ENIGMA investigates a major, little-understood global oceanic and ecological upheaval during the early Miocene (23–17 million years ago). This interval saw distinct biodiversity shifts such as a >70% shark extinction, plankton turnovers, and cetacean radiations, alongside changes in global productivity and ice sheet dynamics. ENIGMA will analyze Atlantic Ocean sediment cores, refine age models, reconstruct climate and biotic records, and model ecosystem responses to Earth system change.