John Greenlee
Graduated MSc Student
John Greenlee received his B.Sc. in Archaeological Sciences (2018) from the Pennsylvania State University, USA. He worked in the Human Paleoecology and Isotope Geochemistry lab, where he prepared samples for radiocarbon dating and stable isotope analysis. His research interests lie in geoarchaeology, paleoclimate reconstruction, isotope biogeochemistry, and human behavioral ecology. His mainly interests are understanding the ecological and climatic conditions under which anatomically modern humans and our hominin ancestors evolved. Currently, his M.Sc. work is focused on the ‘Ubeidiya paleolake lacustrine sequence of the Central Jordan Rift Valley to assess the environmental conditions of early hominin migration sites.
He is an avid outdoorsman (hiking, kayaking, and climbing) and Texas Rangers baseball fan.
John is currently a PhD student at the University of Syracuse (USA).
Research subject
Reconstructing Pliocene environmental conditions in the Levantine Corridor (Near East) with a multi-proxy study on a lacustrine record
The Pliocene was the last significant sustained warm period in Earth climate history. Atmospheric carbon dioxide and global temperatures during this interval are comparable to those modeled for the near future. 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. 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 datasets, especially from the Eastern Mediterranean. The Erk’-el-Ahmar Fm. (3.15-4.5 Ma) is a ~150 m lacustrine succession exposed in the Jordan Valley and includes clay to very find sand layers with carbonate units and excellent preservation of freshwater mollusks, ostracods, and mammal bones (rodents and even a mammoth tusk). This study aims to reconstruct the environmental conditions in the region during this time interval using a multi-proxy approach that includes physical, chemical, and biological measurements carried out on a 23 m long push-core. Our results show major fluctuations in the lake hypsometry, as evidenced by the different parameters, which appear to reflect the local hydro-climate conditions. An orbital-scale dry-wet climate cycle is well identified, which influenced the lake depth, its redox conditions, and sedimentary provenance. The sediment cores capture transitions between a continuous deep to a shallow lacustrine environment, 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 including precipitation patterns.
