Sediments shed from the northern margin of the Tibetan Plateau, the Qilian Mountains, are widely deposited in the foreland basin, the Jiuxi Basin, archiving plenty of information about the mountain surface uplift and erosion history. The Laojunmiao section, 1960 m thick, representing the upper sequence of the Cenozoic basin sediments, is paleomagnetically dated to about 13-0 Ma BP. Detailed sedimentary study of this sequence has revealed five sedimentary facies associations which determine four stages of sedimentary environment evolution. They are: (I) the half-deep lake system before 12.18 Ma BP, (II) the shallow lake system between 12.18 and 8.26 Ma BP, (III) the fan delta dominated sedimentary system in dry climate between 8.26 and 6.57 Ma BP, and (IV) alluvial fan system since 6.57 Ma BP. The associated mountain erosion and uplift are suggested to have experienced three phases, that is, tectonic stable (13-8.26 Ma BP), gradual uplift (8.26-<4.96 Ma BP), and rapid intermittent uplift (>3.66-0 Ma BP). The uplift at ∼3.66 Ma BP is of great importance in tectonics and geomorphology. Since then, tectonic uplift and mountain building have been accelerated and become strong intermittent. At least three significant tectonic events took place with ages at <1.80-1.23, 0.93-0.84 and 0.14 Ma BP, respectively. Thus, the uplift of the northern Tibetan Plateau is a complex process of multiple phases, unequal speed and irregular movements.
Coseismic water level oscillation and correlated deep water temperature changes have been observed in a water well at Tangshan City by high sensitivity measurement. Amount of water temperature changes depend on ampli-tude of water level oscillation. Coseismic water temperatures always decrease as water level oscillates, drop of temperature ranges from 0.001 °C to 0.01 °C corresponding to amplitude of water level oscillation from several centimeters to about one meter. Temperatures usually recover one to several hours after the oscillation. We suggest that the temperature drop is produced by dispersive transfer of heat as the water oscillates, and follow-up thermal conduction makes temperature recovery. Our finite element calculations support quantitatively the idea. High ac-curacy measurements of water temperature at different depths in the future may test our interpretation. 相似文献
A major slip and thrust belt within the eastern Jiaodong Peninsula is located at the eastern terminal of the Qinling-Dabie-Sulu orogenic belt between the Sino-Korea Block and Yangtze Block. Although a lot of isotope chronologic data have been obtained regionally, little structural chronological research has been conducted in this region and this paper corrects that. Syn-deformational minerals were system-atically selected from samples of the NE-ENE trending transpressional shear zones and transpres-sional nappes and carefully analysed using 40Ar/39Ar methods. Two tectonic events were defined with the first event resulting from early movement of transpressional nappes around 190 Ma ago. This ac-cords with the period of syn-orogenic sinistral slip of the Tan-Lu faults and clockwise shear in the Eastern Qinling-Tongbaishan part of the Qinling-Dabie-Sulu orogenic belt. The second event involved strikeslip thrust movement of deep shear zones between 130Ma and 120Ma. This resulted from the onset of Mesozoic tectonic conversion in the eastern Jiaodong Peninsula. The sinistral strikeslip-thrusting in Jiaodong Peninsula and the extensional tectonism (toward ESE) in Liaodong Peninsula probably resulted in the clockwise rotation of Korea Peninsula in late Mesozoic. 相似文献
As the third largest country in the world, China has highly variable environmental condition and ecological pattern in both
space and time. Quantification of the spatial-temporal pattern and dynamic of terrestrial ecosystem carbon cycle in China
is of great significance to regional and global carbon budget. In this study, we used a high-resolution climate database and
an improved ecosystem process-based model to quantify spatio-temporal pattern and dynamic of net ecosystem productivity (NEP)
in China and its responses to climate change during 1981 to 2000. The results showed that NEP increased from north to south
and from northeast to southwest. Positive NEP (carbon sinks) occurred in the west of Southwest China, southeastern Tibet,
Sanjiang Plain, Da Hinggan Mountains and the mid-west of North China. Negative NEP (carbon sources) were mainly found in Central
China, the south of Southwest China, the north of Xinjiang, west and north of Inner Mongolia, and parts of North China. From
the 1980s to 1990s, the increasing trend of NEP occurred in the middle of Northeast China Plain and the Loess Plateau and
decreasing trends mainly occurred in a greater part of Central China. In the study period, natural forests had minimal carbon
uptake, while grassland and shrublands accounted for nearly three fourths of the total carbon terrestrial uptakes in China
during 1981–2000.
Supported by the Ministry of Science and Technology of China (G2002CB412507), the Major Program of the National Natural Science
Foundation of China (Grant No.30590384), the “Hundred Talent” Program of the Chinese Academy of Sciences, and K C WONE Education
Foundation 相似文献