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	JOPC 2014 Vol.16 Number 5
	2014, Vol.16 Num.5
	Online: 2014-10-01

	LITHOFACIES PALAEOGEOGRAPHY AND SEDIMENTOLOGY PALAEOGEOGRAPHY AND MINERAL RESOURCES BIOPALAEOGEOGRAPHY AND PALAEOECOLOGY SPECIAL ISSUE ABOUT “CARBONATE SEDIMENT”

LITHOFACIES PALAEOGEOGRAPHY AND SEDIMENTOLOGY

	569	Jin Zhenkui, Gao Baishui, Li Guizai, Diao Liying, Yan Wei, Li Yan, Zhang Miao

		Problems and discussions about delta depositional models
		Deltas are an important type of sedimentary facies,and are also good reservoirs for oil and gas. A reliable depositional model of deltas is an essential guide for oil and gas exploration and development. However,few people have ever queried the classical delta model and relevant concepts in textbooks. But through our study,it is found that there exist many problems about the depositional model and relevant concepts. For example,definitions of delta plain,delta front and prodelta are vague,while the boundaries between them are not well defined and hard to determine. The boundary between delta plain and delta front is sea(or lake)level,but the level fluctuates frequently due to tide(or alternating raining and drying seasons),so which level should be the boundary？Similarly,the boundaries between delta plain and fluvial plain,delta front and prodelta,as well as prodelta and normal sea(lake)are also inexplicit. Their characteristics and distinctions have not been systematically summarized. Thus different researchers may give different interpretations as to sedimentary environments for the same strata. There are various types of deltas,and each type should have its own depositional model. However,many researchers have tried to apply the meandering delta model to all deltas. In the classical model,delta front develops subaqueous distributary channels and subaqueous levees,but this is proved to be wrong by the authors work in this paper. On delta plain, some new types of sandbodies,branch-mouth bars and branch-coalesce bars are found,but they are not mentioned in the classical delta model. In this paper,the problems within delta models are discussed in depth,and especially the distinction characteristics for subfacies and microfacies of deltas are summarized on the basis of modern deltas study.
		2014 Vol. 16 (5): 569-580 [Abstract] ( 1157 ) [HTML 0KB] [PDF 1788KB] ( 604 )

	581	Shang Xiaofei, Hou Jiagen, Liu Yuming, Li Yongqiang, Ma Ke, Yang Yichen

		Genetic mechanism and distribution patterns of inter(inner)-layers in lacustrine beach-bar sand bodies in Banqiao area, Huanghua Depression
		The Member 2 of Paleogene Shahejie Formation in Banqiao area of Huanghua Depression developed typical lacustrine beach-bar deposits with three kinds of inter(inner)-layer in sand bodies,i.e., muddy,calcareous and compact silty inter(inner)-layer. The beach-bar sand bodies can be divided into three architecture elements using the reservoir architecture analytical method:Compound bar,single bar,and the inner accretion of single bar. The inter(inner)-layers in the beach-bar reservoir can be subdivided into two hierarchies:Inter-layer between single bars and inner-layer in single bar. There are three genetic mechanisms of inter-layer between single bars:①Fine-grained sediments developed in a region superimposed by two-phase single bars sand bodies caused by base-level change;②Retention mud-gravels drawn by storm activities;③Mud deposit in a low wave energy behind bars. The fine-grained inner-layers in single bar are formed by the attenuation of wave energy,and mainly consists of silty mudstone and argillaceous siltstone. Further research is to dissect architecture inner single bar through well-log facies recognition and modern beach-bar prototype geological models in Qinghai Lake and Daihai Lake. It is found that the muddy inner-layers in single bar with thickness about 0.1～1m are nearly horizontal close lakeshore and inclines in low angle towards the center of the lake,with 2°～5° dip angle. Each hierarchy and genetic inter(inner)-layer is found in a certain region in a single bar sand body. The relative position and distribution pattern of each inter(inner)-layer can not only reflects the order of deposition in a single bar,but also be used to predict the scale and morphology of beach-bar. The inter(inner)-layers can lead to the diversity of oil-bearing properties, therefore it is important to reveal the distribution of inter(inner)-layers in beach-bar reservoirs, which is the key to raise oil and gas recovery ratio.
		2014 Vol. 16 (5): 581-596 [Abstract] ( 1248 ) [HTML 0KB] [PDF 5237KB] ( 592 )

	597	He Tingting, Li Shengli, Gao Xingjun, Song Cen, Zhou Xinmao, He Dongxu

		Types and superposed patterns of distributary channels in a shallow lacustrine delta plain
		Shallow lacustrine deltas are well-developed in many continental basins in China. Distributary channel is the main type of the sand body in a delta plain. Most of distributary channels are characterized by frequent diversion,multistage cross and superposition,which usually formed superposed distribution pattern of complex reservoirs. Based on the well-logging of distributary channel sand bodies of the shallow delta plain in Songliao Basin,this paper summarizes channel types and superposed patterns of the distributary channels in the shallow delta plain.Further,the constraint effect of these patterns on the correlation of sand bodies is analyzed. Study shows that channel types of the distributary channels can be classified into three foundational types,including an atypical braided channel type,an atypical meandering channel type and a transitional type. Small scale,shallow cutting and fast branching are the common features of these three channel types. In addition,there are five foundational superposed patterns of the distributary channels. And there are two foundational mud interbed distributions in distributary channels based on channel types and superposed patterns of the distributary channels,such as parallel distributed mud interbeds and low-angle lateral-accretion mud interbeds. Finally,in terms of channel types and superposed patterns,the changed position of certain channel types and the connection of sand bodies between boreholes can be determined,then constraint the reservoir correlation and connection analysis of the sand bodies.
		2014 Vol. 16 (5): 597-604 [Abstract] ( 1192 ) [HTML 0KB] [PDF 2513KB] ( 618 )

	605	Yi Xuefei, Zhang Changmin, Li Shaohua, Du Jiayuan,Li Kang, Wang Haoyu, Li Xiangyang, Zhou Fengjuan

		Simulation experiment of sand injectites
		More and more sand injectites have been identified from outcrops,seismic data,core observation and logging curves in the last decade. They exert great influence upon exploration and development of oil and gas, both positively and negatively. But because of their complex formation process and distribution,fewer studies has been focused on soft sediments deformations formation mechanisms. A set of laboratory simulation device is set up and a whole experimental procedure is designed to discuss their genetic mechanisms. On this basis,5 experiments considered the influence of two main variables on the structures formed during fluidization, i.e., the thickness of the overlying coarse sediment layer and the configuration of inlet pipes, are carried out. Each experiment result is freezed,sliced and been taken photos to reconstruct a 3D model. It is hoped to provide an experimental basis for the formation mechanism analysis on sand injectites.
		2014 Vol. 16 (5): 605-612 [Abstract] ( 994 ) [HTML 0KB] [PDF 1607KB] ( 727 )

PALAEOGEOGRAPHY AND MINERAL RESOURCES

	613	Shao Longyi, Li Yingjiao, Jin Fengxian, Gao Caixia,Zhang Chao, Liang Wanlin, Li Guangming, Chen Zhongshu, Peng Zhengqi, Cheng Aiguo

		Sequence stratigraphy and lithofacies palaeogeography of the Late Triassic coal measures in South China
		The depositional characteristics and environments,and the sequence stratigraphy of the Late Triassic coal measures in South China were studied based on data from outcrops and borehole sections. The third-order sequence-based lithofacies palaeogeography of the coal measures was reconstructed,and the coal accumulation pattern of the Late Triassic in the South China was summerized. Two major facies types,i.e., continental and transitional,were identified within the coal measures based on characteristics of lithofacies and lithofacies associations. The continental facies types include alluvial fan,braided fluvial and meandering fluvial facies,and the transitional facies types include deltaic,lacustrine(mainly shallow lake),tidal-lagoon,coastal plain and neritic facies. The continental facies were mainly distributed in the Upper Yangtze Block,typically in the Sichuan Basin,whereas the transitional facies mainly distributed in the eastern South China,typically in the Hunan-Jiangxi-Guangdong littoral and shallow marine area. Sequence boundaries,including regional unconformities and tectonic stress switching surfaces,fluvial incision surfaces,and abrupt change surfaces of lithology were identified. According to these sequence boundaries,the Late Triassic coal measures were subdivided into five third-order sequences. The lithofacies palaeogeography map of each third-order sequence was reconstructed based on the distribution of facies. The favorable coal accumulating palaeogeographic units were recognized based on the coal thickness and lithofacies palaeogeography maps,and the most favorable coal accumulating palaeogeographic unit was the delta plain unit,followed by fluvial unit,and tidal flat-lagoon unit. It was predicted that the coal-accumulating centers were located in the Leshan-Weiyuan Coalfield and the Huayingshan Coalfield in the Sichuan Basin,and the southeastern Hunan and western Central Jiangxi in the Hunan-Jiangxi-Guangdong littoral and shallow marine area.
		2014 Vol. 16 (5): 613-630 [Abstract] ( 1195 ) [HTML 0KB] [PDF 5578KB] ( 483 )

	631	Guo Biao, Shao Longyi, Zhang Qiang, Ma Shimin, Wang Dongdong, Zhou Qianyu

		Sequence stratigraphy and coal accumulation pattern of the Early Cretaceous coal measures in Hailar Basin, Inner Mongolia
		Sequence stratigraphy and coal accumulation pattern of the Early Cretaceous coal measures in Hailar Basin have been studied using outcrop and borehole data in this paper. Based on the regional unconformity surface,the erosional base of incise valley filled by sandstone and conglomerates, the vertical facies reversal surface and paleontological discontinuous surface,6 third-order sequences were divided in Hailar Basin. Tongbomiao Formation was developed at the initial subsiding stage. Nantun Formation was developed during the rapid subsiding stage. Damoguaihe Formation was formed in the strong extension stage and Yimin Formation was developed during the basin shrinkage stage. The distribution of the Early Cretaceous coal measures showed best in the eastern and northern, middle part come secondly, and southwest worst. Coal accumulated in the Yimin Formation and the second member of Nantun Formation,where the tectonic subsidence was showing the characters of intermittence,concussion and multi-cyclicity,providing the balance between the increasing rate of accommodation space and the peat accumulating rate favored the accumulation of the regional thick coal seams.
		2014 Vol. 16 (5): 631-640 [Abstract] ( 1253 ) [HTML 0KB] [PDF 1397KB] ( 575 )

	641	Chen Chao, Mou Chuanlong, Liang Wei, Xu Penghui

		Lithofacies palaeogeography of the early Katian and lateKatian of Late Ordovician in southern Sichuan-northern Guizhou Provinces
		The turn from the early to the late Katian of the Late Ordovician is considered to be a key point during the history of sedimentary evolution and basin-mountain conversion. At that period,almost all of the carbonate sediments changed into clastic sediments in southern Sichuan-northern Guizhou Provinces. Therefore, the research on sedimentary characteristics and lithofacies palaeogeographic transition has an important significance on recognizing sedimentary evolution and basin-mountain conversion. In order to reveal the change of lithofacies palaeogeography at this turning point,two lithofacies palaeogeography maps of the topof Jiancaogou Formation of the early Katian and the bottom of Wufeng Formation of the late Katian are mapped with the method of sequence lithofacies palaeogeography. The early Katian is divided into seven palaeogeographic units, i.e., pelaeouplift,exposed zone, denuded zone, tidal flat,restricted platform,open platform and shoal;and the late Katian is divided into pelaeouplift,tidal flat,shallow shelf,deep-water shelf and shoal. By the means of sequence lithofacies palaeogeography,the exposed zone and its distribution range is restored for the first time and the evolution process of lithofacies palaeogeography at the turn of the early-late Katian is revealed more clearly.
		2014 Vol. 16 (5): 641-654 [Abstract] ( 1381 ) [HTML 0KB] [PDF 15489KB] ( 1419 )

	655	Wang Qiyu, Mou Chuanlong, Chen Xiaowei, Kang Jianwei

		Palaeogeographic characteristics and basic geologicalconditions of petroleum of the Carboniferous in Junggar Basin and its adjacent areas
		It has the double basement of the Precambrian metamorphic crystallization basement and fold basement in Junggar Basin and its adjacent areas. The Carboniferous was the first full strata and developed well in the study area. Under the instruction that the tectonic controls a basins development, while the latter controls facies, the sedimentary facies and lithofacies palaeogeographic characteristics in the study area was analyzed as follows: during the Early Carboniferous, the sedimentary basins, with active or passive continental marginal marine facies or land-ocean transitional facies,were formed; while in Late Carboniferous, the sedimentary basins of land-ocean transitional facies and the continental volcanic build-ups were developed. Generally, the Carboniferous was divided into three zones of marine, land-ocean transitional, and continental facies; detailedly, 8 types of facies were identified, i.e., continental, marine volcanic and pyroclastic, bathyal-abyssal, neritic, littoral, deltaic, fluvial- lacustrine, and the alluvial-fan facies. Based on the idea that “the sedimentary facies controls the basic geological conditions of petroleum”, the petroleum distribution in Junggar Basin is concluded as: (1) For the Karamay-Baijiantan areas in the northwestern margin, and the Bayingou and Urumqi in the southern margin, it develops bathyal-abyssal dark muddy shales, which are supposed to be relatively good source rocks; (2)The delta facies which are favorable developed in the southeast-northern margin of Junggar Basin, such as the areas of Karamay are the advantageous zone of oil and gas exploration, and the source rocks and reservoir rocks were developed well. (3) The tidal-flat facies and lagoon facies which are favorably developed in the Santanghu area, as well as the neritic carbonate- clastic shelf facies which are favorably developed in the Burerjin-Fuyun and Bogeda mountain areas can form a relatively good assemblage of source-reservoir-cap. These sedimentary facies and zones where source, reservoir and cap rocks distributed trinity are the optimum targets and the top choice areas.
		2014 Vol. 16 (5): 655-672 [Abstract] ( 1462 ) [HTML 0KB] [PDF 5742KB] ( 780 )

	673	Wu Dong, Zhu Xiaomin, Zhang Houhe, Zhu Mao, Zhao Dongna, Geng Mingyang, Li Wei, Liao Zongbao

		Deposition characteristics and hydrocarbon distribution in medium and large basins of Nansha,South China Sea ^Hot!
		Nansha area is rich in oil and gas resources. Major medium and large basins were formed in the Cenozoic and deposited continental-transitional-marine facies from the bottom to the top. Different factors controlled the distribution of sedimentary facies in these basins. Clastic deposition was controlled by three palaeo-river systems. One from the orogen in the southern margin of South China Continent controlled fan deltas in Nanweixi Basin and Beikang Basin. Another one on Sunda Shelf controlled deltas in Mekong Basin and Wan′an Basin. The last one from Borneo Block controlled fan deltas and deltas in Zengmu Basin and Wenlai-Shaba Basin. And carbonate deposition is controlled by water and structural conditions. Warm,clean,moderately shallow turbulent environment is conducive to formation and growth of carbonate platform and reef. Various sedimentary facies formed different types of oil and gas reservoirs. Miocene sandstone and carbonate reservoirs are the most important reservoirs and source rocks are distributed with regularity. Drifting blocks controlled hydrocarbon distribution in these basins in Nansha area,forming three sets of source-reservoir-caprock assemblages and three kinds of stratigraphic traps.
		2014 Vol. 16 (5): 673-686 [Abstract] ( 1536 ) [HTML 1KB] [PDF 2185KB] ( 474 )

BIOPALAEOGEOGRAPHY AND PALAEOECOLOGY

	687	Lu Wenchen, Ye Wei

		Characteristics of pollen assemblage and climate change in the Holocene at Borehole BHQ in Pingyao area, Zhejiang Province
		This research was based on a 14 m long core from the Borehole BHQ in Beihu Lake,Pingyao area of Zhejiang Province. With 4 dating data by AMS¹⁴C method,palynological analysis was performed on 49 samples. It showed that the palynological concentrations varied greatly in different samples,and there were a wide variety of plants,i.e., totally 103 pollen types were recorded. Based on characteristics of palynological assemblages and lithology,3 pollen zones and 9 pollen subzones were divided,and the environmental sequence of vegetation succession and climatic temperature change in the Early and Middle Holocene for the study area was reconstructed. In the interval of 19-8.9 m,corresponding to the Early Holocene,vegetation in the study area was mainly conifer-deciduous broad-leaved forest,including Quercus(deciduous),Pinus,Altingiaceae and Pterocarya as well as Quercus(evergreen), Ulmus,etc. There were low content of evergreen trees,indicating that after the “Younger Dryas Event”at the late period of Late Pleistocene,the study area entered into the Holocene,and climate quickly turned warm. In the interval of 8.9～6.7m,corresponding to the Megathermal,this was the best period of hydrothermal condition in all sections. At this period,evergreen and deciduous broad-leaved mixed forest were dominant,including Quercus(deciduous),Quercus(evergreen),Pinus,Altingiaceae,Pterocarya and Ulmus. And the species and quantity of evergreen trees were far more than that of the former period,indicating warm and humid climate. During the 6.7～4.775m sedimentary period,corresponding to the Middle Holocene,there was an apparent fluctuation in palynological assemblages,and the vegetation in the study area mainly contained deciduous broad-leaved forest such as Quercus(deciduous),Altingiaceae,Pinus and Pterocarya. The number of Quercus(evergreen)dwindled rapidly. It showed that the vegetation type in the study area had evolved into deciduous and broad-leaved forests. It reflected that the area experienced a relatively-drastical climatic deterioration event. And the high concentration of Oryza pollen(≥35μm) during this period might indicate a certain scale of ancient human activity in the study area.
		2014 Vol. 16 (5): 687-702 [Abstract] ( 1175 ) [HTML 0KB] [PDF 1071KB] ( 609 )

	703	Song Huibo, Yu Huixin, Wang Hailin, Fan Daidu, Hu Bin, Wang Fang

		Biogenic traces in modern shoal deposits of Andong area, Hangzhou Bay
		Various trace-makers have been found in the shoal deposits of Andong area,Hangzhou Bay,including mole crickets(Gryllotalpa unispina),mud beetles(Coleptera),mud crabs(Ilyplax ningboensis),Cerithideopsilla cingalata, mud snails(Bullacta),mudskippers or amphibious fishes(Periophthalmua cantonensis),ants and birds. The most abundant traces can be ascribed to Fodinichnia,Domichnia,Repichnia and Pascichnia. Analysis shows that significant variations in type and diversity of traces and their makers are present over the different shoal zonations. (1)The highly-vegetated supratidal flat is featured by the abundance of bird tracks,and feeding and dwelling traces of mole crickets,mud beetles and ants,in which the feeding burrows of mole cricket are the most common. (2)In the upper intertidal flat where a lot of halophilic plants dominate on the muddy substrates,the biogenic traces include the J-,W-or Y-shaped burrows by mud crabs,the pinniform crawling traces by mudskippers,and the arc-shaped,donut-shaped grazing trails and C-shaped reproduction traces by mud snails (Cerithideopsilla cingalata).(3) In the silty substrate of the middle-lower intertidal zones,the biogenic traces are characterized by the irregular grazing trails of mud snails (Cerithideopsilla cingalata) on the bedding plane. It is also found that the distribution of biogenic traces is highly related to the grain sizes and water-saturation of the substrates. This study provides not only a neoichnological approach to tidal-flat sedimentary in the Hangzhou Bay,but also a meaningful modern analogue for sedimentary facies and paleo-environmental interpretations of ancient tidal flats.
		2014 Vol. 16 (5): 703-714 [Abstract] ( 1229 ) [HTML 0KB] [PDF 14339KB] ( 609 )

SPECIAL ISSUE ABOUT “CARBONATE SEDIMENT”

	715	Zhang Jie, Brian Jones, Pan Liyin,, Zhou Jin′gao, Qin Yujuan, Hao Yi, Wu Mingde

		Origin of botryoidal dolostone of the Sinian Dengying Formationin Sichuan Basin
		Sinian Dengying Formation (up to 1000m) in Sichuan Basin is composed of fine crystalline dolostones. In some parts of the formation(mainly in Members 2 and 4) distributed various shaped botyroidal masses of dolomite,up to 75cm long in maximum. They are either parallel to bedding or cutting across bedding. Those cross sections reveal that isopachous bands of various types of dolomite are developed as cements. Large amount of irregular shaped cavities are still present in the central parts of some larger bodies, which formed as a result of subterranean dissolution that was associated with karst development. The surrounding micritic dolostone was originally deposited from seawater protocrystallization, and the subsequent cements can be divided into four stages:(1)the dolomitized automicrite in some samples was the 1^st stage cement,which formed close to the surrounding micritic dolostone due to various physiochemical and possible biological influences;(2)the 2^nd stage fibrous dolomite had an absolute ordering crystal structure and nearly ideal crystal cell parameter,which may have originated from marine waters and adjusted to be ordered during the late diagenesis;(3)the 3^rd stage fine- to medium-crystal dolomite including residual of fibrous dolomite crystals dissolved in a near-surface meteoric environment after tectonic uplift;(4)the 4^th stage medium-coarse crystal dolomite primarily precipitated under a burial environment and partially filled the central parts of the cavities, with some unfilled cavities. It is apparent that the Dengying Formation was subject to multiple phases of diagenesis including karst development,precipitation of various cements,and multiple episodes of dolomitization. Except the paleokarstification,all of the other processes critically reduced the porosity of the petroleum reservoir that developed in the Dengying Formation. The paleokarstification which related to botryoidal dolostone has crucial importance to the Dengying Formation reservoir. The study of botryoidal dolostone in Sinian Dengying Formation conduces to understand the reservoir origin and evolution of the Dengying Formation dolostone,and guide the Precambrian petroleum development of Sichuan Basin
		2014 Vol. 16 (5): 715-725 [Abstract] ( 1369 ) [HTML 0KB] [PDF 7889KB] ( 652 )

	726	Dai Mingyue,Qi Yong′an,Chen Yao,Li Da

		Giant ooids and their genetic analysis from the Zhangxia Formationof Cambrian Series 3 in Mianchi area, western Henan Province
		Giant ooids are those large ooids with diameters greater than 2mm formed in marine environments. They are similar with the normal ooids in structure but have a different origin and limited distribution. Abundant giant ooids occur in the Zhangxia Formation of Cambrian Series 3 in Mianchi area,western Henan Province. Their cores consist of micritic pellets or radial ooids with diameters less than 2mm and are formed in weak-agitating environments. Their concentric layers are characterized by the alternations of the dark laminations of micritic calcites or Girvanella filaments and the light laminations of microspar calcites. Giant ooids are formed by the growth of Girvanella filaments,microbially-induced calcification and chemical precipitation of calcium carbonate in the oolitic inter beach banks environments with the alternation from low to medium energy conditions. Girvanella filaments distribute both in inner or outer concentric layers of the giant ooids, especially dense in the latter. It clearly shows that the microbes play an important role in the formation of giant ooids, and provides an important evidence for the study of origin of giant ooids.
		2014 Vol. 16 (5): 726-734 [Abstract] ( 1109 ) [HTML 0KB] [PDF 3488KB] ( 450 )

	735	Lu Yanlin, Li Shuangying, Zhao Daqian, Wang Bing, Ji Zaifei

		Quantitative analysis of carbonate platform sediments and sea-level changes of the Upper Carboniferous in Susong area, Anhui Province
		The Upper Carboniferous carbonate rocks,with 100meters thickness and abundant fossils,were well developed in Susong area of Anhui Province. These rocks belonged to the typical shallow carbonate platform deposits. The grains quantitative analysis showed that the lithofacies mainly included grainstones and packstones with the content of 81.2％ and 69.6％ respectively; and shallow marine bioclasts predominated. Moreover,there were wackstones and lime mudstones with the grains content of 26.4％ and 4.1％ respectively. The open-marine platform facies and tidal flat facies were mainly developed in study area,which could be divided into five types of subfacies including intra-platform shoal,intra-platform basin,intra-platform flat and inter-tidal flat and supra-tidal flat. Combining the above characteristics,three long-term transgressive-regressive cycles could be recognized from the Upper Carboniferous. The sea-level changes were characterized by the high frequency short-term sea-level fluctuations superimposing on a long-term sea-level fall. These three cycles were roughly corresponding to the long-term transgressive-regressive cycles in other areas of Yangtze Plate and the same-time strata in Euramerican Plate. It also indicated that the sea-level changes were influenced by alternation of the glacial period and non-glacial period in Gondwana.
		2014 Vol. 16 (5): 735-746 [Abstract] ( 1406 ) [HTML 0KB] [PDF 3076KB] ( 440 )

	747	Zhao Rui, Wu Yasheng, Qi Enguang, Jiang Hongxia

		Geochemistry and origin of dolomites of the Upper PermianChangxing Formation in northeastern Sichuan Basin
		The Changxing Formation reservoir in northeastern Sichuan Basin is mainly composed of fine to medium sized crystalline dolomites,and some mud sized crystalline dolomites secondly. Observation of thin sections under cathodoluminescence reveals that the fine-medium sized crystalline dolomites and mud sized crystalline dolomites look very dark. Micro-probe analysis reveals that the Mg,Ca,Fe,Mn,Sr,Na and Ba content is constant from the core of the fine-medium sized crystalline dolomite crystals to their margins,thus it is speculated that the fine-medium sized crystalline dolomites are transformed from previous mud sized crystalline dolomites by recrystallization in penecontemporaneous period. The main factor controlling the recrystallization is the infiltration high-Mg brine caused by evaporation which provides new ideas for determining the reservoir distribution of dolomites in the study area.
		2014 Vol. 16 (5): 747-760 [Abstract] ( 1473 ) [HTML 0KB] [PDF 7883KB] ( 498 )

	761	Zhang Yuying, Jiang Dayong, Fu Wanlu, Ji Cheng, Sun Zuoyu

		Microfacies characteristics of the Lower Triassic containing Chaohusaurus fauna in Chaohu area, Anhui Province and its palaeoenvironment
		The Early Triassic Chaohusaurus fauna was found at No.598-630 layers at the top of the Middle Member-the bottom of the Upper Member of the Nanlinghu Formation in Majiashan section of Chaohu area,Anhui Province. Based on the microfacies characteristics and the carbon and oxygen isotope analysis,the sedimentary environment of the fossil beds where the Chaohusaurus fauna had occurred was studied. 4microfacies types were recognized from the studied layers,which contained the red-grey thick nodular limestone with spicules-bivalves,the gray bioclastic-argillaceous micrite limestone,the gray laminated argillaceous micrite limestone,and the light gray micrite limestone,respectively. It was indicated that the sedimentary environment of the fossil beds was from the foot of the outer ramp-abyssal basin to the outer ramp. The values of the δ¹³C and δ¹⁸O are generally low in the whole of fossil beds. Combined with the above characteristics,it might be inferred that the Chaohusaurus fauna was living in the outer ramp zone with low-energy,less numbers and types of the biocoenose,and high seawater temperature.
		2014 Vol. 16 (5): 761-768 [Abstract] ( 1450 ) [HTML 0KB] [PDF 1193KB] ( 680 )

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