The last 1 million years of the extinct genus Discoaster: Plio–Pleistocene environment and productivity at Site U1476 (Mozambique Channel)
The last 1 million years of the extinct genus Discoaster: Plio–Pleistocene environment and productivity at Site U1476 (Mozambique Channel)
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DOI：
10.1016/j.palaeo.2018.05.043
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发表时间：
2018-09
期刊：
影响因子：
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通讯作者：
D. Tangunan;K. Baumann;J. Just;L. Levay;S. Barker;L. Brentegani;D. De Vleeschouwer;I. Hall;S. Hemming;R. Norris
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文献类型：
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作者：
D. Tangunan;K. Baumann;J. Just;L. Levay;S. Barker;L. Brentegani;D. De Vleeschouwer;I. Hall;S. Hemming;R. Norris
在2.85 ~ 1.85 Myr区间，对西印度洋莫桑比克海峡钙质纳米浮游生物组合进行了详细的古环境重建。这项研究涵盖了最近五种物种相继灭绝的灾难发生期间。从disasterspecies （disasterbrouweri, d.t iradiatus, d.t pentaradiatus, d.d .）的丰度中获得新的生产力数据。surculus,并且。Tamalis)和其他指示性钙质纳米浮游生物类群的丰度变化与100、41和23 kyr天文周期同步。在北半球冰期开始后的~2.4 Ma，生产力和水柱分层指标发生了转变。在这里，我们提出在国际海洋发现计划站点U1476记录的变率反映了与温暖的热带太平洋和寒冷的南大洋影响相关的强迫之间的相互作用。前者表现在温水类群（Calcidiscus leptoporus,Oolithotusspp）的一致出现。，横纹肌，Syracosphaeraspp.，伞形藻)，印度尼西亚典型的通流地表水。另一方面，上球藻的出现表明了寒冷、营养丰富的亚南极表层水的影响。在~2.4 Ma开始了一个更加混合的水柱，随之而来的生产力增加导致了disasterspecies的逐渐减少，直到它们在1.91 Ma灭绝。这一时期的特征是florisphaera profundindex值较低，而上层光带植物区系丰度较高，表明地表水体条件营养丰富。在这一时期，该地区的高生产力也可能被莫桑比克海峡涡流驱动的局部上升流事件放大。
A detailed paleoenvironment reconstruction from the Mozambique Channel, western Indian Ocean, based on the calcareous nannoplankton assemblages was conducted for the interval between 2.85 and 1.85 Myr. This study covers the period during which the successive extinction of the last five species of discoasters occurred. New productivity data obtained from the abundances of theDiscoasterspecies (Discoaster brouweri,D.triradiatus,D.pentaradiatus,D.surculus, andD.tamalis) and other indicative calcareous nannoplankton taxa showed abundance variations, which were at paced with the 100, 41, and 23 kyr astronomical periodicities. A shift in the productivity and water-column stratification proxies occurred at ~2.4 Ma, after the onset of the Northern Hemisphere glaciation. Here we propose that the variability recorded at International Ocean Discovery Program Site U1476 reflects the interplay between forcing associated with warm tropical Pacific and cold southern ocean influences. The former is shown by consistent occurrence of warm water taxa (Calcidiscus leptoporus,Oolithotusspp.,Rhabdosphaera clavigera,Syracosphaeraspp.,Umbellosphaeraspp.), typical of Indonesian Throughflow surface waters. On the other hand, the occurrence ofCoccolithus pelagicusindicates the influence of cold, nutrient-rich sub-Antarctic surface waters. A more mixed water column initiated at ~2.4 Ma, and a consequent productivity increase led to the gradual reduction of theDiscoasterspecies, until their extinction at 1.91 Ma. This period was characterized by the low values of theFlorisphaera profundaindex and high abundances of upper photic zone flora, indicative of nutrient-rich surface water conditions. High productivity at the location during this period could have also been amplified by localized upwelling events driven by the Mozambique Channel eddies.