Significant perturbations in ocean redox states have been thought to be one of the major causes for the biological evolution from the Ediacara biota to the Cambrian fauna. However, the driving force of these changes in the ecosystem across the Ediacaran–Cambrian (E–C) boundary is still a matter of debate. In this study, we reported stratigraphic variations of Hg content and Hg isotopes in E–C sediments from the Mussoorie section, Lesser Himalaya, India. Dolomites from the late Ediacaran Krol D and E members have increasing Hg/Al ratios and decreasing Δ¹⁹⁹Hg values from the base upwards, which were most likely originated from a prolonged and enormous terrestrial-Hg input into the E–C ocean. The overlying cherty phosphorites in the lowest Tal Group are highly rich in Re relative to Mo, indicative of a suboxic-anoxic depositional environment on the earliest Cambrian shelf that was coincident with the disappearance of the Ediacara biota. Such an O₂-deficient condition was possibly led by a consumption of atmospheric O₂ during the oxidative weathering of sedimentary organic matter and shallow-water eutrophication, with evidence from the coupled δ²⁰²Hg and δ¹³C values in late-Ediacaran dolomites and high Cd/TOC and Zn/TOC ratios in early Cambrian phosphorites. The overlying black shales have decreasing contents of Hg and micronutrients (Cd and Zn) and increasing values of Δ¹⁹⁹Hg, representing notable declines of terrestrial flux and seawater nutrient at the Cambrian Stage 2 before the major phase of Cambrian diversification. Therefore, we conclude that enhanced continental erosion and pervasive upwelling had led to major changes in redox state and nutrient content in shallow seawaters on shelves, which in turn had promoted the biological evolution across the E–C boundary.

人们认为，海洋氧化还原状态中的显着扰动是从埃迪卡拉生物群到寒武纪动物群生物进化的主要原因之一。然而，跨越Ediacaran-Cambrian（EC）边界的生态系统中这些变化的驱动力仍然是一个争论的问题。在这项研究中，我们报道了印度小喜马拉雅山穆索里地区E-C沉积物中Hg含量和Hg同位素的地层变化。从晚埃迪卡拉克罗尔d和E成员白云石具有增加汞/ Al比和减小Δ ¹⁹⁹Hg值从底部向上，最有可能是由于长期大量的陆上Hg输入到ec海洋中而产生的。相对于Mo而言，最低的Tal组中的上覆含钙磷矿含丰富的Re，表明最早的寒武纪陆架上存在亚缺氧-缺氧的沉积环境，这与埃迪卡拉生物群的消失相吻合。这样的直径：₂缺陷型条件是可能通过大气的O消耗导致₂沉积有机质和浅水富营养化氧化风化过程中，与从证据耦合δ ²⁰² Hg和δ ¹³Ediacaran晚白云岩中的C值和寒武纪早期磷矿中的高Cd / TOC和Zn / TOC比。覆黑色页岩具有减小的汞含量和微量营养素（Cd和Zn）和Δ的增加的值¹⁹⁹汞柱，表示在寒武纪阶段2寒武纪多样化的主要阶段之前地面通量和海水营养的显着下降。因此，我们得出结论，大陆侵蚀的加剧和普遍的上升流已导致架子上浅海水中氧化还原状态和养分含量的重大变化，进而促进了跨EC边界的生物演化。