Evolution of the Zarqa Valley, Jordan, during the Pleistocene as part of the first hominin migrations outside Africa

Abstract

The Zarqa Valley is a geomorphological feature a few kilometers from Amman (Jordan) that hosts tributary rivers with perennial water from the Jordan River. Its geological and archaeological importance is due to the fact that it has three floors of terraces, high, medium and low, all with hominin tools and distinct stratigraphic characteristics. The recent dating of archaeological levels in the Dawqara Formation (Upper Terrace) from 2.48 million years (Ma) to 1.95 Ma documented the first outflow of hominins from Africa to Asia in the early Pleistocene, being an impactful discovery in evolution and in the expansion of our genre. The current climate of the Zarqa Valley is arid, therefore inhospitable and challenging for the establishment and survival of any species of the genus Homo. Literature sedimentological and pedological data suggest that during the valley's evolution, possibly in the Pleistocene, there was a transition from milder and more humid climates, inviting for these species, to more similar to the current ones. This project proposes to systematically analyze the different terrace levels in the Zarqa Valley, in order to reconstruct the geomorphological history, depositional patterns and paleoenvironmental changes in relation to the Quaternary climatic and tectonic evolution of the region. Furthermore, the top of the high terrace, which ends the oldest and most internationally relevant archaeological sequence, is capped by an Early Pleistocene (2 Ma) carbonate paleosol that will be used as a paleoclimatic proxy through the analysis of stable isotopes and reveal the values of humidity, temperature and vegetation present during its development. The multidisciplinary integration of different methods will promote the geological and paleoenvironmental reconstruction of the Zarqa Valley, focusing on the Pleistocene packages, due to their archaeological importance. Secondarily, geochronological analyzes will be developed, such as U/Pb dating and paleomagnetism, for the correct positioning of data in geological time. (AU)