CONODONTS FROM THE TSAGAANHAALGA FORMATION (EMSIAN?-EIFELIAN) AND THE TENTACULITE MEMBER OF THE GOVIALTAI FORMATION (EIFELIAN-GIVETIAN), TSAKHIR WELL SECTION, GOVI ALTAI TERRANE, SOUTHERN MONGOLIA

In the Govi Altai Terrane, Tsakhir Well section, the lower portion of the Tsagaanhaalga Formation, consisting of thin to medium bedded biowackestones and biopackstones, yielded moderately well preserved icriodids. These taxa have been identified, but not figured, by other workers and associated with the Eifelian costatus Zone. The icriodids are similar to a fauna reported from the Emsian of southern Siberia. Other Emsian conodonts have been described from the Chuluun Formation, which underlies the Tsagaanhaalga Formation, overlying strata in the Tsagaanhaalga Formation have been assigned to the partitus Zone – lowest Eifelian based on the occurrence of Polygnathus costatus partitus.

Thin carbonate beds and concretions within the dark shale dominated Govialtai Formation yielded Polygnathus ensensis, Polygnathus linguiformis klapperi, Polygnathus timorensis, and Latericriodus sp. indicative of the lower Givetian timorensis Zone. The cosmopolitan nature of the conodont fauna indicates the Govi Altai Terrane was in the tropical belt with open communication to other regions in the Paleo-Tethys Ocean during the lower Givetian.