Refinement of the environmental and chronological context of the archeological site El Harhoura 2 (Rabat, Morocco) using paleoclimatic simulations

Abstract

This study illustrates the strong potential of combining paleoenvironmental reconstructions and paleoclimate modeling to refine the paleoenvironmental and chronological context of archeological and paleontological sites. We focus on the El Harhoura 2 cave (EH), an archeological site located on the North Atlantic coast of Morocco that covers a period from the Late Pleistocene to the mid-Holocene. In several stratigraphic layers, inconsistencies are observed between species presence and isotope-based inferences used to reconstruct paleoenvironmental conditions. The stratigraphy of EH also shows chronological inconsistencies in older layers between age estimated by optically stimulated luminescence (OSL) and a combination of uranium series and electron spin resonance methods (combined US–ESR). To infer global paleoclimate variation over the EH sequence in the area, we produced an ensemble of atmosphere-only simulations using the LMDZOR6A model, using boundary conditions and forcings from pre-existing climate simulations performed with the IPSL Earth system climate model to match the different key periods. We conducted a consistency approach between paleoclimatic simulations and paleoenvironmental inferences available from EH. Our main results show that the climate sequence based on combined US–ESR ages is more consistent with paleoenvironmental inferences than the climate sequence based on OSL ages. We also evidence that isotope-based inferences are more consistent with the paleoclimate sequence than species-based inferences. These results highlight the difference in scale between the information provided by each of these paleoenvironmental proxies. Our approach is transferable to other sites due to the increasing number of available paleoclimate simulations.