Abstract:Abstract：The Sichuan basin located far away from the active plate boundaries is well known for its surrounding fold zones whose genesis and tectonic settings have long been one of the key issues in the geotectonic study of South China. Based on a compilation of regional structural geology and an analysis of superimposed folding structures, this paper presents a synthetic discussion on the Mesozoic compressional tectonics in such aspects as its deformation features and structural styles, main tectonic events and their timing. Strudies show that the Sichuan basin and its surrounding zones experienced three major tectonic events during Mesozoic, each one creating fold zones that were compounded spatially and resulted in the formation and reformation of the Sichuan basin. The Triassic collisional orogeny along the northern and western margins of the Yangtze cratonic block resulted in the formation of the proto basin, i.e., the Chuan-Yu-Dian -Qian sedimentary basin whose extending size is larger than the present-day Sichuan basin. Folds created by this tectonic event mainly trend in W-E direction. Tectonic regime changed profoundly during the Middle-Late Jurassic, dominated by multi-directional plate convergences in Asia, which caused rejuvenation of old orogenic belts and formation of new tectonic systems. In particular, the rejuvenation of the Qinling orogenic belt resulted in the development of the Micangsahn-Dabashan foreland fold and fault zone along the northern margin of the Sichuan basin; the westward subduction of the Paleo-Pacific plate activated the Xuefengshan tectonic zone and created the oroclinal folds in east and south Sichuan; the eastward extrusion of the Songpan-Ganze orogenic belt reactivated the Longmenshan-Jinpingshan thrust zone in west Sichuan. This multi-directional compressional event greatly reformed the proto Sichuan basin, and shaped the basic structural pattern surrounding the Sichuan basin. The third major event occurred in latest Cretaceous and was characterized by NW-SE compression, and it strengthened the NE-SW trending structures. It is concluded that the main fold zones in and around the Sichuan basin was characterized by pervasively distributed thin-skinned structures mainly formed in Middle-Late Jurassic, and in consequence of multi-directional intracontinental orogeny, they constituted in turn part of the convergent tectonic system in east Asia.

Abstract:Abstract：442 pairs of Rayleigh wave were selected from 6312 wavefoms recorded by 58 stations in China’s mainland. The attenuation coefficients of the Rayleigh wave in China were obtained by using the phase-matched method and the frequency-domain Wiener filter．The authors made inversion of the attenuation coefficients of the Rayleigh wave in China’s mainland with grids 4o×4o，and obtained the distribution of attenuation coefficients in different periods in China’s mainland. Some conclusions have been reached：i) the attenuation of Rayleigh wave is lower in eastern China than in northwestern China in a short period, which shows that this depth is the upper mantle in eastern China and the crust in western China; ii) the formation of the attenuation of Rayleigh wave is in SN-direction, which divides China’s mainland into three parts: the middle part is from Ordos to Sichuan, characterized by stableness and low attenuation, whereas the other two parts are of high attenuation in the middle period; iii) the attenuation of Rayleigh wave is higher in eastern China than in northwestern China in a long period, probably due to the subduction of Gondwana land to this depth in northwestern China and the upwelling of the back-arc basin in West Pacific Ocean to this depth; iv) the relationship between the attenuation of Rayleigh wave and heat flow is that the regions such as Qinghai-Tibet block and its adjacent areas whose heat flow is high are of high attenuation, and the regions such as eastern China and its adjacent areas whose heat flow is low are of low attenuation; v) the relationship between the attenuation of Rayleigh wave and strong earthquake is intimate, as shown by the facts that more strong earthquakes and high attenuation of Rayleigh wave occur west of 107°E and less strong earthquakes and low attenuation of Rayleigh wave occur east of 107°E.

Abstract:Abstract：As we all know, structure controls sedimentation, while sedimentation controls the reservoir. Lots of sedimentary facies maps, however, were compiled without considering the control of structural factors over the depositional system, which has led to the severe defect that sedimentary facies or/and palaeogeographic maps do not match with contemporaneous structural configuration. Growth faults are the main structural factors, whose activity would control the forming process of sedimentary strata. There were four types of growth faults developed in Shenxian depression in Cenozoic, constituting models of late activity, continuous activity, periodic activity and deep extension. In addiction, based on regional sediments provenance analysis, the authors probed into the control of growth faults over depositional systems, and found that subaqueous fans were developed in the south while deltas were developed in the north. The spread of the fronts of these two depositional systems were further controlled by growth faults, presenting characteristics that lobes spread along faults on the map while wedges overlap in the cross section.

Abstract:Abstract： The Taohuashan granitic pluton in northern Hunan which intruded into Middle Proterozoic Lengjiaxi Formation is composed of early fine-grained sparsely-porphyritic hornblende biotite granodiorite， fine- and medium-grained porphyritic biotite monzonitic granite, medium- and fine-grained sparsely-porphyritic two-mica monzonitic granite and late fine-grained biotite-two-mica monzonitic granite. Zircon SHRIMP dating of the granites yields an age of (140.3±3.8) Ma, belonging to Late Jurassic. The granites belong to the peraluminous High-K calc-alkaline series with SiO2 being 71.10%～73.00% and K2O/Na2O 1.09～1.66. The rocks are enriched in large-ion lithophile elements and depleted in high field-strength elements, with the data Rb/Sr=0.23～1.95, ∑REE=175.1～259.9, δEu=0.55～0.82, （La/Yb）N=13.52～43.71, εNd=-8.1～-10.1）, T2DM=1.59～1.75 Ga. Studies show that the Taohuashan granites belong to muscovite-bearing peraluminous granitoids whose materials were derived from Precambrian basement. The rocks were formed with the weakening of the stress in late collision period, suggesting that northern Hunan has entered into an extensional period since 140Ma BP.

Abstract:Abstract：Mafic dike swarms, trending in NW-SE direction, are widely distributed in North Daba Mountain, intruding the Early Paleozoic strata. Previous studies focused on geochronology and geochemistry of Ziyang-Langao area; nevertheless, very insufficient research work was devoted to Zhenping area. The dating of SHRIMP zircon U-Pb for diabase samples from Zhenping area in North Daba Mountain shows the result that 12 points yield a group of weighted mean 206Pb/238U ages at (439±6)Ma(MSWD=1.7), consistent with the basic dike and volcanic rocks in the middle-northern area of North Daba Mountain, i.e., Ziyang-Langao area. Geochemical data show that basic dikes have high K2O and TiO2, with bimodal characteristics of rocks. They are enriched in large ion lithophile elements (LILE, e.g., Rb, Ba, Th, U) and light rare earth elements (LREE; ((La/Yb)N=11.18～15.67), and depleted in Sr, Y, Yb and heavy rare earths (HREE), suggesting geochemical characteristics of average mass fraction of continental rift basalt. The petrochemical diagrams of Zr/Y-Zr and Nb-Zr-Y also indicate that these rocks are continental rift basalt. Combined with previous studies, the authors hold that North Daba Mountain was a rift during the middle-late stage of Early Silurian, and the basic dikes and volcanic rocks were tensile product under the condition of continental rift.

Abstract:Abstract：The Duobaoshan area in Da Hinggan Mountains is tectonically located in a fold belt between the Songneng Block and the Xing’an Block in the east of the Xingmeng oregenic belt. Large quantities of Neopaleozolc granitic rocks are distributed in this area. This lithology is mainly composed of monzonitic granite and syenogranite. SHRIMP zircon U-Pb dating yielded ages of 309.0± 3.0Ma and 299.3± 2.8 Ma. Major element analyses show high SiO2 and alkali content, slightly high Al2O3 content and low MgO and CaO content. Trace element studies demonstrate the enrichment of Th, Zr, Rb, Nd, K and depletion of Ba, Sr, P, Ti. The samples are enriched in LREE (light rare earth elements) and depleted in HREE (heavy rare earth elements), suggesting a high degree of fractionation. The granites generally belong to the high-K calc-alkaline series and might have been produced by the magma that had experienced a high degree of crystallization differentiation. Petrological geochemistry shows that the granites are quite similar to S-type granite, with the material source derived from the crust.

Abstract:Abstract：Content and characteristic numerical values of major and trace elements contain much genetic information, such as source region, evolution and formation environment of magma. The Dabuxile pluton is located near the northern side of the Erlian-Hegenshan suture belt that is part of the suture zone of the North China plate and the Siberian plate (Xing-Meng orogenic zone) . Sampling of all rock types of the pluton was conducted to analyze content of REE and trace elements, and the results show that granodiorites composed of biotite granodiorite and granodiorite are genetically of I-S transitional type granite, whose rock-forming magma might have resulted from subducted oceanic slab and metagreywacke of the overlying partly-melted continental crust. Granites composed of monzogranite, biotite granite and potassium feldspar granite are genetically of S-type granites, whose rock-forming magma might have been derived from metamorphic pelite. The two types of granites were both generated from the continental arc, and are not adakitic rocks.

Abstract:Abstract：In order to conduct the division and correlation of sedimentary rocks within stratigraphic frameworks, the author holds that the core for sequence-stratigraphic studies should be described as follows： the unconformity is used as the main stratigraphic surface, the stratigraphic unit bounded by the unconformity and its relative conformity is defined as the depositional sequence, and the depositional trend within the depositional sequence is regarded as the elementary content. During the Cambrian period, the North China Platform accepted sedimentation relatively late, and hence only half-mature stratigraphic succession was developed. In this Cambrian stratigraphic succession, a sedimentary succession from the mixed tidal-flat to the ramp carbonate deposits made up a retrogressive succession under the second-order transgressive process. It is necessary to resurvey the sequence-stratigraphic features for the Cambrian in the North China Platform according to the new chronostratigraphic system, with the Xiaweidian section in the western suburb of Beijing as an example. Therefore, this study will provide insight for further understanding the depositional pattern of the skeleton-poor stormy sea during the Cambrian marked by the increase of microbial carbonate together with the radiation of metazoan.

Abstract:Abstract：Northern Youjiang passive continental margin rift basin developed NW-trending tensile synsedimentary faults and NE-trending strike-slip faults in Middle-Llate Devonian period. Guided by dynamics of sequence filling and combined with single profiles, profile correlation and plane changes, the authors analyzed filling material and evolution characteristics of sedimentary facies in the process of sequence filling. A study of the process of sequence filling reveals that there were two pulsing tectonic activities in each transgressive period and high stand period, with the trend of gradually increasing transgression, and intense extension in NE direction resulted in the formation of synsedimentary faults in NW direction which had time-ordered characteristics. The authors have confirmed that the platform-basin stretched into intra-platform and formed platform alternating with platform-basin. It is concluded that the time-ordered characteristics of tectonism resulted in the differentiation of the distribution of the sedimentary facies in different periods.

Abstract:Abstract：Carbonate rock deposition of great thickness occurred in Upper Carboniferous period in southern Guizhou, characterized by wide distribution, integrated strata, well stratigraphic continuity, diverse depositional environments and abundant lithologic combinations. Southern Guizhou is an ideal location for studying carbonate rock sedimentary characteristics and sequence stratigraphy. Based on field measured data (mainly dependent on Jiadaozhai section of Dushan area in association with other sections), this paper employed the relevant theory and methods of sedimentology and outcrop sequence stratigraphy to analyze sedimentary characteristics of outcrop, and then divided sequences and made correlation. It is recognized that southern Guizhou mainly developed restricted platforms, open platforms, platform marginal slopes, and platform basins, whereas Dushan developed only restricted platforms and open platforms. In general, they appear as NNE–trending platforms and SSW-trending basins. The characteristics of sequence filling show that sequence filling was controlled by the third-order sea-level changes at the early stage, and was controlled by both tectonic activity and third-order sea-level changes at the late stage, finding expression in filling and leveling in the carbonate platform.

Abstract:Abstract：Based on paleontology, petrology and well-logging, the authors have studied the stratigraphic features, division and correlation of the Paleogene Shahejie Formation in northern Dongpu Sag. Member 2 and lower Submember of Member 4 of Shahejie Formation are mainly composed of a set of red sandstones and mudstones. There is an unconformity surface between the lower Submember and the upper Submember of Member 4 of Shahejie Formation. There exists a hiatus at the bottom of Member 2 of Shahejie Formation. Member 1, Member 3 and upper Submember of Member 4 of Shahejie Formation are mainly composed of a set of gray sandstones, mudstones and shales with four sets of salt rocks. The stable calcareous mudstones and shales of Member 1 and Member 3 of Shahejie Formation constitute fairly ideal key beds for regional stratigraphic correlation in the Dongpu Sag. Fossils are rare in the lower Submember of Member 4 of Shahejie Formation. The local ostracodes, called Cyprinotus altilis assemblage, began to develop in Member 4 of Shahejie Formation. Member 3 of Shahejie Formation is characterized by very flourishing ostracodes, such as Huabeinia and Candona, called Huabeinia chinensis assemblage. The dinoflagellates of Member 3 of Shahejie Formation are called Bohaidina－Parabohaidina assemblage. Member 2 of Shahejie Formation is characterized by the most prosperous stonewort called Charites producta assemblage. The ostracodes of Member 2 of Shahejie Formation are called Cyprinotus xiaozhuangensis assemblage. Member 1 of Shahejie Formation is characterized by the most prosperous gasteropods called Valvata (Cincinna) rehetaiensis assemblage. The ostracodes of Member 1 of Shahejie Formation are called Phacocypris huiminensis assemblage. The standards adopted by previous researchers were the same as those in dividing each Member of Shahejie Formation in northern Dongpu Sag. However, there existed remarkable differences in determining the specific boundary. What is more, the previous researchers adopted the standards of extinction of Cyprinotus altilis and the lower boundary of Huabeinia acme-zone in dividing the boundary of Member 3 and Member 4 of Shahejie Formation. However, because of the limited accuracy of palaeontologic standards in dividing the strata, the lack of geological data from wells at that time and the existence of complex faults in the Dongpu Sag, the boundaries of different areas defined by the same researcher are different. It is pointed out in this paper that strengthening researches on sedimentology in such aspects as the sequence stratigraphy and variation regularity of sedimentary facies constitute the key to resolving the problems of stratigraphic division and correlation in the Dongpu Sag.

Abstract:Abstract：The Xiangshan Group in Ningxia is dominated by deep-water turbidity current deposits which are mainly a set of low metamorphic terrigenous clastic rocks intercalated with minor carbonate rocks and cherts. The Xiangshan Group is divided into three formations, which are from bottom to top Xujiajuan Formation, Langzuizi Formation and Mopanjing Formation. As relatively much research work was devoted to the formation epoch while the study of other aspects was insufficient in the past, the authors have made an integrated study of tectonic settings from the framework modes, major elements and trace elements of terrigenous sandstones in Xujiajuan Formation, which comprises the lower part of Xiangshan Group. Some conclusions have been reached： ① the framework modes suggest a typical passive margin; ② the discrimination diagrams for major elements suggest a result of uncertainty; and ③ the discrimination diagrams for trace elements suggest a transition tectonic setting. Thus, the tectonic setting during the deposition of Xujiajuan Formation of Xiangshan Group was not a simple passive margin, but most probably a transition source area among the passive margin, the active margin and the continental island arc.

Abstract:Abstract：Provenance system analysis is one of the key means for determining the genetic type, spatial distribution and evolution of the reservoir. In this paper, Based on an integrated analysis of palaeogeomorphology, heavy minerals, composition and structure of debris and dip log data, the authors systematically studied the provenance of 3rd Member of Oligocene Lingshui Formation in Yacheng 13-1 Gasfield within Qiongdongnan Basin and revealed that the provenance system of the study area was derived from the northwest during the deposition of 3rd Member of Lingshui Formation. The clastic sediments are mainly lithic feldspathic quartzite and feldspathic quartzite with high content of quartz. An analysis of heavy mineral assemblages shows that the rock types of the source area were mainly acidic magmatic rocks, metamorphic rocks and reworked sedimentary rocks. Because of the moderate distance from the source area to the study area and the existence of some slopes between them, the source area was likely to produce large debris by mechanical crushing and this type of mother rock might have been the inherent factor responsible for the formation of braided channel delta sandstone and sedimentary characteristics in 3rd Member of Lingshui Formation in the study area.

Abstract:Abstract：Shangshikan stratigraphic section in Luoping of Yunnan Province is a representative fossiliferous bed that produced Luoping Biota. According to the standard microfacies model put forward by Wilson (1975), the authors recognized six types of microfacies, i.e., marlite, bioclastic wackestone, pelleted-bioclastic marlite, laminated micrite, bioclastic packstone and calcirudite, in the fossiliferous bed of Shangshikan section. The fossiliferous bed can be subdivided into two horizons: the Upper Fossil Horizon (UFH) and the Lower Fossil Horizon (LFH). The relationship between microfacies and fossil enrichment in each fossiliferous horizon was further studied. The result reveals that four kinds of microfacies are mainly developed in the fossil-enriched horizons, comprising marlite, bioclastic wackestone, pelleted-bioclastic marlite and laminated micrite, whose assemblage always occurs in the deep, low-energy intra-platform basin. The water in this environment implies a high anoxic and retained condition, This study shows that this intra-platform basin is highly anoxic and retained, which is suitable for the preservation of fossils.

Abstract:Abstract：The Pulang porphyry copper deposit is a typical Indo-Chinese porphyry copper deposit in Zhongdian area, hosted in southern composite body of the Yidun structural—magmatic belt. The composite rock body is a hypabyssal-ultrahypabyssal intermediate-acid porphyry (porphyrite) body, which can be divided into three invasion stages, i.e., quartz diorite porphyrite, quartz monzonite porphyry, and granodiorite—porphyry. Geochemical characteristics show that the rocks are enriched with Ba, La, Rb, Sr, K, chalcophile elements Cu, Pb, and siderophile elements Mo, Ni, and are depleted in Nb, Zr, Hf and Ti. Porphyry (porphyrite) is the same as the rock series of granite island, belonging to calc—alkaline suite, and their genetic types are also similar to each other, belonging to I-type granite. The ore bodies are controlled by structures. The porphyry copper deposit mainly occurs in the Indo-Chinese intermediate-acid porphyry (porphyrite), and the mineralization was controlled by such factors as magmatic rocks, emplacement formation, uranium migration, hydrothermal alteration and structural space, which jointly constituted a porphyry metallogenic system characterized by the structural—magmatic—hydrothermal coupling in Indo-Chinese period.

Abstract:Abstract：The Sankuanggou Cu-Fe-Mo-Cu ore deposit is located in the northwest part of the famous Doubaoshan copper polymetallic metallogenic belt, Heilongjiang Province. In recent years, the resource exploration in crisis mines has been carried out at the edge and on the periphery of this ore deposit, and has discovered an independent Mo ore body and a Cu-Mo ore body of the cryptoexplosion breccia type as well as a gold mineralization belt related to the ductile-brittle shear zone. Therefore, some new understanding of the geological characteristics and mineralization regularity of this ore deposit has been obtained. This paper also summarized and analyzed hydrogeochemical indicators for ore-prospecting in this area, thus providing a more adequate basis for further exploration of medium-size or large-size copper polymetallic deposits.

Abstract:Abstract：Numerous Pb-Zn ore veins were recently found in Luanchuan area, southwestern Henan Province. These veins host enormously huge resources of Pb and Zn. The Chitudian ore deposit is one of these newly-discovered Pb-Zn deposits. Its Pb-Zn ore veins are controlled mainly by WNW-trending fractures. Apart from Pb-Zn ore veins, skarn with Pb-Zn mineralization was also discovered recently in the ore deposit, but the economic value is lower than that of the ore veins. Considering that weak Mo mineralization occurs in skarn close to the intrusion in the ore deposit, the authors put forward a mineralization zoning: Mo mineralization in skarn occurs close to the intrusion, Pb-Zn polymetallic mineralization in skarn occurs away from the intrusion, and Pb-Zn mineralization in veins is controlled by fractures much more distant but is around the periphery of the intrusion. Petrography, microthermometry and laser Raman spectrometry of primary fluid inclusions show abundant content of CO2 in the ore-forming fluid, immiscible separation of CO2 and H2O, and homogenization temperatures in a range of 290℃-340℃ during lead-zinc mineralization. δ34S of sulfides from the Chitudian lead-zinc ore deposit vary between -0.32‰ and 8.30‰ (averagely 4.01‰), and show a bimodal distribution with one peak consistent with the peaks of porphyry Mo-W deposits (2‰ to 4‰) and the other peak shifting the heavy δ34S values to the values close to S content of strata (12.43‰ to 18.63‰), which may indicate that the S of lead-zinc ore veins have two main sources: a magmatic source and a stratatigraphic source. In addition, a pair of paragenetic sphalerite and galena from an ore vein gives a high sulfur isotope equilibrium temperature of 388.29℃. The Pb isotopic compositions of the Chitudian lead-zinc ore deposit are scattered in a relatively small range (206Pb／204Pb=17.005- l7.953，207Pb／204Pb=15.414-15.587，208Pb／204Pb=37.948-39.036), which accords mainly with the zone defined by Yanshannian porphyry, suggesting that the metals might have been mainly derived from Yanshannian porphyry intrusions, and partialy from the strata. In conclusion, it is reasonable to hold that the Chitudian Pb-Zn deposit is genetically related to Yanshannian porphyry and the Pb-Zn ore veins are of magmatic hydrothermal filling-metasomatic genesis.

Abstract:Abstract：Manganese nodules were found for the first time near Zhongmula Village of Litang County in Sichuan Province, along the Garze-Litang suture zone. Based on geological mapping and integrated investigation，it is found that the manganese nodules are distributed in the black silt slate of Waneng Mélange belonging to the suture zone，and its sedmentary sequence is basalt→silicite→black manganese nodules-bearing silt slate. The major chemical compositions of the manganese nodules are characterized by high Mn and low Fe， Si， Ca. The Mn content is 42. 19% which is 1.83 times higher than average Mn content of oceanic nodules; Mn/Fe ratios are relatively high, reaching 8.1. The content of most of the trace elements in the manganese nodules is lower than that of ocean nodules except for Cr whose content is 2～7 times higher than that of ocean ones. Rare elements have distinct Ce positive anomalies, and ΣREE，LREE/HREE，δEu are similar to things of sandstone and siliceous rocks but are very different from things of the basalt. The tectonic environment of the manganese nodules is a continental margin with weak volcanic activity，indicating that sedimentation occurred in an environment of the most strong expansion of the Ganze-Litang Ocean, during which the width of ocean was still limited in comparison with modern oceans.

Abstract:Abstract：The Dounan manganese deposit is a large-size sedimentary manganese deposit in southeastern Yunnan, and a study of its genesis can reveal the model of sedimentary manganese deposits in southeastern Yunnan. Samples from the Dounan manganese deposit were systematically studied by means of manganese phase analysis and IR spectroscopy. Based on a study of the relationship between the type of manganese and redox interface, the authors hold that the model of sedimentary manganese deposits is controlled by redox interface changes caused by sea level changes.

Abstract:Abstract： Polymetallic nodules and cobalt-rich crusts are two types of ferro-manganese deposits in the ocean. In order to probe into their REE geochemical characteristics in different oceanic areas of the Pacific Ocean, the authors collected samples from eastern Pacific basin, central Pacific Ocean and western Pacific Ocean and examined REE characteristics by means of ICP-AES. There are obvious positive Ce anomalies, rich LREE (light REE) and high total REE (∑REE) in the crusts. In contrast, there are rich HREE (heave REE) and relatively low ∑REE in the nodules, Ce anomalies have different styles, such as positive, negative and indistinct anomalies caused by different genetic types of nodules. The “M” type tetrad effects of nodules indicate that the nodules have suffered diagenesis, while the crusts have not been subjected to this effect. There exist different modes of occurrence of REE in nodules and crusts in different oceanic areas. REE in the crusts from central Pacific Ocean and in the nodules from eastern Pacific Ocean probably exist in the Fe-mineral phase, whereas REE in the crusts from western Pacific Ocean might exist in the Mn-mineral phase. REE in the nodules and crusts might have been mainly derived from seawater and seamount altered basalt respectively, with limited hydrothermal contribution.

Abstract:Abstract：This paper mainly deals with the process of using dual-frequency induced polarization in rapid exploration of the mountain area of western Henan Province with the purpose of finding ore bodies and the problems worthy of attention in the field engineering. Through dual -frequency?induced polarization intermediate gradient survey, three induced polarization anomalies in the working area was discovered. An integrated analysis of the induced polarization anomalies was also made on the basis of local geological data, physical properties of rocks and geochemical secondary halos. Drilling has proved that the anomalies are related to concealed molybdenum ore bodies and molybdenum mineralization. It is also proved that dual-band induced polarization can be fully adapted to the rapid exploration and evaluation of the mountain area of western Henan Province with good results achieved.

Abstract:Abstract：The weathering process of terrestrial strata consumes atmospheric/soil CO2, forming an important sink of atmospheric CO2. This study intends to highlight the relationship between CO2 intake by carbonate weathering and land use changes in a typical karst area at Xiaojiang watershed of Yunnan Province. The authors analyzed more than 600 groups of groundwater composition data collected from 25 monitoring points in 1982 and 2003. These monitoring points were chosen from 12 typical areas of land use conversion in the watershed that consisted of four change areas from forestland to cultivated land, three from unused land to cultivated land, four from unused land to forestlands and one from forestland to construction land at Xiaojiang watershed. CO2 intake strength (CIS,%) by carbonate chemical weathering is presumedly defined as the percent of carbon from atmospheric/soil CO2 (representation with HCO-3) in the total carbon during chemical weathering (representation with HCO-3) , and its formula is expressed as CO2 intake strength (CIS,%)=100×[1-(Ca2++Mg2+)total waters)/ HCO-3 total waters]. The estimated results of CIS changes of four land use conversions from 1982 to 2003 show that CIS of forestland (48.84%) is higher than that of unused land (47.66%). From 1982 to 2003 the average CIS decreases in these three land use change areas (unused land to cultivated land, forestland to cultivated land and forestland to construction land) were -7.85%, -8.59% and -1.66%, respectively. CIS increase of the change area from unused land to forestland was 1.74% on average. As for cultivated lands changed from unused land and forestland, construction land from forestland from 1982 to 2003, the ratios of Ca2++Mg2+/ HCO-3 in groundwater were from 0.510 to 0.589, from 0.515 to 0.601, and from 0.508 to 0.525, respectively. All the ratios increased. For the conversion of unused land into forestland, the ratio declined from 0.533 to 0.524. The more the ratio increased, the less CIS and vice versa. In addition, it is found that loss of HCO-3 is positively correlated to SO2-4+NO-3 concentrations (in mmol/l) measured in groundwater, SO2-4+NO-3 tends to increase while loss of HCO-3 increases. The more the loss of HCO-3 is, the less the CIS and vice versa. Adding N-fertilizer such as (NH4)2PO4, (CO(NH2)2), NH4NO3, (NH4)2SO4 after changing from unused land or forestland to cultivated land interferes or counteracts with carbonate weathering due to carbonic acid because such N-ferlitizers can become HNO-3 by nitrification. This results in a relative increase of Ca2+, Mg2+ and a relative decrease of HCO-3 in karst water. When this occurs, it lessens the CIS.

Abstract:Abstract： In the urbanization process of Guangzhou, which is characterized by highly centered economy and fast utilization of resources, groundwater environment has been influenced severely. High content of NO-2 and NH+4 in groundwater is concentrated in the city center, and samples with quota-exceeding NO-3 is distributed around the city and hilly areas, besides in the downtown area. Groundwater contaminations caused by human activities are complex. There have been various causes for nitrite, nitrate and ammonia (NNA) pollutions of the groundwater, and the human activities such as domestic, industrial and agricultural activities have played the dominant role. In addition, the NNA contamination is also related to such factors as stratigraphic sedimentary features in the plain area and the formation and modes of occurrence of groundwater. The nitrogen distribution in Guangzhou groundwater environment is affected significantly by hydrogeological conditions and hydrogeochemical factors, such as redox environment, lithology of the vadose zone, recharge, runoff and discharge conditions, content of Fe and Mn in water and soil, and the degree of acidification.

Abstract:Abstract：Beijing Plain is composed of a suite of considerably thick alluvia and diluvia, and the establishment of the standard stratigraphic sequences of the whole plain is difficult because of the remarkable changes of lithology and lithofacies. With the rapid development of dating technology, the establishment of long dated sequences of sediments has become possible. Through observing the core of unconsolidated strata, this paper divided the core into 8 characteristic lithologic sections on the basis of the characteristics of sediment color, sedimentary environment, cycle and structure. Also, the result of paleomagnetism dating shows that 0-96.59 m of core is the Brunhes Normal Polarity Zone, 96.59-246.79 m is the Matuyama Reversed Polarity Zone, and 246.79-413.64 m is the Gauss Normal Polarity Zone. By mean of pollen analysis and a comparison with the evolution history of Cenozoic climate in North China, the authors hold that the depth of 246.5 m can be regarded as Q/N boundary, the depth of 534.5 m is N/E boundary, and the depth of 803.4 m is E/K boundary. Based on the principle of magnetic and climatic stratigraphy with the aid of rock stratigraphy, the authors studied the new No. 5 borehole and divided Cenozoic stratigraphic sequence into the late, middle and early Pleistocene, with Q/N boundary located at the depth of 248.4 m, N/E at the depth of 511.9 m, and E/K at the depth of 804.1 m.

Abstract:Abstract：Based on the high resolution stratigraphic sequence stratigraphy theory and the principles applicable to conditions as to when climate cycle and ascending and descending cycles of the base level and sea level are over the whole region, this paper carried out a comparative study with high precision and sedimentary environment analysis of 23 drill holes and 2 holocene sections within 46 km2 of the region of interest, and also made an in-depth investigation of the ecological environment for the ancestors living at the cross-lake bridge. The results show that the ancestors at 8000aBP cross-lake bridge lived in an environment almost identical with the current one in terms of its land features, vegetations, animals and climate, and the reason why the ancestors at the cross-lake bridge “disappeared” all of a sudden was that the ascent of the sea level caused the submergence of its site. The sea water didn’t withdraw until 3000aBP, so it was unlikely for the ancestors to move back, which has left the later generations an impression of “mystery”.