Time filter

Source Type

Miao Y.,Chinese Academy of Sciences | Song C.,Lanzhou University | Fang X.,CAS Institute of Tibetan Plateau Research | Meng Q.,Lanzhou University | And 3 more authors.
Gondwana Research | Year: 2015

An extinct palynomorph, Fupingopollenites, was used as the basis for a discussion of the late Cenozoic Asian summer monsoon (ASM) evolution and its possible driving forces. Based on the spatial and temporal variations in its percentages across Inner and East Asia, we found that Fupingopollenites mainly occurred in East Asia, with boundaries to the NE of ca. 42°N, 135°E and NW of ca. 36°N, 103°E during the Early Miocene (ca. 23-17. Ma). This region enlarged westwards, reaching the eastern Qaidam Basin (ca. 36°N, 97.5°E) during the Middle Miocene (ca. 17-11. Ma), before noticeably retreating to a region bounded to the NW at ca. 33°N, 105°E during ca. 11-5.3. Ma. The region then shrank further in the Pliocene, with the NE boundary shrinking southwards to about 35°N, 120°E; the area then almost disappeared during the Pleistocene (2.6-0. Ma). The flourishing and subsequent extinction of Fupingopollenites is indicative of a narrow ecological amplitude with a critical dependence on habitat humidity and temperature (most likely mean annual precipitation (MAP) > 1000. mm and mean annual temperature (MAT) > 10. °C). Therefore, the Fupingopollenites geographic distribution can indicate the humid ASM evolution during the late Cenozoic, revealing that the strongest ASM period occurred during the Middle Miocene Climate Optimum (MMCO, ~. 17-14. Ma), after which the ASM weakened coincident with global cooling. We argue that the global cooling played a critical role in the ASM evolution, while the Tibetan Plateau uplifts made a relatively small contribution. © 2015 International Association for Gondwana Research. Source

Li J.-P.,Shandong University of Science and Technology | Li J.-P.,Geological Survey of Jiangsu Province | Shang T.-X.,Key Laboratory of Earth Fissures Geological Disaster | Shang T.-X.,Geological Survey of Jiangsu Province | And 2 more authors.
Wutan Huatan Jisuan Jishu | Year: 2014

3D abnormal body daujeeapos;s electromagnetic field with arbitrary shape source multiple locations excitation can be inverted using integral equation and damped least squares. Multiple groups of electromagnetic field data in different excitation and receiving point to be uniform consideration in inversion, a matrix is obtained, distribution of resistivity of underground abnormal body is achieved. Model test shows that inversion of fast convergence speed, less dependent on the initial value, the result is accurate and reliable. Source

Zhang W.,Key Laboratory of Earth Fissures Geological Disaster | Zhang W.,Jilin University | Gao L.,Key Laboratory of Earth Fissures Geological Disaster | Jiao X.,Shanghai Institute of Geological Survey | And 5 more authors.
Geosciences Journal | Year: 2014

Earth fissures in Su-Xi-Chang land subsidence area have induced massive damages to the area. The non-linear characteristic associated with the process of earth fissure formation requires non-linear method for evaluating the occurrence of the hazard. Based on quantification of influence factors on breeding the hazard, GA-ANN method, which integrates artificial neural networks (ANN) with genetic algorithms (GA), is developed for evaluating the occurrence of earth fissure hazard. Six indicators, that include the depth of bedrock burial (DBB), the degree of bedrock relief (DBR), water level (WL) (the II confined aquifer), the gradient of land subsidence (GLS), transmissivity (T) (the II confined aquifer) and the thickness of clay soil (TCS), are selected as the input patterns of the integrated approach, and danger index (DI) as the output pattern. A multilayer back-propagation neural network is trained with 30 sets of data samples including 15 sets of earth fissure samples and 15 sets of safety samples for defining the architecture of ANN. Subsequently, GA is employed by optimizing the initial weights of trained ANN by minimizing the deviation of output. The efficacy of the integrated approach is demonstrated by comparing the deviation of output from ANN and GA-ANN for 5 testing samples and the result shows that the GA-ANN method is more accurate than ANN in identifying the occurrence of earth fissure. The integrated method is applied to the assessment of earth fissure hazard in typical regions of earth fissure. According to the classification of DI, the regions are divided into four zones — danger zone, sub-danger zone, sub-safe zone and safe zone. © 2014, The Association of Korean Geoscience Societies and Springer-Verlag Berlin Heidelberg. Source

Lu X.-R.,Geological Survey of Jiangsu Province | Lu X.-R.,Key Laboratory of Earth Fissures Geological Disaster | Yang L.,Geological Survey of Jiangsu Province | Yang L.,Key Laboratory of Earth Fissures Geological Disaster | And 4 more authors.
Acta Geoscientica Sinica | Year: 2014

Based on an analysis of the distribution of iodine content in phreatic water, soil and hydrogeological conditions and land form, the authors have a new understanding on the control factors of iodine content in groundwater: The previous researchers hold that the iodine content in groundwater is proportional to the organic matter, whereas the authors consider that there is no fixed relationship between the iodine content and organic matter content in groundwater, but the organic matter contributes to the increase of water-soluble iodine content, and they are directly proportional in some areas. Groundwater flow conditions impact significantly the iodine content. The iodine content is often low and in compliance with drinking water standards in hilly land where the runoff conditions are better, whereas the iodine content often exceeds drinking water standards in low-lying areas of poor runoff conditions; The iodine content in groundwater is directly proportional to the content in soil under the same hydrogeological conditions. Another important feature of the iodine concentration in groundwater is that it is very stable and changes very little with time and mining activity. Source

Yang L.,Geological Survey of Jiangsu Province | Yang L.,Key Laboratory of Earth Fissures Geological Disaster | Gong X.-L.,Geological Survey of Jiangsu Province | Gong X.-L.,Key Laboratory of Earth Fissures Geological Disaster | And 4 more authors.
Geology in China | Year: 2015

In order to study hydrogeochemistry of the fluoride in groundwater in northern Lianyungang area, the authors analyzed 63 groundwater samples and investigated the distribution and genesis of high-fluoride groundwater. The results show that the concentration of fluoride in groundwater tends to increase with the groundwater flow. The high-fluoride groundwater areas are distributed in low gulf plain and depression. The alkaline water environment with high concentrations of sodium and bicarbonate is the main factor responsible for fluoride enrichment and transfer of fluoride from sediments to groundwater. The formation of high-fluoride groundwater results from prolonged geological and geochemical evolution. The hydrogeochemical processes including mineral dissolution and precipitation, evaporation and concentration, cation exchange and adsorption are the dominant factors for the enrichment of fluoride in groundwater. Source

Discover hidden collaborations