Table of Content

20 March 2007, Volume 13 Issue 1

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Article

Cretaceous Oceanic Red Beds: Characters, Occurrences, and Origin

Hu Xiumian 1，Wang Chengshan 2

2007, 13(1):  1-13. 

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The Cretaceous Oceanic Red Beds (CORB) has become one of hot topics since it was put forward and initiated by Chinese scholars during latest 1990s. This paper try to overview scientific results, especially from our groups, related to the CORB studying. The geological and geochemical characters of the CORB from both southern Tibet, Eastern Tethys Ocean, and central Italy, Western Tethys were introduced in detail. Based on global correlation, the characters and occurrences of the CORB were discussed. We also discussed the implications of the CORB related to the response of the paleoceanographic and paleoclimatic changes. We believe that CORB is deposited in highly oxic environment with high content of dissolved oxygen of deeper water, which the latter may be the result of changes in the location and formation of deep water and changes in ocean circulation.

The 87Sr/86Sr ratios of shell bar section at Charhan Lake, Qaidam Basin and its paleoenvironmental significance

NIU Jie1,ZHANG Hucai2,1★,CHANG Fengqin1, CHEN Yue1,FAN Hongfang1,ZHANG Wenxiang1,YANG Mingsheng1 ,LEI Guoliang1

2007, 13(1):  14-22. 

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The data for 87Sr/86Sr, Rb/Sr and Sr contents of the acetic acid soluble components and insoluble components of shell bar section at southeastern Charhan saline lake, Qaidam Basin were presented. According to the environmental significance of Rb/Sr ratios of lake sediments, our data showed that, 87Sr/86Sr ratios can effectively indicate the catchment chemical weathering intensity and the paleoenvironmental changes of the deposit area; Correlation of 87Sr/86Sr with Sr/Ca and Sr/Ba ratios (salinity parameters) of the carbonate fractions indicates that the variation in carbonate 87Sr/86Sr values can be used to reflect the salinity of the water under formation condition. Based on chemical weathering intensities and salinity variations along the sequence, the environmental change history was reconstructed between 39.6 ka BP and 17.1 ka BP for the studied area. The high lake level was maintained between 33.2 ka BP and 27.4 ka BP, both the temperature and precipitation amount were higher than those of the present day. Till about 18 ka BP, the lake started to shrink, probably suggesting that the climate turned from a warmhumid interstadial into a colddry glacial climate.

Environmental Implications of Pigments from Anoxygenic Phototrophic Bacteria in Sediments

WANG Man1,JI Junfeng1, CHEN Jun1,ZHANG Chuanlun2

2007, 13(1):  23-29. 

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Dense populations of photosynthetic bacteria were discovered not only in water, but also in lacustrine and littoral sediments. The pigments of phototrophic bacteria have been becoming a hot topic of scientific interest since the 1940s. Anoxygenic phototrophic bacteria live in chemocline of meromictic lakes and sea, which is the interface between oxic and anoxic mixolimnion. Depth of the H2S chemocline, which is related to paleoclimatic and paleoenvironmental changes sensitively, is reflected by bacteriochlorophylls (BChls) in the sediment core. This paper illuminates distribution and evolution of anoxygenic photosynthetic bacteria together with their pigments. HPLC is a popular measurement for pigments. Finally, the environmental implications of fossil pigments are discussed: (1) BChls can indicate the existence of photosynthetic prokaryote; (2) As the biomarker, BChls in sediments represent the depth changes of the H2S chemocline; (3) Anoxygenic photosynthetic pigments in sediments also can be used to reconstruct the historical record of anoxygenic primary production.

Distribution and Geological Significance of Four Anaerobic Bacteria in Peats

FAN Ben1, YAO Suping2, LI Shunpeng3, DING Hai2 ,LIAO Jialong2

2007, 13(1):  30-34. 

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Fermentation bacteria (FB), sulfatereducing bacteria (SRB) and anaerobic cellulosedegrading bacteria at different depths in four peat sediments were accounted and the existence of methaneproducing bacteria was investigated. The result showed that the numbers of fermentation bacteria were positively correlated with the content of organic matter, especially with those of humic acid. There is no obvious relationship between the numbers of sulfatereducing bacteria and the contents of sulfate. However, to some extent the SRB are negatively correlated with the depths of samples. The minima of both sulfate contents and SRB numbers were found at the bottoms of four sediments. Anaerobic cellulosedegrading bacteria were only detected in several samples, while methaneproducing bacteria habited in all samples even in coexistence with sulfatereducing bacteria. The corresponding geological effects of these anaerobic bacteria on peat sediments were also analyzed in this paper.

Saline Sedimentary Rhythm of Qiuli’nanmu Lake in Tibet

LI Minghui1,2，KANG Shichang1,3，ZHENG Mianping2，BU Lingzhong2

2007, 13(1):  35-42. 

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Lake sedimentary rhythm provides important information on the reconstruction of the palaeoenvironment and palaeoclimate. This paper presents a rare kind of saline sedimentary rhythm composed of mirabilite，borax and clay．To identify the origin and the climatic significance of the rhythm，we used 14C and U series isotopes to get chronological data，analysed pollen compositions, studied chemistry of different water′s and measured thicknesses of individual layers．Our study indicates that the sedimentary rhythm can be formed under the condition of enough source materials，closed morphological environment and climatic changes. During 20.6-20.5 ka BP. there was abundant vegetation and no mirabilite. The climate was warm and wet. Thick mirabilite layers and desert steppe suggest that from 20.5 to 11.4 ka BP the climate was drycold, and there were three warm pulses in 17.5-17.1 ka BP，15.9-15.2 ka BP and 14.1-13.4 ka BP．It became distinct warm during 11.4-10.1 ka BP when thin mirabilite layers and abundant vegetation were developed．From 10.1 to 7.5 ka BP，the cold climate was supported by thick mirabilite layers，decreased arboreal pollen and disappeared Pediastrum．During 7.5-4.97 ka BP, the typical plain composed of Artemisia and the thin thickness of mirabilite layer suggest relatively wetwarm climate，and the variable thicknesses of mirabilite indicate an alternative climate from cold to warm. There was a wetcold pulse during 7.0-6.2 ka BP for decreased Artemisia and increased hydrophyte．The absence of gramineous pollen and the increase in drysalt vegetation proposes a colddry climate and the increased salinity of lake water from 6.2 to 5.2 ka BP．

The Assemblages of Microfacies and the Sedimentary Environment of the Upper Carboniferous Dalaian to the Lower Permian Longlinian in the Zongdi Section, Guizhou Province

KONG Fanfan1,2, YANG Xiangning1

2007, 13(1):  43-52. 

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The cluster analysis method has been applied in a comprehensive study to investigate the sedimentary environment of the Upper Carboniferous Dalaian to the Lower Permian Longlinian of the Zongdi section, Guizhou Province, Southwest China, based on the statistic materials by microscope and referring to the observation in the field. Results of analyses show that there are 11 microfacies in the Zongdi section, namely, deep restricted lagoon, shallow restricted lagoon, deep alga mound, depression near shallow beach, shallow beach of platform margin, deep lagoon, shallow alga mound, shallow lagoon or tidal flat, tidal bar, restricted shallow beach or lagoon and deep slope. The assemblages and distribution patterns of the microfacies in the section demonstrate that the sedimentary environments during the Upper Carboniferous Dalaian to the Lower Permian Longlinian experienced 6 basic processes, namely, shallow beach, open platform, alga mound, restricted platform, deep slope and restricted mound.

Dessication Cracks and Erosional Surface in the PermianTriassic Boundary Section in Chongqing

JIANG Hongxia1, WU Yasheng1, YUAN Shenghu2

2007, 13(1):  53-59. 

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This paper refers to a 3 m thick microbialite in the PermianTriassic boundary section in Laolongdong, Chongqing. The microbialite comprises a dendroid upper part and a specked lower part. An erosional surface is found at the top of the upper part of the microbialite. Some dessication cracks occurred on the top surface of the lower part of the microbialite. Study on depositional environment of the microbialite indicates that the microbialite was emerged to the earth surface and eroded during the PermianTriassic interval, which provides new data for the sea level changes across the PermianTriassic boundary, an important geological epoch.

A Preliminary Study of Functional Morphology, Paleoecology and Taphonomy of Eocriniods from the Cambrian, Kaili Biota, Guizhou

MAO Yongqin1, PENG Jin2,1, ZHAO Yuanlong1, WANG Yuxuan1

2007, 13(1):  60-68. 

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Eocrinoids are very abundant in the Middle Cambrian Kaili Biota at Balang village, Jianhe County, Guizhou Province. Two species are present: the long stalked Sinoeocrinus lui Zhao, Huang et Gong, 1994 and the short stalked Sinoeocrinus globus Zhao et al., 1999. Over 10000 well preserved specimens have been collected including complete ontogenetic series for the two species. These specimens all show brachioles, thecae, stalks and attached discs, and a few specimens show anal pyramids. The development of surtural pores on the thecae appears as an obvious change during different growth stages. The surtural pores are not developed in juvenile stages, but are welldeveloped in adult individuals of both species. Most eocrinoids exhibit a solitary lifestyle. The theca of short stalked eocrinoids is spheroidal, with a large attached disc, often found attached to fragments of brachiopod shell, or to cranidia, or to thoracic segments of trilobites. The long stalked form possesses a small attached disc, which is often attached directly to the silty mudstone substrate. The brachioles of both species are also distinguished by two different growth modes, in which the long stalked forms grew straight up and the shortstalked forms grew spiral up. These characteristics are important in understanding the diversity, ontogeny and ecology of eocrinoids assemblages from the Kaili biota.

A Comparative Study of Selenium Fractionation in Serich Carbonaceous Rocks of Lower Cambrian and Permian in Southwest China

ZHU Jianming1, QIN Haibo1,2, LUO Taiyi3, LI Lu1,2,SU Hongcan4

2007, 13(1):  69-74. 

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A comparative study was conducted to investigate selenium fractionation in Serich carbonaceous rocks from the lower Cambrian Niutitang and Permian Maokou formations, which are located in Zunyi of Guizhou Province and Enshi of Hubei Province, respectively. Seven operationally defined Se fractions in Serich carbonaceous rocks were determined by the modified sequentialextraction procedure suitable for carbonaceous shale. These fractions include watersoluble, ligandexchangeable, basesoluble (organicbounded), elemental, acetic acidsoluble, sulfide/selenide, and residue. The total Se in rock and Se concentrations in individual fractions were measured by HGAFS. The results showed that the sulfide/selenide and organicbounded Se were the predominant forms of Se present in the carbonaceous chert and carbonaceous shale from the lower Permian Maokou formation while residue Se was generally lower. The sulfide/selenide and organicbounded Se were still the major forms in carbonaceous chert of the lower Cambrian Niutitang formation while the organicbounded, residue and sulfide/selenide fractions were prevalent in carbonaceous shale and NiMo ore. Organicbounded Se and elemental Se were the dominant forms in bentonite, and in lesser amount the ligandexchangeable Se. These facts indicated that there exists certain difference in the biogeochemical process of Se accumulation between two rock types from Lower Permian Maokou and Cambrian Niutitang formations. For the former formation, the Se microbe reduction was prevalent in the carbonaceous chert, while in the carbonaceous shale the algal assimilation or adsorption occurred simultaneously with microbe reduction. For the later formation, the algal assimilation or adsorption was be the main biogeochemical process for Se enrichment, while the Se reduction by microbes played a secondary role.

Fault Throw Profile and Kinematics of Normal Fault: Conceptual Models and Geologic Examples

Ge Hongxing，Jon K. Anderson

2007, 13(1):  75-88. 

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Fault throw profile (TH plot) plots vertical fault throw versus geologic or seismic horizon from a cross section. Conceptual models demonstrate that the profiles can be used to determine the styles, timing of initiation, and kinematic histories of normal faults and simply inverted normal growth faults. A throw profile comprising a vertical line segment indicates a simple postdepositional fault. A profile in which throw decreases as horizon age increases indicates a simple postdepositional keystonestretching fault. A profile in which throw increases as horizon age increases indicates a simple growth fault. Major inflections in a composite profile correspond to the time at which fault style changes. The change of a vertical line segment to a curve with negative slope indicates the change from postdepositional to syndepositional faulting. Stacking of such composite profiles suggests repeated fault burial and rejuvenation. The change of a profile slope from positive to negative indicates change from a postdepositional keystonestretching fault to a growth fault. The maximum throw in the profile corresponds to the start timing of the fault. Local normal drag increases apparent throw, which creates bumps in the profile. Reverse drag decreases the apparent throw, which creates dents in the profile.

Monitoring and Research on Micro Kinematics of the Eastern Segment of the Keping Fault

JING Yan1，2 , ZHANG Shizhong1, XIONG Yuzhen1 , LI Hong1 ,LIU Fengqiu1, SUN Qiwei1, DONG Jianye1 ,ZHANG Hongxu1 ,Wang Haizhong1 ,CHEN Getian1

2007, 13(1):  89-95. 

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The Jan.2, 1997 to Dec. 31, 1998 Jiashi earthquake swarm has greatly affected the nearby tectonic activity and fault slip behavior. In this paper, the observation data of MD model fault deformation monitoring system was used to calculate slip rate of the eastern segment of the Keping fault since 1994. The observation and calculation results show that both the horizontal and vertical slip rates changed obviously after the Jiashi earthquake swarm. The sense of the horizontal slip rate changed from rightlateral strikeslip before it to leftlateral slip after it, and the vertical slip rate was 2 times faster than the old one. The horizontal slip rate was 0.033 mm/a in sinistral sense before the Jiashi earthquake swarm, and 0.016 mm/a in dextral sense after it. The vertical slip rate increased from 0.037 mm/a before it to 0.069 mm/a after it. The stress field also changed after Jiashi earthquake swarm. Although the magnitude of strain rate here remained unchanged, the direction of the principle strain rate rotated 16.7° clockwise.

Different Genetic Models of Ordoviclan Carbonate Weathered Crust Reservoirs and Petroleum Exploration Trend in the Bohai Bay Basin

MA Liqiao1,2, YANG Shufeng1, CHEN Xueshi2, SHEN Jinlong2, SUN Fengxia2, LUO Zhang2

2007, 13(1):  96-104. 

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The characteristics of Ordovician carbonate weathered crust reservoirs (Megakarst) were studied at two localities: the Zhaogezhuang section, Tangshan, Hebei province and the Wennan section, Xintai, Shandong province. They are located in the northern and southern margin of Bohai Bay basin, respectively. The former is of buriedhill type, and the major reservoir is composed of vertical vadose (infiltration & percolation zone) about 200 m thick and horizontal phreatic (saturation) zone. The latter is of plateau type, and the major reservoir is an interlayer paleokarst about 380 m thick. The reservoir space is carbonate solution cave, pore, fracture and their combination in both sections. These different genetic patterns provide a direct and visual model for the petroleum exploration of Ordovician carbonate in the basin. As to the petroleum exploration potential of ancient weathered crust reservoirs, it is usually determined by direct overlying source rock strata with high quality. The plateau paleokarst type is easier than the buriedhill type to be predicted.

3D Burial History Analysis of Hefei Basin since Mesozoic

WANG Li, ZHOU Zuyi, ZHU Yijie

2007, 13(1):  105-111. 

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The Hefei basin, located at the south boundary of NorthChina Block, is a largescale terrestrial basin formed during Mesozoic and Cenozoic period. The sedimentary features and tectonic evolution of Hefei basin were mainly controlled by Dabieshan orogenic belt and the TanLu fault zone. Based on the seismic and borehole data, 3D burial history analysis is carried out on MesoCenozoic strata of Hefei basin following the principle of backstripping. The overall thickness of Mesozoic and Cenozoic strata is more than 10 km in the Hefei basin, with Middle to Upper Jurassic strata constituting its major part. The analysis also shows that Hefei basin experienced 3 major tectonic erosion events since the Mesozoic. The location and migration history of the deposition center of different strata in the basin demonstrates that the deposition history of Hefei basin was jointly controlled by the Dabieshan orogenic belt and the adjacent TanLu fault zone. While Dabieshan orogenic belt played the dominant role in the Jurassic and Cenozoic, the largescale strikeslip movement of TanLu fault zone was the most important controlling factor in the Cretaceous.

The Algorithm and Application of Remaining Oil Distribution in Single Layer

YAN Ke, YANG Shaochun

2007, 13(1):  112-116. 

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A new approach for determining the remaining oil distribution in single layer was put forward in view of the various controlling factors, the discrete distribution and the difficulty in discrimination of remaining oil in nonmarine mature developed reservoir. Four controlling factors of remaining oil distribution, which include structure, heterogeneity, well pattern and water flood behavior of reservoir, were applied to build a fuzzy mathematic model. The degrees of attribution of all the controlling factors were calibrated by the production performance of single layer wells, the log interpretation of the new drilled wells and the remaining oil saturation monitoring wells. The comprehensive evaluation indexes of individual well points can be obtained to quantitatively characterize the distribution of remaining oil through the fuzzy calculation. The 11 layer, member 2 of the Shahejie Formation in segment 1 of Shengtuo oilfield was taken as an example. It belongs to fluvial reservoir and has been exploited for more than 40 years. The distribution model of comprehensive evaluation indexes was built up, which guilds the development and stimulation treatment satisfactorily.

Research Progress in the Petrogenesis of the Proterozoic Anorthosite Massifs

CHEN Wei1,2, ZHAO Taiping1

2007, 13(1):  117-126. 

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Anorthosite refers to igneous rocks consisting of over 90% plagioclase. Massiftype anorthosite is the most common type of anorthosite and with distinct characteristics. Most massiftype anorthosite bodies are Proterozoic ranging from 2.1 Gato 0.9 Ga in formation ages, representing an important tectonothermal event in the earth evolution. The anorthosite massifs are usually domeshaped or layered. Anorthosites often show cumulate texture composed of highAl pyroxene and plagioclase megacrysts containing exsolution lamellaes of plagioclase and Kfeldspar. The exsolution of the megacrysts indicates a polybaric crystallization process, which indicates the feature of deep generation and shallow emplacement. There exist different points of view in the petrogenesis of massiftype anorthosite. Many workers considered that the anorthosite massifs were generated from the upper mantlederived basaltic magma. Whereas, especially in recent decade,some geologists argued that they were formed from the lower crust. The composition of the parental magma of anorthosite is considered to be more like jotunite and ferrodiorite. Two models are very common to interpret the formation of anorthosite massifs: the underplating model and the crustal tongue melting model.Most massiftype anorthosite bodies are spatially and temporally associated with rapakivigranites, constituting an AMCG suite (anorthositemangeritecharnockitegranite), as a result of anorogenic magmatism in a continentalrift setting. However, some massifs might be formed at the late stage of orogeny, representing a postcollisional setting. Proterozoic massiftype anorthosite bodies are also hosts of Prich FeTi oxide deposits and a few of CuNi sulfide deposits. These deposits are considered to be formed by fractional crystallization, primary cumulates or immiscible oxide melts.

Application of Multivariate Statistic Analysis to Two Kinds of Ores in Jinchuan CopperNickel Sulfide Deposit

ZHAO Zhenhua,QIAN Handong,HUANG Sheng

2007, 13(1):  127-136. 

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The cluster analysis and factor analysis for the trace elements of different orebearing samples from Jinchuan coppernickel oredeposit were conducted. We classified the ore samples using the Qcluster analysis, and studied the classified samples with Rfactor analysis to discuss the key factors, which play important parts in the mineralization process. The results of factor analysis show distinct differences for different mineralization stages between the stockwork type ores and the spotted ores. Besides, it is also indicated that there exist late stage middlelow temperature hydrothermal alterations during the mineralization process of the stockwork type ores, which made the ores enrich Cu, Bi, Se, Te and some precious metal elements. The factor analysis not only provides new genetic evidence for pulsating mineralization mechanism, but also provides useful information about the valuable accompanying elements.