Provenance characteristics from the Mesozoic to the Cenozoic era and their implications for basin-mountain system evolution in the southwestern Junggar Basin: Insights from field outcrop observations in the Tostai area

Abstract The Mesozoic-Cenozoic formations in the southwestern Junggar Basin are a key target for oil and gas exploration. However, complex provenance conditions hinder a comprehensive understanding of sedimentary reservoirs. Based on the petrology and elemental geochemistry analysis of field outcrops in the Tostai area, research is conducted on the tectonic background, sediment transport distances, compositions of parent rocks, and evolutionary characteristics of provenance conditions in the provenance areas. It is generally believed that there have been three notable shifts in basin-mountain relationships during this period. Initially, from the Triassic to the Jurassic, the Northern Tianshan magmatic rock area predominated as the primary provenance, with decreasing basin-mountain proximity and predominantly magmatic rock sediment composition indicating near provenance. Subsequently, heightened Cretaceous tectonic activity in the Tianshan Mountains leads to significant uplift of metamorphic rock regions in the Middle Tianshan Mountains, gradually becoming the provenance for the study area. This increased distance between the provenance and sedimentary areas is marked by a substantial presence of metamorphic rocks in sediments, indicating a far provenance. Finally, the Cenozoic Himalayan movement resulted in the vigorous uplift of the magmatic rock area in the northern Tianshan Mountains, re-establishing it as the primary provenance. This minimized the basin-mountain distance, leading to the deposition of the near-provenance transported alluvial fans, braided rivers, and predominantly magmatic rock sediments.