Partitioning of oblique convergence coupled to the fault locking behavior of fold-and-thrust belts: Evidence from the Qilian Shan, northeastern Tibetan Plateau

Unconformities in foreland basins may be generated by tectonic processes that operate in the basin, adjacent fold-thrust belt, and broader convergent margin. Foreland basin unconformities represent shifts from high accommodation to nondepositional or erosional conditions in which the interruption of subsidence precludes net sediment accumulation. This study explores the genesis of long duration (>1–20 Myr) unconformities and condensed stratigraphic sections by considering modern and ancient examples from the Andes. These cases highlight potential geodynamic mechanisms of accommodation reduction and hiatus development in Andean-type retroarc foreland settings, including: (a) shortening-induced uplift in the frontal thrust belt and proximal foreland; (b) growth and advance of a broad, low-relief flexural forebulge; (c) uplift of intraforeland basement blocks; (d) tectonic quiescence with regional isostatic rebound; (e) cessation of thrust loading and flexural subsidence during oblique convergence; (f) diminished accommodation or sediment supply due to changes in sea level, climate, erosion, or transport; (g) basinwide uplift during flat-slab subduction; and (h) dynamic uplift associated with slab window formation, slab breakoff, elevated intraplate (in-plane) stress, or related mantle process. These contrasting mechanisms can be distinguished on the basis of the spatial distribution, structural context, stratigraphic position, paleoenvironmental conditions, and duration of unconformities and condensed sections.Thematic collection: This article is part of the Fold-and-thrust belts collection available at: https://www.lyellcollection.org/cc/fold-and-thrust-belts

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Numerical Constraints on Folding and Thrusting in Jiudong Basin: Implication for the Northeastward Growth of Qinghai–Tibetan Plateau

Frontiers in Earth Science ◽

10.3389/feart.2021.778905 ◽

2022 ◽

Vol 9 ◽

Author(s):

Qizhi Chen ◽

Caibo Hu ◽

Felipe Orellana-Rovirosa ◽

Longshou Zhou ◽

Huai Zhang ◽

...

Keyword(s):

Tibetan Plateau ◽

Surface Deformation ◽

Equivalent Plastic Strain ◽

Model Parameters ◽

Thrust Faults ◽

Northern Margin ◽

The North ◽

Thrust Belts ◽

Fold And Thrust Belts ◽

North Qilian

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.

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Two-phase intracontinental deformation mode in the context of India-Eurasia collision: Insights from a structural analysis of the West Kunlun-southern Junggar transect along the NW margin of the Tibetan Plateau

Journal of the Geological Society ◽

10.1144/jgs2021-029 ◽

2021 ◽

pp. jgs2021-029

Author(s):

Hanlin Chen ◽

Xiubin Lin ◽

Xiaogan Cheng ◽

Junfeng Gong ◽

Shuang Bian ◽

...

Keyword(s):

Tibetan Plateau ◽

Deformation Mode ◽

The Tibetan Plateau ◽

The West ◽

Two Phase ◽

Phase Deformation ◽

Thrust Belts ◽

Fold And Thrust Belts ◽

West Kunlun ◽

Weak Zones

The India-Eurasia convergence since early Cenozoic has established the Tibetan Plateau and the Circum-Tibetan Plateau Basin and Orogen System (CTPBOS). When and how the convergence-driving strain has propagated into the CTPBOS is of significant importance in deciphering the growth process of the Tibetan Plateau. In this study, we conduct a structural analysis of the West Kunlun-southern Junggar transect along the NW margin of the Tibetan Plateau to establish the deformation propagation and through this to determine the plateau growth processes. The results suggest a two-phase deformation mode. The first stage features deformation confined in pre-existing weak zones like the West Kunlun orogen, Buchu Uplift and Tian Shan orogen during Paleogene, in which the intracontinental strain was speculated to be mainly consumed by shortening of these weak zones. The second stage is characterized by deformation propagating into foreland regions since early Miocene, in which shorting along foreland fold-and-thrust belts of a scale of tens of kilometers and decreasing basinwardly plays a key role in absorbing intracontinental strain. We suggest that this two-phase deformation mode possibly reflects a shift of governing mechanism of the expansion of the Tibetan Plateau from a rigid-block manner to a critical wedge taper style.Thematic collection: This article is part of the Fold-and-thrust belts collection available at: https://www.lyellcollection.org/cc/fold-and-thrust-belts

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