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首页> 外文期刊>Paleoceanography >Constraints on glaciation in the middle Eocene (46-37 Ma) from Ocean Drilling Program (ODP) Site 1209 in the tropical Pacific Ocean
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Constraints on glaciation in the middle Eocene (46-37 Ma) from Ocean Drilling Program (ODP) Site 1209 in the tropical Pacific Ocean

机译：来自热带太平洋海洋钻探计划（ODP）站点1209的始新世中期（46-37 Ma）的冰化约束

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摘要

The presence of glacial ice in the late middle Eocene has been vigorously debated. Recently published sedimentary data from the high latitudes is suggestive of episodic cooling events and near-freezing sea surface temperatures during parts of the late middle Eocene. Constraints on ice volumes and the significance of excursions in open ocean foraminifera and seawater δ~(18)O reconstructions are less clear, and there are few high-resolution δ~(18)O records. We present a new detailed record of benthic foraminiferal δ~(18)O from Site 1209 that exhibits variations (δ~(18)Obenthic) of 0.6‰-1.3‰. Different approaches have previously been used to interpret δ~(18)Obenthic, including (1) an a priori assumption of a 50% contribution of temperature, similar to what is reconstructed for the Last Glacial Maximum-recent change; (2) applying Oligocene calibrations between apparent sea level (ASL) and δ~(18)Obenthic; or (3) assuming temperature and seawater δ~(18)O contributions can be partitioned through comparison with benthic Mg/Ca. Using assumption 1, the record from Site 1209 indicates changes in seawater δ~(18)O of 0.3‰-0.7‰, equivalent to ～33-72 m (m) of ASL (assuming mean ice δ~(18)O of ～-45‰). Using assumption 2 and two different end-member calibrations, the δ~(18)Obenthic record implies changes in ASL of 23-50 m or 50-108 m. The third approach yields changes in seawater δ~(18)O of up to 0.6‰ to 1.4‰. We explore the compatibility of the results of each of these approaches with other studies that discuss evidence for ephemeral glaciations during the middle Eocene with variable ice storage at one or both poles.
机译：在始新世中期晚期，冰川冰的存在已经引起了激烈的争论。最近发布的来自高纬度地区的沉积数据表明，在始新世中期中后期发生了偶发性降温事件和接近冰点的海面温度。远洋有孔虫和海水中δ〜（18）O重建对冰量的限制以及漂移的意义尚不十分清楚，高分辨率的δ〜（18）O记录也很少。我们提供了来自站点1209的底栖有孔虫δ〜（18）O的新详细记录，其变化（δ〜（18）Obenthic）的变化为0.6‰-1.3‰。以前已经使用了不同的方法来解释δ〜（18）底栖动物，包括（1）对温度贡献50％的先验假设，类似于为上一次冰河最大最近变化重建的假设。 （2）在表观海平面（ASL）和δ〜（18）底栖动物之间应用渐新世标定;或（3）假设可以通过与底栖Mg / Ca比较来划分温度和海水δ〜（18）O的贡献。使用假设1，站点1209的记录表明海水δ〜（18）O的变化为0.3‰-0.7‰，相当于ASL的〜33-72 m（m）（假设平均冰δ〜（18）O为〜）。 -45‰）。使用假设2和两个不同的端构件标定，δ〜（18）Obenthic记录暗示ASL的变化为23-50 m或50-108 m。第三种方法产生的海水δ〜（18）O变化最大为0.6‰至1.4‰。我们探讨了每种方法的结果与其他研究的兼容性，这些研究讨论了始新世中期短暂冰期的证据，其中一个或两个极点都有可变的储冰量。

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