Climate change in the subtropical Paleo-Tethys before the late Ordovician glaciation
Climate change in the subtropical Paleo-Tethys before the late Ordovician glaciation
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晚奥陶世冰期前副热带古特提斯洋气候变化
DOI：
10.1016/j.gloplacha.2021.103432
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发表时间：
2021
影响因子：
3.9
通讯作者：
Yi Wang
中科院分区：
文献类型：
--
作者：
Yuchen Zhang;Peng Tang;Jisuo Jin;Shuo Sun;Xiaole Zhang;Pu Huang;Jue Sun;Yi Wang
晚奥陶世生物多样性大事件（GOBE）是晚奥陶世生物大灭绝（洛梅）之前的第三次生物多样性高潮。本文利用化学蚀变指数（CIA）对塔里木盆地喀田组阿日苏段、粉砂岩段和砂岩段的古环境变化进行了研究。将这些成员的CIA值分别绘制成A-CN-K三元相图。线性回归和95%置信区间估计结果表明，这些矿床来自同一母岩，校正后的CIA（CIAcorr.）值揭示了显着的古气候变化在晚奥陶世。通过比较31个现代河口系统，估算了海表温度（SST）。这些数据显示，CIAcorr.值从77.41下降到64.83，对应于卡提安上游Dicellograptus complex笔石生物带（Ka-4）的解释温度从20.5 °C下降到10.2 °C。CIAcorr.值变化范围为67.63-70.16，表明太平洋副正笔石生物带中下部的温度波动在12.5 - 14.6 °C之间。CIAcorr.值再次从69.09上升到76.05，对应于最后一个Katian的上Paraorthograptus pacificusgraptolite生物带的温度从13.7上升到19.4 °C。这被解释为一个冷却和变暖循环，对应于博达中期冷却和博达晚期变暖事件。这一研究表明，晚喀田期的气候变化比以往认为的更为剧烈，特别是在古特提斯亚热带地区。这一冷却事件加强了温盐海洋环流，成为著名的晚期卡蒂安动物群扩散（即博达事件）的主要因素之一。赫南冰川作用将进一步促进全球海洋变冷，过度强调生态系统，并引发了洛梅。
The latest Katian (Late Ordovician) is marked by the third biodiversity climax of the Great Ordovician Biodiversification Event (GOBE) prior to the Late Ordovician mass extinction (LOME). In this study, the Chemical Index of Alteration (CIA) is used to determine the paleoenvironmental change recorded in the Arisu Member, the Siltstone Member, and the Sandstone Member of the Terekawat (= Tierekeawati) Formation (upper Katian) in the Tarim Basin, northwestern China. CIA values from these members are plotted in A–CN–K ternary diagrams respectively. Linear regression and 95% confidence interval estimation results indicate that these deposits were derived from the same parent rock, and the corrected CIA (CIAcorr.) values reveal significant paleo-climate changes during Late Ordovician. Sea-surface temperatures (SSTs) have been estimated by comparing 31 modern estuary systems. These data show that the CIAcorr.values dropped from 77.41 to 64.83, corresponding to an interpreted temperature drop from 20.5 to 10.2 °C in theDicellograptus complexusgraptolite Biozone of the upper Katian (Ka-4). CIAcorr.values varied within a range of 67.63–70.16, implying temperature fluctuations between 12.5 and 14.6 °C in the lower to middleParaorthograptus pacificusBiozone. CIAcorr.values rose again from 69.09 to 76.05, corresponding to a temperature rise from 13.7 to 19.4 °C in the upperParaorthograptus pacificusgraptolite Biozone of the latest Katian. This is interpreted to be a cooling and warming cycle, corresponding to the mid-Boda cooling and the late-Boda warming events. This study suggests that the climate change during late Katian was more intense than previous thought, especially in subtropical zones of Paleo-Tethys. This cooling event enhanced the thermohaline ocean circulation and became one of the major factors causing the well-known late Katian faunal dispersal (i.e. the Boda event). Hirnantian glaciation would have further promoted global oceanic cooling, over-stressed the ecosystems, and triggered the LOME.