Search results for "paleomagnetism"
showing 10 items of 22 documents
Volcanological evolution of Pantelleria Island (Strait of Sicily) peralkaline volcano: a review
2022
International audience; Pantelleria volcano has a particularly intriguing evolutionary history intimately related to the peralkaline composition of its explosively erupted magmas. Due to the stratigraphic complexity, studies over the last two decades have explored either only the pre-Green Tuff ignimbrite volcanism or the post-Green Tuff activity. We here focus on the whole evolutionary history, detailing the achievements since the first pioneering studies, in order to illustrate how the adoption and integration of progressively more accurate methods (40 Ar/ 39 Ar, paleomagnetism, petrography, and detailed field study) have provided many important independent answers to unresolved questions…
Palaeomagnetic investigations in the Hercynian mountain belt of central Europe
1983
Abstract The palaeomagnetism of sediments and volcanics of Middle Devonian to Early Carboniferous age has been studied in the Hercynian realm of the Vosges, Harz and Franconian Forest (France and Germany). After appropriate cleaning, characteristic directions of natural remanent magnetization (NRM) have been determined, which are considered to be of pretectonic origin according to rock magnetic and structural geological evidence. A mean palaeopole for the Devonian rocks in the areas investigated was determined at — 29.7°N and 9.0°E. The site latitude derived from the Devonian rocks agrees very well with that observed in Great Britain and Britanny. The significant difference in longitude bet…
First Early Pliocene micromammal faunas from Venta del Moro (Cabriel Basin, Spain) : new data on the Messinian dispersal of Debruijnimys
2021
The localities of La Bullana 3 and LA Bullana 2B (Valencia, E Spain) have yielded remains of Apodemusgorafensis, Paraethomys aff. abaigari, Stephanomys dubari, Apocricetus barrierei, Sciuridae indet. and Asoriculus cf. gibberodon the former, and Apodemusgorafensis, Paraethomys aff. abaigari, Stephanomys dubari, Apocricetus barrierei, Sciuridae indet., Asoriculus cf. gibberodon, Castillomysgracilis, Occitanomysbrailloni, Occitanomys sp., Paraethomys meini, Ruscinomys sp., Eliomys intermedius, Debruijnimys cf. julii and Atlantoxerussp. the latter. Based on the study of these micromammal assemblages, we propose an Early Pliocene age (MN14) for both sites. The pres-ence a gerbilid related to De…
Chemostratigraphy, magnetostratigraphy, chronology, palaeoenvironments and correlations.
2013
4 pages
Palaeomagnetic results from the late Precambrian Chela Group of southwest Angola
1992
Abstract Palaeomagnetic results from fourteen sites (56 samples) in the late Precambrian Chela Group of southwest Angola are reported. After alternating field demagnetization eight of the sites have mean directions closely grouped around D = 123°, I = −44 1 2 ° ; the dispersion of these directions increases substantially after tectonic corrections suggesting magnetic overprinting. Intensive thermal demagnetization proved more effective than alternating field demagnetization in resolving magnetic components. After removal of viscous components, samples from five sites (Group I) show a single component, similar to that observed after alternating field demagnetization. At four more sites (Grou…
Cesi, an early Middle Pleistocene site in the Colfiorito Basin (Umbro-Marchean Apennine), central Italy
1997
Near the village of Cesi, at the head of the Chienti River, in the Colfiorito Basin (Umbro-Marchean Apennines, central Italy), fluvio-lacustrine deposits have yielded mammal fossil remains. The results of a multidisciplinary investigation indicate that the vertebrate-bearing sediments date about 700 ka and accordingly provide a fossil assemblage for the Middle–Late Galerian. Palynological investigations carried out from sediments underlying the fossiliferous level suggest predominantly cold and dry conditions, whereas the fauna suggests a slight climatic amelioration towards cool and moist conditions in the uppermost part of the sequence. © 1997 John Wiley & Sons, Ltd.
Successes and failures in geodynamics
2001
Abstract The evolution of Earth models is reviewed and the open questions and problems are highlighted. Generally, evolution of science was not linear, but proceeded in “steps” of paradigms; where old ones remained within useful limits. “Geodynamic hypotheses”, while embedded into the general concepts of space and time, were often mutually exclusive and competing until the 1900s. Wegener's concept of continental drift was the first successful globally unifying view, but it was discarded by most Earth scientists. The “real” change of paradigms did not come before mid-century through geophysical observations in paleomagnetism, seismology, bathymetry, seafloor geology and dating, leading to th…
First Early Permian Paleomagnetic Pole for the Yili Block and its Implications for Late Paleozoic Postorogenic Kinematic Evolution of the SW Central …
2018
International audience; We conducted a paleomagnetic study on the Early Permian volcanic and sedimentary rocks, and the Neoproterozoic mafic dikes in the Yili Block, NW China. Magnetite and hematite were proven to be the principal magnetic remanence carriers. Demagnetizations revealed stable characteristic remanence magnetizations with a sole reversed magnetic polarity. The magnetic remanence of only the Early Permian strata turned out to be primary based on positive fold tests; meanwhile, the magnetic remanence age of the mafic dikes is ambiguous. Accordingly, the first Early Permian paleomagnetic pole for the Yili Block is calculated at λ = 81.5°N, φ = 256.5°E, N = 11, and A95 = 10.9°. Co…
La cueva de El Sidrón (Borines, Piloña, Asturias): primeros resultados
2003
Se exponen los resultados preliminares de las excavaciones arqueológicas llevadas a cabo en la Cueva de El Sidrón entre 2000 y 2002, de acuerdo con los tres objetivos principales que conciernen al registro fósil humano: las características antropológicas, cómo y cuándo llegaron allí y la relación entre fósiles y cultura. Las primeras conclusiones obtenidas son que los restos humanos pertenecen al Neandertal, que el registro arqueológico corresponde a un tecno-complejo del Paleolítico Medio y que están en posición secundaria
Palaeomagnetism of the central Cuban Cretaceous Arc sequences and geodynamic implications
2009
Abstract A detailed palaeomagnetic study of Cretaceous age volcanic and sedimentary arc rocks from central Cuba has been carried out. Samples from 32 sites (12 localities) were subjected to detailed demagnetisation experiments. Nineteen sites from the Los Paso, Matagua, Provincial and Cabaiguan Formations yielded high unblocking temperature, dual polarity directions of magnetisation which pass the fold tests with confidence levels of 95% or more and are considered to be primary in origin. The palaeomagnetic inclinations are equivalent to palaeolatitudes of 9°N for the Aptian, 18°N for the Albian. A synfolding remanence identified in 5 sites from the younger Hilario Formation indicates a lat…