Coupled sedimentary and δ13C records of western Thailand and South China from Middle to Late Ordovician: Sea-level and climate changes prior to the Hirnantian glaciation
Coupled sedimentary and δ13C records of western Thailand and South China from Middle to Late Ordovician: Sea-level and climate changes prior to the Hirnantian glaciation
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DOI：
10.1016/j.palaeo.2023.111686
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发表时间：
2023-09
期刊：
影响因子：
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通讯作者：
Wenjie Li;Zhongyang Chen;C. Burrett;X. Fang;Chao Li;M. Udchachon;Jitao Chen;Yuandong Zhang
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文献类型：
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作者：
Wenjie Li;Zhongyang Chen;C. Burrett;X. Fang;Chao Li;M. Udchachon;Jitao Chen;Yuandong Zhang
中晚奥陶世的沉积记录具有重要的意义，因为它们可能包含触发大奥陶世生物多样性事件和晚奥陶世大灭绝的关键特征。一些学者提出了一个漫长的气候变冷过程，该过程可能始于中奥陶世，最终在晚奥陶世（Hirnantian）冰期达到顶峰，但对这一变冷-冰期事件的起源、频率、规模和持续时间仍存在争议。对中晚奥陶世过渡记录的沉积学和多地层学研究有助于揭示这一重大气候变化的演化历史。在这里，我们记录和对比的沉积相，牙形石生物地层和碳同位素化学地层的最新Darriwilian通过早期Katian石灰岩序列在坎恰纳布里地区的泰国西部和中国南部。这一对比揭示了两次明显的跨区域海侵事件及其随后的海平面高位期。第一次海侵发生在Darriwilian晚期，导致泰国Nautiloid Site地质公园Sibumasu地体的Tha Manao组的限制碳酸盐相沉积，以及中国南方的庙坡和富含燧石的Hulo组的黑色页岩相沉积。第二次海侵发生在最早的卡田期，形成了台地环境下广泛分布的Pa Kae组和Pagoda组的开阔海相碳酸盐岩和斜坡环境下富含碎屑的Yenwashan组的深水碳酸盐岩。我们还记录了沉积相和碳同位素组成的耦合变化，表明古滕贝格同位素碳漂移（GICE）的上升翼与第二次海侵期同时发生。中国南部和泰国的Sibumasu记录与许多北美的继承记录相当，表明在早期的卡蒂安，可能是由潜在的Darriwilian-Sandbian冰盖的减弱引起的全球海平面上升。
The Middle to Late Ordovician sedimentary records are of great interest because they potentially contain critical signatures about triggers of the Great Ordovician Biodiversification Event and the Late Ordovician Mass Extinction. A long climate cooling has been proposed by some scholars, which may have initiated in Middle Ordovician and eventually culminated in the Late Ordovician (Hirnantian) glaciation; however, the origin, frequency, magnitude and duration of this cooling-glaciation event are still in debate. A sedimentary and multi-stratigraphic study of the Middle to Late Ordovician transition records may help reveal the evolutionary history of this great climate change. Here we document and correlate the sedimentary facies, conodont biostratigraphy and carbon isotope chemostratigraphy of latest Darriwilian through early Katian limestone successions in the Kanchanaburi area of western Thailand and in South China. This correlation reveals two remarkably cross-regional transgression events and their following sea-level highstand periods. The first transgression happened in the latest Darriwilian, leading to the deposition of the Tha Manao Formation of restricted carbonate facies at the Nautiloid Site Geopark in Thailand, Sibumasu Terrane, and the Miaopo and chert-rich Hulo formations of black shale facies in South China. The second transgression was initiated in the earliest Katian, forming the extensively distributed open-marine carbonates of the Pa Kae and Pagoda formations in platform settings, and the debrite-rich, deep-water carbonate of the Yenwashan Formation in slope settings. We also document coupled changes in depositional facies and carbon isotopic compositions, showing that the rising limb of the Guttenberg Isotopic Carbon Excursion (GICE) co-occurred with the second transgression period. The South China and Thailand Sibumasu records are comparable to those of many North American successions, indicating a presumably global sea-level rise in the early Katian, which may have been caused by the waning of the potential Darriwilian–Sandbian icecaps.