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[en] Defining the occupation sequence of medieval rural farming sites in Northern Iberia is complicated, since they feature low density of stratigraphic relationships and few finds and because of the intensive agricultural activities developed there during the last few decades. This paper presents the chronological characterization of the medieval village of Zornoztegi, located in the Basque Country, in the province of Alava. At this site, dwellings extend over an area of approximately two hectares and consist mainly of negative structures excavated in the bedrock. Radiocarbon dating measurements carried out on 32 samples, together with mortar optical microscopic analyses and other information obtained from stratigraphic relationships, changes in the settlement organization and the study of material culture, allowed structuring and characterizing the occupation sequence of the site of Zornoztegi. Furthermore, Bayesian statistics was used to reduce the range of the calibrated dates and to refine the chronology of the sequence.
[en] The selection and pre-treatment of a reliable organic fraction from which to acquire radiocarbon dates is fundamental to obtain accurate chronologies. Sampling from tropical lakes is particularly challenging given the adverse preservation conditions and diagenesis in these environments. Our research is the first to examine and quantify the differences between the radiocarbon date results from different carbon fractions and pretreatments from the same depths from a tropical lake sediment core (1.72 m long) located in north Australia to assess which one(s) are more reliable. Six different organic fractions (bulk organics, pollen concentrate, cellulose, stable polycyclic aromatic carbon (SPAC), charcoal >250 um and charcoal >63 um), for a total of 27 radiocarbon dates, were compared in six different depths along the core. Acid-base-acid (ABA), modified ABA (30 % hydrogen peroxide + ABA), 2chlorOx (a novel cellulose pre-treatment method) and hydrogen pyrolysis (hypy) were used to pre-treat the correspondent organic fractions. The oldest date is 31,295 calibrated years before present (cal yr BP) and the youngest is 2,048 cal yr BP, spanning 29,247 years. The smallest offset between the minimum and the maximum age in a given depth was found to be 975 years (between SPAC and charcoal >63 um) and the largest 16,527 years (between pollen concentrate and SPAC). The SPAC fractions pre-treated with hypy consistently yielded older ages compared to all other fraction in most cases, while bulk organics yielded consistently younger ones. The magnitude and consistency of the offsets and the physical and chemical properties of the tested organic fractions suggest that SPAC is the most reliable fraction to date in tropical lake sediments and that hypy successfully removes contamination sourced from exogenous carbon.
[en] Microsyenitic and microdioritic dykes from Alconera on the northern side of Burguillos del Cerro Anticlinarium give a K-Ar age of 281+-7 M.A. This age is close to that reported for the nearly Feria syenite which has similar petrographical and geochemical characteristics and whose intrusions fall on a common axis NW-SE. This confirms that these alkaline subvolcanic rocks were emplaced during a period from Stephanian to lower Permian, subsequent to the last phase of varisc deformation
[fr]Les dykes d'Alconera situes sur le flanc septentrional de l'Anticlinarium de Burguillos del Cerro et constitues de microsyenite et de microdiorite donnent un age K-Ar de 281+-7 M.A. Cet age est proche de celui indique pour la syenite de Feria, petrographiquement et geochimiquement voisine et dont les intrusions sont sur le meme axe NW-SE. Ces resultats semblent accrediter la these d'une mise en place de ces roches alcalines subvolcaniques entre le Stephanien et le Permien Inferieur, apres la derniere phase de deformation varisque
[en] Radiometric data for the Westcarpathian neovolcanites did not include basalts. Using the argon method a basanitoid group of ages of about 7,5 mil. years near B. Stiavnica and N from Lucenec (Maskova, Podrecany), and about 2,5 mil. years old basanites in the surroundings of Filakovo were identified. (author)
[en] Full text: Crustal and upper mantle xenoliths are hosted in basanitic dikes and necks that intruded into continental sediments of the Cretaceous Salta Rift at Qebrada Las Conchas, Province Salta, Argentina. Most of the crustal xenoliths have granitoid composition ( quartz - plagioclase - k-feldspar -garnet) whereas mafic compositions (plagioclase - clinopyroxene -garnet ±hornblende) are exceedingly rare. The xenoliths show a well equilibrated granoblastic structure and the minerals are compositionally unzoned. Metamorphic conditions have been of granulite facies temperature ca. 850 - 900 at lower crustal depth with pressure of ca. 10 kbar from thermo barometric calculations. Sm-Nd mineral isochron ages are 94.9±8.4Ma, 91.6±13.5Ma, 89.0±4.2Ma (granitoid composition), and 110.7±23.2Ma (mafic composition). These ages are within the errors in good agreement with the age of basanitic volcanism. Sm-Nd isochron ages are considered as closure ages and temperature at the respective time has been still above the Sm-Nd systems' closure temperature (>600-700 ). Sm-Nd and Rb-Sr isotopic signatures (147Sm/144Nd t0=0.1225 - 0.1608); 143Nd/144Ndt0 0.512000 - 0.512324; 87Rb/86Sr = 0.099 - 0.172; 87Sr/86Sr = 0.708188 - 0.7143161) and common lead isotopic signatures (206Pb/204Pb = 18.43 - 18.48; 207Pb/204Pb = 15.62-15.70; 208Pb/204Pb = 38.22 - 38.97) of the granitoid xenoliths are indistinguishable from the isotopic composition of the Early Paleozoic metamorphic basement from NW Argentina apart from the lower 208Pb/204Pb ratios of the Early Paleozoic basement. Sm-Nd depleted mantle model ages of c. 1.8 Ga from granitoid xenoliths and Early Paleozoic basement point to a Proterozoic protoliths for both with distinct ages of the last thermal overprint. Time constraints, the well equilibrated granulite fabric, P-T conditions and lack of chemical zoning of minerals point to a high temperature gradient in a crust of nearly normal thickness at c. 90 Ma and to a prominent thermal anomaly in the lithosphere. If this anomaly has been caused by uplift of the lithosphere/asthenosphere boundary by extensional tectonics the extension must have been restricted to the mantle lithosphere. Interpretation of the tectonic setting remains ambiguous and both a 'true rift' and a rifting in a possible Cretaceous back arc have to be considered in future investigations. The crustal composition is identical with the compositionally homogeneous Early Paleozoic crust of NW Argentina and N Chile. A thick mafic lower crust seems unlikely considering low frequency of mafic xenoliths and composition of the granitoid xenoliths. (author)
[en] Pyrogenic carbon constitutes a significant portion of organic carbon in soils of the planet, and in some soils its share raises to 30%. The charcoal-rich archives of forest paleofires are often localized in the geomorphological traps that reveal numerous profiles of pyrogenic soils buried due to the repeated post-fire episodes of erosion and accumulation. The paleokarst and active karst landscapes provide a unique matrix that records pyrogenic and depositional events of the past at the local scale. Polypyrocyclical Podzols of the karst landscapes at the north of the Arkhangelsk region (Russia) are the objects of this study. The fields of closed karst funnels (n x 10 m in diameter, 1–5 m elevation difference) demonstrate accumulative and denudation models of soil formation that are realized at the close distance with the pyrogenic soil archives of the bottoms, slopes and high flat sides of the funnels complementary to each other. This regular grid of archives contains information on pyrogenic events and stages of soil formation throughout the Holocene. We report and discuss here 42 radiocarbon dates (AMS) obtained both for the charcoal material and the total organic carbon (TOC) of the soil organic matter. The 14C age (conventional) of charcoal from the lowest horizons was as old as 9115±30 BP - 8770±30 BP, and the charcoal material of the top pyrogenic horizons was as young as 325±20 BP - 45±20 BP. The 14C age of the soil TOC was in general younger than the age of charcoal enclosed in this soil material. We combine the study of soil horizons morphology and stratigraphy with the set of 14C data to experiment with the several age-depth models explaining post-pyrogenic sedimentation rates on various geomorphological elements of the karst landscape. This study is supported by the Russian Foundation for Basic Research, Project No. 19-29-05238.
[en] While uncertainty is ubiquitous in medical practice, minimal work to date has been performed to analyze the cause and effect relationship between uncertainty and patient outcomes. In medical imaging practice, uncertainty in the radiology report has been well documented to be a source of clinician dissatisfaction. Before one can effectively create intervention strategies aimed at reducing uncertainty, it must first be better understood through context- and user-specific analysis. One strategy for accomplishing this task is to characterize the source of uncertainty and create user-specific uncertainty profiles which take into account a number of provider-specific variables which may contribute to report uncertainty. The resulting data can in turn be used to create real-time report uncertainty metrics aimed at providing uncertainty analytics at the point of care, for the combined purposes of decision support, improved communication, and enhanced clinical/economic outcomes.