In this study the transgressive-regressive developments and depositional environment of the Frysjaodden Formation in the Central Tertiary Basin, Spitsbergen have been reconstructed. The depositional environment has been analyzed combining sedimentary field data, XRD and geochemical analyses. Special emphasis has been on clay minerals as an indicator of paleoclimate and the presence of one of the most abrupt and dramatic climatic events in the Cenozoic era; the Paleocene Eocene Thermal Maximum.The studied section, core BH 9/05, displays a shallowing upwards development from the Grumantbyen Formation to the Gilsonryggen Member of Frysjaodden Formation. The maximum flooding zone has been identified in the basal Gilsonryggen Member based on shale characteristics, pyrite content and Th/U ratio. The upper parts of the section display a regressive development from the dark gray, laminated shales of lower/middle Gilsonryggen Member to the soft-sediment deformed siltstones and hummocky cross-stratified sandstones of the upper Gilsonryggen Member/Lower Battfjellet Formation.The PETM has been identified just below maximum transgression in the lower parts of Gilsonryggen Member. The presence of PETM is based on kaolinite/(kaolinite + chlorite) and kaolinite/(kaolinite + illite) ratios and benthic foraminifera extinction coinciding with earlier δ13C studies. Furthermore, the stratigraphic position coincides with the position of PETM in other studies from the Arctic and Antarctic.