The Early Cretaceous mass-occurrence of Olcostephanus (Olcostephanus) guebhardi morph. querolensis BULOT from the Late Valanginian Saynoceras verrucosum Zone of the KB1-A section, Ternberg Nappe, the Northern Calcareous Alps (Upper Austria) is described. This horizon, spanning an interval of almost 3 metres, is interpreted as a long-term accumulation from the water column combined with temporary redeposition from local submarine highs. The fauna of the Olcostephanus horizon is composed of nine genera and ten species. The Olcostephanus mass-occurrence represents a widespread phenomenon. It appears most commonly at oceanographic elevations where olcostephanid shells accumulated on the sea-floor during see-level highs.
