GP23A-1283
New paleomagnetic and paleointensity results from plio-pleistocene volcanic sequences from southern Georgia

Tuesday, 15 December 2015
Poster Hall (Moscone South)
Elisa María Sánchez Moreno1, Manuel Calvo-Rathert1, Avto Gogichaishvili2, Giorgi T. Vashakidze3, Vladimir A. Levedeb4, Juan Morales5, Ángel Carrancho1, Juan Jose Villalain1 and Ana Caccavari6, (1)University of Burgos, Burgos, Spain, (2)UNAM National Autonomous University of Mexico, Morelia, Mexico, (3)Ivane Javakhishvili Tbilisi State University, Alexandre Janelidze Institute of Geology, Tbilisi, Georgia, (4)Russian Academy of Sciences (IGEM – RAS), Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry, Moscow, Russia, (5)Universidad Nacional Autonoma de Mexico, Laboratorio Interinstitucional de Magnetismo Natural, Mexico City, Mexico, (6)Universidad Nacional Autonoma de Mexico, Instituto de Geofísica-Delegación Coyocan, Mexico D.F., Mexico
Abstract:
The Plio-Pleistocene volcanism in the Djavakheti Highland is characterized by a great number of consecutive lava flows of great extension and reduced thickness. These features combined with available K-Ar dates (Lebedev et al., 2008 and per. com.), provides the right context to study a reliable and constant record of the EMF. The present study was performed on 2 different volcanic sequences. The first one, Apnia is formed of 20 basaltic lava flows and the second one, Korxi, of 27 andesitic lava flows.

Paleomagnetic measurements yielded a characteristic component in all flows with normal, transitional and reverse polarities being obtained. The Apnia sequence, (3.75 ± 0.25 and 3.09 ± 0.10 My), starts with 13 reverse-polarity flows, which are followed by 2 transitional ones with 5 normal ones in the uppermost part of the section. Comparison with the expected EMF direction shows that while the direction of the reverse polarity group agrees well with the expected one, the direction of the normal polarity group shows a significant difference. The Korxi sequence is divided into two different subsequences of 17 and 10 flows separated by an erosional surface. The lower group has an age of 3.25 ± 0.25 My, and shows a succession of normal polarity flows close to the expected direction. The upper one, (1.9 ± 0.2 My), mainly displays reverse polarity flows with 3 interspersed transitional ones.

Rock magnetic measurements including thermomagnetic, IRM acquisition and hysteresis curves were performed to check the suitability of the studied rocks for paleointensity experiments.

Paleointensities were determined using three different methods: Multi-specimen, Thellier-Thellier and IZZI. The ultimate goal is to find out how paleointensity varies in relation to the observed polarity changes and anomalous directions. Using different techniques for determining the paleointensity, will also increase the reliability of determinations in cases in which an agreement in the results is observed.

Keywords: Paleomagnetism, Rock-magnetism, Paleointensity, Plio-Pleistocene lava flows, Caucasus

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