New paleomagnetic and paleointensity data from Pliocene lava flows from the Lesser Caucasus |
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| Institution: | 1. Departamento de Física, EPS, Universidad de Burgos, c/Francisco de Vitoria, s/n, 09006 Burgos, Spain;2. Laboratorio Interinstitucional de Magnetismo Natural, UNAM, Campus Morelia 58098, Mexico;3. Caucasus International University, Chargali St. 63, 380192 Tbilisi, Georgia;4. Alexandre Janelidze Institute of Geology – I. Javakhishvili Tbilisi State University, Tbilisi, Georgia;1. Department of Earth Sciences, Chiba University, 1-33 Yayoi, Inage, Chiba 263-8522, Japan;2. Department of Earth Sciences, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan;1. Department of Planetology, Kobe University, Kobe, 657-8501, Japan;2. Research Fellow of the Japan Society for the Promotion of Science (PD), Japan;3. Research Center for Inland Seas, Kobe University, Kobe, 657-8501, Japan;4. Research Centre for Palaeoclimatology, Ritsumeikan University, Kusatsu, 525-8577, Japan;5. Institute of Natural and Environmental Sciences, University of Hyogo, Sanda, 669-1546, Japan;1. Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011, PR China;2. Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China;3. Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, School of Space Science and Physics, Shandong University at Weihai, Weihai 264209, PR China;4. University of Chinese Academy of Sciences, Beijing 100049, PR China;1. Institute of Geophysics, ETH Zurich, Rämistr. 101, CH-8092 Zurich, Switzerland;2. University Fribourg, Av. Europe 20, CH-1700 Fribourg, Switzerland;1. Don State Technical University. 1, Gagarin Square, Rostov-upon-Don, 344000, Russia;2. Bryansk State Technical University. 7, 50th October Anniversary Avenue, Bryansk, 241035, Russia |
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| Abstract: | A paleomagnetic, rock-magnetic and paleointensity study has been carried out on 14 basaltic lava flows from two Pliocene (K–Ar age between 3.09 ± 0.10 Ma and 4.00 ± 0.15 Ma) sequences (Apnia and Korxi) from the eastern Djhavakheti Highland in southern Georgia (Caucasus).Measurement of strong-field magnetisation versus temperature curves yielded three types of thermomagnetic curves: (i) Reversible curves with magnetite as only remanence carrier (type H); (ii) irreversible curves with magnetite as only carrier of remanence (type H−) and (iii) irreversible curves showing a low Curie-temperature phase and magnetite (type L). Analysis of hysteresis curves showed that samples were characterised by a mixture of single-domain and multi-domain grains.Paleomagnetic experiments allowed determining characteristic components for all flows and normal polarities (6 flows), reversed polarities (7 flows) and intermediate polarities (1 flow) were observed.. Paleomagnetic poles were calculated using only those sites unequivocally showing normal or reversed polarities. The paleomagnetic pole obtained from flows of both combined sequences (latitude λ = 77.9°N, longitude ϕ = 152.1°E, n = 13, A95 = 11.8°, k = 13.4) showed a good agreement with the 5 Ma window of the European synthetic apparent polar wander path of Besse and Courtillot (2002). The paleomagnetic direction of the combined Apnia-Korxi flows agrees well with the expected one, showing no significant tectonic rotation. The latter cannot be however, completely excluded in the Korxi section. In that section, analysis of the angular dispersion of virtual geomagnetic poles yields a much higher value than expected.Paleointensity experiments using the Coe method were performed on 31 specimens from 10 flows. After application of specific selection criteria, 19 samples from 8 flows were observed to provide successful determinations, with mean flow values showing a wide scatter. If only flows with more than one successful paleointensity determination are taken into account, virtual dipole moments (VDMs) vary between 3.5 × 1022 A m2 and 8.3 × 1022 A m2. In intermediate polarity site AP2 no weak transitional paleostrength values were observed. |
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| Keywords: | Paleomagnetism paleointensity Caucasus Pliocene |
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