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Early Oligocene glaciation and productivity in the eastern equatorial Pacific: Insights into global carbon cycling

机译：赤道东太平洋的渐新世早期冰川和生产力：对全球碳循环的认识

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The onset of sustained Antarctic glaciation across the Eocene-Oligocene transition (EOT) marks a pivotal change in Earth's climate, but our understanding of this event, particularly the role of the carbon cycle, is limited. To help address this gap we present the following paleoceanographic proxy records from Ocean Drilling Program Site 1218 in the eastern equatorial Pacific (EEP): (1) stable isotope (δ~(18)O and δ~(13)C) records generated in epifaunal benthic foraminifera (Cibicidoides spp.) to improve (double the resolution) the previously published records; (2) δ~(18)O and δ~(13)C records measured on Oridorsalis umbonatus, a shallow infaunal species; and (3) a record of benthic foraminifera accumulation rate (BFAR). Our new isotope data sets confirm the existence at Site 1218 of a two-step δ~(18)O increase. They also lend support to the hypothesized existence of a late Eocene transient δ~(18)O increase and early Oligocene Oi-1a and Oi-1b glacial maxima. Our record of BFAR indicates a transient (～500 kyr) twofold to threefold peak relative to baseline Oligocene values associated with the onset of Antarctic glaciation that we attribute to enhanced biological export production in the EEP. This takes the same general form as the history of opal accumulation in the Southern Ocean, suggesting strong high-to-low-latitude oceanic coupling. These findings appear to lend support to the idea that the EOT δ~(13)C excursion is traceable to increased organic carbon (C_(org)) burial. Paradoxically, early Oligocene sediments in the EEP are extremely C_(org)-poor, and proxy records of atmospheric pCO _2 indicate a transient increase associated with the EOT.
机译：始新世-渐新世过渡（EOT）期间南极持续冰川的开始标志着地球气候的关键变化，但是我们对这一事件的理解，特别是碳循环的作用是有限的。为了解决这一差距，我们提供了以下来自赤道东太平洋（EEP）海洋钻探计划站点1218的古海洋学代用记录：（1）稳定同位素（δ〜（18）O和δ〜（13）C）记录产生于表生底栖有孔虫（Cibicidoides spp。）以改善（两倍分辨率）先前公布的记录; （2）在稀有种臭OrOridorsalis umbonatus上测得的δ〜（18）O和δ〜（13）C记录; （3）底栖有孔虫积累率（BFAR）的记录。我们的新同位素数据集证实了站点1218处存在两步δ〜（18）O增大。他们还支持了始新世晚期δ〜（18）O的增加和渐新世Oi-1a和Oi-1b冰川最大值的假设存在。我们的BFAR记录表明，与南极冰期开始有关的渐新世基线值是一个相对于基线渐新世值的两倍（至500 kyr）峰值，这归因于EEP中生物出口产量的增加。这与南部海洋中蛋白石的积累历史具有相同的一般形式，这表明高低纬度海洋耦合很强。这些发现似乎支持了EOTδ〜（13）C偏移可追溯到增加的有机碳（C_（org））埋葬的想法。矛盾的是，EEP中的渐新世早期沉积物的C_（org）极度贫乏，大​​气pCO _2的替代记录表明与EOT相关的短暂增加。

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