Comprehensive lithofacies and biofacies analysis provided constraints on the origin of Upper Ordovician clastic and carbonate deposits in northeastern Gorny Altai, which form large low-elevated flat carbonate banks located relatively close to the shore. The sediments were deposited during the Sandbian and early–middle Katian stages, according to new conodont data. Upper Ordovician sections in northeastern Gorny Altai store record of two global regressions: the early Sandbian (Vollen Lowstand) and early Katian (Frognerkilen Lowstand) events.