording hominin diffusion/migration out of Africa and into Eurasia. The unique sedimentological and hydrological conditions prevailing in the Hula, along with extensive and intensive tectonic activ…
Experimental study of the combined RES-based generators and electric storage systems for public buildings
2019
Abstract In the present paper, a new approach to the management of energy resources in the Research and Technology Centre of Energy (CRTEn -Tunisia) is proposed and evaluated by the monitoring of a PV installation realized for the cooperation project DE.DU.ENER.T, using renewable energy and economic criteria. The aim of this project is to improve energy efficiency order to minimize the electricity cost consumed at the CRTEn laboratory. According to the bills of electricity received, we noticed that there is a high consumption of electrical current. So, we targeted to install a photovoltaic field of 12KWc to reduce these bills by using the sustainable, green and clean sources. A theoretical …
An Analysis of the Intertial Response of Small Isolated Power Systems in Presence of Generation from Renewable Energy Sources
2018
Renewable Energy Sources are posing critical issues related to the mining of power systems stability, essentially due to a decrement of the inertial response during system's contingencies. As a consequence, to preserve the security and the reliability of the system, it is necessary to adopt new frequency adjustments mechanisms. This issue becomes particularly critical in isolated power systems, like those of small islands not supplied by the main grid, in the case of high shares of production from unpredictable renewabies such as photovoitaic and wind sources. In this framework, the present work deals with the analysis of the variation of the inertia time constant of a small island in vario…