Paleoclimatic Evolution And Mechanism Of The Mass Extinction During The K-Pg Boundary

During the Cretaceous-Paleogene(K-Pg) boundary, the climatic states-- high CO2 content, high temperature from low to high latitudes, and low equator-to-pole gradients-- were totally different from the near-modern climates. The paleoclimate records of this interval are of great interest, as they may provide analogs for a near-future greenhouse world. In addition, the Cretaceous-Paleogene mass extinction represents one of the largest biologic catastrophe in the geological history. Many geological events, such as asteroid impact, Deccan Traps eruption, marine regression, and global/regional climate changes, should be blamed for this mass extinction. However, the roles of these events played in the mass extinction are still not strictly confirmed. An integrated climate record will help to clarify the relationship among the geological events, corresponding climate changes, and biotic turnovers. However, most temperature estimates during this period have come from marine sections, the terrestrial temperature estimates have been impeded by fragmentary and poor-temporal-resolution terrestrial sections, and a lack of unambiguous proxies. Furthermore, obtained paleoclimate information can not apply to modern climate classification, there is a gap between modern and deep time climate studies.Here we propose a new paleoclimate classification based on the widely used K?ppen climate classification. The new classification is simple, quantitative, but bridges the gap between the modern and deep time climate studies. Then we apply the unambiguous clumped isotope(Δ47) paleothermometry to paleosol carbonates from East China, which allows for the direct estimation of paleotemperature and gets rid of the constraint of the δ18O of paleo-water.The integrated paleoclimate record shows not hot but variable paleoclimate during the KPg boundary. The terrestrial temperatures during this period were overall similar to the marine records, and the low-latitude terrestrial temperatures were underestimated in the previous studies. The low-latitude continent interiors were much warmer than today, indicates hot tropics and smaller equator-to-pole temperature differences during the Cretaceous-Paleogene boundary. The hot temperatures in low latitudes likely to have approached a tolerable threshold on land, which supports the speculation that hot tropical temperatures are required to maintain the warm high-latitude temperatures. The mass extinction was composed by two stages of extinction. The volcanism, marine regression, and climate changes during the Latest Cretaceous firstly destabilized the ecosystem. Then the asteroid impact threw the frail ecosystem critical strike, collapsed the ecosystem and burst the mass extinction.