Advanced Search

2008 Vol. 26, No. 6

The Oceanic Environment During the Early Devonian in Longmen Shan Area:geochemical evidence from brachiopod shells
CHENG Hongguang
2008, 26(6): 897-903.
Abstract:
The Longmenshan section is a classical Devonian section in the world, and hence becomes the focus of Paleozoic paleocliamte studies. But in the early Devonian, it is short of geochemical isotopic attestation for the paleoenvironment. It will affect the comparison of geochemical signals between the Longmenshan and the other areas in the world, and also hinder the studying of the paleoclimate in Paleozoic. In this study, geochemical signals that came from well preserved brachiopod shells were used to discuss the paleoenvironment. The preservation show: brachiopod shells are well; noncathodoluminscence and Mn<250 μg/g, Sr>400 μg/g. It is witness that diagenetic alteration was small and even not. The δ18O values -4.5‰ ~-9.9‰ was evidently lower than that of other region’s δ18O values (-1.7‰ ~-6.9‰) in the world. And the trace elements Fe and Mn have inverse isochronous trend to the δ18O values. It is possible that the seawater circulation in the Longmenshan was unsmooth, and its δ18O value was desalinized by the input of continental fresh water. Current study will provide a convincing theoretical basis for contrast of isotope and trace elements on the worldwide scale.
The Study on Reservoir Property and Characteristics of the Emeishan Basalts of Zhougongshan and Its Neighbour Area in the Southwest Sichuan
FENG Renwei WANG Xingzhi ZHANG FAN
2008, 26(6): 913-924.
Abstract:
In the southwest of Sichuan, Upper Permian Formation, the thickness of Emeishan basalts of Zhougongshan and its neighbor area is from 40m to 500m,and it is formed by 12 cyclic basaltic volcanic rock. The volcanic breccias in the bottom and the stomatal basalts in the upper have some reservoir capability in cyclicity. The reservoir spaces mainly are air voids,basaltia jointing split and tectoclase. Generally, they form lower porosities, medium permeability or lower porosities,higher permeability reservoirs. In other sections, if there are not the superposition of tectonic movement,most of them can not form reservoir rocks,during the formation and evolution of this set of reservoirs, the condensation contract fissure of magmatic melt,tectonic rupture,organic maturation and chemical erosion. All of these have promoted the forming of reservoir spaces. But hydrothermal alterations and 4 stage cementation and 3 stage packing action have obvious damage affection to reservoir spaces.
Provenance Analysis of Chang6 Oil Reservoir Set in Jiyuan Region in Ordos Basin
WANG Changyong
2008, 26(6): 933-938.
Abstract:
Provenance analysis is the basis and promise of depositional system and palaeogeography. To some extend provenance analysis is the reference for microfacies and sandbody distribution, sandbody forecast and evaluation. There were several ancient lands around Ordos Basin during Late Triassic, including Yinshan Old Land of the north, Alxa Old Land to the northewest, QilianQinlin Old Land of the south and Longxi Old Land of the southwest and so on. These Old Lands were the main source of the detrital sediment in the Basin. Jiyuan region locate in west of Ordos Basin in Chang6 depositional stage, Provenance analysis especially pointing out the main source orientation is significant for sedimentary facies and sandbody distribution. By the analysis of debris components, heavy minerals assemblage, lithic fragment components, cathodoluminescence image, REE, and paleosalinity recovery, it indicated that northeast were main source orientation and northwest is the subordinate source orientation of the studied area, and southwest supply sediment at the same time.
Sedimentation Microfacies Identification Based on Direction Probability Density and Wavelet Descriptor
WANG Renyi
2008, 26(6): 947-956.
Abstract:
For the sedimentation microfacies identification based on the well logging curves of different shapes, three conditions including the invariance of translation and dimension scaling and the modifiability of rotation should be satisfied. In this paper, a new method of sedimentation microfacies identification using the shape of well logging curves which can satisfy the three conditions above was set .Through computing the boundary direction probability density of different shapes of well logging curves, then the wavelet transformation should be made, and few low frequency wavelet descriptors whose direction probability density can be reconstructed can be used as the sedimentation microfacies identification and the wavelet descriptor identification of different sedimentation microfacies can be set at the same time. The wavelet analyze should be made for the direction probability density function of different well logging curve, so the sedimentation microfacies information should be mapped to a reduced dimensionality characteristic vector space consist of few low frequency wavelet descriptors from the high dimensionality characteristic vector space, therefore, the discrepancy information of different sedimentation microfacies can be enlarged. For the complicated problem of sedimentation microfacies identification based on the shapes of well logging curves, this method can degenerate it into a simple problem that judging few low frequency wavelet descriptors and the wavelet descriptors can also be used for the sedimentology analysis.
SoftSediment Deformation Structures of Neogene Related to Earthquake and Its Geological Significance in the Southwestern Margin of Qaidam Basin
YANG Jianping
2008, 26(6): 967-974.
Abstract:
Based on studies of regional tectonic setting and observation of drilling cores, softsediment deformation structures of Neogene related to earthquake are recognized in the southwestern margin of the Qaidam Basin. The softsediment deformation structures consist of liquefied sandstone vein,water escape structures,load casts,flame structures,pillow structures,ball structures,pillow beds,microfaults, seismocracks,pinch and swell structures,seismofolds, mixed layers structures and seismic brecciated structures. There are five kinds of sand dikes, such as throatlike sand dikes, venationlike sand dikes, beltlike sand dikes, upward wedge sand dikes and vshape sand dikes. They are caused by shakingfluidization, shakingliquefactionpushing and after shakingpulling softsediments filling in cracks. The load casts,flame structures,pillow structures and ball structures are formed by sinking and instilling caused from oscillation of earthquake along the face between sandy and muddy beds. The seismocracks,microfaults and seismofolds are cracks, faults and folds formed directly by oscillation of earthquake. The pillow beds form by dehydration, sinking and deforming of the sandy beds during earthquake′s oscillation. The integrity of mixed layers structure depends on the magnitude and duration of earthquake. The seismic brecciated structures are made up of autoclastic breccias, plastic breccias and brittle breccias formed by the cracking of basal undisturbed laminate bed because of oscillation of earthquake. The discovery demonstrates that the movement of earthquake was violent on the time of Neogene in the north of Kunlun Orogenic Belt from sedimentology, and it provides a theoretical foundation for the tectonic evolution studies of the Qaidam Basin. Seismic events affect greatly on the physical properties of reservoirs, and the permeability of reservoirs can be improved obviously.
Framework of Sequence Stratigraphy , Sedimentary System and Evolution of Cretaceous Hefei Basin
TANG Hongsan
2008, 26(6): 982-993.
Abstract:
According to seismic, welllogs, outcrop & cores data, we identified sequence stratigraphy boundarys. CretaceousPaleogene strata can be recognized as 3 firstorder sequence, 1 secondorder sequences and 4 thirdorder sequences. Based on the principle of base level cycles,the author distinguished & established sequence stratigraphy framework, sedimentary system setting & evolution in CretaceousPaleogene.That is: 1) Early Cretaceous sequence series(Zhuxiang & Xiangdaopu Formations): a semigraben basin which onlapped in the west & faulted in the east, developed great scale alluvial fanalluvial plaindelta plain on the westernnorthern & westernsouthern respecially. On eastern & easternnorthern growth aseries fandeltas & shore semideepdeep lacustrine. 2) Late Cretaceous sequence series(Zhangqiao Formation): similar with Early Cretaceous basically,buta semigraben basin which onlapped in the south & faulted in the north more salience.3) Paleogene Sequence series(Dingyuan Formation): The north of Feizhong fault uplift since tectonic movement so that bisect the basin, Dingyuan depression on the north and Shucheng depression on the south.
Sequence Stratigraphy of Late Paleozoic CoalBearing Measures in Northeastern Ordos Basin
YANG Minghui
2008, 26(6): 1005-1013.
Abstract:
By the identified the regional unconformity, sedimentary system conversion, tectonic stress conversion and exposed surface, the authors divided the Late Paleozoic coalbearing measures in northeastern Ordos basin into seven 3rd sequences. Based on the study, the ternary texture of epicontinental sequence indicate that they also consist of lowstand systems tract, transgressive systems tract and highstand systems tract. Some fluvial sandbodies developed in the northern Ordos basin characteristic by filling of valleyincised in the lowstand systems tract that is sheet sandstone such as Jinci sandstone, Qiaotou sandstone and Beichagou sandstone. The position of coal seams in the sequence framework has relationship to the transformation time of sea level change, and develops mainly at the lower part of transgressive systems tract in epicontinental sequence and the upper part of highstand systems tract in nonmarine sequence.
emiquantitative Analytic Technique on Base Level Variation Range and Its Application
PENG Chuansheng
2008, 26(6): 1021-1026.
Abstract:
Base level is an imaginary level surface and as a matter of fact, a very physical potential energy level at the same time, which controls stratum depositional and conservation by increasing or decreasing accommodation space. Lacustrine sedimentation is mainly controlled by tectonic action. Seismic onlap pinch out boundary is difficult to be used for confirming excursion of the base level. The sediment types and their superimposed features in log data can conversely verify the rangeability of relative accommodation space. In the light of thickness distribution of the sand shale sequence cycle, we can semiquantitatively analysis rangeability of the base level by selecting middle thickness or average thickness of the maximal bearing value area as statistics area, then accounting thickness of sand and shale of every area from bottom to top, and calculating percentage of the mudstone which endowed with different “base level variety numerical value”. The method is suitable to make definite the changing features of accommodation space, to recognize transform surfaces and base level cycle, and to analysis the dominance for precipitation facies partition. It is applied in base level cycle division and comparison of offshore sedimentation sand or sand shale alternate layer to establish high resolution equitime framework.
The Areal Characteristics of Chlorophyll α Distribution in the Sediments and Seawater in the Surveyed Area, Arctic Ocean
LIU Zilin
2008, 26(6): 1035-1042.
Abstract:
Investigations of chlorophyll α was carried out in the seawater and sediment in the Chukchi Sea, Chukchi Plateau, the Slopflow area, the Mendeleev Ride and the Canada Basin during the 2nd Chinese National Arctic Research Expedition in the summer of 2003. The results showed that chlorophyll α concentrations were 0.002~39.008 μg/dm3 at the surveyed waters; the surface chlorophyll α concentrations were 0.037~4.644 μg/dm3 and the average value was 0.612 μg/dm3 in the surveyed area. Chlorophyll α concentrations at the depths 20~30 m of the subsurface water were higher than that in the surface and under layer. Chlorophyll α concentration distribution was obviously areal characteristics. The areal arrange order of the watercolumn chlorophyll α concentration is the Chukchi Sea > the Slopflow area > the Chukchi Plateau > the Canada Basin > the Mendeleev Ride. Chlorophyll α concentrations were 0~3.978 μg/g (wet mug) in the sediment of the surveyed stations; and the average value was 0.934 μg/g(wet mug) in 7 surveyed stations. Chlorophyll α concentrations at the surface sediments were higher than that in the underlayer. The areal arrange order of the sediments chlorophyll α concentration is the Chukchi Sea > the Slopflow area > the Mendeleev Ride, and chlorophyll α concentration can not be examined in the sediments of the Chukchi Plateau and the Canada Basin. 
Magnetic Properties of Loess Deposit in Eastern Qinling Mountains and An Investigation on the Magnetic Susceptibility Enhancement
ZHAO Jun
2008, 26(6): 1052-1062.
Abstract:
We have carried out a relatively complete rock magnetism investigation on loess deposit in the eastern Qinling Mountains, central China. 251 and 341 samples were obtained from Shangbaichuan (SBC) and Erlongshan (ELS) loesspaleosol sections at 10 cm and 5cm intervals, respectively. Magnetic susceptibility was measured on all these samples. Isothermal Remanent Magnetization (IRM) and Anhysteretic Remanent Magnetization(ARM) were measured on 24, 26 and 6 samples selected from SBC, ELS and Liuwan (LW) sections, respectively. The thermal properties and hysteresis properties were measured on 14, 14 and 6 samples from SBC, ELS and LW sections. The results indicate that most of loess and paleosol samples are dominated by ferrimagnetic minerals (magnetite and maghemites) and the paleosols have more ferrimagnetic minerals than that in the loess, but there are still some cases that antiferromagnetic minerals (hematite) play a more important role in the magnetic properties. Both of the concentration of ferrimagnetic minerals and antiferromagnetic minerals systematically increase with the intensified degree of pedogenesis. The finegrained ferrimagnetic minerals, which were formed in pedogenesis, are dominated by single domain and/or pseudosingle domain grains which contribute significantly to the magnetic susceptibility enhancement. The results reveal a strong linkage between the magnetic properties and the palaeoclimate. The rock magnetic properties of the three loesspaleosol sections are generally similar to that in the Loess Plateau, but with a minor difference. In addition, the rock magnetic properties among the three loesspaleosol sequences are slightly different; this may be caused by a warmer and more humid climate in this region.
Element Balance Method and Application of Appraising Biogenic GasLow Maturity Gas in Tuha Basin
LU Shuangfang
2008, 26(6): 1063-1070.
Abstract:
The proved reserves of nonhigh temperatureoriginated natural gas (biogenic gaslow maturity gas)in Tuha basin is already near 100×109 m3, but we didn’t sees the reported about appraises to the effective method of generation quantity and resource quantum yet, this has affected the decisionmaking to its exploration potential and the favorable target. In view of this problem, considering regardless the generation mechanism of biogenic gas and low maturity gas, they were an organic element balance process; this article explored and established element balance method to appraise the gasgenerated amount of biogenic gas and low maturity gas.We use massive actual analysis data of Tuha basin to demarcate and apply this assessment method. The result indicated that biogenic gaslow maturity gas generation rate of ⅡOM is higher than III OM in Tuha basin, the two accumulate separately may reach 134.40ml/g and 83.99ml/g, total generation quantity of biogenic gaslow maturity gas in Tuha basin approximately 1436.28×1012m3; The resource quantum is possibly situated between 7.09×1011m3~24.42×1011m3 it indicated that nonhigh temperature originated natural gas in the Tuha basin has big exploration potential. J2x and J1 and the nearby position in Taibei hollow are the favorable exploration target.
Distribution and Hydrocarbon Generation of the Eogene Source Rocks in aSequence Stratigraphic Framework in the Nanpu Sag,Bohai Bay Basin
ZHAO Yande
2008, 26(6): 1077-1085.
Abstract:
Nanpu Sag is rich in oil and gas and the main hydrocarbon source rocks of the Eogene are distributed within Es3,Es1 and Ed3 Formations. Based on the sequence stratigraphy study, the hydrocarbongenerating potential and distribution of source rocks in the Eogene sequence stratigraphic framework of Nanpu sag are discussed in this paper by the methods of organic petrology, geochemistry and organic facies. The results show that the heterogeneity of source rocks varies in different systems tracts. The hydrocarbon source rocks which were deposited in the early highstand systems tract and extent systems tract have the best hydrocarbongenerating potential in the SQ9, SQ5SQ8, SQ2 and SQ1 of Eogene, because the characteristics of sedimentation in the different systems tracts affect the type and conservation of organic materials in source rocks.
沉积与能源、矿产
Research on Coral Reef Ecosystem of the Late Carboniferous in the Southern of Guizhou
CHANG Honglun DONG Xuming GONG Enpu
2008, 26(6): 904-912.
Abstract:
A largescale metazoa framebuilding reef system was developed in the southern Guizhou Province during the LateCarboniferous, which was rarely reported in the geological records after the F/F mass extinction event. The reef structure was mainly built by rugosan corals Fomitchevella, and is, from the bottom to top, composed of four subunits: bioclastic shore, patchy reef and mud mound, bioclastic limestone and Fomitchevella framestone. The organisms in ecosystem of each unit are variable, due to different tropic level in which producers, consumers and decomposers are differentiated in view of their behavior in the food chain, reefbuilder and reefdwellers in view of their functions in the reefbuilding process. The analysis shows that the organisms play different roles in reefbuilding process due to their status in the food chain. According to the contribution of the organisms and energy and macronutrient flow diagram, a new understanding that the coral reef ecosystem rapidly uptake the macronutrient is obtained. According to the composition and the relationship of the organisms, the development process of the ecosystem is supposed based on the organisms and their spatial location relationships, and can be divided into bioclastic shoal stage, patchy reef and mud mound stage, Fomitchevella colonizing stage and Fomitchevelladominant stage. The different behaviors and growth forms of Fomitchevella and Ivanovia cf. manchurica determined their status in the coral reef ecosystem, and the ecosystem maintained survivorship and development of the species by rapidly up taking the macronutrient.
Mineral Elemental Response to the Evolution of Terrestrial Brine Faultedbasin:a case study in the Paleogene of Well Haoke1, Dongying Sag
CHEN Zhonghong
2008, 26(6): 925-932.
Abstract:
In order to investigate the relation between the distribution of mineral elements and sedimentary environment including the salinity and depth of water body, and the evolution of lakebasin, emission spectrograph of inductive coupling plasma was used to intensively testing and dissection the content of mineral elements in the deep death of the Paleogene from the Well Haoke1 in Dongying sag. The involved formation contained the Member 3, Member 4 of Shahejie Formation and Kongdian Formation, in which the main source rocks distributed. The results demonstrate that: in the oxidized sedimentary environment of shallow shorelacustrine the content of Sr, Ca and the parameters of Ca/Mg, Sr/Ba, Sr/Ca have low value response, the content of Fe, Al, Ba, V and the parameter of (Fe+Al)/(Ca+Mg) have high value response; in the brinelake sedimentary environment the content of Mn, Ba,V and the parameters of V/Ni, (Fe+Al)/(Ca+Mg) have low value response, the content of Sr, Na and the parameters of Sr/Ba, Fe/Mn, Sr/Ca have high value response; in the reductive brackish sedimentary environment of halfdeep lacustrine lake the content of K, Na, Fe and the parameters of Fe/Mn have low value response, the content of Ca, Mn have high value response. In the cosedimentary environment of saline deposit and mud of the middle part of Sha4 Formation, the distribution of mineral elements has obvious characteristics of discretion and fluctuation. Sr/Ba, Sr/Ca have obvious high value response in the saline lake and are verified to be good parameters for salinity of waterbody. The parameters of Fe/Mn and (Fe+Al)/(Ca+Mg) are approved to be good parameters for the depth of waterbody and their value increased with deepening of waterbody. The parameters abovementioned should be applied and synthetically analyzed to determine characteristics of geological factors for the parameters were influenced by many geological factors including sedimentary environment and lithologic character. 
he MicroTransmutation Structures and the Reservoir Significance of mmclass Mudfilm in the Silt in Yingtai Area〖
ZHOU Yongbing
2008, 26(6): 939-946.
Abstract:
There are many thin mud laminas of mmclass in the Cretaceous equal silt stone in Yingtai area, western Songliao Basin, which we call them mudfilms, have a thickness between 0.2 and 3 mm, and the main component is shale while some are carbon dust layers. They are three kinds of conformation of mudfilms on section: close straight line, serrated denticle and irregular curve. There are many micro transmutation structures with the scale less than 3 mm on the surface of mudfilms, we divide all the micro transmutation structures into 9 types: straight line, C/S, circle, ellipse, and leaf of bamboo, ripple mark, twig, mesh and irregular patterns. Some micro transmutation structures are too hard to be breakthrough and so the silt stone up and below the mudfilm can connect each other. The origin of the mud films are mud subsidence or sideway mud erosion in may momentary sedimentary break. There are many causes of formations of the mudfilms such as syndeposit interfere, differential compaction, bedding glide, bioturbation, diagenesis shrink and earthquake activities. The study on the cause of formations and micro transmutation structures of the mudfilms will have an important significance for the research of sedimentary environment and the fine space structure of the reservoirs.
Feature and Origin of Dolomite Filling in the Upper CambrianLower Ordovician Dolostone of the Central Uplift, Tarim Basin
ZHANG Juntao
2008, 26(6): 957-966.
Abstract:
Two genetically distinct dolomite fillings are recognized in Lower Paleozoic dolostone in the Upper CambrianLower Ordovician dolostone of the Central uplift, Tarim basin: rhombus and saddle dolomite fillings, which occur in different diagenetic considerations and have different character. The former crystal exhibits homogeneous, the later crystal is composed of three distinct parts that are rim, clitellum and core. Stratigraphic, petrographic and geochemical date suggest, rhombus dolomite filling deposited steadily and source of Mg2+ is from the altered seawater. However, material source of saddle dolomite filling is hydrothermal dissolution of dolomite. The formation of saddle dolomite filling, three parts of which formed in different phase, is associated with faulting. The deposition of dolomite filling is porosity decreasing, but saddle dolomite is a sign of dissolution. 
The Evidence for Seismism in Cretaceous of South Beir Sag, Mongolia
WANG Huaai
2008, 26(6): 975-981.
Abstract:
Based on studies of regional tectonic background and the observation of drilling cores, the seismite is recognized which mainly occurred in Cretaceous in South Beir sag, Mongolia. Many kinds of soft sedimentary deformation structures have been found in seismite, such as step microfaults, pleated within layers, liquefaction sandstone veins, vibrational liquefaction deformation structure and seismic breccias. It is the first time that seismite has been found in South Beir sag, Mongolia. The complete vertical sequence of seismite developed in Well Ta219, which include bottom unshaken layer, liquefied sandstone vein bed, vibration liquefaction deformation structure bed, intraclastic parabreccia bed, laddershaped faulted and vibration split bed, seismic turbidite bed and top unshaken layer. It is rare among the reported examples about such complete sequence of seismite in one Well's core, so it is a good example and offers power evidences to study seismism. 
Lower Cretaceous Sequence Stratigraphy of Fula Depression, Muglad Basin, Sudan
YANG Junsheng
2008, 26(6): 994-1004.
Abstract:
Abu Gabra Formation of Cretaceous Fula depression, which is formed during the first rifting cycle, can be divided into three secondorder sequences, namely, sequence K1SSI, sequence K1SSII and sequence K1SSIII. They can correspond separately to the strata deposited in the early, middle and late rift period. Of the three secondorder sequences, the sequence K1SSI and sequence K1SSIII can be subdivided into two thirdorder sequences, the sequence K1SSII into three thirdorder sequences. Based on the integrated analysis of seismic data, core and well logging, the distribution of sedimentary facies and the prediction of sedimentary system are achieved. Through investigation, 7 types of sedimentary facies are recognized, namely, fluvial deposit, delta, fan delta, braided delta, proximal sublacustrine fan, lacustrine facies.
Due to the evolution of their sedimentary facies, five chief depositional systems are established in the Fula depression. They are fan delta system in the NE, delta system in the NW, proximal sublacustrine fan in the west, braided delta system in the ES and fluvial system produced in the early period. The distribution and evolution of the depositional systems is controlled by tectonics, probably influenced by paleotopography and paleogeography.
Sedimentary Evolution in the Framework of High Resolution Sequences of Dongying Formation and Prediction of Favorable Zones in Qingshui Sag, Liaohe
XIAO Yi
2008, 26(6): 1014-1020.
Abstract:
On the principle of baselevel cycling and through the integrated analysis of cores, well logs and 3D seismic data, we divided the Dongying Formation (Ed) in Qingshui Depression into 4 thirdorder sequences, namely Lower Ed3, Upper Ed3, Ed2 and Ed1, and recognized three types of sedimentary systems, i.e. the semideep lacustrine subaqueous fan system, the shallow lacustrinedelta system and the alluvialfloodplain system. On the basis of the sequence identification and the sedimentary system recognition, we then studied the configuration of sedimentary systems and the development of reservoir sandbodies in the sequential context. Finally, after evaluating the oilgeneration, preservation and seal conditions, we concluded that, Lower Ed3 and Upper Ed3 sequences are the most favorable sections vertically, and exploration targets are subwater fans and delta front sands, mainly channel sands, mouth bars and sheet sands.
Geochemical Characteristics of Rare Earth Elements of Coal in Zibo Coalfield
LIU Changjiang
2008, 26(6): 1027-1034.
Abstract:
The aboudances of the rare earth elements (REEs) of 35 coal samples (including 12 samples of floor and roof seam and 1 gangue sample) in Zibo coalfield were determined by inductively coupleplasma mass spectrometry (ICPMS), and the content of ash and some correlative associated elements are also tested. The contents of the REE, geochemical parameters, spatial distribution and distribution patterns were studied in this paper. Furthermore, the author discussed the characteristics and origin of REE in the samples. The results are as follows: Compared with others areas at home and abroad, the REE are obviously enriched in Zibo coalfield. The REE contents in the Taiyuan Formation are higher than that in the Shanxi Formation. They rise from top to bottom in the coal seam and enrich in the floor and roof and gangue samples. The negative anomalies exists in the value of δEu and normal value in δCe indicate that the sedimentary environment of coal may shallow or close sea. The REE in coal is correlative to the ash contents in those coals, and they have good relativity with the terrigenous elements while weak with the marine elements. 
现代沉积与环境
Study on the Characteristics of Temporal and Spatial Changes in Properties 〖JZ〗 of Surface Sediment on NearShore Seabed of StrongTide Bay:a case from the north bank of Hangzhou Bay in Shanghaia
ZHAO Jianchun
2008, 26(6): 1043-1052.
Abstract:
Grain size parameter is the most important information of sediment, which can point out the characteristics of distribution and transportation. Based on analysis data of 167 samples which were collected from the north coast of Hangzhou Bay in June 2005 and December 2006, a study on the rules of temporal and spatial changes in properties of seabed surface sediment in strongtide bay is conducted. As well as, through the Grain Size Transport Analysis model, a conveying trend analysis of sediment in this basin has been studied, in the base of which a research of sand sources is primarily discussed. Finally, the response process of tidal flat sediment to the highenergy hydrodynamic environment is also analyzed. The results indicate that: (1) The grain size of tidal flat sediment in north coast of Hangzhou Bay is generally small, and silty clay is the main sediment types in this basin; (2) The vertical difference of grain size characteristics is more obvious than the transversal, and also there is some seasonal variation between flood season and withered season; (3)The results of GSTAmodel show that,the sediment of this basin is mainly from the upstream and the sea waters. As well as , the interregional sediment exchange is another important method to get the balance of sediment supply in this basin;(4) Agency coverage where tide current can stir surface sediment is mostly the Nanhui and Fengxian water area, while the wave stirring agency coverage almost covers the whole section of the research basin, on which the wave height below 1.5m effect most significantly.
油气地质地球化学
Carbon Isotope Characteristics and the Influencing Factors of the Oils from Lunnan and Hadexun Oil Fields
MI Jingkui
2008, 26(6): 1071-1076.
Abstract:
The analytical results of the whole and the monomer paraffin hydrocarbons carbon isotope of the 20 oils from Lunnan and Hadexun oil fields show that the whole carbon isotope of the oils from Lunnan area is more than 32‰, and that of the oils from Hadexun area is less than 32‰, the carbon isotope of monomer paraffin hydrocarbons of the oils from Lunnan area is also heavier than that of the oils from Hadexun area. That the carbon isotope of oils from Lunnan area heavier than that of oils from Lunnan area caused the difference between the oil pools formation in the two areas. The main factor resulted in the carbon isotope of oils from Lunnan area heavier than that of oils from Hadexun area is the mixture between the degraded oil from the Cambrian source rock and the oils from MiddleUpper Ordovician source rock, instead of the different source rocks of the oils.