THE AGE OF VOLCANIC SEQUENCE IN THE MIDDLE PALEOZOIC DEPOSITS OF SOUTHERN MONGOLIA

Recent finds of conodonts indicate that the volcanogenic sequence in t he Gobi Altai-Suhe Bater Zone of southern Mongolia (the Gobi Altai For mation in the Dzhinsetu Ulul Range area and the Minzhin Formation in t he Mandal Obo area), earlier regarded as barren of fossils, was formed in the interval between the Givetian of the Middle Devonian and the e arly Fammennian of the Late Devonian. The ratio of effusive and volcan iclastic rocks in the studied sections suggests that centers of volcan ism moved from east to west during the indicated period.