A comparative study of the central Sichuan paleo-uplift and the northwest Sichuan paleo-uplift during Caledonian period

The Caledonian paleo-uplifts in the Sichuan Basin are mainly located in the mid-west and northwest parts of the basin. Reconstructing and analyzing the formation and evolution of the Caledonian Middle Sichuan paleo-uplift and the northwest Sichuan paleo-uplift can provide new insights and perspectives for the future oil and gas exploration in the Sichuan Basin. Based on the results of the published borehole and seismic data, this study has carried out comparative analyses of the stratigraphic features between the middle and northwest parts of the Sichuan basin, and then identified the distribution of the pinching point, unconformity truncation point, and onlap point for each layer of the Caledonian paleo-uplift in the Sichuan Basin. On this basis, using seismic profiles and cross well lines, we have detailedly depicted and reconstructed the formation and tectonic evolution process of Caledonian paleo-uplifts in the Sichuan Basin. The evidence shows that the Caledonian paleo-uplifts were initially formed from the Late Ordovician to the Early Silurian, and they were slightly readjusted during the Late Silurian Hanjiadian period. The paleo-uplifts reached their maximum distribution range in the Early Silurian and finalized before Permian. The Duyun Movement and the Yunan Movement in the region were key tectonic movements affecting the formation of Caledonian paleo-uplifts in the Sichuan Basin. It is concluded that the Caledonian paleo-uplifts in the Sichuan Basin mainly experienced four stages of tectonic evolution: the differential uplift-fall stage (Z—∈₁m), the developmental stage (∈₁q—S₁), the denudation and flattening stage (S₂—C), and the stable burial stage (P—T₂).