Pliocene environmental changes in the Levantine Corridor (Near East): insights from a new multi-proxy study from a lacustrine record in the central Jordan Valley

The Pliocene (5.33-2.58 Ma) was the last significant sustained warm period in Earth 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 similar to current continental and oceanic positioning, it is possible to assume similar oceanic and atmospheric circulation patterns, and hence reliable climate archives dated to this interval may serve as a good analogue for providing a base of comparison to the future climate conditions of our planet. Current data on the Pliocene mostly focus on marine sediments with terrestrial data arriving from loess and paleosol records. Yet, there is a lack of information from continental lacustrine formations, especially from the Eastern Mediterranean. The Erk’-el-Ahmar Formation (3.15-4.5 Ma) is exposed in the central Jordan Valley and includes a ~150 m succession of mostly lacustrine deposits (clay, silt, very find sand, and carbonate layers), with excellent preservation of freshwater mollusk shells, ostracod bivalves, micromammal bone fragments, and even a mammoth tusk. This study aims to reconstruct the paleoenvironmental conditions in the region during this time interval using a multi-proxy approach that includes physical parameters (grain size distribution, magnetic susceptibility), chemical compositional data (X-ray fluorescence and total organic carbon/inorganic carbon), with preliminary results of ostracod and biomarker data from three push-cores (60 m) and the formation’s outcrop.

Our results show major fluctuations in the lake hypsometry, as evidenced by the different parameters, which are suggested to reflect the local hydro-climate conditions. An orbital-scale dry-wet climate cyclicity is well identified in the sedimentary record, which probably influenced the lake depth and structure, redox conditions, sedimentary provenance, and the habitat for faunal species. The sediment cores capture transitions between continuous deep to shallow 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 warmer climate phase, challenging previous estimations on the governing mechanisms for climate variability in the region, such as humidity provenance.