Paleoenvironment and Paleoclimatic Study of the Paleogene From IODP-ICDP Expedition 364 Site M0077, Chicxulub Crater

The IODP-ICDP Expedition 364 drilled the peak ring of Chicxulub crater at Site M0077, recovering a continuous sequence from 505.7 to 1334.7 mbsf (meters below sea floor). For this study, we analyzed 112 m of sedimentary rocks from 505.7 to 617.67 mbsf, to reconstruct the Paleogene paleoenvironmental and paleoclimatic conditions. We report the preliminary results of a broad range of geochemical proxies: bulk carbonate δ13C and δ18O, Corgand Ba/Ti as productivity/redox indicators, and K/Ti as chemical weathering intensity index, as well as a preliminary biochronological framework based on planktonic foraminifera. The Paleogene of the Hole M0077A cores spans from the Zone P-alpha (lowermost Danian) to plausibly Zone E7 (upper Ypressian). Several hiatuses have been recognized with the most important one affecting the Selandian and Thanetian. Bulk carbonate δ13C values ranged from 1.36 to -2.4 ‰ and δ18O oscillated between -6.94 and -1.36 ‰. The sequence right above the K/Pg boundary cocktail unit at 617 mbsf (suevites breccias, impact melt rocks, and uppermost calcareous siltstones), correspond to Zone P-alpha (lowermost Danian) with low values of Corg and Ba/Ti, suggesting a sudden drop in primary productivity. Besides the long-term climatic trends, we found the following evidence for warming/hyperthermal events: - Negative shifts in bulk δ13C and δ18O between 607.2 (presumably Zone E1) and 605.58 mbsf (Zone E2) with the lower part of this interval likely corresponding to the hyperthermal event PETM. High K/Ti ratios suggest that hydrologic and weathering cycles were strengthened during these intervals. - Negative shifts in bulk δ13C and δ18O from 597.95 to 596.86 mbsf (biozone not determined due to scarce planktonic foraminifera). This interval shows high values of Corg and Ba/Al with three conspicuous peaks around 597.95, 597.2 and 596.86, suggesting high productivity and the likelihood of anoxia in the bottom waters. This interval could correspond to the hyperthermal events at the beginning of the EECO (ETM2 and H2).