Abstract
Under regional tectonic shortening in the northern margin of Qinghai–Tibetan Plateau, the fold-and-thrust belts composed of four thrust faults (North Qilian-Shan, North Yumu-Shan, South Heli-Shan, and North Jintanan-Shan) formed from southwest to northeast discontinuously sequentially in the Jiudong Basin area during Late Cenozoic. Meanwhile, the North Qilian-Shan, Yumu-Shan, and Heli-Shan ranges were formed successively, as the Earth's local surface was unequally uplifted. In this study, based on geological and geophysical observations, a simple two-dimensional elastic-plastic numerical finite element method model for a southwest-northeast section in Jiudong Basin is successfully established to simulate the spatiotemporal evolution of the local fold-and-thrust belts. Results show that the computed equivalent plastic strain concentration zones and the four observed thrust faults are consistently correlated in spatial position orientation and time sequence. The simulated upper-surface deformation is congruent with the observed topographic peaks and uplift sequences of the North Qilian-Shan, Yumu-Shan, and Heli-Shan ranges. This study provides a geodynamic basis for understanding the growth mechanism of the northern margin of Qinghai–Tibetan Plateau under tectonic horizontal shortening. Also, we provide a thorough sensitivity analysis for the model parameters of this particular geologic setting. Our sensitivity simulations, considering systematic case variations about the regional geometrical-material parameters, suggest the manifestation of three different possible evolution patterns of fold-and-thrust belts for a wedge above a decollement layer, with wedge plastic deformation migrating from 1) thick to thin end (well-known), 2) thin to thick end, and 3) both ends to middle. Finally, our results suggest that in this region, further growth of mountain ranges is expected to continue in the future.
Highlights
Influenced by the far-field effect of the India–Eurasia plate collision, the northern margin of Qinghai–Tibetan Plateau has been continuously growing outward since the Late Cenozoic (Tapponnier et al, 2001)
We study the main features of the tectonic evolution of four thrust belts and three mountain ranges in the Jiudong Basin region since the Late Cenozoic, compare and analyze the spatiotemporal evolution of our models with observational data, and quantitatively try to explain the growth and development of fold-and-thrust belt in Jiudong Basin
It is inferred from the model results that the wedge deforms episodically with the progressive horizontal contraction, and the fold-and-thrust belt will likely grow further with time, which is useful for determining whether the northeast margin of the Qinghai–Tibetan Plateau continues to grow
Summary
Influenced by the far-field effect of the India–Eurasia plate collision, the northern margin of Qinghai–Tibetan Plateau has been continuously growing outward since the Late Cenozoic (Tapponnier et al, 2001). We study the main features of the tectonic evolution of four thrust belts and three mountain ranges in the Jiudong Basin region since the Late Cenozoic, compare and analyze the spatiotemporal evolution of our models with observational data, and quantitatively try to explain the growth and development of fold-and-thrust belt in Jiudong Basin It is inferred from the model results that the wedge deforms episodically with the progressive horizontal contraction, and the fold-and-thrust belt will likely grow further with time, which is useful for determining whether the northeast margin of the Qinghai–Tibetan Plateau continues to grow
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