An Asthenospheric Upwelling Beneath Central Mongolia——Implications for Intraplate Surface Uplift and Volcanism

Intraplate processes,such as continental surface uplift and intraplate volcanism,are enigmatic and the underlying mechanisms responsible are not fully understood.Central Mongolia is an ideal natural laboratory for studying such processes because of its location in the continental interior far from tectonic plate boundaries.

Differential surface uplift: Cenozoic paleoelevation history of the Tibetan Plateau

The surface uplift history of the Tibetan Plateau has provided a key boundary criterion for various geological, climatic,and environmental events since the Cenozoic. The paleoelevation history of the plateau is organically associated with interactions amongst deep geodynamics, earth surface processes, and climate change. Understanding of plateau uplift history has been advanced by the development of a number of paleoaltimetries and their application to studies of the Tibetan Plateau: the paleogeomorphic scenario for the Early Eocene Tibetan Plateau is thought to include two high mountains, the ca. 4500 m Gangdese Mountains to the south, and the ca. 5000 m Qiangtang Center Watershed Mountains to the north. Between these ranges, a low-elevation basin(ca. 2500 m) is thought to have been present. The Himalayas in the southern Tibetan Plateau was close to sea level at this time,while the Hoh Xil Basin in the north reached an elevation of no more than 1500 m. Thus, the so-called "Roof of the World" Tibetan Plateau formed subsequent to the Miocene. Nevertheless,, the uplift histories of the different terranes that comprise this plateau currently remain unclear, which constrains the uplift history reconstruction of the entire Tibetan Plateau. Additional paleoelevation data from different areas, obtained using multi-paleoaltimeters, is required to resolve the forms and processes of Tibetan Plateau uplift and extension.

Mechanism of grout bulb expansion and its effect on ground uplifting

In order to study the uplifting effect of compensation grouting on ground surface and the upper structures,the ground heave induced by stratum expansion was considered as a stochastic process and the stochastic medium theory was applied to determine the heave and deformation of ground surface under uniform and non-uniform expansion models of spherical grout bulb.The corresponding calculating formulas and simplified methods were derived based on the hypotheses of radial expansion.Then,a numerical model,in which radial velocity was imposed on the outer nodes of grout bulb to simulate the expansion process reaching a required volume strain,was established simultaneously.This new method avoids repeated trial calculation needed in the traditional method which applies a "fictitious" expanding pressure in the grouting elements.The results show that the numerical solutions have good consistency with the theoretical ones.Meanwhile,though the heave resulting from non-uniform expansion is larger than that from uniform expansion for shallow grouting,both of them tend to be convergent with the increasing of grouting depth.

Numerical simulation of flooding induced uplift for abandoned coal mines:simulation schemes and parameter sensitivity

Numerical simulation approaches have been widely applied to study mining induced subsidence,and they are potential methods to study the flooding induced uplift for abandoned mines.This paper gives an overview about different numerical approaches to simulate uplift induced by flooding abandoned underground mines,including three different hydraulic conditions,considering both unconfined and confined water conditions.Four basic simulation schemes using 1-dimensional rock column models verified by analytical solutions demonstrate these procedures.The results reveal that flooding induced uplift is mainly related to the pore pressure in the mine goaf.The parameter study documents that height and stiffness of the mine goaf have the strongest influence on maximum surface uplift.

Sequences and genesis of the Yellow River terraces from Sanmen Gorge to Kouma

Based on field landscape investigations, thermoluminescence （TL）, magnetostratigraphy and Ioess-paleosol sequence, we found that there are at least four Yellow River terraces, whose ages are 0.86 Ma, 0.62 Ma, 0.13 Ma and 0.05 Ma, in Yuxi Fault-Uplift （from Sanmen Gorge to Mengjin） and at least three Yellow River terraces, whose ages are 1.24 Ma, 0.25 Ma and 0.05 Ma, in Huabei Fault Depression （from Mengjin to Kouma）. All the terraces have a similar structure that several meters of paleosols directly develop on the top of fluvial silt. It shows that the Yellow River incised and consequently abandoned floodplain converted to terrace during the interglacial period. Therefore, there may be a link between the formation of terraces and glacial-interglacial climatic cycles. However, the differences in the Yellow River terrace sequences and ages between Yuxi Fault-Uplift and Huabei Fault Depression indicate that the surface uplift should play an important role in the formation of these terraces.

Higher palaeoelevation in the Baoshan Basin:Implications for landscape evolution at the southeastern margin of the Tibetan Plateau

Surface uplift at the southeastern margin of the Tibetan Plateau has been widely studied,but more palaeoaltimetry data are required to better understand the elevation history of this geologically complex region.In this study,fossil leaves of Abies(Pinaceae),a cool-temperate element,recovered from the latest Miocene-Pliocene Yangyi Formation of the southern Baoshan Basin,were used as a proxy to estimate the local palaeoelevation.Based on the regional modern altitude range(2100-4280 m)of the genus as well as regional temperature discrepancy(1.5℃)between the past and present,the palaeoelevation of the study area was calculated to be>2360 m above sea level as compared to 1670 m at present.Our result suggests that the southern Baoshan Basin experienced pronounced uplift prior to the time of fossil deposition,probably as a result of crustal shortening and thickening of the northern Baoshan Terrane during the Eocene-Oligocene.We infer that surface growth in areas south of the Dali Basin may have been greater than previously interpreted,and that a widespread plateau or plateau patches higher than 2000 m probably extended southwards into at least the Baoshan Basin by the latest Miocene-Pliocene.We also infer that the elevation of the southern Baoshan Basin has decreased by at least 690 m since then,in contrast to most other scenarios in which the elevation of the southeastern margin of the Tibetan Plateau has increased or remained close to modern levels since the late Miocene.The major cause of the inferred altitude decline is likely tectonic deformation.As a transtensional graben basin,the Baoshan Basin has experienced pull-apart and base-fall movement since the late Miocene,which would reduce the altitude of its southern part located on the hanging wall.Surface erosion associated with the increased summer rainfall might also have played a role especially in reducing the local relief,although its contribution can be limited.Our study provides one of the few palaeoelevation estimates from areas south of the Dali Basin and an example of past elevation loss at the southeastern margin of the Tibetan Plateau,thus shedding important light on the landscape evolution of this region.