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Magnetism of Volcanic Materials-Tribute to Works of Michel Prevot
Auteur(s) : Goguitchaichvili, A. Rathert, M. C. Camps, Pierre
Auteurs secondaires : Laboratorio Interinstitucional de Magnetismo Natural, Instituto Geofísica, Universidad Nacional Autónoma de México ; Université du Québec Departamento de Física [Burgos] ; Universidad de Burgos Géosciences Montpellier ; Université des Antilles et de la Guyane (UAG) - Institut national des sciences de l'Univers (INSU - CNRS) - Université de Montpellier (UM) - Centre National de la Recherche Scientifique (CNRS)

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Gilbert-Gauss geomagnetic reversal recorded in Pliocene volcanic sequences from Georgia (Lesser Caucasus): revisited
Auteur(s) : Goguitchaichvili, A. Cervantes, M. A. Rathert, M. C. Camps, Pierre Sologashvili, J. Maissuradze, G.
Auteurs secondaires : Laboratorio Interinstitucional de Magnetismo Natural, Instituto Geofísica, Universidad Nacional Autónoma de México ; Université du Québec Departamento de Física [Burgos] ; Universidad de Burgos Géosciences Montpellier ; Université des Antilles et de la Guyane (UAG) - Institut national des sciences de l'Univers (INSU - CNRS) - Université de Montpellier (UM) - Centre National de la Recherche Scientifique (CNRS) Tbilisi State University, Tbilisi nstitute of Geology, Tbilisi ; Université du Québec

Éditeur(s) : HAL CCSD Springer/Terra Scientific Publishing Company
Résumé : International audience
We carried out a detailed paleomagnetic, rock-magnetic, and Thellier paleointensity study of all similar to 3.6 My Pliocene lava flow succession in southern Georgia. An earlier study (Camps et al., 1996) revealed that several consecutive lava flows record an intermediate polarity direction at the base of the section followed by a thick reverse polarity zone. The transitional field was interpreted as an excursion within chron 2Ar or all upper Cochiti-Gilbert reversal. New paleomagnetic data reported here have been obtained from nearby lava successions. In total, about 170 standard paleomagnetic cores belonging to 22 lava flows were collected during the 2005 sample collection campaign. Rock-magnetic experiments showed that the remanence is carried by Ti-poor titanomagnetite in most of the samples. The fraction of grains with multidomain magnetic structure does not seem to be important. Characteristic remanent magnetization was successfully determined oil all samples. The direct correlation with the original (Thoki) sequence, previous preliminary measurements of natural remanent magnetization (Sologashvili, 1986), and field observations allowed us to establish a new magnetic stratigraphy. The lower part of section is characterized by intermediate magnetic polarity followed by thick reversely magnetized lavas. The upper sequence, represented by 18 consecutive flows yielded normal magnetic polarity. The mean paleointensity of the intermediate field is drastically reduced with respect to the post-transitional field strength. Based on all available radiometric ages and new paleomagnetic data, it may be speculated that Gilbert-Gauss (R-N) reversal was recorded at the upper part of sequence. Lower intermediate polarity flows possibly represent a form of precursor of this reversal that is similar to the Matuyama-Brunhes geomagnetic transition.
ISSN: 1343-8832

hal-00413099
https://hal.archives-ouvertes.fr/hal-00413099

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