Search results for "Geochemistry"
showing 10 items of 2967 documents
Influence of dissolved organic matter on rare earth elements and yttrium distributions in coastal waters
2010
International audience; Data collected during this study indicate that dissolved Y and REE (rare earth element) behaviour can be monitored through shale-normalised ratios. Relationships occurring between these ratios suggest that leaching from lithogenic materials is the main source of REE in the studied area. This process involves riverine detrital matter in the inner area of the Gulf of Palermo. Features of shale-normalised patterns and the relationship recognised between dissolved Fe and Y/Ho suggest that REE are released from Fe-rich coatings of atmospheric dust. Observed similarities between dissolved Fe and chlorophyll- content suggest that leaching of Fe-rich atmospheric particulates…
Variations morphologiques des Toxaster (Echinoida : Spatangoida) en regard des fluctuations spatiales (Arc de Castellane, SE France) et temporelles (…
2006
Resume L'impact du milieu sedimentaire sur l'installation, la croissance et la morphologie de spatangues primitifs du Cretace inferieur, est analyse chez le genre Toxaster dans le Valanginien et l'Hauterivien de l'Arc de Castellane au Nord de la plate-forme provencale. Les analyses concernent la dimension spatiale a partir de l'etude comparative de six populations isochrones de Toxaster granosus kiliani de la biozone a Verrucosum distribuees le long d'un gradient proximo-distal, puis la dimension temporelle a partir de l'etude d'une coupe de reference (Carajuan) couvrant l'intervalle stratigraphique Valanginien superieur–Hauterivien superieur et concernant principalement les especes T. gran…
ESR/U-series chronology of early Neanderthal occupations at Cova Negra (Valencia, Spain)
2019
Abstract The spatiotemporal repartition of Neanderthal populations throughout the late Middle and early Upper Pleistocene is of great interest for our understanding of human evolution. Establishing a reliable chronology for human-bearing layers from prehistoric sites is thus essential for the study of Neanderthal population dynamics prior to modern human arrival in Europe. Cova Negra (Valencia, Spain) is one of the richest sites documenting Neanderthal fossil bones in the Iberian Peninsula (Arsuaga et al., 1989, 2007; Villaverde et al., 2014). The stratigraphic sequence includes 15 Middle Palaeolithic layers. Among them, four were dated by the ESR/U-series dating method on enamel from six h…
Erratum to “Palaeoecological context for the extinction of the Neanderthals: A small mammal study of Stratigraphic Unit V of the El Salt site, Alcoi,…
2021
El Salt is an important reference site for understanding the extinction of Neanderthal populations in the eastern Iberian Peninsula during MIS 3. In this paper, we describe the small mammal assemblage from Stratigraphic Unit V, the youngest unit with evidence of human presence, based on nearly 1300 specimens. A total of seven rodents (Microtus arvalis, Microtus duodecimcostatus, Microtus cabrerae, Sciurus vulgaris, Arvicola sapidus, Eliomys quercinus and Apodemus sylvaticus), three insectivores (Talpa occidentalis, Crocidura sp., Sorex sp.) and one lagomorph (Oryctolagus cf. cuniculus) were identified. Palaeocological analyses point to drier conditions in this part of the stratigraphic sequ…
Palaeoecological context for the extinction of the Neanderthals: A small mammal study of Stratigraphic Unit V of the El Salt site, Alcoi, eastern Spa…
2019
El Salt is emerging as a reference site for the study of the extinction of Neanderthal populations in the Eastern Iberian Peninsula during MIS 3. The small vertebrate assemblage analysed in this work is framed within this general objective and comes from Stratigraphic Unit V, the most recent unit with human presence. Nearly 1300 small mammal remains have been studied in order to reconstruct the palaeoecological conditions of this debated period. A total of seven rodents (Microtus arvalis, Microtus duodecimcostatus, Microtus cabrerae, Sciurus vulgaris, Arvicola sapidus, Eliomys quercinus and Apodemus sylvaticus), three insectivores (Talpa occidentalis, Crocidura sp., Sorex sp.) and one lagom…
Pre-Hirnantian (latest Ordovician) benthic community assemblages: controls and replacements in a siliciclastic-dominated platform of the eastern Anti…
2007
17 pages; International audience; Lower-middle Ashgill sedimentary strata from the Mediterranean region have recorded a key episode of temperate-to-cold water, carbonate productivity predating the onset of the Hirnantian glaciation. The latitudinal position of the Moroccan margin of North Gondwana during Ashgill should have been adequate for the recorded development of carbonate factories. However, carbonate productivity was neither homogeneous nor laterally persistent, as documented in the eastern Anti-Atlas. Whereas in the Erfoud area, the bryozoan-dominated limestones of the Ashgill Khabt-el-Hajar Formation indicate the intensive activity of carbonate factories, these were dramatically r…
First shark record from the Upper Cretaceous of the Kuril Islands, Far East Russia
2020
Abstract The first find of a Late Cretaceous shark tooth, or of any cartilaginous fish for that matter, from the Kuril Islands in the Russian Far East is recorded as Carcharias sp. (Lamniformes, Carchariidae). The specimen originates from Maastrichtian strata on the island of Shikotan that are assigned to the Malokurilsk Formation. It constitutes an extremely rare find from rocks of this age in the northwest Pacific region. External and internal dental structures have been reconstructed by the use of computed tomography. The vasculature of this lamniform tooth is first modelled by CT scanning and shown under different angles, which allows an assessment of the spatial arrangement of hierarch…
Highly-resolved radiocarbon measurements on shells from Kalba, UAE, using carbonate handling system and gas ion source with MICADAS
2019
Abstract The Mini Carbon Dating System (MICADAS) represents a flexible AMS system for measuring radiocarbon samples either in the form of graphite or CO2 gas. We used the possibility to attach a carbonate handling system (CHS) to the gas ion source (GIS) to measure smaller amounts of carbonates ( 3) are used to clean the system. We tested the CHS-GIS combination on heated and unheated archaeological shells of Anadara uropigimelana from Kalba, Sharjah Emirate, United Arab Emirates (UAE). Even though the amount of carbon in the samples was small (4–22 µg C) the performance of the CO2 dating system permits the comparison of trends in the 14C data to stable isotope measurements (δ18O and δ13C)…
High-resolution clay mineralogy as a proxy for orbital tuning: example of the Hauterivian-Barremian transition in the Betic Cordillera (SE Spain).
2012
11 pages; International audience; The response of clay mineral assemblages to potential orbital forcing is tested in Mesozoic hemipelagic marl- limestone rhythmites of the Río Argos section (Betic Cordillera, Southeastern Spain). Along the section, marls are pervasively enriched in kaolinite and illite, whereas limestones are enriched in smectite-rich illite/smectite mixed-layers, suggesting that marl-limestone alternations are produced by cyclic high-frequency fluctuations of continental runoff. Spectral analyses show that clay mineral assemblages evolve accordingly to precession, obliquity and eccentricity cycles. Durations of ammonite zones are assessed at 535 kyr for the Late Hauterivia…
The end of the Messinian salinity crisis: Evidences from the Chelif Basin (Algeria).
2007
How did the Messinian Salinity Crisis end is a matter of intense debate between two opposite concepts i.e., the generalised dilution event, the so-called Lago–Mare, followed by the sudden restoration of the marine conditions at the base of the Zanclean, or the early partial or complete marine refill that would have happened earlier during the upper Messinian. The Chelif Basin of Northwestern Algeria, one of the greatest Messinian marginal basins of the Mediterranean, provides an exceptional opportunity to study in detail how this major paleoenvironmental change occurred through continuous sedimentary records of the Miocene–Pliocene boundary. Five sections representative of both the central …