Palaeomagnetic and rock-magnetic study of a Pliocene volcanic section in southern Georgia (Caucasus)

Abstract

Twenty-six basaltic flows were sampled for a paleomagnetic and rock-magnetic study of the Tchuntchka section in the Akhalkalaki volcanic region in southern Georgia (Caucasus). Three to five samples from each flow were subjected to thermal or alternating-field demagnetization. The upper part of the section yields normal (D = 355.5°, I=54.2°,N= 17, α95=2.5°, k=226),and the lower part reversed polarity directions (D= 180.3°, l= - 59.4,° N = 8, α95 = 4.8°, k = 135). An anomalous direction was found in one flow in the upper part (D = 118.5°, I = - 77.3°). Rock-magnetic experiments show that the remanence is carried in most cases by magnetite or low-Ti titanomagnetite. The fraction of grains with a multidomain magnetic structure does not seem to be important. The remanence carried by such grains is removed only partly by low-temperature demagnetization. A tentative magnetostratigraphic correlation between the 3.8-Ma-old Thoki and Tchuntchka sites is proposed.