THE RELEASE OF CLIMATIC GASES BY THE CHICXULUB IMPACT

The cause of the K-Pg mass extinction remains a matter of some debate. Here, we revisit the release of climatically-active gases from carbonates and evaporites at the Chicxulub impact site, and use the multi-phase SOVA hydrocode to simulate the impact. Due to improvements in EOS, hydrocode capability, and computational power, we are able to more accurately estimate the proportion of degassed sedimentary rocks that are ejected to sufficiently high altitudes (> 25 km) to have had global consequences. New evidence from 3D simulations of crater formation suggests that the impact angle was about 60 degrees with a downrange direction to the southwest, which means that we can better constrain the location of the sedimentary rock sequence that was degassed. We estimate the thickness and composition of the sedimentary section using the nearest onshore boreholes and marine seismic reflection profiles. We explore the effect of varying impact angle by ±10 degrees, as well as changing the shock pressure at which incipient and complete degassing of calcite occurs by ±20 GPa. We also investigate the difference in released sulfur if the evaporite is anhydrite or gypsum, and the effect of submerging the sedimentary sequence under water. Recent Global Climate Models indicate that the released sulfur and CO₂would lead to a dramatic decrease of > 20 degrees C in temperature at the Earth’s surface, sub-freezing temperatures for > 3 years, and changes in ocean temperatures for 100s years.

The European Consortium for Ocean Drilling (ECORD) implemented Expedition 364 with funding from the International Ocean Discovery Program (IODP) and the International Continental scientific Drilling Project (ICDP). Artemieva was supported by NASA Grant 15-EXO15_2-0054, Morgan by NERC Grant NE/P005217/1 and Collins by NERC Grant NE/P011195/1. Co-authors: IODP-ICDP Expedition 364 Scientists