Stable carbon and oxygen isotope record of Maastrichtian sediments from DSDP Site 74-528 in the South Atlantic Ocean@en

The upper Maastrichtian interval of mid-latitude South Atlantic Deep Sea Drilling Project site 528 spans approximately the last 4 million years of the Cretaceous. The isotopic record of this sequence indicates that relatively large (0.5-1.0‰) late Maastrichtian oxygen and carbon isotopic shifts occurred on geologically short time scales (less than 100-500 kyr). Comparison with previous oxygen isotopic data suggests that in high- and mid-latitude southern oceans the multimillion-year Maastrichtian cooling trend largely resulted from geologically rapid climatic 'steps'. Coincidence of the largest carbon and oxygen isotopic excursions suggests that relatively large and geologically rapid changes in marine and atmospheric carbon content may have directly contributed to the long-term cooling of the Late Cretaceous 'greenhouse'.南大西洋中纬度深海钻探计划（Deep Sea Drilling Project, DSDP）528站位的上马斯特里赫特阶（Maastrichtian）地层段，大致对应白垩纪最后约400万年的地质时期。该序列的同位素记录显示，晚马斯特里赫特期存在幅度为0.5‰~1.0‰的显著氧、碳同位素偏移，且这些偏移发生在地质短时间尺度（小于100~500千年（kyr））内。对比此前的氧同位素数据可知，南大洋高中纬度区域持续数百万年的马斯特里赫特期降温趋势，主要由地质尺度上快速发生的气候“阶跃”所主导。规模最大的碳、氧同位素漂移事件的同步性表明，海洋与大气碳含量发生的较大幅度、地质快速的变化，可能直接推动了晚白垩世“温室”气候的长期降温过程。