GSA Connects 2021 in Portland, Oregon

Paper No. 172-10
Presentation Time: 4:10 PM


DEAN, Silas1, GREENLEE, John1, HALL, Christine2, PARK BOUSH, Lisa3 and WALDMANN, Nicolas1, (1)Department of Marine Geosciences, University of Haifa, Haifa, Israel, (2)Department of Marine Geosciences, University of Haifa, Haifa, Israel; Department of Geosciences, University of Connecticut, Storrs, CT 06269, (3)Department of Geosciences, University of Connecticut, Storrs, CT 06269

Over the past 250 years, atmospheric carbon dioxide (CO2) levels increased by nearly 40%, from preindustrial levels (ca. 280 ppmv) to 395 ppmv in 2013. This augmentation, clearly driven by anthropogenic impact, is an order of magnitude faster than any rise that occurred since at least the Cretaceous. Since the Pliocene is the last interval with continuous high CO2 levels similar to those predicted for the future, reconstructing environmental conditions during this epoch is important for disentangling anthropogenic influences in contemporary records. Our research focuses on the Erk al-Ahmar lacustrine formation outcropping on the Israeli side of the River Jordan, which has a chronology constrained to ~3-4 Ma by prior cosmogenic and paleomagnetic dating studies. We apply a suite of physical, chemical and biological techniques for reconstructing environmental conditions to a newly retrieved ~20 m long core. The core displays a lithology of coarse to fine sands including large quartz grains, which fine downwards into fine to coarse silts, which might be part of an orbital forcing cycle in the magnitude of 104 years. Complementary XRF data indicates several distinct compositional groupings in these silts, which together with ostracods, attest to different environments or perhaps oscillating lake levels. A unit composed of very coarse carbonate fragments and micro-mammal fossil bones near the bottom of our retrieved record stands out as a sudden interruption in lacustrine dominance, probably pointing to shallow water conditions or total desiccation. Given the absence of an existing detailed record of Pliocene conditions in this region, Erk al-Ahmar is an excellent site for reconstructions of terrestrial environment in the Levantine corridor, which later served as a natural land bridge for faunal migration between Africa and Eurasia.