熊轶伟,潘兵,吕苗,冯倩,孙晓娟,杨爱华,朱茂炎

• 1:中国科学院南京地质古生物研究所现代古生物学和地层学国家重点实验室
• 2:中国科学院生物演化与环境卓越创新中心
• 3:中国科学院大学地球与行星科学学院
• 4:南京大学地球科学与工程学院关键地球物质循环前沿科学中心

摘要(Abstract)：

扬子台地作为中国埃迪卡拉纪-寒武纪过渡时期地层研究的重要区域,已经建立起一套较为完整的生物地层序列。然而,扬子台地寒武系下部地层的划分和对比目前依然存在一些困难和争议。在生物地层尚未得到很好限定的情况下,使用非生物地层标准,特别是碳同位素异常事件作为辅助标准来划分和对比寒武系下部地层值得尝试。本文选择四川南部乌斯河大桥剖面与范店剖面的灯影组和麦地坪组开展碳同位素地层学研究,结果显示乌斯河大桥剖面碳同位素值自下而上在稳定正值后,在麦地坪组底部出现了一次显著的负异常事件,由0左右快速降至-3.86‰;而范店剖面碳同位素值自下而上在稳定负值后,在麦地坪组上段出现了一次正异常事件,由-1.12‰左右快速升至3.43‰。在小壳化石生物地层学框架下,通过与扬子台地内其他地区寒武系下部典型剖面的碳同位素变化曲线进行对比后发现:乌斯河大桥剖面麦地坪组底部的碳同位素负异常事件为BASE事件;范店剖面麦地坪组上部碳同位素正异常的底部与Watsonella crosbyi首现点一致,是ZHUCE事件的可靠记录。本研究不仅补充了该地区碳同位素化学地层信息,也为认识扬子台地不同地区间寒武系下部地层发育差异与地层划分对比提供了有价值的证据。此外,通过综合分析华南、西伯利亚、蒙古和摩洛哥四个地区的经典剖面的同期地层碳同位素曲线与相关化石记录及同位素年龄的关系,本文认为碳同位素事件BACE与ZHUCE具有全球可对比性。虽然全球小壳化石的首现与BACE事件底部负异常的开始点不完全一致,但在有一定生物地层限定的情况下,结合同位素年龄, BACE事件可以作为寒武系底界对比的标志。而在大部分地区, ZHUCE事件底部与Watsonella crosbyi首现点一致,具有作为寒武系纽芬兰统第二阶地层划分对比辅助标准的潜力。

关键词(KeyWords)： 埃迪卡拉纪;寒武纪;灯影组;麦地坪组;碳同位素化学地层;小壳化石

Abstract:

Keywords:

基金项目(Foundation): 中国科学院战略性先导科技专项(B类)(XDB26000000);; 国家自然科学基金(41872011、41921002)共同资助

作者(Author): 熊轶伟,潘兵,吕苗,冯倩,孙晓娟,杨爱华,朱茂炎

DOI: 10.19839/j.cnki.dcxzz.2022.0015

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