The Upper Viséan-Serpukhovian ammonoid-rich carbonates in the Dombar Hills (Aktobe Region, western Kazakhstan)
provide an exzellent opportunity to calibrate the ammonoid and conodont zonations around the base of the Serpukhovian
Stage, and are important for interregional correlation.  A section in the Dombar Hills spanning the Viséan-Serrpukhovian
boundary is measured and its fossil content is analyzed.  Two ammonoid genozones (Hypergoniatites-Ferganoceras and Uralopronorites-Cravenoceras) and two conodont zones (Lochriea nodosa and Lochriea ziegleri) are recognized.  The section displays a contact between the Hypergoniatites-Ferganoceras and Uralopronorites-Cravenoceras ammonoid
genozones in a continuous succession and an evolutionarily early appearance of the genus Cravenoceras.The base of the Serpukhovian Stage is drawn at the level of the first appearance datum (FAD) of the conodont Lochriea ziegleti, which, as in the Verkhnyaya Kardailovka section (potential GSSP candidate, South Urals, Russia) enters within the Hypergoniatites-Ferganoceras ammonoid Genozone.