Clay mineralogical evidence for mid-latitude terrestrial climate change from the latest Cretaceous through the earliest Paleogene in the Songliao Basin, NE China

From the latest Cretaceous (late Campanian to Maastrichtian, ~76-66 Ma) through the earliest Paleogene, changes of greenhouse climate were linked to catastrophic geological events and massive biotic extinction and were primarily derived from marine records. Here we present a high-resolution, tightly age-constrained, clay mineralogical record from the Sifangtai and Mingshui formations of the terrestrial Songliao Basin, northeast China. Smectite and illite are the dominant clay species and are derived from the weathering of parent rocks and/or pedogenesis in paleosols. We use the percentage ratio of smectite and illite, the illite chemistry index, and the percentage ratio of phyllosilicate clay minerals and quartz in clay fractions for paleoclimatic reconstruction. Our results show that from the latest Cretaceous through the earliest Paleogene, values of all three clay mineralogical proxies in the Songliao Basin are generally higher during warming intervals than those during cooling intervals. This dataset suggests that warming caused strengthened moisture delivery from the Pacific, increasing precipitation and intensified chemical weathering, whereas cooling was accompanied by increasing dryness and physical weathering. Across the Cretaceous-Paleogene boundary, the warming likely related to Deccan volcanism, the transient cooling afterwards, and the warming in the earliest Paleogene are characterized by changes in the illite chemistry index and paleosol carbonate stable isotopic excursions as shown in previously published records, reflecting fluctuations in hydroclimate and weathering intensity. Our work demonstrates that terrestrial climate and weathering intensity in the mid-latitude Songliao Basin fluctuated during the latest Cretaceous through the earliest Paleogene and sensitively responded to global climate changes.