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Isotopic interrogation of a suspected late Eocene glaciation

机译：怀疑是始新世晚期冰川的同位素询问

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Ephemeral polar glaciations during the middle-to-late Eocene (48–34 Ma) have been proposed based on far-field ice volume proxy records and near-field glacigenic sediments, although the scale, timing, and duration of these events are poorly constrained. Here we confirm the existence of a transient cool event within a new high-resolution benthic foraminiferal δ~(18)O record at Ocean Drilling Program (ODP) Site 738 (Kerguelen Plateau; Southern Ocean). This event, named the Priabonian oxygen isotope maximum (PrOM) Event, lasted ~140 kyr and is tentatively placed within magnetochron C17n.1n (~37.3Ma) based on the correlation to ODP Site 689 (Maud Rise, Southern Ocean). A contemporaneous change in the provenance of sediments delivered to the Kerguelen Plateau occurs at the study site, determined from the<63 μmfraction of decarbonated and reductively leached sediment samples. Changes in the mixture of bottom waters, based on fossil fish tooth ε_(Nd), were less pronounced and slower relative to the benthic δ~(18)O and terrigenous ε_(Nd) changes. Terrigenous sediment ε_(Nd) values rapidly shifted to less radiogenic signatures at the onset of the PrOM Event, indicating an abrupt change in provenance favoring ancient sources such as the Paleoproterozoic East Antarctic craton. Bottom water ε_(Nd) reached a minimum value during the PrOM Event, although the shift begins much earlier than the terrigenous ε_(Nd) excursion. The origin of the abrupt change in terrigenous sediment provenance is compatible with a change in Antarctic terrigenous sediment flux and/or source as opposed to a reorganization of ocean currents. A change in terrigenous flux and/or source of Antarctic sediments during the oxygen isotope maximum suggests a combination of cooling and ice growth in East Antarctica during the early late Eocene.
机译：根据远场冰量代理记录和近场成冰沉积物，已经提出了中晚始新世（48-34 Ma）的短暂极地冰川作用，尽管这些事件的规模，时间和持续时间受到了限制。 。在这里，我们确认了海洋钻探计划（ODP）站点738（科格伦高原;南大洋）在新的高分辨率底栖有孔虫δ〜（18）O记录中存在短暂的低温事件。这次事件被称为普里伯尼亚氧同位素最大值（PrOM）事件，历时约140年，根据与ODP站点689（南海莫德上升）的相关性，暂定在磁时限C17n.1n（约37.3Ma）之内。在研究地点发生的沉积物来源同时发生变化是由脱碳和还原滤出的沉积物样品的<63μmfraction确定的。相对于底栖δ〜（18）O和陆源性ε_（Nd）变化，基于化石鱼齿ε_（Nd）的底水混合物变化较不明显且较慢。 PrOM事件开始时，陆源沉积物的ε_（Nd）值迅速转移到较少的放射源特征，这表明物源的突然变化有利于古代资源，如古元古代的南极克拉通。在PrOM事件期间，底水ε_（Nd）达到最小值，尽管偏移比陆源性ε_（Nd）偏移开始得早得多。陆源沉积物来源的突然变化的起源与南极陆源沉积物通量和/或源的变化是相容的，而不是洋流的重组。氧同位素最大值期间南极沉积物的陆源通量和/或源的变化表明，始新世晚期晚期南极东部的冷却和冰的生长兼有。

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