Planktonic foraminifera, nannofossils and stable isotope record across tghe Paleocene-Eocene thermal maximum of ODP Hole 113-690B

The carbonate saturation profile of the oceans shoaled markedly during a transient global warming event known as the Paleocene-Eocene thermal maximum (PETM) (circa 55 Ma). The rapid release of large quantities of carbon into the ocean-atmosphere system is believed to have triggered this intense episode of dissolution along with a negative carbon isotope excursion (CIE). The brevity (120-220 kyr) of the PETM reflects the rapid enhancement of negative feedback mechanisms within Earth's exogenic carbon cycle that served the dual function of buffering ocean pH and reducing atmospheric greenhouse gas levels. Detailed study of the PETM stratigraphy from Ocean Drilling Program Site 690 (Weddell Sea) reveals that the CIE recovery period, which postdates the CIE onset by ~80 kyr, is represented by an expanded (~2.5 m thick) interval containing a unique planktic foraminiferal assemblage strongly diluted by coccolithophore carbonate. Collectively, the micropaleontological and sedimentological changes preserved within the CIE recovery interval reflect a transient state when ocean-atmosphere chemistry fostered prolific coccolithophore blooms that suppressed the local lysocline to relatively deeper depths. A prominent peak in the abundance of the clay mineral kaolinite is associated with the CIE recovery interval, indicating that continental weathering/runoff intensified at this time as well (Robert and Kennett, 1994). Such parallel stratigraphic changes are generally consonant with the hypothesis that enhanced continental weathering/runoff and carbonate precipitation helped sequester carbon during the PETM recovery period (e.g., Dickens et al., 1997, doi:10.1130/0091-7613(1997)025<0259:ABOGIT>2.3.CO;2 ; Zachos et al., 2005, doi:10.1126/science.1109004).

在约55 Ma的古新世-始新世极热事件（Paleocene-Eocene Thermal Maximum, PETM）这一突发性全球变暖事件期间，全球海洋的碳酸盐饱和度剖面发生了显著变浅。学界普遍认为，大量碳快速向海-气系统的释放，触发了此次强烈的碳酸盐溶蚀事件，同时引发了碳同位素负偏移（Carbon Isotope Excursion, CIE）。
古新世-始新世极热事件的持续时长为120~220 kyr，其短暂性反映出地球外生碳循环内的负反馈机制被快速强化——该机制兼具缓冲海洋pH值与降低大气温室气体水平的双重功能。
对威德尔海大洋钻探计划（Ocean Drilling Program）690站位的古新世-始新世极热事件地层开展的精细研究显示：晚于碳同位素负偏移起始约80 kyr的CIE恢复期，以一套厚度约2.5 m的扩张沉积层段为代表，该层段中包含一套独特的浮游有孔虫组合，且被颗石藻碳酸盐显著稀释。
综合来看，保存在CIE恢复期内的微古生物学与沉积学变化，反映出一段过渡状态：彼时海-气化学环境催生了繁盛的颗石藻水华，将当地溶跃面压低至相对更深的深度。
黏土矿物高岭石的丰度峰值与CIE恢复期密切相关，这表明当时的大陆风化与径流作用也有所增强（Robert and Kennett, 1994）。
这类同步的地层变化，总体上与“增强的大陆风化与径流及碳酸盐沉积在古新世-始新世极热事件恢复期助力碳固存”这一假说相符（例如：Dickens et al., 1997, doi:10.1130/0091-7613(1997)025<0259:ABOGIT>2.3.CO;2；Zachos et al., 2005, doi:10.1126/science.1109004）。