Late Ediacaran to Early Cambrian stratigraphic correlation and its geological implications in the northwestern Sichuan Basin: insights from phosphorus, isotopes, and small shelly fossils

IF 2 3区地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY

Frontiers in Earth Science Pub Date : 2024-09-03 DOI:10.3389/feart.2024.1440117

Wenzheng Li, Jianyong Zhang, Xinjian Zhu, Yongxiao Wang, Xingwang Tian, Xiaodong Fu, Hua Jiang, Yuan Zhong, Shugen Liu, Rong Li, Bing Pan, Bin Deng

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Abstract

The characteristics of elements, isotopes, and small shelly fossils were investigated for Late Ediacaran to Early Cambrian stratigraphy division and to discuss their geological implications in the northwestern Sichuan Basin. The results reveal that small shelly fossils can be detected in the high-phosphorous section, with the concentration of phosphorus mainly ranging from 2% to 8%, suggesting that this interval belongs to the Early Cambrian, which is also consistent with the carbon isotopic composition results. In addition, the Early Cambrian is denudated in the Sichuan Basin due to tectonic movement, and the characteristics of some isotopes and small shell fossils are different from those in other basins. It can be proposed that P content can support the recognition of lithological boundaries, and the high phosphorus content can be used as a reference to identify the top and bottom boundaries of the Maidiping Formation in the study area. According to the elemental compositions in the Ediacaran Dengying Formation, the variations in Si, Al, Fe, and K contents are similar in the platform area and rift area, suggesting that the third and fourth member of the Dengying Formation are also developed in the Deyang–Anyue Rift. The results suggest that both the Deng-4 member and Maidiping Formation feature contemporaneous deposition of different facies in the northwestern Sichuan Basin. The strata consist of shale intercalated with thin carbonate rock deposits in the Deyang–Anyue Rift, while carbonate rock deposits in the platform. The Deyang–Anyue Rift expanded gradually in the Late Ediacaran and eventually filled in the Early Cambrian. The data in this study illustrate that elemental compositions, isotopes, and small shelly fossils can be combined to correlate the Late Ediacaran to Early Cambrian strata and provide new evidence for Deyang–Anyue Rift evolution. The results offer some new insights for deep oil and gas exploration in the Sichuan Basin and for the tectonic–depositional–environmental–biological synergistic evolution in the Late Ediacaran to Early Cambrian transition.

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四川盆地西北部晚埃迪卡拉纪至早寒武纪地层关联及其地质影响：磷、同位素和小型搁浅化石的启示

研究了四川盆地晚二叠世至早寒武世地层划分的元素、同位素和小架化石特征，并探讨了其在四川盆地西北部的地质意义。结果表明，在高磷段中可发现小型搁石化石，磷的浓度主要在2%-8%之间，表明该区间属于早寒武世，这也与碳同位素组成结果相一致。此外，早寒武世在四川盆地因构造运动而剥蚀，一些同位素和小贝壳化石的特征与其他盆地不同。可以提出，P 含量可以支持岩性边界的识别，高磷含量可以作为识别研究区内麦地坪地层顶底边界的参考。根据二迭纪邓营地层的元素组成，平台区和裂谷区的硅、铝、铁、钾含量变化相似，表明邓营地层的第三、第四系也发育于德阳-安岳裂谷。研究结果表明，四川盆地西北部登4层和麦地坪地层具有同时沉积不同岩相的特征。在德阳-安岳断裂中，地层由页岩夹薄层碳酸盐岩沉积组成，而在平台中则由碳酸盐岩沉积组成。德阳-安岳裂谷在晚埃迪卡拉纪逐渐扩大，最终在早寒武纪被填平。本研究的数据说明，元素组成、同位素和小型搁浅化石可以结合起来，将晚埃迪卡拉纪地层与早寒武纪地层关联起来，为德阳-安岳裂谷的演化提供新的证据。研究结果为四川盆地深层油气勘探以及晚埃迪卡拉纪向早寒武纪过渡时期的构造-沉积-环境-生物协同演化提供了新的启示。

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来源期刊

Frontiers in Earth Science Earth and Planetary Sciences-General Earth and Planetary Sciences

CiteScore

3.50

自引率

10.30%

发文量

2076

审稿时长

12 weeks

期刊介绍： Frontiers in Earth Science is an open-access journal that aims to bring together and publish on a single platform the best research dedicated to our planet. This platform hosts the rapidly growing and continuously expanding domains in Earth Science, involving the lithosphere (including the geosciences spectrum), the hydrosphere (including marine geosciences and hydrology, complementing the existing Frontiers journal on Marine Science) and the atmosphere (including meteorology and climatology). As such, Frontiers in Earth Science focuses on the countless processes operating within and among the major spheres constituting our planet. In turn, the understanding of these processes provides the theoretical background to better use the available resources and to face the major environmental challenges (including earthquakes, tsunamis, eruptions, floods, landslides, climate changes, extreme meteorological events): this is where interdependent processes meet, requiring a holistic view to better live on and with our planet. The journal welcomes outstanding contributions in any domain of Earth Science. The open-access model developed by Frontiers offers a fast, efficient, timely and dynamic alternative to traditional publication formats. The journal has 20 specialty sections at the first tier, each acting as an independent journal with a full editorial board. The traditional peer-review process is adapted to guarantee fairness and efficiency using a thorough paperless process, with real-time author-reviewer-editor interactions, collaborative reviewer mandates to maximize quality, and reviewer disclosure after article acceptance. While maintaining a rigorous peer-review, this system allows for a process whereby accepted articles are published online on average 90 days after submission. General Commentary articles as well as Book Reviews in Frontiers in Earth Science are only accepted upon invitation.