The Upper Cretaceous Abtalkh Formation of the Kopet-DaghBasin (northeastern Iran) was studied in four stratigraphic sections (Bahadorkhan, Hammam Galeh, Type section and Shorab). All sections display limestones, shales and calcareous shales. The Bahadorkhan section is approximately 480 m thick. We identified 32 planktonic foraminifera species belonging to 13 genera in 6 biozones:1.Dicarinella asymetricaTotalRangeZone,2.Globotruncanita elevataPartialRangeZone,3.Contusotruncana plummerae Interval Zone, 4. Radotruncana calcarata Total Range Zone, 5. Globotruncanella havanensis Partial Range Zone and Globotruncana aegyptiaca Interval Zone. Based on foraminiferal biostratigraphy, the Bahadorkhan section was dated to the latest Santonian to late Campanian.Thisstudyidentifies11generaand25speciesofplanktonicforaminiferainthe1500mthickHammamGalehsection,spanning 7 biozones: 1. Dicarinella asymetrica Total Range Zone, 2. Globotruncanita elevata Partial Range Zone, 3. Contusotruncana plummerae Interval Zone, 4. Radotruncana calcarata Total Range Zone, 5. Globotruncanella havanensis Partial Range Zone, 6. Globotruncana aegyptiacaIntervalZone,7.Gansserina gansseriIntervalZone.LatestSantoniantolateCampanianageshavebeenestablishedfortheAbtalkhFormation.ThetypelocalityoftheAbtalkhFormationis750mthickandcontains31planktonicforaminiferal speciesbelongingto12genera.Basedonthisfossilcontent,weidentified6biozones. TheageoftheformationisestimatedtobethelatestSantoniantolateCampanian,asfortheBahadorkhantypesection.TheShorabsectionoftheAbtalkhFormationis990mthick.Inthis section, 19 species belonging to 10 genera were identified, as were 5 biozones: 1. Globotruncanita elevata Partial Range Zone, 2. Contusotruncana plummerae Interval Zone, 3. Radotruncana calcarata Total Range Zone, 4. Globotruncanella havanensis Partial Range Zone, 5. Globotruncana aegyptiaca Interval Zone. Based on this fossil assemblage, the Shorab section dates to the early to late Campanian.

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