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New geochemical constraints on the Paleocene–Eocene thermal maximum: Dababiya GSSP, Egypt

Khozyem, Hassan, Adatte, Thierry, Spangenberg, Jorge E., Keller, Gerta, Tantawy, Abdel Aziz, Ulianov, Alexey
Palaeogeography, palaeoclimatology, palaeoecology 2015 v.429 pp. 117-135
aerobic conditions, anaerobic conditions, barium, cadmium, carbon, carbon dioxide, copper, crystals, iron, kaolinite, manganese, microbial activity, molybdenum, nickel, organic matter, phosphorus, potassium, pyrite, silicon, stable isotopes, surface water, titanium, uranium, vanadium, weathering, zirconium, Egypt
The Paleocene-Eocene Thermal Maximum (PETM) shows an extraordinary drop in the δ13C of carbonate and organic matter across the globe, suggesting massive release of 13C-depleted carbon dioxide into the ocean and atmosphere over a very short time interval (probably <20ky). We report a geochemical and mineralogical study of 106 samples spanning the most expanded PETM at the Dababiya Global Stratotype Standard section and Point (GSSP) near Luxor, Egypt. The field and laboratory observations reveal that the deposition occurred in a submarine channel extended laterally about 200m with the deepest part (~0.88m) at the designated GSSP, although all bio-zones are present. Stable isotope records of both carbonate and organic carbon show decreases starting 0.6m below the Paleocene-Eocene boundary (PEB) and culminating at the erosion surface. A persistent shift in δ15Norg values to near zero reflects a gradual increase in bacterial activity. High Ti, K and Zr and low Si contents at the PEB coincide with increased kaolinite contents, which suggests intense chemical weathering under more humid conditions at the PETM onset. Two negative Ce-anomalies indicate intervals of anoxic conditions during the lower and middle PETM (base and top of zone E1). The first anoxic event is represented by a negative Ce-anomaly, high V/C rand V/V+Ni ratios, negative Mn* and an abundance of idiomorphic pyrite crystals that indicate anoxic to euxinic conditions. The anoxic event (middle PETM) is marked by high U, Mo, V, Fe and abundant small sized (2–5μm) pyrite framboids, increased Cu, Ni, and Cd at the same level suggesting anoxic conditions linked to high surface water productivity. Above this interval, oxic conditions returned as indicated by the precipitation of phosphorus and barium. These data reveal an expanded PETM interval marked by intense weathering as a crucial parameter during the recovery phase.