The marine Middle Miocene deposits from the western border of the Transylvanian Basin belong to the Gârbova de Sus Formation (Badenian), lithologically dominated by algal-bioclastic limestones. The rich and well preserved foraminiferal assemblages correspond to planktonic foraminiferal Zone M5b–M6 (Berggren et al. 1995) and the "Upper Lagenid Zone" of the Central Paratethys. The sediments are set in two sequences of about 20 m in thickness, the first mostly siliciclastic, displaying coastal onlap, and the second mainly carbonatic, with a regressive character. The sedimentary and paleontological features reflect sea level changes, the main event — recorded between the first and the second sequence — probably being correlable with a global sea-level drop in the Middle Miocene (15.5–16 Ma).