Paleoenvironmental change during greenhouse periods spanning 65Ma

在这项研究中，我们重点研究了跨越65年的温室时期的古环境和生物相的变化。第一个温室时期是中白垩世(阿普提亚至图罗尼亚)，此时出现了热带至亚热带珊瑚和有孔虫的极地分布。在大陆架和深海海洋环境中都记录到了以含有丰富有机质的海洋黑色泥浆为标志的大约5次缺氧事件，表明海洋循环停滞。相比之下，晚白垩世(科尼亚期至马斯特里赫期)表明气候相对凉爽。气候由热向凉的转换年龄为90 Ma左右，第二个时期为晚古新世最热时期。我们在这里发现了底栖生物灭绝事件(BEE)，其特征是从古新世到始新世由氧化和真翻转到始新世的缺氧性和稀有性组合的动物群迁徙。然而，在LPTM期间，浮游有孔虫没有发生显著的周转。这些暖事件是由于脊系/超羽流的强烈火山活动释放的温室气体增加所致。

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.