美国布朗大学Marie-Pierre Aubry课题组取得一项新突破。他们报道了由烯烃衍生的白垩纪二氧化碳分压估算。2024年4月23日，国际知名学术期刊《地质学》发表了这一成果。

烯酮是由浮游植物产生的长链酮类。它们在重建过去海洋表面温度方面有着广泛的作用，这得益于它们在新生代海洋中无处不在的存在。烯酮和溶解无机碳之间的碳同位素分馏(εp)也可以作为过去大气pCO2的代表，并提供了追溯到ca.45 Ma的连续pCO2估计。

课题组研究了这些中生代烯酮的分子结构和分布特征，并对其与新生代烯酮的系统发育关系进行了评价。利用C37甲基烯酮(C37:2Me)的δ13C值，首次导出了中生代烃源岩中以烯酮为基础的pCO2估算值。这些估计表明二氧化碳分压升高了5484090 ppm(中值908 ppm)，与基于植烷的pCO2重建结果一致。最后，对白垩纪可能合成烯烃的粒石藻进行了鉴定。

附：英文原文

Title: Alkenone-derived estimates of Cretaceous pCO2

Author: Weimin Si, Joseph B. Novak, Nora Richter, Pratigya Polissar, Ruigang Ma, Ewerton Santos, Jared Nirenberg, Timothy D. Herbert, Marie-Pierre Aubry

Issue&Volume: 2024-04-23

Abstract: Alkenones are long-chain ketones produced by phytoplankton of the order Isochrysidales. They are widely used in reconstructing past sea surface temperatures, benefiting from their ubiquitous occurrence in the Cenozoic ocean. Carbon isotope fractionation (εp) between alkenones and dissolved inorganic carbon may also be used as a proxy for past atmospheric pCO2 and has provided continuous pCO2 estimates back to ca. 45 Ma. Here, an extended occurrence of alkenones from ca. 130 Ma is reported. We characterize the molecular structure and distribution of these Mesozoic alkenones and evaluate their potential phylogenetic relationship with Cenozoic alkenones. Using δ13C values of the C37 methyl alkenone (C37:2Me), the first alkenone-based pCO2 estimates for the Mesozoic are derived. These estimates suggest elevated pCO2 with a range of 5484090 ppm (908 ppm median) during the super-greenhouse climate of the Early Cretaceous, in agreement with phytane-based pCO2 reconstructions. Finally, insights into the identity of the Cretaceous coccolithophores that possibly synthesized alkenones are also offered.

DOI: 10.1130/G51939.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G51939.1/638755/Alkenone-derived-estimates-of-Cretaceous-pCO2redirectedFrom=fulltext