Early Cretaceous vegetation and climate change at high latitude: Palynological evidence from Isachsen Formation, Arctic Canada

Quantitative palynology of the marginal marine and deltaic-fluvial Isachsen Formation of the Sverdrup Basin, Canadian Arctic, provides insight into high latitude climate during much of the Early Cretaceous (Valanginian to early Aptian). Detrended Correspondence Analysis of main pollen and spore taxa is used to derive three ecological groupings influenced by moisture and disturbance based on the botanical affinities of palynomorphs: 1) a mixed coniferous assemblage containing both lowland and upland components; 2) a conifer-filicopsid community that likely grew in dynamic lowland habitats; and, 3) a mature dry lowland community composed of Cheirolepidiaceans. Stratigraphic changes in the relative abundance of pollen and spore taxa reflect climate variability in this polar region during the ~20 Mya history of the Isachsen Formation. The late Valanginian was relatively cool and moist and promoted lowland conifer-filicopsid communities. Warming in the Hauterivian resulted in the expansion coniferous communities in well-drained or arid hinterlands. A return to relatively cool and moist conditions in the Barremian resulted in the expansion of mixed lowland communities. This work demonstrates the utility of a multivariate statistical approach to palynology to provide insight into the composition and dynamics of ecosystems and climate of high latitude regions during the Early Cretaceous

L'Egypte et l'occupation Anglaise.

Dedication:Pagination: 651-682,890-923,169-186, 391-425, 581-605Part of a collected volume. ( Revue des Deux Mondes)Text Genre:Pros

Évolutions des tactiques rebelles et de leurs conséquences humanitaires dans les Grands lacs d'Afrique entre 1981 et 2013

Ce travail cherche à comprendre en quoi les causes de l’instabilité sécuritaire de la région des Grands Lacs sont rationnelles et interdépendantes, en dépit d’explications simplistes largement répandues (déterminisme ethnique, violence endogène, cupidité, etc.). Il s’agit donc d’identifier ces causes, pour saisir les mécanismes des conflits récurrents qui secouent la région dans notre période d’étude. Nous entendons ainsi étudier la modernité du phénomène insurrectionnel en Afrique, en nous attachant à l’analyse de ses différentes expressions dans la région des Grands Lacs, qui a hébergé de 1981 à 2013 des exemples empruntant à toutes ses évolutions contemporainesThis work seeks to understand how the causes of chronic insecurity in the Great Lakes region are both rational and interdependent, despite widespread simplistic explanations (ethnic determinism, endogenous violence, greed, etc.). We intend to identify these causes to better understand the mechanisms behind the recurring conflicts that shook the region in the period under study. In doing this, we gain greater understanding of contemporary insurrectionary practices and the evolutions of guerrilla tactics in Africa through their expression in rebel movements in the Great Lakes between 1981 and 201

Les races jaunes : les célestes

En cubierta: Bibliothèque Littéraire de Vulgarisation Scientifique. Les livres d'or de la science. Section ethnografique. Petite encyclopédie populaire illustré

Uganda

International audienc

Rape as a Weapon of War

International audienc

Responsibility to Protect (R2P)

International audienc

China and the Chinese,

Mode of access: Internet