Discussion on the initial timing of the Indosinian movement in the Ordos basin and the Sichuan basin: Constraints from growth strata evidence

The formation and evolution of the orogenic belt and the peripheral basin were controlled by some genetic tectonic events. The "basin" and "range" are coupled to some extent both in structure and sedimentation. Sedimentary structures can always respond to related orogenic events, such as growth strata and convolute bedding. Growth strata are sedimentary records of the tectonic events, and the analysis of their deposit age can effectively constrain the timing of the tectonic events. The Central China Orogen is distributed in the east-west direction. The north side of the central segment is the Ordos block, and the south side is the Yangtze block. The Central China Orogen mainly resulted from the closure of the Pro-Paleo Tethys Ocean, the extinction of ProTethys Ocean happened in the Paleozoic and the Paleo-Tethys Ocean was closed in the Mesozoic. Notably, the latter modified the orogen resulting from the former and responded to the global Indosinian movement. The Indosinian movement not only facilitated the final assembly of supercontinent Pangea, but also was of great significance in the formation of the rudimentary sketch of China's mainland today. In the process of the Indosinian movement, the South China block and the North China block were collaged, and the Indosinian movement was initiated. The Ordos Basin and the Sichuan Basin recorded the orogenic events well in sedimentary strata. In this paper, the authors identified growth strata in the Upper Triassic on the south margin of the Ordos Basin. The starting time of the Indosinian movement in the Ordos Basin is about 233 Ma. A sets of growth strata were identified in the Upper Triassic on the north margin of the Sichuan Basin and the start time was about 216 Ma.