Folded fluvial terraces in a young, actively deforming intramontane basin between the Yumu Shan and the Qilian Shan mountains, NE Tibet

Hu, Xiaofei; Pan, Baotian; Fan, Yuxin; Wang, Jun; Hu, Zhenbo; Cao, Bo; Li, Qingyang; Geng, Haopeng

doi:10.1130/l614.1

Cited by 17 publications

(36 citation statements)

References 52 publications

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“…However, it should be noted that deformation was concentrated in the north Tibetan crust over at least ~40 m.y., with minimal foreland advancement. The prominent exception is the northward-propagating thrusts underlying the Yumu Shan that advanced into the Hexi Corridor, which has occurred only over the last several million years (e.g., Tapponnier et al, 1990;Hu et al, 2017). That said, the North Qilian Shan remained the approximate northern plateau boundary during Cenozoic deformation (Clark, 2012).…”

Section: Integrated Kinematic Model For the Development Of The Qilianmentioning

confidence: 99%

Underthrusting and duplexing beneath the northern Tibetan Plateau and the evolution of the Himalayan-Tibetan orogen

Zuza

Wang

et al. 2018

Lithosphere

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The Cenozoic Qilian Shan thrust belt is the northern margin of the Tibetan Plateau, which developed in part due to progressive India-Asia convergence during Himalayan-Tibetan orogeny. Available geologic observations suggest that this thrust belt started deforming shortly after initial India-Asia collision at 60-55 Ma, and thus its kinematic development is intrinsically related to the construction and evolution of the Tibetan Plateau. Here, we present new field observations from a geologic traverse across the Qilian Shan to elucidate the style of deformation across the active thrust belt. In particular, we infer protracted out-of-sequence deformation here that is consistent with this thrust system remaining a stationary northern boundary to the Tibetan Plateau since the early Cenozoic. We present a lithosphere-scale model for this region that highlights the following: (1) coupled distributed crustal shortening and underthrusting of the North China craton beneath Tibet, which explains the spatial and temporal distribution of observed crustal shortening and thickness, (2) this underthrusting exploited the south-dipping early Paleozoic Qilian suture paleo-subduction mélange channel, and (3) development of a lower-crustal duplex at the lithospheric underthrusting ramp. This last inference can explain the relatively high elevation, low relief, and thickened crust of the central Qilian Shan, as well as the comparative aseismicity of the region, which experiences fewer earthquakes due to less upper-crustal faulting. Both the northern and southern margins of the Himalayan-Tibetan orogen appear to have developed similarly, with continental underthrusting and crustal-scale imbrication and duplexing, despite vastly different climatic and plate-velocity boundary conditions, which suggests that the orogen-scale architecture of the thrust belt is controlled by neither of these forcing mechanisms. Instead, strength anisotropies of the crust probably control the kinematics and style of deformation, including the development of northern Tibet, where thrust systems are concentrated along pre-Cenozoic suture zones.

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Section: Integrated Kinematic Model For the Development Of The Qilianmentioning

confidence: 99%

Underthrusting and duplexing beneath the northern Tibetan Plateau and the evolution of the Himalayan-Tibetan orogen

Zuza

Wang

et al. 2018

Lithosphere

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“…In tectonically active regions, both strath and fill terraces have been used to infer tectonic deformation rates (e.g., Hu et al, 2017;Lavé and Avouac, 2000;Litchfield and Berryman, 2006;Peters and van Balen, 2007 derived from reconstructed longitudinal channel profiles, have been used to infer local deformation rates (e.g., Hu et al, 2017;Lavé and Avouac, 2000). The observed slope differences between terrace surfaces and the active channel after upstream perturbations in our experiments (Fig.…”

Section: Differences In Terrace Surface Slopesmentioning

confidence: 62%

Alluvial channel response to environmental perturbations: Fill-terrace formation and sediment-signal disruption

Tofelde¹,

Savi²,

Wickert³

et al. 2018

Preprint

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Abstract. The sensitivity of fluvial fill terraces to tectonic and climatic boundary conditions make them potentially useful archives of past climatic and tectonic conditions. However, we currently lack a systematic understanding of the impacts of base-level, water discharge, and sediment discharge changes on terrace formation and associated sediment storage and release. This knowledge gap precludes a quantitative inversion of past environmental changes from terraces. Here we use a set of seven physical experiments to explore terrace formation and sediment export from a braided channel system that is perturbed by changes in upstream water discharge and sediment supply, or downstream base-level fall. Each perturbation differently affects (1) the geometry of terraces and channels, (2) the timing of terrace formation, and (3) the transient response of sediment discharge. In general, an increase in water discharge leads to near-instantaneous channel incision across the entire fluvial system and consequent local terrace cutting, preservation of the initial channel profile on terrace surfaces, and a transient increase in sediment export from the system that eventually returns to its pre-perturbation rate. In contrast, changes in the upstream sediment supply rate may result in longer lag-times before terrace cutting, leading to a less well-preserved pre-perturbation channel profile, and may also produce a gradual change in sediment output towards a new steady-state value. Finally, downstream base-level fall triggers the upstream migration of a knickzone, forming terraces with upstream-decreasing ages. The gradient of terraces triggered by base-level fall mimicks that of the newly-adjusted active channel, whereas gradients of terraces triggered by variability in upstream sediment or water discharge are steeper compared to the new equilibrium channel. Our findings provide guidelines for distinguishing between different types of perturbations when interpreting fill terraces and sediment export from fluvial systems.

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“…Windblown loess may have some influence on the composition of the sediments in the core, but its contribution is believed to be minor. Specifically, the following observations suggest that the influence of windblown loess on our results can be excluded: (1) the oldest loess accumulation in the Jiudong subbasin commenced at ~104.0 ± 10.1 ka based on optically stimulated luminescence dating (Hu et al, 2017; Zhang et al, 2015), which is more recent than the upper age limit of the sediments considered herein. (2) The combination of low temperatures and high wind speeds prevented the development of vegetation and resulted in dust bypassing the Qilian Shan through the Hexi Corridor (Küster et al, 2006).…”

Section: Discussionmentioning

confidence: 87%

Paleoclimatic record from the clay mineralogy of Quaternary sediments of drill core DWJ from Jiudong subbasin (western Hexi Corridor), NW China

Chen

Pan

et al. 2019

Quat. res.

Self Cite

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The thick sedimentary deposits of the Jiudong subbasin in the western Hexi Corridor of NW China can potentially provide important records of climate change in arid and semiarid areas subject to the interaction of the East Asian summer monsoon (EASM) and the westerlies. Here we present the results of a study of the clay mineralogy of the sediments of drill core DWJ from the Jiudong subbasin. The clay minerals consist mainly of illite, followed by chlorite, kaolinite, and smectite. The clay mineral assemblages are used to define four paleoclimatic stages since ~1.8 Ma: (1) During ~1.8–1.2 Ma, the climate was relatively cold and arid; (2) during ~1.2–0.9 Ma, it was relatively warm and wet, with strongly seasonal precipitation; (3) during ~0.9–0.3 Ma, there was a long-term trend of cooling and drying; and (4) during ~0.3–0.1 Ma, the climate was warmer and wetter than during the previous period, with strongly seasonal precipitation. The paleoclimatic record of the Jiudong subbasin since ~1.8 Ma is consistent with records from the Tengger Desert and typical monsoonal areas. This suggests that the EASM penetrated into the central regions of the North Qilian Shan and Zhangye–Jiudong subbasin during ~1.2–0.9 and ~0.3–0.1 Ma.

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Folded fluvial terraces in a young, actively deforming intramontane basin between the Yumu Shan and the Qilian Shan mountains, NE Tibet

Cited by 17 publications

References 52 publications

Underthrusting and duplexing beneath the northern Tibetan Plateau and the evolution of the Himalayan-Tibetan orogen

Underthrusting and duplexing beneath the northern Tibetan Plateau and the evolution of the Himalayan-Tibetan orogen

Alluvial channel response to environmental perturbations: Fill-terrace formation and sediment-signal disruption

Paleoclimatic record from the clay mineralogy of Quaternary sediments of drill core DWJ from Jiudong subbasin (western Hexi Corridor), NW China

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