![]() | Some characteristics of the rift valley in the atlantic ocean near 36°48' north Auteur(s) : Needham, H.d. Francheteau, Jean Éditeur(s) : North-Holland Publishing Company Résumé : The Rift Valley between 36° 42'N and 36° 55'N in the Atlantic Ocean is 31 km wide, with half-widths of 12 and 19 km for the western and eastern sides respectively. Both outer edges of the Rift Valley stand about 1500 m above an Inner Floor where very fresh pillow lavas occur. The Inner Floor probably includes the locus of new crust ; and its bordering slopes, which are particularly well-defined on the western side, limit to less than about 2.5 km the width of the zone over which new crust may have evolved with little or no vertical displacement. The width of the locus of new crust may be less than 0.5 km between 36° 45'N and 36° 47'N, where the deepest slopes of the Rift Valley walls nearly merge. Near 36° 50'N, the Inner Floor accommodates an approximately 1 km wide, 4 km long Central High, with a height of up to 250 m. In this area, the locus of new crust may also occupy a very narrow zone ; it may lie either along the Central High or along a trough flanking the Central High. The magnetic anomaly pattern indicates that, since the beginning of the Brunhes epoch (6.9 X 10(5) yr B.P.), the eastern limb has grown approximately twice as fast as the western limb. Using extrapolated spreading rates, the ages of the outer edges of the Rift Valley are 1.3 and 1.7 m.y. for the eastern and western sides respectively. Comparison with data for the Rift Valley in other parts of the ocean further suggests that the residence time of new crust in the Rift Valley is about 1.5 m.y. Uplift of crust from the Inner Floor, which may be dominated by lithospheric thickening, may thus be primarily a function of age. [NOT CONTROLLED OCR] Earth and Planetary Science Letters (North-Holland Publishing Company), 1974 , Vol. 22 , P. 29-43 Droits : North-Holland Publishing Company, Amsterdam http://archimer.ifremer.fr/doc/1974/publication-5159.pdf http://archimer.ifremer.fr/doc/00000/5159/ | Partager |
![]() | Marginal fracture zones as Structural framework of continental margins in south atlantic ocean Auteur(s) : Francheteau, Jean Le Pichon, Xavier Éditeur(s) : The American Asscoiation of Petroleum Geologists Résumé : A plate tectonic model of the early opening of the south atlantic is used to des cibe the structural framework of the continental margins and adjacent oceanic and coastal areas on both sides of the ocean. It is proposed that major offsets of the continental margins necessarily induce the subsidence of coastal basins where fracture zones intersect the continents. The configuration of the accreting plate-margin boundary gradually developed throughout the opening of the ocean after Late Jurassic time. [NOT CONTROLLED OCR] The American Asscoiation of Petroleum Geologists Bulletin (The American Asscoiation of Petroleum Geologists), 1972 , Vol. 56 , N. 6 , P. 991-1007 Droits : The American Asscoiation of Petroleum Geologists http://archimer.ifremer.fr/doc/1972/publication-5033.pdf http://archimer.ifremer.fr/doc/00000/5033/ | Partager |
![]() | Les colonies pendant la Révolution : la Constituante et la réforme coloniale Auteur(s) : Deschamps, Léon (1849-19..) Année de publication : Éditeur(s) : Paris : Perrin Description : Dans son introduction, cet ouvrage prétend combler la lacune concernant l'histoire de la Constituante dans les colonies françaises. L'auteur s'est pour cela aidé de nombreuses sources dont il présente une bibliographie. Durant cette période, les idées de liberté et d'égalité en droite ligne de 1789 sont mis en application, et ce, bien que de manière plus tardive et différente dans les colonies françaises. Ces nouvelles réformes politiques, économiques, commerciales, administratives... ne sont pas sans conséquences sociales et créent de nombreux troubles et agitations voir même guerre civile. Il termine finalement en proposant une analyse critique des actions de la Constituante dans les colonies. Siècle(s) traité(s) : 18 Droits : Domaine public Provenance : Collectivité territoriale de Guyane. Bibliothèque Alexandre-Franconie Permalien : http://www.manioc.org/patrimon/HASH5184fd4ff9063df686784e HASH5184fd4ff9063df686784e | Partager |