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Triple oxygen isotope evidence for limited mid-Proterozoic primary productivity
Nature ( IF 50.5 ) Pub Date : 2018-07-01 , DOI: 10.1038/s41586-018-0349-y
Peter W Crockford 1, 2, 3 , Justin A Hayles 4, 5 , Huiming Bao 5, 6 , Noah J Planavsky 7 , Andrey Bekker 8 , Philip W Fralick 9 , Galen P Halverson 1 , Thi Hao Bui 1 , Yongbo Peng 5 , Boswell A Wing 10
Affiliation  

The global biosphere is commonly assumed to have been less productive before the rise of complex eukaryotic ecosystems than it is today1. However, direct evidence for this assertion is lacking. Here we present triple oxygen isotope measurements (∆17O) from sedimentary sulfates from the Sibley basin (Ontario, Canada) dated to about 1.4 billion years ago, which provide evidence for a less productive biosphere in the middle of the Proterozoic eon. We report what are, to our knowledge, the most-negative ∆17O values (down to −0.88‰) observed in sulfates, except for those from the terminal Cryogenian period2. This observation demonstrates that the mid-Proterozoic atmosphere was distinct from what persisted over approximately the past 0.5 billion years, directly reflecting a unique interplay among the atmospheric partial pressures of CO2 and O2 and the photosynthetic O2 flux at this time3. Oxygenic gross primary productivity is stoichiometrically related to the photosynthetic O2 flux to the atmosphere. Under current estimates of mid-Proterozoic atmospheric partial pressure of CO2 (2–30 times that of pre-anthropogenic levels), our modelling indicates that gross primary productivity was between about 6% and 41% of pre-anthropogenic levels if atmospheric O2 was between 0.1–1% or 1–10% of pre-anthropogenic levels, respectively. When compared to estimates of Archaean4–6 and Phanerozoic primary production7, these model solutions show that an increasingly more productive biosphere accompanied the broad secular pattern of increasing atmospheric O2 over geologic time8.Triple oxygen isotope measurements of 1.4-billion-year-old sedimentary sulfates reveal a unique mid-Proterozoic atmosphere and demonstrate that gross primary productivity in the mid-Proterozoic was between 6% and 41% of pre-anthropogenic levels.

中文翻译:

三氧同位素证据表明有限的中元古代初级生产力

通常认为,在复杂的真核生态系统兴起之前,全球生物圈的生产力低于今天 1。然而,这种说法缺乏直接证据。在这里,我们展示了大约 14 亿年前来自 Sibley 盆地(加拿大安大略省)的沉积硫酸盐的三重氧同位素测量值 (Δ17O),这为元古代中期生物圈生产力较低提供了证据。据我们所知,我们报告了在硫酸盐中观察到的最负的 Δ17O 值(低至 -0.88‰),除了来自低温纪末期的那些。这一观察表明,中元古代大气与过去大约 5 亿年持续存在的大气不同,直接反映了此时大气 CO2 和 O2 分压与光合 O2 通量之间的独特相互作用 3。氧气总初级生产力在化学计量上与进入大气的光合 O2 通量有关。根据目前对中元古代大气 CO2 分压的估计(是人为前水平的 2-30 倍),我们的模型表明,如果大气中的 O2 介于分别为前人为水平的 0.1-1% 或 1-10%。与太古代4-6 和显生宙初级生产7 的估计值相比,这些模型解决方案表明,随着地质时间8 大气O2 增加的广泛长期模式伴随着生产力日益提高的生物圈。
更新日期:2018-07-01
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