The series of two papers presents a comprehensive isotope-geochronological and petrological-geochemical study of the Late Quaternary Tendurek Volcano (Eastern Turkey), one of the greatest volcanoes within the Caucasian-Eastern Anatolian segment of the Alpine foldbelt. The first article discusses the results of chronostratigraphic reconstruction and provides the main petrographic characteristics of the Tendurek's igneous rocks. The K-Ar dating results show that the magmatic activity of the Tendurek Volcano developed in the Late Pleistocene time, over the period of the last 250 thousand years. Five discrete phases (I-250-200 ka, II-200-150 ka, III-150-100 ka, IV-100-70 ka, and V-< 50 ka) of the youngest magmatism were identified in this study. The first two phases were represented by the fissure eruptions of alkaline basic lavas and subsequent formation of vast lava plateaus, the CaldA +/- ran and DogubeyazA +/- t plains. In the following phases, the intermediate and moderately-acid volcanic rocks of mildly-alkaline or alkaline series started to dominate among the eruption products. According to their petrographic characteristics, the rocks of Tendurek Volcano are assigned to the alkaline association with Na-specifics (hawaiites-mugearites-benmoreites). The available geological, isotope-geochronological, and geomorphological data suggest that the Tendurek Volcano is potentially active. Nowadays, Tendurek reaches the caldera stage of its development.