High terrestrial temperature in the low-latitude Nanxiong Basin during the Cretaceous-Paleogene boundary interval

As CO2 keeps emitting, it is urgent to project future climatic changes by quantitatively reconstructing deep time paleoclimate in high atmospheric CO2 concentrations. However, there are still unneglected discrepancies between the terrestrial temperatures based on the climatic proxies and climate models, especially at low latitudes, which limits our interpretation of the terrestrial responses to global climate changes at low latitudes. In this study, the clumped isotope concentrations (A47) and total mercury signals are analyzed for the uppermost Cretaceous-lowermost Paleogene strata in the low-latitude Nanxiong Basin, South China. After excluding the potential diagenesis by both recrystallization and solid-state reordering, our study presents an extremely high mean annual terrestrial temperature of ca. 30 degrees C in the low latitudes. Our result is significantly higher than the previous estimates and supports a hot and expanded tropics during the latest Cretaceous-earliest Paleocene (i.e., K-Pg boundary interval). In addition, we suggest that the hot climate was plausibly caused by Deccan Traps (DT) volcanism, although the mercury concentrations in the section show relatively low peaks during the main eruptions. We speculate that the mercury sequestration in the Nanxiong Basin may have been affected by the extremely hot and arid regional climate.