Abstract

The Ulungu Depression, located in the northeastern Junggar Basin, adjacent to the Altai Orogenic Belt, exhibits distinctive tectonic relationships and evolutionary mechanisms. Through integrated interpretation of seismic and electromagnetic data, a composite transect was established to characterize the deep-to-shallow geological architecture of the Altai Orogenic Belt–Ulungu Depression system. The tectonic evolution since the Late Paleozoic was reconstructed, revealing three distinct phases: (1) Late Paleozoic peripheral foreland basin development, (2) Mesozoic intracontinental foreland basin formation, and (3) Cenozoic intracontinental foreland basin reactivation. The Late Paleozoic phase records the formation of a peripheral foreland basin in the northeastern Junggar Basin, driven by the Altai-Junggar collision orogeny. During the Mesozoic, intracontinental orogeny along the Altai Belt controlled the development of an intracontinental foreland basin in this region. Paleogene tectonic quiescence facilitated regional subsidence and stable sedimentary deposition. From the Neogene to Quaternary, the Ulungu Depression experienced weak compressional deformation dominated by minor thrust faults, with intermittent regional extensional structures, attributable to the far-field effects of the India-Eurasia collision. This distant tectonic stress primarily localized intracontinental orogeny in the North Tianshan, while the Ulungu Depression, situated farther north, exhibited attenuated strain partitioning. Reconstruction of this multi-phase tectonic evolution provides critical insights into the accretionary orogenic processes of Central Asia. Furthermore, it offers practical implications for hydrocarbon exploration in the Ulungu Depression, particularly regarding structural traps and reservoir distribution patterns.

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