Vegetation responses to rapid climatic changes during the last deglaciation 13,500-8,000 years ago on southwest Andoya, arctic Norway

The late-glacial vegetation development in northern Norway in response to climate changes during the Allerod, Younger Dryas (YD), and the transition to the Holocene is poorly known. Here we present a high-resolution record of floral and vegetation changes at lake Lusvatnet, south-west Andoya, between 13500 and 8000 cal b.p. Plant macrofossil and pollen analyses were done on the same sediment core and the proxy records follow each other very closely. The core has also been analyzed using an ITRAX XRF scanner in order to check the sediment sequence for disturbances or hiatuses. The core has a good radiocarbon-based chronology. The Saksunarvatn tephra fits very well chronostratigraphically. During both the Allerod and the Younger Dryas time-periods arctic vegetation prevailed, dominated by Salix polaris associated with many typically arctic herbs such as Saxifraga cespitosa, Saxifraga rivularis and Oxyria digyna. Both periods were cold and dry. Between 12450 and 12250 cal b.p. during the Younger Dryas chronozone, the assemblage changed, particularly in the increased abundance of Papaver sect. Scapiflora and other high-Arctic herbs, suggesting the development of polar desert vegetation mainly as a response to increased aridity. After 11520 cal b.p. a gradually warmer and more oceanic climate initiated a succession to dwarf-shrub vegetation and the establishment of Betula woodland after 1,000 years at c. 10520 cal b.p. The overall late-glacial aridity contrasts with oceanic conditions in southern Norway and is probably related to sea-ice extent.

Timing and climate forcing of volcanic eruptions for the past 2,500 years

Volcanic eruptions contribute to climate variability, but quantifying these contributions has been limited by inconsistencies in the timing of atmospheric volcanic aerosol loading determined from ice cores and subsequent cooling from climate proxies such as tree rings. Here we resolve these inconsistencies and show that large eruptions in the tropics and high latitudes were primary drivers of interannual-to-decadal temperature variability in the Northern Hemisphere during the past 2,500 years. Our results are based on new records of atmospheric aerosol loading developed from high-resolution, multi-parameter measurements from an array of Greenland and Antarctic ice cores as well as distinctive age markers to constrain chronologies. Overall, cooling was proportional to the magnitude of volcanic forcing and persisted for up to ten years after some of the largest eruptive episodes. Our revised timescale more firmly implicates volcanic eruptions as catalysts in the major sixth-century pandemics, famines, and socioeconomic disruptions in Eurasia and Mesoamerica while allowing multi-millennium quantification of climate response to volcanic forcing.

500 años de evangelización en América: Aportes para la reflexión

La conmemoración de los "500 años de descubrimiento del América", ha provocado un serio debate de ideas del mÁs variado signo, que tocan de lleno el rol que la lglesia ha venido desempeñando a Io largo de 500 años de evangelizacíón en eI Continente. Así, hay quienes ven en la acción eclesial, la causa histórica de la desestructuración total del mundo indígena, el principio de la explotación y de Ia alíenación cultural, perspectiva propia de organizacíones indlgenas y cientistas sociales. Frente a ella, desde una visión apologética y triunfalista, otros se niegan a ver el conjunto de luces y sombras que arroja la historía y entrever siquiera la enorme complejidad del problema. A este cuadro hay que sumar el punto de vista oficial de los gobiernos empeñados en festejar el V Centenario de un "encuento de dos mundos", dejando a un lado el drama de pueblos desaparecídos y tratados sin igualdad de condiciones.

7-3-20, course de côte d'Argenteuil [motocyclisme], Péan sur Peugeot [500 cmc] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 58371

500 cm3, Naas sur A.B.C. [critérium motocycliste de l'A.A.M.M., Association des anciens motocyclistes militaires à Auxerre, le 24 mai 1920] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 59359

500 cm3, Barthelemy sur Norton [critérium motocycliste de l'A.A.M.M., Association des anciens motocyclistes militaires à Auxerre, le 24 mai 1920] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 59362

500 cm3, Bonnefond sur Rover [critérium motocycliste de l'A.A.M.M., Association des anciens motocyclistes militaires à Auxerre, le 24 mai 1920] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 59365

500 cm3, Moret sur Blériot, Brunet sur Blériot, Pernette sur Blériot [critérium motocycliste de l'A.A.M.M., Association des anciens motocyclistes militaires à Auxerre, le 24 mai 1920] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 59367

Arrêt du Conseil d'Etat qui proroge jusqu'au 8 décembre 1713, le payement des billets des cautions de François Fontaine, pendant lequel temps, fait Sa Majesté défenses à tous huissiers et sergents de faire aucunes poursuites contre lesdites cautions, à peine de nullité, cassation de procédure, et de 500 l. d'amende

[Acte. 1712-12-13. Versailles]