Depth dependency of the Paleocene‐Eocene carbon isotope excursion: Paired benthic and terrestrial biomarker records (Ocean Drilling Program Leg 208, Walvis Ridge)
Depth dependency of the Paleocene‐Eocene carbon isotope excursion: Paired benthic and terrestrial biomarker records (Ocean Drilling Program Leg 208, Walvis Ridge)
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DOI：
10.1029/2008gc002116
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发表时间：
2008-10
期刊：
影响因子：
3.7
通讯作者：
H. McCarren;Ellen Thomas;Takashi Hasegawa;U. Röhl;J. Zachos
中科院分区：
文献类型：
--
作者：
H. McCarren;Ellen Thomas;Takashi Hasegawa;U. Röhl;J. Zachos
古新世 - 始新世极热事件（PETM）与陆地和海洋记录中碳酸盐和有机物的碳同位素负偏移（CIE）同时发生。因此，PETM导致的全球升温5 - 6°C被归因于大量同位素较轻的碳快速排放到海洋 - 大气系统中，并且CIE的幅度已被用于估算排放的碳温室气体的量。然而，在陆地物质和海洋物质中的CIE幅度、不同类型的海洋碳酸盐记录（整体碳酸盐、浮游有孔虫碳酸盐和底栖有孔虫碳酸盐）以及不同地点的海洋碳酸盐记录之间存在很大差异。由于海洋酸化和海底碳酸盐的广泛溶解，在大多数深海（半深海 - 深海）区域，CIE的海洋碳酸盐记录可能不完整。我们证明，底栖有孔虫稳定同位素记录中的CIE相对突然，并不像沃尔维斯海岭深度剖面（东南大西洋）的整体碳酸盐记录所描绘的那样渐进。在古深度3600米处，底栖CIE约为 - 1.5‰，而在1500米古深度处约为 - 3.5‰，这与碳酸盐溶解导致的深度相关截断一致。从同一岩芯（即1263站）分离出的底栖记录与陆地正构烷烃的稳定碳同位素值之间的强协方差支持至少 - 3.5‰但不超过 - 5.0‰的相对快速偏移。
The Paleocene Eocene Thermal Maximum (PETM) coincided with a negative carbon isotope excursion (CIE) in carbonate and organic matter, in terrestrial and marine records. Consequently the PETM global warming of 5–6°C has been attributed to the rapid emission of a large amount of isotopically light carbon into the ocean‐atmosphere system, and the magnitude of the CIE has been used to estimate the amount of carbon greenhouse gas emitted. However, there are large discrepancies between the magnitude of the CIE in marine and in terrestrial material, in different types of marine carbonate records (bulk carbonate, planktic and benthic foraminiferal carbonate), and in marine carbonate records from different locations. The marine carbonate record of the CIE may be incomplete in most deep‐sea (bathyal‐abyssal) locations because of ocean acidification and widespread dissolution of seafloor carbonates. We demonstrate that the CIE in benthic foraminiferal stable isotope records is relatively abrupt and not as gradual as portrayed in bulk carbonate records along the Walvis Ridge depth transect (SE Atlantic). The benthic CIE is about −1.5‰ at 3600 m paleodepth, in contrast to about −3.5‰ at 1500 m paleodepth, consistent with depth‐dependent truncation by carbonate dissolution. Strong covariance between the benthic record and the stable carbon isotope values of terrestrial n‐alkanes isolated from the same core (i.e., Site 1263) supports a relatively rapid excursion of at least −3.5‰ but no more than −5.0‰.