We explore the potential of high-resolution carbon isotope stratigraphy to provide an independent record of global sea-level changes in a 1600-m-thick succession representing ∼5 m.y. of slope sedimentation in the Eocene Ainsa Basin of Spain. The restricted physiographic setting of the basin results in a bulk δ13Ccarb signal that accurately correlates with the coeval eustatic curve from the New Jersey (USA) passive margin. We show that much of the deep-water sediment gravity flow (SGF) deposits are emplaced during eustatic lowstands and fine-grained marly intervals between SGFs correlate with rising and highstand sea levels. However, we also detect a substantial interval of SGF deposition during a sea-level highstand, confirming the nonuniqueness of the controls on clastic deposition. This approach provides a new way to assess the origin of depositional sequences and improve stratigraphic predictions in basins with limited chronostratigraphic control.