Sequence stratigraphy and tectono-depositional evolution of a late Ediacaran epeiric platform in the upper Yangtze area, South China

Constraints on the Organic Matter Accumulation of Lower Cambrian Niutitang Shales in the Middle Yangtze Region, South China

“…Therefore, the E-C successions of the Yangtze Block across the platform-basin transect are quite variable (Figure 2). As shown in Figure 2, in the upper Ediacaran, the dolomite-dominated Dengying Formation covers platform and slope margin; however, slope and basinal settings are covered by the chert-dominated Liuchapo Formation, which is equivalent to Dengying Formation [39,40,42,43]. Towards the basin, the Liuchapo Formation appears as a diachronous unit, straddling the E-C boundary [42,43].…”

“…2 Lithosphere due to intense rifting [37,38]. The Yangtze block underwent an intense extensional (rifting) tectonism during the E-C transition [36,39,40,41], as indicated by the existence of a hydrothermal eruption system related to extensional faults along the southern margin of the middle Yangtze Block.…”

“…The Yanjiahe and Yangjiaping Formations constitute the lowermost Cambrian strata in the platform successions, which change into the upper Liuchapo Formation towards the basin. These formations are further overlain by the widely distributed Niutitang (or correlative Shuijingtuo) Formation, the basal age of which is 522 Ma (Figure 2; [39,40,43]).…”

New Facies Model and Carbon Isotope Stratigraphy for an Ediacaran Carbonate Platform From South America (Tamengo Formation—Corumbá Group, SW Brazil)

“…The shales dominating the middle part of the Corcal, facies C8, represent a significant decreasing of the energy and of the carbonate input. They can be attributed to episodes of relative sea level rise, in which the flooded carbonate factory decreased its productivity, and the environment reached higher depths, below the storm wave base (Walker, 1984;Łabaj and Pratt, 2016;Oliveira et al, 2019;Amorim et al, 2020;Ding et al, 2021). The limestone intervals within the shales display facies C1, C5, and C6, indicative of higher energy conditions that can be attributed to a mid-ramp setting (Burchette and Wright, 1992;Schlager, 2005).…”

“…These facies can indicate a low energy environment, however, the presence of syn-sedimentary fractures and occasional brecciation suggests post depositional destabilization, possibly related to the still ongoing opening of the rift or to the gravitational slides onto a steep substrate (e.g., Sanders and Höfling, 2000;Basilone et al, 2016). The absence of fluidification and slumping structures makes more likely a gravitational than a seismic trigger (Audemard and Michetti, 2011) Consequently, the lenticular massive breccia devoid of basement clasts (facies L12), occurring between 5 and 10 m, can be related to a local sediment slide, with reworking of intraclasts, forming a small fan downdip (Ding et al, 2021). Besides, the calcimudstones with bird-eyes structures, occurring repeatedly above (facies L13), indicate shallow tidal or peritidal conditions, reached after the rapid filling of the graben in a still relatively low sea level phase (Figures 6, 9; Tucker and Wright, 1990;Burchette and Wright, 1992;Flügel, 2004;Ding et al, 2021).…”