Distribution of calcareous nannofossils in Cretaceous to Paleogene sediments of ODP Hole 208-1262C at Walvis Ridge, South Atlantic Ocean (Appendix A)

Site 1262 in the South Atlantic Ocean has provided a stratigraphically continuous deep Cretaceous/Paleogene boundary sequence. High resolution calcareous nannofossil quantitative analyses were carried out across the K/P boundary, and provided a remarkable record of the abrupt and catastrophic extinction. The calcareous nannofossil assemblages are abundant and well preserved allowing to obtain a precise bioevent sequence and to document in detail the survivors and victims and the subsequent recovery across the K/P boundary. Late Maastrichtian diversity and absolute abundance is high and no decrease towards the boundary has been observed. The relative abundance of Cretaceous species does not suffer important changes during the latest Maastrichtian. However, the increase in abundance of cool-water taxa, paralleled with a decrease of warm water taxa in the uppermost 2 cm of the Maastrichtian, revealed a pulse of surface water cooling. The K/P boundary is marked by an important decrease in calcareous nannofossil absolute abundance, the increase of Cretaceous-persistent species such as Cyclagelosphaera reinhardtii together with the dinoflagellate cysts of Thoracosphaera operculata and the appearance of the new-Paleocene taxa Cyclagelosphaera alta and Biantholithus sparsus. These events are followed by the successive relative abundance increases of other Cretaceous survivors as Zeugrhabdotus sigmoides, Markalius inversus and Biscutum recognized as r-selected taxa, adapted to eutrophic and cold water environments. In the early Danian several first occurrences of small new-Paleocene species have been observed: calcareous nannoplankton evolutionary attempts to colonize vacant niches left by the extinct Cretaceous species. Only some forms succeed and become ancestors to the Cenozoic assemblages - the other disappear in few kiloyear. The presence of a reworking/mixing interval above the K/P boundary hampered to unequivocally interpret if the few Cretaceous-vanishing taxa may have survived for a very short time after the K/P extinction.南大西洋1262站位产出一套地层连续的白垩系-古近系（K/P）界线深水沉积序列。研究人员对该剖面K/P界线开展了高分辨率钙质超微化石定量分析，获得了反映该突发性灾变灭绝事件的珍贵记录。该剖面钙质超微化石组合丰富且保存完好，可用于构建精准的生物事件序列，并详细记录K/P界线处的灭绝类群、残存类群以及后续的生物复苏过程。 马斯特里赫特阶晚期，钙质超微化石的多样性与绝对丰度均处于较高水平，未出现向界线方向递减的趋势；白垩纪特有种的相对丰度在马斯特里赫特阶最末期也未发生显著变化。然而，在马斯特里赫特阶最顶部2 cm地层中，冷水类群丰度上升、温水类群丰度下降，这指示了一次表层海水降温事件。 K/P界线以钙质超微化石绝对丰度显著下降为标志，同时伴随白垩纪残存种（如*Cyclagelosphaera reinhardtii*）与*Thoracosphaera operculata*甲藻孢囊的丰度升高，以及古新世新生类群*Cyclagelosphaera alta*与*Biantholithus sparsus*的首现。上述事件之后，其他白垩纪残存类群（如*Zeugrhabdotus sigmoides*、*Markalius inversus*与*Biscutum*）的相对丰度依次上升——这些类群被认为是适应富营养冷水环境的r选择类群。 丹尼阶早期，学界已观测到多种小型古新世新生钙质超微浮游生物的首现事件，这代表钙质超微浮游生物对灭绝类群遗留的空缺生态位的演化拓殖尝试。仅有部分类群成功存续，并成为新生代超微化石组合的祖先类群；其余类群则在数千年内彻底消失。K/P界线之上发育再沉积混合层，这使得我们无法明确判断：少数白垩纪末消失类群是否可在K/P灭绝事件后短暂存活。