3 resultados para URANIUM DIOXIDES
em Acceda, el repositorio institucional de la Universidad de Las Palmas de Gran Canaria. España
Resumo:
[EN] The emergent marine deposits of the Mediterranean basin have been recognized as an important record of Quaternary sea level history for more than a century. Previous workers identified what have been interpreted to be two separate high stands of sea in the late Quaternary, namely the "Eutyrrhenian" (thought to be ~ 120 ka) and the "Neotyrrhenian" (thought to be either ~ 100 ka or ~ 80 ka). On Mallorca, Spain, both of these named deposits lie close to present sea level, implying paleo-sea levels slightly above present during both marine isotope stages (MIS) 5.5/5e and either 5.3/5c or 5.1/5a. If these interpretations are correct, they conflict, at least in part, with sea level records from far-field localities.
Resumo:
[EN]We present the first U-series ages of corals from emergent marine deposits on the Canary Islands. Deposits at +. 20. m are 481 ± 39 ka, possibly correlative to marine isotope stage (or MIS) 11, while those at +. 12 and +. 8. m are 120.5 ± 0.8. ka and 130.2 ± 0.8. ka, respectively, correlative to MIS 5.5. The age, elevations, and uplift rates derived from MIS 5.5 deposits on the Canary Islands allow calculations of hypothetical palaeo-sea levels during the MIS 11 high sea stand. Estimates indicate that the MIS 11 high sea stand likely was at least +. 9. m (relative to present sea level) and could have been as high as +. 24. m.
Resumo:
[EN] The last 5 Myr are characterized by cliamatic variations globally and are reflected in ancient fossiliferous marine deposits visible in the Canary Islands. The fossils contained are identificated as paleoecological and paleoclimatic indicators. The Mio-Pliocene Transit is represented by the coral Siderastrea micoenica Osasco, 1897; the gastropods Rothpletzia rudista Simonelli, 1890; Ancilla glandiformis (Lamarck, 1822); Strombus coronatus Defrance, 1827 and Nerita emiliana Mayer, 1872 and the bivalve Gryphaea virleti Deshayes, 1832 as most characteristic fossils and typical of a very warm climate and littoral zone. Associated lava flows have been dated radiometrically and provides a range between 8.9 and about 4.2 Kyr. In the mid-Pleistocene, about 400,000 years ago, the called Marine Isotope Stage 11, a strong global warming that caused a sea level rise happens. Remains of the MIS 11 are preserved on the coast of Arucas (Gran Canaria), and associated with a tsunami in Piedra Alta (Lanzarote). These fossilifeorus deposits contains the bivalve Saccostrea cucullata (Born, 1780), the gastropod Purpurellus gambiensis (Reeve, 1845) and the corals Madracis pharensis (Heller, 1868) and Dendrophyllia cornigera (Lamarck, 1816). Both sites have been dated by K-Ar on pillow lavas (approximately 420,000 years) and by Uranium Series on corals (about 481,000 years) respectively. The upper Pleistocene starts with another strong global warming known as the last interglacial or marine isotope stage (MIS) 5.5, about 125,000 years ago, which also left marine fossil deposits exposed in parallel to current in Igueste of San Andrés (Tenerife), El Altillo, the city of Las Palmas de Gran Canaria and Maspalomas (Gran Canaria), Matas Blancas, the Playitas and Morrojable (Fuerteventura ) and in Playa Blanca and Punta Penedo (Lanzarote ). The fossil coral Siderastrea radians (Pallas , 1766 ) currently living in the Cape Verde Islands , the Gulf of Guinea and the Caribbean has allowed Uranium series dating. The gastropods Strombus bubonius Lamarck, 1822 and Harpa doris (Röding , 1798 ) currently living in the Gulf of Guinea. Current biogeography using synoptic data obtained through satellites provided by the ISS Canary Seas provides data of Ocean Surface Temperature (SST) and Chlorophyll a (Chlor a) . This has allowed the estimation of these sea conditions during interglacials compared to today .