Paleoenvironmental change during greenhouse periods spanning 65Ma

在本研究中，我们重点研究了跨越65m . y的温室期的古环境和生物相的变化。温室的第一个时期是中白垩世（阿普梯至土鲁纪），热带至亚热带的珊瑚和有孔虫物种向两极分布。在大陆架和深海环境中都记录了以含丰富有机物的海洋黑色泥为标志的5次缺氧事件，表明海洋环流停滞。相比之下，白垩纪晚期（Coniacian到Maastrichtian）的气候相对较冷。从炎热气候到凉爽气候的转换年龄约为90 Ma。第二个时期是晚古新世热极大期（LPTM）。在此，我们认识到底栖生物灭绝事件（BEE）的特征是由古新世的缺氧和富营养化组合到始新世的缺氧和少营养化组合的动物群混乱。然而，在LPTM期间浮游有孔虫没有发生明显的翻转。这些暖化事件是由脊状系统/超级羽流的强烈火山活动释放的温室气体增加造成的。

In this study, we focused on changes of paleoenvironments and biofacies during greenhouse periods spanning 65 m. y.. The first period of greenhouse is the middle Cretaceous (Aptian to Turonian) when polarward distributions of tropical to subtropical species of corals and foramminifers occurred. Some five anoxic events marked by marine black muds containing abundant organic matters had been recorded on both continental shelf and deep marine environments, suggesting stagnation of ocean circulations. In contrasts, the late Cretaceous (Coniacian to Maastrichtian) indicates relatively cooler climate. The turnover age from hot to cool climates was bout 90 Ma.The second period is the Late Paleocene Themal Maximum (LPTM). We recognized here the benthic extinction event (BEE) which is characterized by a faunal turmover from Paleocene assemblage consisting of oxic and eutoropic to Eocene anoxic and oligotropjic ones. However, no remarkable turnovers of planktonic foraminifers occurred during LPTM. These warm events resulted from the increase of greenhouse gasses released by intense volcanic activity of ridge systems/superplumes.