Inversion of two-phase extensional basin systems during subduction of the Paleo-Pacific Plate in the SW Korean Peninsula:Implication for the Mesozoic “Laramide-style” orogeny along East Asian continental margin

During subduction, continental margins experience shortening along with inversion of extensional sedimentary basins. Here we explore a tectonic scenario for the inversion of two-phase extensional basin systems, where the Early-Middle Jurassic intra-arc volcano-sedimentary Oseosan Volcanic Complex was developed on top of the Late Triassic-Early Jurassic post-collisional sequences, namely the Chungnam Basin. The basin shortening was accommodated mostly by contractional faults and related folds. In the basement, regional high-angle reverse faults as well as low-angle thrusts accommodate the overall shortening, and are compatible with those preserved in the cover. This suggests that their spatial and temporal development is strongly dependent on the initial basin geometry and inherited structures.Changes in transport direction observed along the basement-sedimentary cover interface is a characteristic structural feature, reflecting sequential kinematic evolution during basin inversion. Propagation of basement faults also enhanced shortening of the overlying sedimentary cover sequences. We constrain timing of the Late Jurassic-Early Cretaceous(ca. 158-110 Ma) inversion from altered K-feldspar 40 Ar/39 Ar ages in stacked thrust sheets and K-Ar illite ages of fault gouges, along with previously reported geochronological data from the area. This "non-magmatic phase" of the Daebo Orogeny is contemporaneous with the timing of magmatic quiescence across the Korean Peninsula. We propose the role of flat/low-angle subduction of the Paleo-Pacific Plate for the development of the "Laramide-style" basement-involved orogenic event along East Asian continental margin.     

New progress of research on water cycle in atmosphere in China

1 Precipitation characteristics Since the 1980s, Chinese climatologists have conducted a lot of researches on the law of precipitation variation in recent 100 years. Zhang Xiangong et al. (1982)[1], Tu Qipu (1984)[2], Wang Shaowu (1994)[3], Chen Longxun, et al. (1998)[4] have carried out researches on temperature and precipitation changes of the last 100 years in China, viewing that China has the characteristics of cold-wet and warm-dry alternations. Shi Neng et al. (1983) studied the rel…     

TEMPORAL AND SPATIAL VARIATION OF EMISSIONFACTORS IN CHINA

1.IntrodctionEnvirorun~lehassionsarebyproduCtsofeconoAncadivihes.ThelevelofedrissionsgenerallyincreasesastheleveIOfeconondcaCtivitiesincreases.AsameasureofpollutioninimsihescausedbyeconoAncaedvihes,aneAnssionfaCtorgenerallytakesthefOrmofarati0bforantOtalpollutantquantityandtotaleconohacaCtivity[l],orThenumerator,totalwaSteorpollthentqUantitymaybemeasuredinwegh,orvoIumeor,somedmes,nuybemulhpliedbyahealthriskfaCtor(tokicityindex)0fthepollutant.Thedenondnator,totaleconothecaCtivities,canbe…     

INERTIAL THEORY FOR OCEANIC CROSS-EQUATORIAL JET

In this paper, a theory for inertial boundary layer is developed to study the northward forcedand the southward induced cross-equatorial jets by easterlies in the Southern Hemisphere in westand east boundaries respectively. The solutions of the nonlinear potential vorticity equation and theBernoulli equation show that subtle changes of the physical parameters can produce different equi-librium states and the velocity of these jets all can reach 10°m/s which are comparable to observa-tions. Simulations show that the induced current in the east boundary is very important to the for-mation of the local eastward equatorial current in the east boundary. This can be used to study thecharacteristics of the local surface eastward equatorial current during E1 Nino periods,     

NUMERICAL MODELING OF THE SEABED MORPHOLOGY OF THE SUBAQUEOUS YELLOW RIVER DELTA

1 wrsoorCnoxThe Yenow mver delta is ereated by the river transponing sediment bom the Loess Plateau to the shallOWBOhai Gulf during the paSt l45 years. lh recent years, the water discharge and sediment load enedg thesea have bein ched dramacaily The river end chann shital northeastWed hom QingshulgOuN to qngshulgou-Chah chaDnel in 1996, resulting in a new regfor of sedimenboon and erosion ofthe subaqucous delta.,A nUInerial model for river sediInen dispersion and seabed mOrPhofogy of t…     

IMPACTS OF FEBRUARY ANTARCTIC OSCILLATIONS ON SUMMER PRECIPITATION IN EASTERN CHINA*

Impacts of February Antarctic oscillations (AAO) on the subsequent summer precipitation in the eastern part of China are analyzed in this paper in the context of the NCEP/NCAR reanalysis data and the monthly precipitation data at 160 weather stations.Results show that on interannual time-scale,the correlation coefficient between February AAO index and July-August rainfall in North China is 0.53,which exceeds the confidence level of 99.9%.When February AAO is strong,then the subsequent summer precipitation in North China is more-than-average,and meanwhile the summer precipitation in the Changjiang River Valley is less-than-average:and vice versa.Changes of AAO affect the subsequent intensity and position of the Northwest Pacific subtropical high,thus resulting in the south-north direction shift of the summer monsoon rain belt in China.     

A preliminary study on the distribution characteristics of nutrients （N, P, Si, C） in the Wujiang River Basin

The distribution of nutrients (N, P, Si, C) in the Wujiang River surface water was studied during the high-flow and low-flow periods in 2002. The results showed that nitrate nitrogen (NO3-N) is the main form of dissolved inorganic nitrogen (DIN) in the Wujiang River Basin. It accounts for about 90% of DIN. The average NO3-N concentrations in the mainstream are 147.5 μM in the high-flow period and 158.0 μM in the low-flow period, respectively. The average concentrations of total phosphorus (TP) are 6.43 μM in the high-flow period and 4.18 μM in the low-flow period, respectively. Of the various forms of phosphorus, particulate phosphorus (PP) has the highest percentage ( 62.9%) of TP in the high-flow period. In the low-flow period, however, phosphate is the main form of phosphorus, which accounts for 49% of TP. With the Wujiangdu Reservoir as the boundary, the concentrations of DIN and phosphorus in the upper reaches are different from those in the lower reaches of the Wujiang River. As a whole, the concentrations of DIN and phosphorus are both higher in the low-flow period than in the high-flow period. The spatial and temporal variations of DIN and phosphorus concentrations suggested that DIN and phosphorus come from agricultural and domestic wastewaters and groundwaters and that the Wujiangdu Reservoir has an important impact on the concentrations and distribution of DIN and phosphorus in the Wujiang River. The distribution patterns of dissolved silica (DSi) and dissolved organic carbon (DOC) are similar. Both of them maintain no change in the whole course of the river and their concentrations (with the exception of the reservoir itself) are higher in the high-flow period than in the low-flow period. The average DSi and DOC concentrations in the mainstream are 85.4, 84.6 μM in the high-flow period and 60.8, 53.9 μM in the low-flow period, respectively. The concentrations of nutrients in most of the major tributaries are lower than in the mainstream. This suggested that the contributions of most tributaries are relatively small but importance should be attached to the influence of some individual tributaries such as the Qingshuijiang River and the Weng'an River on the mainstream.     

Land cover changes in the rural-urban interaction of Xi’an region using Landsat TM/ETM data

1 Introduction Urbanization process in Xi’an has been accelerated after the Chinese governmentimplemented the strategy ofW estern Region Developmentof China aboutfouryears ago,which has caused the loss offarm land in urban peripheralareas.W hatis more,ur…     

利用Landsat TM/ETM数据分析西安地区城乡土地利用/覆被变化

Landsat ETM/TM data and an artificial neural network (ANN) were applied to analyse the expansion of the city of Xi'an and land use/cover change of its surrounding area between 2000 and 2003. Supervised classification and normalized difference barren index (NDBI) were used respectively to retrieve its urban boundary. Results showed that the urban area increased by an annual rate of 12.3%, with area expansion from 253.37 km2 in 2000 to 358.60 km2 in 2003. Large areas of farmland in the north and southwest were converted into urban construction land. The land use/cover changes of Xi'an were mainly caused by fast development of urban economy, population migration from countryside, great development of infrastructure such as transportation, and huge demands for urban market. In addition, affected by the government policy of "returning farmland to woodland", some farmland was converted into economic woodland, such as Chinese goosebeery garden, vineyard etc.     

Environmental geography in China: retrospect and prospect

1FromchemicalgeographytoenvironmentalgeographyThe growth of environmental geography in China can be traced back to the early 1960s when a group of geographers and soil scientists initiated a chemical geography program in China following the speciality created by Russian geographers. The main fields of studies conducted during the mid-1950s to the early 1970s involved aquatic, terrestrial and atmospheric chemistry of major elements, which focused on geochemical taxonomy of inorganic elements i…