Nikhil Sharma , Alexander C Whittaker, Thierry Adatte, Sebastien Castelltort 

Water discharge and sediment flux variations are important parameters controlling the morphodynamical behavior of rivers. Although quantitative estimates for discharge and flux variability are well constrained for modern rivers, far fewer assessments of flow and sediment flux intermittency in ancient fluvial systems from the rock record are available. In this study we explore the relationship between water discharge, sediment flux variability and patterns of changing fluvial stratigraphic architecture in the Middle Eocene Escanilla Formation, Spain. We estimate water discharge intermittency factor (IWF) to range from 0.03 – 0.11 in the HA intervals and from 0.10 – 0.32 in the LA intervals. Sediment flux intermittency factor (ISF) is in the range of 0.008 – 0.01 in the HA intervals and from 0.01 – 0.03 in the LA intervals. Consequently, we suggest that high amalgamation (HA) intervals were most likely deposited under more intermittent and short-lived intense precipitation events, while low amalgamation (LA) intervals were the result of less intermittent flows spread throughout the year. Overall, our estimates are consistent with values from modern ephemeral rivers typically found in arid to semi-arid climatic conditions, which is in agreement with available proxy data for the Middle Eocene climatic context of the studied alluvial system. Our data highlights the important connection between hydroclimate, river morphodynamics and landscape evolution, and has implications to predict river flow and sediment transport across the Earth’s surface in the geological past.