Oceanic upwelling is an important process in ocean cycling and has implications for climate change and ocean productivity. During the Late Ordovician to early Silurian (O/S) transition, many dramatic geologic events occurred, including the Hirnantian Glaciation, enhanced organic matter accumulation, and upwelling events. Upwelling is thought to be closely linked to contemporary geologic events; however, the internal relationships and mechanisms involved remain poorly understood due to a reliance on qualitative evidence and low-resolution data. To better determine the presence and development of upwelling, as well as its underlying mechanisms and potential implications for environmental changes during the O/S transition, we report new evidence and insights based on data for South China. Detailed petrographic and geochemical analyses of a well-sequenced drill core from the Lower Yangtze region are presented and compared with other extensively examined sections from the Upper Yangtze region. We show that the excessive biogenic silica content associated with certain geochemical fingerprints (i.e., Cd/Mo, Co × Mn, and Co_EF × Mn_EF) offer compelling evidence for widespread upwelling in the Yangtze region during the O/S transition. This upwelling was strong during the late Katian to Hirnantian, significantly weaker during the early Rhuddanian, and was generally more intense in the relatively deep waters of the Yangtze region. The glacially-influenced temperature difference between the poles and equator, as well as longshore trade winds, may have been the drivers of this widespread upwelling. The upwelling event may have increased surface productivity, driving the accumulation of organic matter in the Wufeng Formation in South China. Moreover, the upwelling event can be regarded as a broad indicator of Late Ordovician glaciation and may be the geochemical basis for the Boda warm Event that occurred prior to Hirnantian cooling.

海洋上升流是海洋循环的重要过程，对气候变化和海洋生产力具有影响。在奥陶纪晚期至志留纪（O / S）过渡期间，发生了许多戏剧性的地质事件，包括希南山脉冰期，有机质积累增加和上升事件。人们认为上升流与当代地质事件密切相关。但是，由于依赖定性证据和低分辨率数据，所涉及的内部关系和机制仍然知之甚少。为了更好地确定上升流的存在和发展，及其在O / S转换过程中对环境变化的潜在机制和潜在影响，我们基于华南地区的数据报告了新的证据和见解。介绍了下扬子地区井眼井眼井眼的详细岩相和地球化学分析结果，并将其与上扬子地区其他经过广泛检查的断面进行了比较。我们表明，与某些地球化学指纹（即Cd / Mo，Co×Mn和Co_EF  ×锰_EF）提供了令人信服的证据，表明在O / S转换期间，扬子地区出现了广泛的上升趋势。在卡迪安晚期至海南天时期，这种上升趋势很强，在Ruddandan初期则明显减弱，而在长江地区相对较深的水域，这种上升趋势更为强烈。两极和赤道之间受冰川影响的温度差以及沿岸航行的风向可能是造成这种普遍上升的原因。上升流事件可能增加了地表生产力，推动了华南五峰组有机质的积累。此外，上升流事件可被视为奥陶纪晚期冰川活动的广泛指标，并且可能是在赫南迪安降温之前发生的博达热事件的地球化学基础。