Preservation and detection of microstructural and taxonomic correlations in the carbon isotopic compositions of individual Precambrian microfossils
Preservation and detection of microstructural and taxonomic correlations in the carbon isotopic compositions of individual Precambrian microfossils
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单个前寒武纪微化石碳同位素组成的微观结构和分类学相关性的保存和检测
DOI：
10.1016/j.gca.2012.11.005
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发表时间：
2013
影响因子：
5
通讯作者：
J. Valley
中科院分区：
文献类型：
--
作者：
Kenneth H. Williford;T. Ushikubo;J. William Schopf;K. Lepot;K. Kitajima;J. Valley
本文介绍了利用二次离子质谱（西姆斯）对前寒武纪过矿化显微化石进行原位碳同位素（δ 13 C）分析的技术和新数据，其重复性为1-2‰。对元古代冈弗林特组（1880 Ma）、比特泉组（1830 Ma）、敏亚尔组（1740 Ma）和奇奇坎组（1775 Ma）的叠层石硅质岩的岩石学薄片中保存完好的个体微体化石进行了分析。46个个体的δ 13 C值（-34.6 ‰至-22.1 ‰ VPDB）福尔斯核酮糖二磷酸羧化酶（RuBisCO）光合自养碳固定的预期范围内，与这些标本基于形态学的分类学分配一致。Gunflint组、Bitter Springs组和Min'亚尔组中分类为蓝细菌的微化石（已发表的碳酸盐碳同位素数据可用于估算原始溶解无机碳基质的δ 13 C）显示出一致的~ 19‰的总分馏（溶解无机碳的δ 13 C-生物质的δ 13 C）与在活体蓝细菌中观察到的相似，δ 13 C carb值范围很广（−2.9‰至3.4‰）。在Min'亚尔组的叠层石燧石中，保存在微生物垫的100 mm 2部分中的形态多样的微体化石在分类群之间和分类群内部表现出系统的同位素差异，这些差异与它们的形态推断的生物亲和力相关，并表明它们原始生物合成过程的同位素特征（例如，脂质和肽聚糖合成）被保留。同位素偏移与蓝细菌和光合真核生物典型的不同的基于RuBisCO的分馏相一致，通过位于叠层石奇奇坎燧石中相距<1 cm的群体蓝细菌（−22.6±0.5‰）和植物共生原生类疑源类（−28.9±1.0‰）的不同δ 13 C值来证明。这些研究结果首次表明，为了区分复杂的微生物生态系统和财团内的代谢指纹，使用化石微生物垫和古代沉积物的原位同位素微量分析的可能性。
Here we present techniques for, and new data from, in situ carbon isotope (δ13C) analysis of Precambrian permineralized microscopic fossils with a reproducibility of 1–2‰ using secondary ion mass spectrometry (SIMS). Individual microfossils, selected for their excellent preservation, were analyzed in petrographic thin sections of stromatolitic cherts from the Proterozoic Gunflint (∼1880Ma), Bitter Springs (∼830Ma), Min’yar (∼740Ma), and Chichkan (∼775Ma) Formations. The range of δ13C values (−34.6‰ to −22.1‰ VPDB) among the 46 individuals analyzed falls within that expected for photoautotrophic carbon fixation by ribulose bisphosphate carboxylase (RuBisCO), consistent with morphology-based taxonomic assignments for these specimens. Microfossils classified as cyanobacteria from the Gunflint, Bitter Springs, and Min’yar Formations (for which published carbonate carbon isotope data can be used to estimate the δ13C of the original dissolved inorganic carbon substrate) exhibit a consistent ∼19‰ total fractionation (δ13C of dissolved inorganic carbon−δ13C of biomass) similar to that observed in living cyanobacteria, over a wide range of δ13Ccarbvalues (−2.9‰ to 3.4‰). In stromatolitic chert of the Min’yar Formation, morphologically diverse microfossils preserved in a ∼1mm2part of a microbial mat exhibit systematic isotopic differences among and within taxa that correlate with their morphologically inferred biological affinities and suggest that isotopic signatures of their original biosynthetic processes (e.g., lipid and peptidoglycan synthesis) are preserved. Isotopic offsets consistent with the different RuBisCO-based fractionations typical of cyanobacteria and photosynthetic eukaryotes are documented by the differing δ13C values of a colonial cyanobacterium (−22.6±0.5‰) and a phytoplanktonic protistan acritarch (−28.9±1.0‰) situated <1cm apart in the stromatolitic Chichkan chert. These findings show for the first time the possibility of using in situ isotopic microanalysis of fossil microbial mats and ancient sediments in order to distinguish metabolic fingerprints within complex microbial ecosystems and consortia.