The History of Formation of Pliocen-Quaternary Valley Lava Rivers in the Northeast Part of the Javakheti Volcanic Highland (Lesser Caucasus)

The article presents new results of geological-stratigraphic and isotope-geochronological study of young lavas in the northeast part of the Javakheti Highland (Lesser Caucasus, Republic of Georgia). A valley lava river (Algeti flow) with a complex structure and total length about 55 km was described for the first time (no information about this valley lava river was previously published in the scientific literature). It was shown that a young magmatism in the northeast of the Javakheti area developed in the time interval of 3.2–1.5 Ma. Its early phase (3.19 ± 0.10 Ma) was marked by the formation of the longest (up to 100 km) valley lava river (Khrami flow), composed of basalts, among the similar geological objects known in the Lesser Caucasus. Subsequently (2.7–2.5 Ma), the continuation of eruptions led to the formation of extensive lava plateaus in the region (Tsalka, Gomareti and others). The formation of the Algeti valley lava river (Algeti flow), composed of basaltoids, began from the end of Piacenzian and continued over ~1 m.y. until the beginning of Gelasian (2.7–2.0 Ma) as a result of the activity of volcanoes in the northern part of the Javakheti Range. The final stage of formation (1.9–1.5 Ma) of Algeti flow was likely associated with eruptions of volcanic cones near Tabatskuri Lake. The obtained data, along with the reconstruction of the history of young magmatism, made it possible to follow the main features in the formation of modern relief and the river valley system in the considered part of the Lesser Caucasus.