Pasquier V, Bryant R N, Fike D A, Halevy I
Earth and Planetary Sciences, Weizmann Institute of Sciences, Rehovot, Israel.
Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, MO, USA.
Sci Adv. 2021 Feb 26;7(9). doi: 10.1126/sciadv.abb7403. Print 2021 Feb.
Understanding variation in the sulfur isotopic composition of sedimentary pyrite (δS) is motivated by the key role of sulfur biogeochemistry in regulating Earth's surface oxidation state. Until recently, the impact of local depositional conditions on δS has remained underappreciated, and stratigraphic variations in δS were interpreted mostly to reflect global changes in biogeochemical cycling. We present two coeval δS records from shelf and basin settings in a single sedimentary system. Despite their proximity and contemporaneous deposition, these two records preserve radically different geochemical signals. Swings of ~65‰ in shelf δS track short-term variations in local sedimentation and are completely absent from the abyssal record. In contrast, a long-term ~30‰ decrease in abyssal δS reflects regional changes in ocean circulation and/or sustained pyrite formation. These results highlight strong local controls on δS, calling for reevaluation of the current practice of using δS stratigraphic variations to infer global changes in Earth's surface environment.
了解沉积黄铁矿硫同位素组成（δS）的变化，其动机源于硫生物地球化学在调节地球表面氧化态方面的关键作用。直到最近，局部沉积条件对δS的影响仍未得到充分认识，δS的地层变化大多被解释为反映生物地球化学循环的全球变化。我们展示了来自单一沉积系统中陆架和盆地环境的两个同时期的δS记录。尽管它们距离相近且同时沉积，但这两个记录保留了截然不同的地球化学信号。陆架δS约65‰的波动追踪了局部沉积的短期变化，而深海记录中则完全没有。相反，深海δS长期约30‰的下降反映了海洋环流的区域变化和/或持续的黄铁矿形成。这些结果突出了对δS的强烈局部控制，要求重新评估目前利用δS地层变化来推断地球表面环境全球变化的做法。
