PAN style="FONT-FAMILY: ’Times New Roman’,’serif’" lang=EN-US>Based on paleontological and geochemical characteristics of the Upper Cretaceous mudstone cuttings in wells of Saha-1 and Helit-1, located in the Tenere and Termit depressions, respectively, this paper provides evidences for marine transgression happened in the eastern Niger Basin in the Late Cretaceous. Paleontological results of cutting samples in well Saha-1 show that they contain marine microfossils. The main geochemical characteristics of these samples are high abundance of gammacerane, β-carotane and dinosteranes which are marine biomarkers. Both microfossil distribution and geochemical characteristics suggest that the Upper Cretaceous strata were deposited in a marine environment.