The Paleocene-Eocene thermal maximum (PETM) at 55 Ma provides an unparalleled opportunity to explore the causes and consequences of rapid global warming. Associated with PETM warming were major changes in the Earth's climate, oceans, biota, and global carbon cycling, all of which occurred in a geologic instant. Neodymium isotope data from an array of deep-sea sites enable reconstruction of the pattern of deep-sea circulation before, during and after the PETM. The data suggest a single, dominant source of deep waters that formed off Antarctica and circulated throughout the Atlantic and proto-Indian Oceans. Stratigraphic records of Nd isotopes indicate that a fundamental change in the pattern of deep-sea circulation did not precede PETM deep-water warming. This project provides the first evidence for a period of sea-surface and deeper-water warming prior to the rapid onset of the carbon isotope excursion, supporting a thermal mechanism for dissociation of methane hydrate. The top-down progression of the carbon isotope excursion indicates that much of the initial methane released from hydrate dissociation may have reached the atmosphere prior to oxidation. (modif. auth. abstr.)