Bulk sediment organic carbon isotopes, and total organic content values from IODP site 378-U1553 (166°11.4801′E, 52°13.4294′S) located on the Campbell Plateau are presented. These data were collected between 2021 and 2025 at the Kentucky Stable Isotope Geochemistry Lab. The samples analyzed were from the Paleocene mudstones recovered between 480 and 580 CSF-A. The organic carbon values were collected by analyzing bulk sediments using an using an EA-Isolink elemental analyzer connected in continuous flow to a MAT253 IRMS. The samples were analyzed with a minimum of 10% duplicates and were calibrated to the V-PDB scale with a standard deviation of 0.2‰ based on repeated measurements of the UKY-1 internal standard which has been verified using international standards. These data were collected to investigate the presence of a deep sulfate-methane transition zone and to evaluate how the presence of an SMTZ affected the chemistry and composition of the recovered sediments.