对出露于塔里木盆地北缘阿克苏地区寒武系纽芬兰统玉尔吐斯组上部和寒武系第二统肖尔布拉克组下部海相沉积碳酸盐岩进行了氧化-还原敏感元素(Mo、V、Cd和U)及稳定C、O同位素的地球化学剖面研究,以探讨早寒武世沉积碳酸盐岩的沉积环境.研究揭示,尤尔美那克剖面肖尔布拉克组底部和下部含有两个δ13C负异常,谷值分别为-2.1‰和-2.4‰同时伴随着氧化-还原敏感元素的富集.研究认为,δ13C负异常可能与底层水体上涌引起的生物产率降低有关.剖面中肖尔布拉克组底部(样品YR-3、YR-4和YR-5层位)的氧化-还原敏感元素含量明显的负漂移及Mn的局部富集,反映了氧化-还原条件的急剧波动和短暂的强氧化沉积环境;样品YR-9、YR-10、YR-11、YR-12和YR-13层位的氧化-还原敏感元素含量较地壳沉积碳酸盐岩平均含量富集且V/Cr和V/Sc比值亦较高,指示了缺氧的沉积环境;尤尔美那克剖面上部具有较低的氧化-还原敏感元素含量及V/Sc比值,呈现出水体的相对含氧特征.基于玉尔吐斯组及肖尔布拉克组出现大量生物化石的证据,认为研究区内早寒武世海水应是分层的,即碳酸盐岩沉积的浅海含氧水体和大洋底层的次氧化/氧化-缺氧水体,底水上涌是造成次氧化-氧化及缺氧沉积环境变化的主要因素.%The concentrations of redox-sensitive elements Mo, V. Cd. U, and carbon and oxygen isotope data of marine carbonates from the Cambrian Terreneuvian, the upper Yuertusi Formation and the Cambrian Series 2 the lower Xiaoerbulake Formation in the Akesu area, northern of Tarim Basin (China) were investigated to understand bottom water redox conditions during the Early Cambrian. Two negative shifts of δ13C appear in the Xiaoerbulake Formation of the Youermeinake section with valley values of -2.1‰ and -2.4‰, respectively, associated with the enrichment of redox-sensitive elements Mo. V. Cd. and U. Through these analyses, we demonstrate that the δ13C negative shifts might indicate that the bio-productivity was decreasing due to the upwelling water. In the samples YR-3. YR-4. and YR-5, the contents of redox-sensitive elements reveal negative shift. connecting to Mn enrichment. which reflect the changes of the sedimentary conditions and the oxic surroundings. The contents of redox-sensitive elements Mo. V. Cd. and U are dramatically richer than average element contents from the sedimentary carbonates of the Earth Crust, with high V/Cr and V/Sc ratios in the samples YR-9. YR-1O. YR-11,YR-12, and YR-13. and indicate an anoxic deposition environment. On the top of the Youermeinake section. lower concentrations of redox-sensitive elements, especially low V/Sc ratios, might imply near-oxic/suboxic conditionsin the water column. A large amount of fossils were found in the Yuertusi Formation and Xiaoerbulake Formation.Those imply that the ocean was stratified during the Early Cambrian, which was oxic on the surface andsuboxic-oxic with transitory anoxic event in the bottom water. The upwelling water might have resulted in changesin the sedimentary conditions.
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