Reconstructing Pliocene environmental changes in the East Mediterranean: results from a new multi-proxy study on a lake sedimentary record from the central Jordan Valley

The Pliocene (5.33-2.68 Ma) was the last significant warm period in Earth's climate history. Atmospheric carbon dioxide and global temperatures during this interval are comparable to those estimated for our planet’s future climate trajectory. Considering a comparable to present continental and oceanic positioning, it is possible to assume similar oceanic and atmospheric circulation patterns, and hence reliable Pliocene climate archives may serve as a strong analogue for future climate conditions of the planet. Current data on the Pliocene mostly focus on marine sediments with terrestrial data stemming from loess and paleosol records. Yet, there is a lack of information from continental lacustrine formations, especially from the East Mediterranean. The ‘Erk-el-Ahmar Formation (3.15-4.5 Ma) lies in the central Jordan Valley and includes a ~150 m succession of fluvio-lacustrine deposits (clay, silt, very find sand, and carbonate layers), with excellent preservation of freshwater mollusk shells, ostracods, micromammal bone fragments, and mammoth remains. This study will reconstruct the paleoenvironmental conditions of the region during this time interval using a multiproxy approach that includes physical parameters (grain size distribution, magnetic susceptibility), geochemical compositional data (X-ray fluorescence and total organic carbon/inorganic carbon), with preliminary results of ostracod and biomarker data from two push-cores (40 m) and the formation’s outcrop.

Our results show major fluctuations in the lake hypsometry, as evidenced by the different parameters, which might reflect the local hydro-climate conditions. An orbital-scale dry-wet climate cyclicity is well identified in the sedimentary record, which influenced the lake depth, redox conditions, sedimentary provenance, and the habitat for faunal species. The cores capture transitions between continuous shallow and deep lacustrine environments, with potential short intermittent events (perhaps seismic or climate-induced), indicating the sustainability of this perennial water body. Results from this study provide an important understanding of the hydrological conditions that may have dominated the region during a warm climate phase, challenging previous estimations.