Department of Earth & Planetary Sciences, Washington University in St. Louis, St. Louis, MO, USA.
Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, USA.
Science. 2023 Nov 24;382(6673):912-915. doi: 10.1126/science.adg6103. Epub 2023 Nov 23.
Reconstructions of past environmental conditions and biological activity are often based on bulk stable isotope proxies, which are inherently open to multiple interpretations. This is particularly true of the sulfur isotopic composition of sedimentary pyrite (δS), which is used to reconstruct ocean-atmosphere oxidation state and track the evolution of several microbial metabolic pathways. We present a microanalytical approach to deconvolving the multiple signals that influence δS, yielding both the unambiguous determination of microbial isotopic fractionation (ε) and new information about depositional conditions. We applied this approach to recent glacial-interglacial sediments, which feature over 70‰ variations in bulk δS across these environmental transitions. Despite profound environmental change, ε remained essentially invariant throughout this interval and the observed range in δS was instead driven by climate-induced variations in sedimentation.
重建过去的环境条件和生物活动通常基于整体稳定同位素示踪剂，这些示踪剂本质上存在多种解释。这在沉积黄铁矿（δS）的硫同位素组成中尤为明显，它被用来重建海洋-大气氧化状态，并追踪几种微生物代谢途径的演化。我们提出了一种微观分析方法来分解影响 δS 的多种信号，从而明确确定微生物同位素分馏（ε）并提供有关沉积条件的新信息。我们将这种方法应用于最近的冰期-间冰期沉积物，这些沉积物在这些环境转变中具有超过 70‰的整体 δS 变化。尽管环境发生了巨大变化，但 ε 在整个期间基本保持不变，而 δS 的观测范围则是由气候变化引起的沉积变化驱动的。
