Radiolarian faunal turnover and paleoceanographic change around Eocene/Oligocene boundary in the central equatorial Pacific, ODP Leg 199, Holes 1218A, 1219A, and 1220A
Radiolarian faunal turnover and paleoceanographic change around Eocene/Oligocene boundary in the central equatorial Pacific, ODP Leg 199, Holes 1218A, 1219A, and 1220A
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DOI：
10.1016/j.palaeo.2005.07.014
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发表时间：
2006-01-30
影响因子：
3
通讯作者：
Nigrini, CA
中科院分区：
文献类型：
--
作者：
Funakawa, S;Nishi, H;Nigrini, CA
在赤道中部太平洋海洋钻探计划第 199 段钻探的 1218A、1219A 和 1220A 孔中获得了始新世到渐新世的连续沉积剖面。对始新世上部至渐新世下部沉积层序之间放射虫组合的定量分析表明，放射虫区系的主要变化发生在始新世晚期（35.5-35.7 Ma；亚纪元C16n1）、始新世/渐新世边界周围（33.7-33.8 Ma；上部亚纪元C13r）和早渐新世（30.9-31.3 Ma；最上面的Subchron C12r）。始新世晚期动物区系变化的特点是热带始新世物种逐步减少，而世界性的、可能耐冷水的放射虫增加；然而，物种多样性和放射虫积累率没有显着变化。这种晚始新世更替的地层水平发生在始新世晚期撞击事件之后，并且可能与全球变冷和相关海洋变化比与小行星撞击更相关。始新世/渐新世边界周围的更替，对应于Oi-1事件，是始新世-渐新世过渡期间最关键的。许多生物事件，例如物种多样性的突然下降、世界性放射虫群体的增加、大量的物种更替以及放射虫积累率的下降，都发生在这个水平或略高于这个水平。这些指标共同表明放射虫组合从高多样性的始新世动物群到低多样性的渐新世动物群发生了重大重组。渐新世早期的第三次更替事件表现为优势物种的更替和放射虫积累率的突然下降。然而，渐新世的更替与其他主要的 6 180 同位素事件（例如 Oi-1b 和 Oi-2）不一致。 (c) 2005 Elsevier B.V. 保留所有权利。
Continuous Eocene through Oligocene sedimentary sedimentary sections were obtained at Holes 1218A, 1219A, and 1220A drilled during Leg 199 of the Ocean Drilling Program in the central equatorial Pacific. Quantitative analysis of radiolarian assemblages between the upper Eocene through lower Oligocene sedimentary successions revealed that major faunal changes of radiolarians occurred in the late Eocene (35.5-35.7 Ma; Subchron C16n1), around the Eocene/Oligocene boundary (33.7-33.8 Ma; upper Subchron C13r) and in the early Oligocene (30.9-31.3 Ma; uppermost Subchron C12r).The faunal change in the late Eocene is characterized by a stepwise decrease of tropical Eocene species and an increase in cosmopolitan, probably cool-water-tolerant, radiolarians; however, without a significant change in species diversity and radiolarian accumulation rates. The stratigraphic level of this late Eocene turnover came after the late Eocene impact event, and may have been more related to global cooling and associated oceanographic changes than to asteroid impact.The turnover around the Eocene/Oligocene boundary, corresponding to the Oi-1 event, is the most critical during the Eocene-Oligocene transition. Many biotic events such as a sudden drop of species diversity, an increase in the cosmopolitan radiolarian group, a large number of species turnovers, and a drop in radiolarian accumulation rates occurred at or just above this level. Together these indicators suggest a major restructuring of radiolarian assemblages from the high diversity Eocene fauna to a low diversity Oligocene one. The third turnover event within early Oligocene is represented by a replacement of dominant species with a sudden decrease in radiolarian accumulation rates. However, this Oligocene turnover is not consistent with other major 6 180 isotope events, such as Oi-1b and Oi-2. (c) 2005 Elsevier B.V. All rights reserved.