Magnetic dating of the Holocene monogenetic Tkarsheti volcano in the Kazbeki region (Great Caucasus)

The radiocarbon technique is widely used to date Late Pleistocene and Holocene lava flows. The significant difference with palaeomagnetic methods is that the 14C dating is performed on the organic matter carbonized by the rock formation or the paleosols found within or below the lava flow. On the contrary, the archaeomagnetic dating allows to date the moment when the lava is cooling down below the Curie temperatures. In the present study, we use the paleomagnetic dating to constrain the age of the Tkarsheti monogenetic volcano located within the Kazbeki Volcanic Province (Great Caucasus). A series of rock-magnetic experiments including the measurement of hysteresis curves, isothermal remanence, back-field and continuous thermomagnetic curves were applied. These experiments indicated that Pseudo-Single-Domain Ti-poor titanomagnetite is responsible for remanence. A characteristic remanent magnetization was obtained for all twenty analyzed samples yielding a stable single magnetization component observed upon both thermal and alternating field treatments. Comparison of the mean directions obtained (Inc = 48.6º, Dec = 6.4º, A95 = 4.0° and K = 67) with the SCHA.DIF.14k model yielded two main time intervals (4740–4650 or 4427– 4188 BC) as the best age estimate of the Lesser Tkarsheti lava flow. These results suggest an earlier age (between approximately 200 and 700 years) for this monogenetic lava flow than expected from the estimated age provided by a former 14C dating obtained in 1973 on woody remains. This first attempt to use the archaeomagnetic technique in the Caucasus indicates that the SCHA.DIF.14k geomagnetic model may be successfully used for dating purposes in the region.Projects BU0066U16 and BU235P18 (Junta de Castilla y Leon, Spain) and the European Regional Development Fund (ERDF). AG is grateful for financial support of CONACyT 252149 and UNAM-PAPIIT project 101717. MC-R and AC acknowledge the financial support given by the Junta de Castilla y León (project BU235P18) and the European Regional Development Fund (ERD)

Tectonic control over the abuli samsari volcanic ridge, lesser caucasus, Georgia

The purpose of the present work is to integrate previous research focused on the Abuli Samsari Volcanic Ridge, situated in the Javakheti Highland, Georgia. Through a synergic approach, consisting in the collection and analysis of field and satellite data, combined with the results of previously published research, we have been able to define the overall structure of the volcanic ridge, which, on its northern sector, is cut across by two parallel pipelines, carrying oil and gas from the Caspian Sea to the western countries. Despite the likelihood of seismic or volcanic events in the area, geohazard assessment had never been adequately performed for this section of the pipelines’ route across Southern Georgia. The most relevant outcomes of our effort, aimed at filling this critical gap, consist in: the identification and mapping of eruptive centers and tectonic lineaments; the reconstruction of magma pathways; the definition of the expected moment magnitude for possible earthquakes; the assessment of orientation of the maximum horizontal stress from the Late Miocene to the present day. We have used these results to evaluate the current seismic and volcanic hazards affecting the Abuli Samsari Volcanic Ridge, which may have major impacts on the security of the pipelines. The calculated, about N-S directed maximum horizontal stress may play a key role in volcanic reactivation, which might occur in the form of fissure eruptions and the formation of new vents and monogenetic as well as composite volcanoes. As the track of the pipelines lies just north of the younger volcanic edifice in the ridge we suggest that these lifelines could be severely affected by possible future volcanic eruptions, which might bring about a major interruption in oil delivery from the Caspian Sea towards the west