Sediment supply controls on Early Eocene delta sequences (South Pyrenean Foreland Basin; Spain)

Sediment supply variations are often overlooked when interpreting depositional sequences, which tend to emphasize changes in accommodation. Here, we focus on a temporally well-constrained shallow-marine succession in the South Pyrenean Foreland Basin to test the control of sediment supply on the development of deltaic sequences during the Early Eocene. We analyzed the paleoenvironmental record (sedimentary facies and δ13Corg values) of the Morillo Limestone and the Castigaleu Formation (52.2 to 50.3 Ma). During this period, a series of hyperthermal events occurred, globally recorded as negative carbon isotopic excursions (CIEs). The major progradation of the deltaic system is marked by the abrupt appearance of thick delta-front sandstones and coincides with the first recorded negative CIE. Subsequent phases of progradation/aggradation align with subsequent negative CIEs. Conversely, positive CIEs correspond to finer-grained, more distal prodelta and offshore deposits. We therefore suggest that during deposition of this Early Eocene shallow-marine succession, the primary trigger behind sequence generation was the high-frequency climate-induced variation in sediment supply, specifically the hyperthermal events, rather than changes in accommodation. This linkage underscores the complex interactions between climate dynamics and sedimentary responses, shaping the stratigraphic architecture of shallow-marine settings.