Carbon Isotope Stratigraphy of the Ediacaran–Cambrian Transition in the Sichuan Basin, South China: Implications for the Assembly Between Yangtze Block and Gondwana

ABSTRACT

The Ediacaran–Cambrian transition (ECT) represents a key interval of basin reorganization in the Yangtze Block, yet the relationship between stratigraphic completeness and lithospheric processes remains poorly constrained in the Sichuan Basin. Here, we integrate chemostratigraphy, lithology, well‐logging analysis and seismic data, along with previous studies, to investigate the Dengying Formation across the Deyang–Anyue intracratonic rift in the Sichuan Basin. The lower Dengying Formation exhibits a consistent P1‐N1‐P2 pattern of δ ¹³ C, with P1 peaks ranging from +1.29‰ to +6.45‰, intervening N1 minima from −1.39‰ to +1.50‰ and P2 peaks from +2.18‰ to +5.28‰, whereas the upper Dengying Formation exhibits a relatively stable positive δ ¹³ C signature. Stratigraphic and sedimentary evidence indicates significant spatial variability in formation completeness, with preferential preservation of lower members and erosion of upper units across structural domains. Geophysical and thermochronological constraints indicate pronounced lithospheric thinning and thermal enhancement during the ECT, with Moho depths of ~40 km beneath the Deyang–Anyue rift compared with ~50 km beneath adjacent platform areas, together with elevated heat flow during this interval. These observations are consistent with a lithospheric‐scale reorganization during the ECT. Integrated evidence suggests that the Sichuan Basin may have experienced tectonically controlled lithospheric extension, with subsequent structural reconfiguration, which was associated with early Cambrian Gondwana assembly.