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The Blake geomagnetic excursion recorded in a radiometrically dated speleothem

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Osete López, María Luisa and Martín Chivelet, Javier and Rossi Nieto, Carlos and Edwards, R. Lawrence and Egli, Ramon and Muñoz García, María Belén and Wang, Xianfeng and Pavón Carrasco, Francisco Javier and Heller, Friedrich (2012) The Blake geomagnetic excursion recorded in a radiometrically dated speleothem. Earth and Planetary Science Letters , 353-354 . pp. 173-181. ISSN 0012-821X

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Abstract

One of the most important developments in geomagnetism has been the recognition of polarity
excursions of the Earth’s magnetic field. Accurate timing of the excursions is a key point for
under standing the geodynamo process and for magnetostratigraphic correlation. One of the best-
known excursions is the Blake geomagnetic episode, which occurred during marine isotope stage MIS 5, but its morphology and age remain controversial. Here wes how, for the first time, the Blake excursion
recorded in a stalagmite which was dated using the uranium-series dis equilibrium techniques. The characteristic remanent magnetisation is carried by fine-grained magnetite. The eventis documented
by two reversed intervals (B1 and B2). The age of the eventis estimated to be between 116.5 ± 0.7 kyr
BP and 112.0 ± 1.9 kyr BP, slightly younger (~3–4 kyr)than recent estimations from sedimentary
records dated by astronomical tuning. Low values of relative palaeointensity during the Blake episode
are estimated, but a relative maximum in the palaeofield in tensity coeval with the complete reversal
during the B2 interval was observed. Duration of the Blake geomagnetic excursion is 4.5 kyr, two times
lower than single excursions and slightly higher than the estimated diffusion time for the inner core
(~3 kyr).


Item Type:Article
Uncontrolled Keywords:Geomagnetic excursions, Speleothems, Radioisotope, Geochronology, Palaeointensity, Rrock magnetism, Quaternary geochronology
Subjects:Sciences > Geology > Stratigraphic geology
ID Code:20089
Deposited On:22 Feb 2013 11:44
Last Modified:11 Dec 2018 08:42

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