Sensitivity of clumped isotope temperatures in fossil benthic and planktic foraminifera to diagenetic alteration
Sensitivity of clumped isotope temperatures in fossil benthic and planktic foraminifera to diagenetic alteration
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化石底栖和浮游有孔虫中团簇同位素温度对成岩蚀变的敏感性
DOI：
10.1016/j.gca.2019.05.005
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发表时间：
2019-07
影响因子：
5
通讯作者：
T. Leutert;Philip Sexton;A. Tripati;A. Piasecki;Sze Ling Ho;A. N. Meckler
中科院分区：
文献类型：
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作者：
T. Leutert;Philip Sexton;A. Tripati;A. Piasecki;Sze Ling Ho;A. N. Meckler
将聚集同位素（Δ47）温度计应用于有孔虫微体化石，由于其对海水的同位素组成不敏感（与传统的氧同位素（δ 18 O）分析不同），有可能显着改善古气候重建。然而，在成岩作用期间，有孔虫方解石的原始Δ 47特征的改变程度还不清楚。本文介绍了大西洋ODP/IODP 1408、1409、1410、1050、1260和1263号站中始新世底栖和浮游有孔虫的Δ 47数据以及高分辨率（约10 kyr）δ 18 O和δ 13 C时间序列。所检查的地点跨越各种海洋学制度，包括西热带到中纬度北大西洋和东中纬度南大西洋。通过对比不同保存状态的同生有孔虫的资料，我们测试了成岩蚀变对海洋深部和表层古温度重建的影响。我们发现，总的来说，主要的Δ 47签名似乎类似的敏感性成岩叠加的δ 18 O，敏感性的差异取决于孔隙流体化学和次生方解石的量。当南极有孔虫发生显著变化时，由Δ 47和δ 18 O值得出的海表温度偏向于低温。相比之下，底栖和保存完好的南极有孔虫的Δ 47和δ 18 O值受成岩作用的影响较小，因此可能产生稳健的有孔虫钙化温度。通过对成岩方解石组分的独立估计，可以使用端元建模和基于底栖有孔虫的Δ47温度来校正次生叠印。
Applying the clumped isotope (Δ47) thermometer to foraminifer microfossils offers the potential to significantly improve paleoclimate reconstructions, owing to its insensitivity to the isotopic composition of seawater (unlike traditional oxygen isotope (δ18O) analyses). However, the extent to which primary Δ47signatures of foraminiferal calcites can be altered during diagenesis is not well known. Here, we present Δ47data as well as high-resolution (∼10 kyr) δ18O and δ13C middle Eocene time series, measured on benthic and planktic foraminifera from ODP/IODP Sites 1408, 1409, 1410, 1050, 1260 and 1263 in the Atlantic Ocean. The sites examined span various oceanographic regimes, including the western tropical to mid-latitude North Atlantic, and the eastern mid-latitude South Atlantic. Comparing data from contemporaneous foraminifera with different preservation states, we test the effects of diagenetic alteration on paleotemperature reconstructions for the deep and surface ocean. We find that overall, primary Δ47signatures appear similarly sensitive to diagenetic overprinting as δ18O, with differences in sensitivity depending on pore fluid chemistry and the amount of secondary calcite. Where planktic foraminifera are significantly altered, sea surface temperatures derived from Δ47and δ18O values are biased towards cool temperatures. In comparison, Δ47and δ18O values of benthic and well preserved planktic foraminifera are less affected by diagenesis and thus likely to yield robust foraminiferal calcification temperatures. With independent estimates of diagenetic calcite fractions, secondary overprints could be corrected for, using end-member modeling and Δ47-based temperatures from benthic foraminifera.