MID-LATITUDE TERRESTRIAL CLIMATE OF EAST ASIA LINKED TO GLOBAL CLIMATE IN THE LATE CRETACEOUS: EVIDENCES FROM STABLE ISOTOPES AND CLAY MINERALS OF THE SCIENTIFIC CORE IN THE SONGLIAO BASIN

The Late Cretaceous (late Campanian to Maastrichtian) was characterized by a variable greenhouse climate, with evidence for cooling and/or glaciation and warming events. Most of these climatic signals are derived from marine records, and knowledge of the terrestrial climate, especially in the mid-latitudes, is limited due to fragmentary geological records on continents. Here we report mid-latitude terrestrial stable oxygen and carbon isotopic and clay mineralogical data in the nearly continuous Late Cretaceous age SK-1 core drilled in the Songliao Basin, northeastern China. Our data indicate a punctuated, mid-latitude terrestrial climate in the Late Cretaceous. A large negative δ¹⁸O excursion (~3‰) documented by the SK-1 pedogenic carbonate nodule in the early Maastrichtian (~70Ma) is interpreted to be the result of decreasing temperature and/or strengthened westerlies during global cooling and possible glaciation, providing valuable mid-latitude terrestrial evidence for this previously documented event. At the same time, increases in illite content and the quartz/clay ratio, and decreases in illite chemistry index indicate increasing physical weathering and therefore a more arid climate. The negative δ¹³C isotopic excursion at ca. 66Ma and 69Ma are modeled as higher primary productivity caused by increasing temperature and precipitation in response to a warming climate in the latest Cretaceous. Clay mineralogical proxies also indicate increasing chemical weathering and a more humid climate. Our results demonstrate the sensitivity of mid-latitude terrestrial climate in a greenhouse world.