Search results for " dating"
showing 10 items of 230 documents
Unraveling the exhumation history of high-pressure ophiolites using magnetite (U-Th-Sm)/He thermochronometry
2020
International audience; Magnetite is a ubiquitous oxide in ultramafic and mafic rocks, which is present in a large range of geological and tectonic settings. In the case of high-pressure ultramafic rocks, exhumation timing is commonly constrained by geochronometers in nearby lithologies. The development of the magnetite (U-Th-Sm)/He method (MgHe) has opened new perspectives to refine the exhumation history of such rocks. However no thermal history has been deduced using MgHe data so far. Here we applied MgHe dating to magnetite from an HP-LT alpine ophiolite body (Rocher Blanc) from the Schistes lustres units (Western Alps, France) where part the P-T-t history is constrained to further refi…
Natural and anthropogenic influences on the geochemistry of Quaternary lake sediments from Holzmaar, Germany
1997
The accumulation of heavy metals and trace elements has been investigated in a well laminated sequence of Holocene and late Pleistocene lake sediments composed of diatomaceous gyttja, tuff and silt and clay sediments. Varve chronology of the annually deposited gyttja yielded a continuous high-resolution time sequence and allowed the absolute age dating of the sediment. Fluxes of elements remained largely uniform from the late Pleistocene into the Holocene. Higher trace element and heavy metal fluxes occur from 2322 to 862 VT years ago (VT: varve time, years before 1950) and reached their maxima in the uppermost sediments (<845 VT years ago). These increasing element fluxes correlate with in…
The Early Palaeozoic break-up of northern Gondwana, new palaeomagnetic and geochronological data from the Saxothuringian Basin, Germany
2002
Early Palaeozoic volcanic and sedimentary rocks from the Saxothuringian Basin (Franconian Forest, northern Bavaria) have been subjected to detailed radiometric and palaeomagnetic studies in order to determine the tectonic environment and geographic setting in which they were deposited. Two hand samples were collected from the as yet undated pyroclastic flow deposits for 207Pb/206Pb age dating. Radiometric results for these samples, obtained by the single-zircon evaporation technique, are identical within error, and the mean age of all measured grains is 478.2±1.8 Ma (n=11). This age is considered to be primary and firmly constrains the eruption of the ignimbrites and formation of the subaqu…
Palaeozoic pre- and post-collision calc-alkaline magmatism in the Qinling orogenic belt, central China, as documented by zircon ages on granitoid roc…
1996
Based on large-scale reconnaissance mapping, we identified two calc-alkaline plutonic assemblages from the northern Qinling orogenic belt. central China. The older assemblage of intrusions. closely associated and deformed coevally with their host volcanic arc sequences, seems to represent the fractionation product of basaltic arc magma. It therefore predates the collision of the North China Block with the Central Qinling island-arc system that developed in a SW Pacific-type oceanic domain south of the North China Block. Single-zircon 207Pb/206Pb evaporation dating yielded early to middle Ordovician ages for this assemblage. with a relatively small range from 487.2 ± 1.1 to 470.2 ± 1.3 Ma. I…
The triumphal cross of the cathedral of Nevers: painting technique and examination
2019
The large polychrome wooden cross preserved in the Saint-Cyr et Sainte-Julitte cathedral in Nevers was badly damaged during the bombing in July 1944. Restored and put on display on a modern cross in front of the choir, the sculpture suffered a new fall in 2015. The conservation of the work, directed by DRAC-CRMH of Burgundy-Franche-Comté, was preceded by a phase of technical study. Micro-stratigraphic, taxonomic and radiometric analyses and the dendrochronology of the cross were carried out. The dendrochronology of the cross of Nevers and the comparison with radiocarbon dating place the elaboration of the work in the last quarter of the 12th century while confirming the contemporaneousness …
Bayesian chronological analyses consistent with synchronous age of 12,835-12,735 Cal BP for Younger Dryas boundary on four continents
2015
The Younger Dryas impact hypothesis posits that a cosmic impact across much of the Northern Hemisphere deposited the Younger Dryas boundary (YDB) layer, containing peak abundances in a variable assemblage of proxies, including magnetic and glassy impact-related spherules, high-temperature minerals and melt glass, nanodiamonds, carbon spherules, aciniform carbon, platinum, and osmium. Bayesian chronological modeling was applied to 354 dates from 23 stratigraphic sections in 12 countries on four continents to establish a modeled YDB age range for this event of 12,835-12,735 Cal B.P. at 95% probability. This range overlaps that of a peak in extraterrestrial platinum in the Greenland Ice Sheet …
Psychometric properties of the Cyber-Violence Scale in Adolescent Couples (Cib-VPA)
2018
Resumen La utilización que los adolescentes hacen de las redes sociales, móviles e internet, para ejercer violencia hacia la pareja resulta preocupante. Por esta razón, es necesario disponer de instrumentos fiables, específicos para población adolescente y que permitan evaluar tanto situaciones de acoso como de victimización. El objetivo de este estudio fue analizar las propiedades psicométricas de la Escala de Ciber-violencia en Parejas Adolescentes (Cib-VPA). Esta escala consta de dos subescalas, ciberacoso perpetrado y cibervictimización, con 10 ítems cada una relativos a conductas agresivas y de control que pueden ser perpetradas o sufridas a través de redes sociales en parejas adolesce…
Historical building dating: refinement of established sample preparation protocol
2010
Abstract: The application of thermal (TL) and optical (OSL) stimulated luminescence on pottery and building materials has allowed to resolve numer-ous problems in both the fields of retrospective do-simetry and dating. Routine measurements request the registration of TL signals obtained on polymineral fine-grained frac-tion (FG) extracted from pottery sherds and bricks used as building material with the Added Dose (AD) technique. One of the reasons of the dispersion of the lumi-nescence measurements when using this fraction is the variability of relative contents of quartz and feld-spars, which due to their differing behaviour influ-encing the equivalent dose (ED) and therefore its uncertai…
Reconstruction of human subsistence and husbandry strategies from the Iberian Early Neolithic: A stable isotope approach
2018
Objectives The Early Neolithic involved an important social and economic shift that can be tested not only with the material culture, but also through biomolecular approaches. The Iberian Peninsula presents few Early Neolithic sites where fauna and humans can be analyzed together from an isotopic perspective. Here we present an isotopic study on the site of Cueva de Chaves as an example for understanding the dietary and economical changes that took place during Early Neolithic in Iberia. Material and methods Here we apply carbon and nitrogen stable isotope analysis to bone collagen from 4 humans and 64 faunal samples from 14 different species. The large dataset belongs to the same unique ch…
Possible influence of Zoophycos bioturbation on radiocarbon dating and environmental interpretation
2002
Abstract In paleoenvironmental studies of marine sediments bioturbation is often neglected and/or only treated as a diffusion-like process affecting only the uppermost sediment with decreasing intensity with depth. Deep dwelling animals, like the Zoophycos producing animal, however, affect the sediment composition by transporting material over vertical distances of up to 1 m below the seafloor. In Arabian Sea sediment cores 70KL, 64KL and 57KL a significant downward transport of particles by Zoophycos can be observed. Within the Zoophycos burrows the faunal composition of both planktonic and benthic foraminiferal assemblages as well as the isotopic signature of foraminiferal carbonate diffe…