Re-evaluating modern and Palaeogene GDGT distributions: Implications for SST reconstructions
Re-evaluating modern and Palaeogene GDGT distributions: Implications for SST reconstructions
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DOI：
10.1016/j.gloplacha.2013.06.011
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发表时间：
2013-09
影响因子：
3.9
通讯作者：
K. Taylor;M. Huber;C. Hollis;M. Hernández-Sánchez;R. Pancost
中科院分区：
文献类型：
--
作者：
K. Taylor;M. Huber;C. Hollis;M. Hernández-Sánchez;R. Pancost
本文综述了TEX 86古温度计的研究进展，并对其在古近系的应用进行了评价，重点讨论了影响甘油二烷基甘油四醚（GDGT）分布的主要生态、物理或化学过程。最近对古近纪沉积物的调查揭示了两种不同的基于GDGT的方法TEX 86和TEX 86 H之间的温度偏移，前者与来自无机代理的SST估计值一致（Hollis等人，2012年）。这是令人惊讶的观察结果，因为这两种GDGT方法虽然基于两组不同的化合物，但在现代海洋中SST> 15 °C时显然是一致的。在这里，我们重新评估原始GDGT分布和用于构建TEX 86和TEX 86在现代岩心顶部数据集和新的古近纪数据汇编的比率之间的关系。我们证明了TEX 86和TEX 86 L之间的偏移（ΔH-L）是GDGT-2/GDGT-3比值的函数（[2]/[3]比率），并且这可以用于分离现代核心顶部数据集中的低纬度和高纬度GDGT分布：[2]/[3]比值和ΔH-L值的范围出现在极区，而在温度> 15 °C时，[2]/[3]比值较高，ΔH-L值较小。然而，在古近纪数据集中，我们观察到了广泛的[2]/[3]比值，即使对于高于15 °C的SST估计也是如此。重要的是，我们发现在现代和古近纪组合数据集中，水深是ΔH-L值和[2]/[3]比的更好的参数：ΔH-L值较低（< 3.0 °C）和[2]/[3]比率高（> 5.0）水深> 1000 m。现代水柱研究表明，悬浮颗粒物（SPM）中的[2]/[3]比值随深度增加，这表明，高[2]/[3]比率反映了生活在深水柱中的海洋生物的贡献。这表明，出口动态影响GDGT派生SST估计。我们认为新的方法来SST重建：1）继续使用核心顶部校准，其中输出动态已隐含地纳入到当前的核心顶部校准数据集，但考虑到水深的影响;和2）使用SPM或基于中尺度的校准，水深和古输出动态独立评估。
In this paper, we review the TEX86palaeothermometer for sea surface temperature (SST) and evaluate its application to the Palaeogene, with a focus on the principal ecological, physical or chemical processes that can bias glycerol dialkyl glycerol tetraether (GDGT) distributions. Recent investigations of Palaeogene sediments have revealed temperature offsets between two different GDGT-based approaches, TEX86Land TEX86H, with the former agreeing with SST estimates derived from inorganic proxies (Hollis et al., 2012). These are surprising observations because the two GDGT approaches, although based on two distinct groups of compounds, apparently agree at SSTs > 15 °C in modern oceans. Here we reassess the relationship between raw GDGT distributions and the ratios used to construct TEX86Hand TEX86in both the modern core-top dataset and a new compilation of Palaeogene data. We show that the offset between TEX86Hand TEX86L(ΔH–L) is a function of the GDGT-2/GDGT-3 ratio ([2]/[3] ratio), and that this can be used to separate low- and high-latitude GDGT distributions in the modern core-top dataset: a range of [2]/[3] ratios and ΔH–L values occur in polar regions, whereas [2]/[3] ratios are high and ΔH–L values are small at temperatures > 15 °C. However, in the Palaeogene dataset, we observe a wide range of [2]/[3] ratios, even for SST estimates above 15 °C. Crucially, we find that water depth is a better discriminator of ΔH–L values and [2]/[3] ratios than SST in the combined modern and Palaeogene dataset: ΔH–L values are low (< 3.0 °C) and [2]/[3] ratios are high (> 5.0) where water depth is > 1000 m.Modern water column studies show that the [2]/[3] ratios in suspended particulate matter (SPM) increase with depth, suggesting that high [2]/[3] ratios reflect a contribution from Archaea living in the deeper water column. This suggests that export dynamics influence GDGT-derived SST estimates. We argue for new approaches to SST reconstruction: 1) continued use of core-top calibrations, in which export dynamics have been implicitly incorporated into the current core-top calibration datasets, but with the influence of water depth taken into account; and 2) use of SPM or mesocosm-based calibrations, with water depth and palaeo-export dynamics independently assessed.