ABSTRACTIn this study, we characterized the glacial meltwater flow through a proglacial area with a focus on proglacial lakes, their hydrological regime and their connection to the stream. The studied lakes – the Adygine ice-debris complex, northern Tien Shan – showed a distinct development throughout an ablation season: at Lake 2, the mean daily water-level fluctuation amplitude increased from 0.07 m to 0.18 m (June, August), then dropped to 0.07 m in September. Glacial meltwater flows through the lakes and further downstream through a rock glacier rather fast, moving at 0.085 m s?1. However, based on the low dye recovery in the stream (0.03%), only a small portion of water was routed efficiently. The complexity of the site’s drainage system was supported by varying isotopic composition of water in the tarns situated on the rock glacier, with Tarn a (δ2H: –36.08‰; δ18O: –6.25‰) being the most enriched and Tarn c (δ2H: 78.68‰; δ18O: 11.9‰) the most depleted in heavy isotopes. 相似文献
The Gobi Altai region of southwestern Mongolia is a natural laboratory for studying processes of active, transpressional, intracontinental mountain building at different stages of development. The region is structurally dominated by several major E—W left-lateral strike-slip fault systems. The North Gobi Altai fault system is a seismically active, right-stepping, left-lateral, strike-slip fault system that can be traced along the surface for over 350 km. The eastern two-thirds of the fault system ruptured during a major earthquake (M = 8.3) in 1957, whereas degraded fault scarps cutting alluvial deposits along the western third of the system indicate that this segment did not rupture during the 1957 event but has been active during the Quaternary. The highest mountains in the Gobi Altai are restraining bend uplifts along the length of the fault system. Detailed transects across two of the restraining bends indicate that they have asymmetric flower structure cross-sectional geometries, with thrust faults rooting into oblique-slip and strike-slip master faults. Continued NE-directed convergence across the fault system, coupled with left-lateral strike-slip displacements, will lead to growth and coalescence of the restraining bends into a continuous sublinear range, possibly obscuring the original strike-slip fault system; this may be a common mountain building process.
The largely unknown Gobi-Tien Shan fault system is a major left-lateral strike-slip fault system (1200 km + long) that links the southern ranges of the Gobi Altai with the Barkol Tagh and Bogda Shan of the easternmost Tien Shan in China. Active scarps cutting alluvial deposits are visible on satellite imagery along much of its central section, indicating Quaternary activity. The total displacement is unknown, but small parallel splays have apparent offsets of 20 + km, suggesting that the main fault zone has experienced significantly more displacement. Field investigations conducted at two locations in southwestern Mongolia indicate that late Cenozoic transpressional uplift is still active along the fault system. The spatial relationship between topography and active faults in the Barkol Tagh and Bogda Shan strongly suggests that these ranges are large, coalescing, restraining bends that have accommodated the fault's left-lateral motion by thrusting, oblique-slip displacement and uplift. Thus, from a Mongolian perspective, the easternmost Tien Shan formed where it is because it lies at the western termination zone of the Gobi-Tien Shan fault system. The Gobi-Tien Shan fault system is one of the longest fault systems in central Asia and, together with the North Gobi Altai and other, smaller, subparallel fault systems, is accommodating the eastward translation of south Mongolia relative to the Hangay Dome and Siberia. These displacements are interpreted to be due to eastward viscous flow of uppermost mantle material in the topographically low, E–W trending corridor between the northern edge of the Tibetan Plateau and the Hangay Dome, presumably in response to the Indo-Eurasian collision 2500 km to the south. 相似文献
High-density array MT soundings of the crust in the seismically active northern Tien Shan were performed using Phoenix MTU-5 stations in the Bishkek Geodynamic Polygon, at the junction of the Chu basin and the Kyrgyz Range. The MT transfer functions were determined to an accuracy of 1–2% (amplitude) and about 0.5–0.8 deg (phase) in most of 145 soundings. Preliminary analysis of the collected data aimed at estimating the geoelectrical dimensionality. The Bahr decomposition analysis indicated the presence of local 3D structures in the crust of the area superposed on the regional 2D structure. 相似文献
The coseismic surface uplift of the Longmen Shan(LMS) created an instantaneous topographic load over the western margin of the Sichuan Basin, where surface subsidence, decreasing eastward, has been measured using several methods, such as GPS, SAR and levelling. Using an elastic flexural model, we aim to interpret the coseismic surface uplift and subsidence, and constrain the effective lithospheric elastic thickness(T_e) of the Sichuan Basin. Using different effective elastic thickness values for the Sichuan Basin, a series of subsidence curves were computed by the elastic flexure model equation for a broken elastic plate. The curves, produced by models using an effective elastic thickness of 30–40 km, provided the best fit to the general pattern of observed coseismic subsidence of the Sichuan Basin. However, the calculated subsidence(~40–70 cm) at the front of the LMS is evidently lower than the observed values(~100 cm), suggesting that the effective elastic thickness therein should be lower. These results indicate that the lithospheric strength may decrease westward from the Sichuan Basin to the LMS. 相似文献
Small thrust faults in the Daqing Shan that were previously mapped as separate structures belong to a single Mesozoic thrust,
herein named the Daqing Shan thrust. It extends more than 155 km along the northern margin of the Daqing Shan, obliquely cutting
the Daqing Shan along the western flank of the Jinluandian peak to the southeast and taking its way to Chayouzhongqi to the
east. Kinematic markers indicate tectonic transport of the thrust sheet to the NNW. Minimum displacement, based on the observable
outcrops, is 22 km, and the inferred thrusting distance may be larger than 35 km. The thrust sheet covers the whole eastern
area of the Daqing Shan. The thrust truncates the E-W trending, somewhat older South-directed Panyanshan thrust and, therefore,
the two faults are not as a result of counter thrusting. Such major intraplate tectonic deformation that occurred in the Inner
Mongolia Axis or the Yin Shan latitudinal tectonic belt during late Jurassic time calls for deep thought on its tectonic significance
in dynamics. It is most likely that the Daqing Shan thrust represents major intraplate shortening during Jurassic-Cretaceous
closure of the Mongolo-Okhotsk ocean about 1000 krn away to the north.
Project supported by the National Natural Science Foundation of Chlna (Grant No. 49070135) and by the Natlonal Science Foundation
of the Unlted States (Grant No.EAR-9627909). 相似文献