Calcareous nannofossil extinction and survivorship across the Cretaceous-Paleogene boundary at Walvis Ridge (ODP Hole 1262C, South Atlantic Ocean)
Calcareous nannofossil extinction and survivorship across the Cretaceous-Paleogene boundary at Walvis Ridge (ODP Hole 1262C, South Atlantic Ocean)
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DOI：
10.1016/j.palaeo.2007.02.045
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发表时间：
2007-11-02
影响因子：
3
通讯作者：
Monechi, Simonetta
中科院分区：
文献类型：
--
作者：
Bernaola, Gilen;Monechi, Simonetta
位于南大西洋的1262号站点提供了一个地层连续的白垩纪/古近纪深部边界层序。高分辨率的钙质超微化石定量分析跨越了K/P界线，并提供了一个显着的记录的突然和灾难性的灭绝。钙质超微化石组合丰富且保存完好，可以获得精确的生物事件序列，并详细记录幸存者和受害者以及随后跨越K/P边界的恢复。马斯特里赫特晚期的多样性和绝对丰度很高，并且没有观察到边界的减少。白垩纪物种的相对丰度在马斯特里赫特晚期没有发生重大变化。然而，在马斯特里赫特阶最上部2厘米处冷水类群丰度的增加，伴随着温水类群的减少，揭示了地表水冷却的脉冲。K/P边界的标志是钙质超微化石绝对丰度的重要减少，白垩纪的增加-持续存在的物种，如Cyclagelosphaera reinhardtii，以及Thoracosphaera operculata的甲藻孢囊，以及新的-古新世分类群Cyclagelosphaera阿尔塔和Biantholithus sparsus。这些事件之后的连续相对丰度增加的其他白垩纪的幸存者Zeugrhabdotus sigmoides，Markalius inversus和Biscutum公认的r-选择类群，适应富营养化和冷水环境。在早期的Danian几个第一次出现的小型新古新世物种已被观察到：石灰质nannoplankton进化的尝试，殖民空置的壁龛留下的灭绝白垩纪物种。只有一些类型成功并成为新生代组合的祖先-其他在几千年内消失。一个改造/混合间隔以上的K/P边界的存在阻碍了明确的解释，如果少数的灭绝类群可能存活了很短的时间后，K/P灭绝。(c)2007 Elsevier B. V.保留所有权利。
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. (c) 2007 Elsevier B.V. All rights reserved.