The data set contains raw datafiles from a TESCAN VEGA3 scanning electron microscope (SEM). The SEM data was collected in 2019 on 13 samples from core E-8X. Of these, two samples were chosen in the pre Paleocene-Eocene Thermal Maximum (PETM), five in the main phase of the PETM, and six in the recovery phase. For each sample, the diameters of 100 specimens of pyrite framboids were measured. The attached file includes a raw data compilation of pyrite framboid diameters in µm from samples before, during and after the PETM. The size of pyrite framboids are utilised to describe bottom water redox changes in the central North Sea during the Paleocene-Eocene Thermal Maximum.