Rapid changes in continental sedimentation triggered by monsoon-type event during EECO hyperthermals, Minervois Basin, Southern France

Recent studies on early Eocene climate have established that climatic fluctuations characterized by negative carbon isotopic excursions (CIE, hyperthermals) in the atmosphere associated to global warming, are responsible for drastically changes in the terrestrial sedimentary record of sub-tropical basins. Here we present a key sedimentary record to understand geological and climatological changes in order to evaluate the impact of hyperthermals on sediment transport and deposition in alluvial setting during Early Eocene Climatic Optimum (EECO). Based on an integrative study combining sedimentology, sequential stratigraphy, magnetostratigraphy and chemostratigraphy (δ¹³C), we propose a detailed constrained chronostratigraphic framework of continental sedimentary series of the French Minervois Basin. Using facies association analysis, the sedimentary succession is divided into three continental sequences bounded by subaerial unconformity deposited through the development of an endoreic underfilled basin. Sequences are composed of cyclically siliciclastic fluvial and carbonated palustrine-shallow lacustrine deposits. Palustrine-shallow lacustrine systems reflect arid climate conditions during EECO which are interrupted by sudden arrivals of detrital fluxes reflecting intense and extreme rainfall events in the hinterland. The latter coincide to CIEs corresponding to transient hyperthermals identified as C24n.1nH1/K/ETM3, C23rH2/M, and C23n.2nH1/N-C23n.2nH2/O interval. Extreme monsoon-type events triggered by intense warm-ups during hyperthermals are proposed to explain sudden detrital inputs in the basin. Finally, we present a new model in which variation in continental stratigraphic architecture enable us to emphasize hydrological changes associated to transient hyperthermals, and that the corresponding sedimentary response is almost identical to that of more intense events such as the PETM.