Fig. 5 Terreneuvian small shelly fossils from the Maidiping Formation at the Maidiping (sample No begins with MD2), Yushan (sample No begins with MDP) and Daqiao Mine (sample No begins with GWS3) sections, South Sichuan, China. ( a – d ), Rugatotheca typica He in Yin et al. , 1980 , ( a, b

Fig. 6 Terreneuvian small shelly fossils from the Maidiping Formation at the Maidiping (sample No begins with MD) and Yushan (sample No begins with MDP) and Daqiao Mine (sample No begins with GWS3) sections, Gaoqiao Town, Emei City of Sichuan Province, China. ( a , b ), Quadrosiphogonuchites

Fig. 7 Terreneuvian small shelly fossils from the Maidiping Formation at the Maidiping section, Gaoqiao Town, Emei City of Sichuan Province. ( a – c ), Maikhanella cf. cambrina (Jiang in Luo, et al. 1982 ), No MD235-001; ( a ) distal view; ( b ) front view; ( c ) lateral view. ( d – f

Fig. 8 Terreneuvian small shelly fossils from the Maidiping Formation at the Maidiping section, Gaoqiao Town, Emei City of Sichuan Province, China. ( a – c ) Ocruranus finial   Liu, 1979 , No MD235-011; ( a ) distal view; ( b ) lateral view; ( c ) front view. ( d – f ) Eohalobia diandongensis

Fig. 9 Terreneuvian small shelly fossils from the Maidiping Formation at the Maidiping section, Gaoqiao Town, Emei City of Sichuan Province, China. ( a – c ) Zhijinites longistriatus   Qian, 1978 , No MD230-013; ( a , b ) lateral view; ( c ) distal view. ( d , e ), Lopochites latazonalis

Fig. 6. Representative outcrop photographs of the Lower Cambrian at the Longzikou section, Beichuan County. ( a ) Black thin-bedded siliceous shale from the lower Maidiping Formation. ( b ) Interbedded thin dolomite and chert from the lower Maidiping Formation. ( c ) Black thin-bedded siliceous

of the Maidiping and Daqiao Mine sections in Sichuan Province. ( c ) The lower phosphorite of the Maidiping Formation in an abandoned mining tunnel in the Madiping section (red arrow in ( d )). ( d ) Overview of the Maidiping section. ( e ) Overview of the complementary section (Yushan section) about 0.5 km

Fig. 3 Stratigraphic column of the Yushan section near to the Maidiping section ( a ) and the Daqiao Mine section ( b ) with the distribution of early Cambrian small shelly fossils in the Maidiping Formation.

Fig. 2 Stratigraphic column of the Maidiping section with the δ 13 C values of carbonates and distribution of early Cambrian small shelly fossils in the Maidiping Formation. For the legend of the lithology see Figure 3 .

Figure 7. Paleogeographic evolution map of the South China cratonic basin during the critical period. (A) Nanhua Datangpo Formation. (B) Ediacaran Doushantuo Formation. (C) Cambrian Maidiping Formation. (D) Cambrian Qiongzhusi Formation.

Figure 18. Thickness contour map of key strata source rocks in South China cratonic basin. Modified from Zhu et al. (2023b) and Zhu et al. (2020b) . (A) Nanhua Datangpo Formation. (B) Ediacaran Doushantuo Formation. (C) Cambrian Maidiping Formation. (D) Cambrian Qiongzhusi Formation.

Fig. 11. Upper continental crust (UCC) normalized element patterns of Maidiping Formation ( a ), Qiongzhusi Formation ( b ) and Canglangpu Formation ( c ) samples from the Longzikou section. UCC composition data are from Taylor and McLennan (1985).

Fig. 4. Evolution model of the Deyang–Anyue intracratonic rift. 1 , dolostone; 2 , fault; 3 , algal mound; 4 , Dengyingzu Formation argillutite; 5 , Maidiping Formation marl; 6 , argillutite.

Figure 12. Histograms displaying concentrations (A) and relative percentages (B) of detrital, diagenetic, and other silica in studied samples of lower Cambrian (A) and lower Silurian (B) successions of the middle–upper Yangtze platform. MDP = Maidiping Formation; STJ/QZS = Shuijingtuo/Qiongzhusi

Figure 13. Post-Archean average shale (PAAS)-normalized rare earth elements and Y values of three Maidiping Formation mudstone samples (high SiO 2 and low Al 2 O 3 concentrations; see Figure 11A ) and North Pacific seawater ( Alibo and Nozaki, 1999 ).

. (2014) . Ed. = Ediacaran; Fm. = Formation; GYQ = Guanyinqiao Member; MDP = Maidiping Formation; Upp. = Upper; YJH = Yanjiahe Formation.

= the third member of the Dengying Formation; Є 1 m = the Lower Cambrian Maidiping Formation; Є 1 q = the Lower Cambrian Qiongzhusi Formation.

; 21 , platform-margin beach; 22 , intraplatform mound; 23 , platform-margin mound; 24 , Maidiping Formation; 25 , Member 3 of the Dengying Formation; 26 , Doushantuo Formation.