Origins of archaeal tetraether lipids in sediments : Insights from radiocarbon analysis
Origins of archaeal tetraether lipids in sediments : Insights from radiocarbon analysis
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DOI：
10.1016/j.gca.2008.06.021
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发表时间：
2008-09
影响因子：
5
通讯作者：
S. Shah;G. Mollenhauer;N. Ohkouchi;T. Eglinton;A. Pearson
中科院分区：
文献类型：
--
作者：
S. Shah;G. Mollenhauer;N. Ohkouchi;T. Eglinton;A. Pearson
了解海洋沉积物中甘油二植烷基甘油四醚（GDGT）的供应和保存有助于了解其在古海洋学中的应用。化合物特定的放射性碳测量沉积烯酮从多种环境已被用来深入了解的过程，影响[公式：见文字]古温度重建。类似的分析是必要的，以调查如何影响GDGT影响TEX 86古温度的类似过程。在这里，我们提出了放射性碳测量个别GDGT从百慕大上升和圣莫尼卡盆地沉积物和讨论的背景下，以前的研究共沉积烯酮和有孔虫的结果。百慕大海隆GDGT和南极有孔虫的14 C含量非常相似，表明是一个本地来源;与[公式：见正文]温度相比，TEX 86得出的温度与有孔虫温度更接近。相比之下，圣莫尼卡盆地GDGT相对于烯酮和有孔虫的14 C值都是亏损的，TEX 86温度与已知的地表水值不一致。我们提出了三个可能的因素，可以解释这些结果：（一）GDGT可能是不稳定的相对于烯酮在平流运输过程中通过含氧沃茨;（二）古菌生产在水柱深处可能contribute 14 C-贫化GDGT沉积物;（三）一些GDGT也可能来自沉积古菌群落。这三个过程中的每一个都可能发生，其相对重要性因地理位置而异。后两个可能有助于解释为什么从圣莫尼卡盆地的TEX 86温度重建似乎没有反映实际的海面温度。陆源GDGT不太可能是百慕大隆起或圣莫尼卡盆地沉积物的主要贡献者，根据BIT指数的值。结果还表明，crenarchaeol区域异构体是由不同于其他GDGT的过程。个别测量crenarchaeol区域异构体显着耗尽14 C相对于共同发生的GDGT，表明这种化合物的替代来源，目前仍然未知。重新检查的贡献crenarchaeol区域异构体的TEX 86指数表明，它是一个显着的温度重建的灵敏度的影响。
Understanding the supply and preservation of glycerol dibiphytanyl glycerol tetraethers (GDGTs) in marine sediments helps inform their use in paleoceanography. Compound-specific radiocarbon measurements of sedimentary alkenones from multiple environments have been used to gain insight into processes that affect [Formula: see text] paleotemperature reconstructions. Similar analyses are warranted to investigate how analogous processes affecting GDGTs impact TEX86paleotemperatures. Here we present radiocarbon measurements on individual GDGTs from Bermuda Rise and Santa Monica Basin sediments and discuss the results in the context of previous studies of co-depositional alkenones and foraminifera. The14C contents of GDGTs and planktonic foraminifera in Bermuda Rise are very similar, suggesting a local source; and TEX86-derived temperatures agree more closely with foraminiferal temperatures than do [Formula: see text] temperatures. In contrast, GDGTs in Santa Monica Basin are depleted in14C relative to both alkenones and foraminifera, and TEX86temperatures agree poorly with known surface water values. We propose three possible factors that could explain these results: (i) GDGTs may be labile relative to alkenones during advective transport through oxic waters; (ii) archaeal production deep in the water column may contribute14C-depleted GDGTs to sediments; and (iii) some GDGTs also may derive from sedimentary archaeal communities. Each of these three processes is likely to occur with varying relative importance depending on geographic location. The latter two may help to explain why TEX86temperature reconstructions from Santa Monica Basin do not appear to reflect actual sea surface temperatures. Terrigenous GDGTs are unlikely to be major contributors to Bermuda Rise or Santa Monica Basin sediments, based on values of the BIT index. The results also indicate that the crenarchaeol regioisomer is governed by processes different from other GDGTs. Individual measurements of the crenarchaeol regioisomer are significantly depleted in14C relative to co-occurring GDGTs, indicating an alternative origin for this compound that presently remains unknown. Re-examination of the contribution of crenarchaeol regioisomer to the TEX86index shows that it is a significant influence on the sensitivity of temperature reconstructions.