No oxygen isotope fractionation for subfossil cellulose during diagenesis

IF 3.6 2区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Chemical Geology Pub Date : 2025-06-23 DOI:10.1016/j.chemgeo.2025.122945

Junbo Ren , Chenxi Xu , Brian A. Schubert , Heng Zhong , Fangming Jin , Chunchun Wang , Zhengtang Guo

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引用次数: 0

Abstract

Nonpermineralized, subfossil wood samples collected from within Cenozoic aged sediments are an important substrate for reconstructing paleoclimate under different levels of atmospheric carbon dioxide. Stable oxygen isotope composition (δ¹⁸O) of cellulose chemically extracted from these samples have been used to quantify seasonal to interdecadal climate; however, the effect of diagenesis on δ¹⁸O values in subfossil cellulose is not clear. In this paper, (1) we experimentally simulate the factors influencing isotopic fractionation during diagenesis, including hydrothermal conditions and fungal degradation, and demonstrate that the δ¹⁸O values of the reacted residues remained nearly unchanged after cellulose extraction; (2) analyze intra-annual δ¹⁸O variation for a subfossil wood sample exhibiting varying degrees of diagenesis, and showed that δ¹⁸O across different degradation levels follow a similar pattern (p < 0.001). Based on these results from both laboratory experiments and analysis of subfossil samples, we conclude that the δ¹⁸O value of cellulose is not affected by diagenesis. Thus, the δ¹⁸O of cellulose can be used to reliably reconstruct palaeoclimate in deep time.

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亚化石纤维素在成岩过程中无氧同位素分馏

从新生代沉积物中采集的非过矿化亚化石木材样品是重建不同大气二氧化碳水平下古气候的重要基质。从这些样品中化学提取的纤维素的稳定氧同位素组成（δ18O）已被用于量化季节至年代际气候；然而，成岩作用对亚化石纤维素δ18O值的影响尚不清楚。本文(1)实验模拟了成岩过程中影响同位素分馏的因素，包括热液条件和真菌降解，结果表明纤维素提取后反应残渣的δ18O值基本保持不变；(2)对不同成岩程度的亚化石木材样品进行年内δ18O变化分析，发现不同降解程度的δ18O具有相似的变化规律(p <；0.001)。根据室内实验和亚化石样品的分析结果，我们认为纤维素的δ18O值不受成岩作用的影响。因此，利用纤维素的δ18O可以可靠地重建深时古气候。

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来源期刊

Chemical Geology 地学-地球化学与地球物理

CiteScore

7.20

自引率

10.30%

发文量

374

审稿时长

3.6 months

期刊介绍： Chemical Geology is an international journal that publishes original research papers on isotopic and elemental geochemistry, geochronology and cosmochemistry. The Journal focuses on chemical processes in igneous, metamorphic, and sedimentary petrology, low- and high-temperature aqueous solutions, biogeochemistry, the environment and cosmochemistry. Papers that are field, experimentally, or computationally based are appropriate if they are of broad international interest. The Journal generally does not publish papers that are primarily of regional or local interest, or which are primarily focused on remediation and applied geochemistry. The Journal also welcomes innovative papers dealing with significant analytical advances that are of wide interest in the community and extend significantly beyond the scope of what would be included in the methods section of a standard research paper.