High-frequency sequences, geochemical characteristics, formations, and distribution predictions of the lower Cambrian Yuertusi Formation in the Tarim Basin

Reconstruction of the paleo-marine environment during the Ediacaran-Cambrian transition: new insights from geochemical proxies, northern Tarim Platform, Northwest China

“…These patterns suggest a strong hydrothermal influence during the Ediacaran-Cambrian transition (Figures 6,10). In particular, samples of Yuertusi Formation group A of both sections display increasing heavier left-leaning REE enrichment, extremely elevated Eu anomalies (5.21-82.66; average = 26.39), moderate Y anomalies (1.37-1.66; average = 1.55), and field features including barite layers (Figure 4D), and siliceous bands within marlstone, all consistent with deposition in association with hydrothermal activity during the Early Cambrian Terreneuvian (Figure 10; Gao et al, 2022;Zhu et al, 2016;Kimura and Watanabe, 2001). However, the weak Eu anomalies (Eu/Eu * avg.…”

“…U-Pb ages of the basement span from 1791 ± 1 Ma to 1848 ± 7 Ma (Yang X. et al, 2017). The basement has been generated in association with Tarim Movement in the middle Neoproterozoic (time equivalent to the Jinning Movement of South China), which resulted in the separation of the Tarim and South China plates (Figure 1; Gao et al, 2022;Feng, 2005;Li, 2010).…”

“…= 1.01) displayed by groups C and D of the Yuertusi Formation and Xiaoerbulake Formation (Eu/Eu * avg. = 0.99) may reflect hypoactive hydrothermal activity and degradation of organic matter (Gao et al, 2022). Instead, heterogeneous distributions of Eu anomalies in vertical direction (with peak value of Eu/Eu * at SG8-4, and YT8-2) and significantly enrichments of platinum group elements (PGEs) in the basal Yuertusi Formation (Figure 10) both illustrate episodic hydrothermal activity.…”

“…The critical Ediacaran-Cambrian transition (635-514 Ma) has witnessed numerous fundamental events of Earth history, including the melting of the snowball Earth, the break-up of Rodinia, and the Ediacaran bio-explosion (Cowie and Glaessner, 1975;Gao et al, 1981;Kimura and Watanabe, 2001;Tyson, 2005;Jiang et al, 2007;Yao et al, 2014a;Yao et al, 2014b). Moreover, triggered by the transition from glacial period to interglacial period, the Cambrian transgression during that interval has laid a foundation of oilbearing basins with deposits of marine facie, such as Al Noor Oilfield of Oman, Kovykta Oilfield of East Siberia, Anyue Gasfiled of Sichuan, and Tarim Oilfield (Yao et al, 2014a;Gao et al, 2022;Zhu et al, 2017). It also resulted in fundamental geological events that closely linked to the hydrocarbon source rocks from the Sinian to Cambrian.…”

“…Based on the deep-layer exploration project, Yu et al (2003), Yu et al (2005), and Yu et al (2009) have reported rare earth elements (REEs) concentrations, Re-Os dating, and Nd isotope data from chert of the basal Yuertusi Formation of the Penglaiba section. Recently, several researchers have focused on petrologic classifications of cherts and their hydrocarbon potential (Gao et al, 2022;Yao et al, 2014a;Yang et al, 2017;Zhu et al, 2017).…”