Along the western Kunlun-Tarim-Tianshan geoscience transect in the northwestern China, an integrated geophysical investigation was carried out. Owing to the abominable natural conditions there, the sounding profile co...Along the western Kunlun-Tarim-Tianshan geoscience transect in the northwestern China, an integrated geophysical investigation was carried out. Owing to the abominable natural conditions there, the sounding profile could not cross the whole transect, consequentially, a variety of velocity structures in the transverse and vertical orientations beneath the whole transect were not obtained, such as the case within the western Kunlun orogenic belt. To supply a gap of deep seismic soundings within the western Kunlun orogenic belt, we used the Bouguer gravity anomaly data and the relationship between the compressive wave and the density to obtain the density structure of the crust beneath the western Kunlun and the southern Tarim basin by a forward fitting of gravity anomalies within the two-dimensional polygonal model of uniform medium. The crust of the Tarim basin with a rigid basement was like an asymmetrical arc, whose surface feature was the Bachu uplift in the middle of the Tarim basin. Beneath the conjoint area between the Tarim basin and the western Kunlun belt, there was a V-shape structure located just up to the top of the uplifted Moho. The multi-seismological structures jointly revealed that the face-to-face continent-continent collision beneath the western Kunlun is a new structural style within the continent-continent collision zone, which is a real model proved by the numerical modeling.展开更多
Upfreezing is an important geomorphic process in the periglacial environment.It is a product of cold climate and thus an important part of the cryospheric processes.Based on the long-term positioning observations in t...Upfreezing is an important geomorphic process in the periglacial environment.It is a product of cold climate and thus an important part of the cryospheric processes.Based on the long-term positioning observations in the source area of the Urumqi River,this article represents an in-depth discussion of the characteristics of sorted circles and upfreezing mechanisms in the Tianshan Mountains.In the source area of the Urumqi River,the intensity of upfreezing is the highest within the top 25 cm near the surface,while targets with a diameter of 3 cm are least affected by upfreezing.There is no distinct difference between the centre with fine grains and the margin with coarse debris within the same sorted circle in terms of the intensity of upfreezing.The correlation analysis demonstrates that temperature plays an important role in upfreezing and the development of sorted circles.A long-time positioning observation of sorted circles reveals that periglacial landforms are sensitive to regional climate change and respond quickly to the temperature increase of the recent two decades.Enhanced upfreezing was found to be due to increased soil moisture content.展开更多
基金supported by the National Natural Science Foundation of China (40404011, 40774051, 49734230)the basic outlay of scientific research work from Ministry of Science and Technology of the People’s Republic of China in 2007 and 2008 (J0707, J0803)+2 种基金Sino-American collaboration project from Ministry of Science and Technology of the People’s Republic of China (2006DFA21340)China National Probing Project (SinoProbe-02)Open Fund of Geo-detection Laboratory, Ministry of Education of China, and China University of Geosciences (No. GDL0602)
文摘Along the western Kunlun-Tarim-Tianshan geoscience transect in the northwestern China, an integrated geophysical investigation was carried out. Owing to the abominable natural conditions there, the sounding profile could not cross the whole transect, consequentially, a variety of velocity structures in the transverse and vertical orientations beneath the whole transect were not obtained, such as the case within the western Kunlun orogenic belt. To supply a gap of deep seismic soundings within the western Kunlun orogenic belt, we used the Bouguer gravity anomaly data and the relationship between the compressive wave and the density to obtain the density structure of the crust beneath the western Kunlun and the southern Tarim basin by a forward fitting of gravity anomalies within the two-dimensional polygonal model of uniform medium. The crust of the Tarim basin with a rigid basement was like an asymmetrical arc, whose surface feature was the Bachu uplift in the middle of the Tarim basin. Beneath the conjoint area between the Tarim basin and the western Kunlun belt, there was a V-shape structure located just up to the top of the uplifted Moho. The multi-seismological structures jointly revealed that the face-to-face continent-continent collision beneath the western Kunlun is a new structural style within the continent-continent collision zone, which is a real model proved by the numerical modeling.
基金supported by the National Natural Science Foundation of China(40971002 and 41101003)
文摘Upfreezing is an important geomorphic process in the periglacial environment.It is a product of cold climate and thus an important part of the cryospheric processes.Based on the long-term positioning observations in the source area of the Urumqi River,this article represents an in-depth discussion of the characteristics of sorted circles and upfreezing mechanisms in the Tianshan Mountains.In the source area of the Urumqi River,the intensity of upfreezing is the highest within the top 25 cm near the surface,while targets with a diameter of 3 cm are least affected by upfreezing.There is no distinct difference between the centre with fine grains and the margin with coarse debris within the same sorted circle in terms of the intensity of upfreezing.The correlation analysis demonstrates that temperature plays an important role in upfreezing and the development of sorted circles.A long-time positioning observation of sorted circles reveals that periglacial landforms are sensitive to regional climate change and respond quickly to the temperature increase of the recent two decades.Enhanced upfreezing was found to be due to increased soil moisture content.
