Relative environmental stability in the Hula Valley (northern Israel) during the last glacial-interglacial transition

Abstract

This study presents the first multidecadal-resolution, carbonate stable isotope record from Paleolake Hula, a hydrologically-open freshwater lake located along the Dead Sea Transform in northern Israel. This lake was an important landscape feature to prehistoric hunter-fisher-gatherer societies since at least the early Middle Pleistocene, and some of the Levant's most important archeological sites are located along its paleoshorelines. The lacustrine sedimentary sequence studied here is the first known from the southern Levant to preserve both a continuous record of regional environmental conditions as well as artifacts attributed to cultures from all three stages of the Epipaleolithic period: the Early Epipaleolithic Masraqan, the Middle Epipaleolithic Geometric Kebaran and the Late/Terminal Epipaleolithic Natufian. While the Epipaleolithic was a time of dramatic cultural change in this region, and the transition from the last glacial to the present (Holocene) interglacial brought with it a dramatic reorganization of global climate systems, our record shows that environmental conditions in the Hula Valley were mild, stable, and continuously favorable for human habitation. Here average ostracod carbonate δ¹⁸O and δ¹³C values measured exhibit variation within a narrow range (c. 3 ‰) and show no evidence for extreme temperatures or aridity. High intra-sample variability of the dataset indicates that short-term (day-to-week scale) variability in the water isotopic composition and temperature was significant. This is especially pronounced during times of lower lake volume, when thermal and isotopic buffering capacity were reduced. The multidecadal resolution of this sedimentary sequence allows for the identification of centennial-scale climate developments previously poorly known from the eastern Mediterranean region, including evidence for a two-phase Younger Dryas. Although shifts in the local hydroclimate are recognizable in the proxy datasets, their real-world expressions are expected to have been modest, and unlikely to have significantly impacted the valley's terrestrial biota. Results confirm the importance of both the eastern Mediterranean Sea as the primary moisture source for precipitation and the contribution of northern moisture sources to the water balance of downstream lakes. The results also highlight the complexity of interpreting carbonate stable isotope records from hydrologically-open lakes and the importance of viewing them in conjunction with other proxies such as grain size, geochemical, lithological and micropaleontological data.