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	JOPC 2018 Vol.20 Number 4
	2018, Vol.20 Num.4
	Online: 2018-08-01

	MESO-NEOPROTEROZOIC SEDIMENTOLOGY AND STRATIGRAPHY LITHOFACIES PALAEOGEOGRAPHY AND SEDIMENTOLOGY GEOCHEMISTRY AND SEDIMENTARY ENVIRONMENTS QUATERNARY PALAEOGEOGRAPHY AND SEDIMENTOLOGY NEW TECHNIQUES AND NEW METHODS

MESO-NEOPROTEROZOIC SEDIMENTOLOGY AND STRATIGRAPHY

	523	Kuang Hong-Wei, Liu Yong-Qing, Fan Zheng-Xiu, Peng Nan, Geng Yuan-Sheng, Zhu Zhi-Cai, Xu Huan, An Wei, Wang Neng-Sheng, Xia Xiao-Xu, Wang Yu-Chong

		Sedimentary characteristics of the Mesoproterozoic Shennongjia Group in northern margin of Yangtze Craton
		The Shennongjia Group(ca. 1400-1000Ma)in the northern margin of the Yangtze Craton in northwestern area of Hubei Province consists of the Dayanping,Macaoyuan,Luanshigou,Dawokeng and Kuangshishan Formations in ascending order in its lower subgroup,the Taizi,Yemahe,Wenshuihe and Shicaohe Formations from the base to top in its middle subgroup and the Songziyuan and overlying Wagangxi Formations in its upper subgroup. Each subgroup was deposited as relatively deep water clastics and then as shallow water carbonates. According to a series of rock association,macroscopic and microscopic depositional fabric and structures,four types of sedimentary assemblages including peritidal algal carbonates,shallow marine clastics,platform margin shoal carbonates,and foreslope carbonates were recognized in the Shennongjia Group. They were deposited in a gentle dipping carbonate platform setting with a distally steepened slope. The peritidals are distributed most widely and are composed of peritidals carbonates,and different types of stromatolites were developed. They consitute a shallowing upward sequence with a strong progradation. Dry cracks and evaporates are common. They were deposited as shallow subtidal,tidal flat and supratidal facies. The shallow marine clastic sedimentary assemblage is mainly composed of sandstones,siltstones and mudstones and developed mainly in the Taizi and Dayanping Formations. Well-sorted and rounded quartz sandstones,common autochthonous glauconite in sandstones and autochthonous pyrites in mudstones,parallel bedding,horizontal and wavy bedding show that the Taizi Formation generally experienced a highly frequent sea level fluctuation. As a result,the sedimentary facies changed from coastal beach-platform margin shoal,to deep and shallow shelf sandy barrier-detrital tidal flat-restricted platform. The high energy shoal at the edge of the platform is mainly found in the Luanshigou and Yemahe Formations. It is characterized by oolitic dolomites,dolorudites(or intraclastic dolomite)and conical and columnar stromatolites. The Dawagou and Shicaohe Formations are characterized by oolitic and dolarenite-dolorudites and algal detritus(and lumps or phosphates). Large-medium scale cross bedding,grading bedding,and scour and erosion structures show an environment with strong hydrodynamic conditions in a shallow subtidal setting. The lenticular,thick,tremendous to coarse breccias and sandstones from collapse were developed in the Dayanping and Macaoyuan Formations. Sedimentary structures,such as cross bedding,ripple mark,scour and erosional structures,represent the foreslope and shallow water shelf environment. This study provides basic data and evidence for the sedimentary evolution and reconstruction,the depositional process of the basin and sequence correlation of the Late Mesoproterozoic in the Yangtze Craton for further studies of the sedimentary sequence,sedimentary characteristics and sedimentary evolution process of the Shennongjia Group.
		2018 Vol. 20 (4): 523-544 [Abstract] ( 796 ) [HTML 1KB] [PDF 28290KB] ( 484 )

	545	Fan Zheng-Xiu, Kuang Hong-Wei, Liu Yong-Qing, Peng Nan, Zhu Zhi-Cai, Wang Yu-Chong, Xia Xiao-Xu, Chen Xiao-Shuai, Zheng Hang-Hai

		Types of stromatolites of the Mesoproterozoic Shennongjia Group in northern margin of Yangtze Craton and their sedimentary significance
		Stromatolites of the Luanshigou Formation of Mesoproterozoic Shennongjia Group were developed very well in the northern margin of Yangtze Craton. Their types are abundant. The forms of the stromatolites include colonnella,domal,stratiform,conophyton,strati-columnar,cabbage-like stromatolites and stromatolite bioherm. They are mainly small-medium sized,with some of them large- or huge-sized. Most of them have no walls, and some of them have a single wall. Their symmetry and inheritance are mainly good. The study shows that the morphology and size of stromatolites are closely related to the corresponding hydrodynamic conditions,water depth and the content of terrestrial components. Stratiform stromatolites grew up primarily in the intertidal;columnar stromatolites were found in the intertidal and the subtidal environment. Domal stromatolites were formed in the intertidal zone and the subtidal zone. Conophyton stromatolites were often seen in the subtidal zone and the intertidal zone. Strati-columnar and cone-columnar stromatolites were developed dominantly in the intertidal zone. Stromatolites bioherm were located in the intertidal zone and the subtidal zone. The combinations of macro and micro characteristics of different types of stromatolites, the vertical supperpositions of different stromatolites, the relationship between their sedimentary structure and their corresponding facies, as well as the carbon and oxygen isotopes, all infer that the formation of stromatolites was mainly influenced by the content of microbacteria and sedimentary environment. Biological factors affected the microscopic constitution of stromatolites;hydrodynamic condition controlled the types of stromatolites,and the water depth affected their size. The environment with biological prosperity and less terrigenous materials was favorable for the development of stromatolites.
		2018 Vol. 20 (4): 545-561 [Abstract] ( 792 ) [HTML 1KB] [PDF 13338KB] ( 623 )

	563	Xia Xiao-Xu, Kuang Hong-Wei, Song Tian-Rui, Liu Yong-Qing, Peng Nan, Zhu Zhi-Cai, Xu Huan, An Wei, Wang Neng-Sheng, Fan Zheng-Xiu, Wang Yu-Chong

		Sedimentary characteristics of the Mesoproterozoic Taizi Formation of Shennongjia Group in northern margin of Yangtze Craton
		Sedimentary environments of the Mesoproterozoic Taizi Formation of Shennongjia Group in Shengnongjia area, northern margin of Yangtze Craton are all along in debate. In this study,we further constrain the sedimentary environments of the Taizi Formation based on the comprehensive field and laboratory experiments. The lower part of the Taizi Formation consists of gray green silty-fine dolostone. The middle part of the Taizi Formation is composed of gray green,grayish quartz medium-fine sandstones,siltstones and dark grey siltstones,silty mudstones,muddy siltstones rhythms,while its upper part comprises siltstone-mudstone rhythm. Massive beddings and parallel beddings occur in the quartz sandstone,while siltstones and mudstones contain the horizontal and lenticular beddings. The cumulative probability curve of sandstones shows a steep slope,which are made up mainly of jumping components with two or more groups and little suspended components without rolling components. The sedimentary structures and grain size characteristics suggest that the Taizi Formation was formed in the coastal and tidal flat depositional environments. Meanwhile,the vertical sedimentary sequences are represented by the grain size evolution of coarse-fine-coarse-fine,which is combined with that the sedimentary facies from the bottom to the top show littoral facies-carbonate ramp platform facies-lagoon facies-tidal flat lagoon facies succession,constitute a complete transgressive-regressive sedimentary sequence with patterns of progradation-retrogradation-progradation.
		2018 Vol. 20 (4): 563-578 [Abstract] ( 540 ) [HTML 1KB] [PDF 37591KB] ( 305 )

	579	Wang Yu-Chong, Kuang Hong-Wei, Peng Nan, Liu Yong-Qing, Fan Zheng-Xiu, Xia Xiao-Xu, Chen Xiao-Shuai, Zheng Hang-Hai, Sun Yu-Xiang

		Freezing and thawing structures: An evidence of cold climate in the Neoproterozoic Liantuo Formation in Shennongjia of northern margin of Yangtze Craton
		The palaeoclimates(i.e.,greenhouse or icehouse)in South China before the Sturtian period of the Neoproterozoic Cryogenian are still controversial. Recently,a series of soft sedimentary deformation structures(SSDSs)were recognized in the upper part of the Liantuo Formation of the Shennongjia in the northern margin of the Yangtze Craton. They are represented by gray-green sandy veins host in purple mudstone or sandstone matrix. Based on their marco-mirco morphology,texture and structure,and geochemistry characteristics,we interpret them to be a type of freezing and thawing structures developed under cold climates,or perhaps being suggestive of the existence of permafrost. According to their morphologies,the documented Liantuo SSDSs are categorized into four main types,namely reticulate,dendritic veins bearing rigidity fracture,along with banded,mottled veins bear plastic deformation. our results suggest that the characteristics of the veins were more matrix debris supported less clay minerals,weak particles directionality lining the wall,loss of Fe(Ⅲ),indicating that the veins had been liquefied. Moreover the veins are more depleted in trace element such as Bi,Pr,W,La than those in the matrix. However,different REE distribution patterns of veins and matrices also indicate that there is no effect on the alteration during the later diagenesis. The dual structures in debris rocks(i.e.,low Sr/Ba ratio of 0.05 to 0.25 versus low V/Ni ratio of 0.05 to 0.5)suggest that the structures were developed in microenvironments like floodplains of meandering rivers. The low CIA values of 55-65and negative carbon and oxygen isotope negative excursion(i.e.,δ¹³C_PDB of-17‰~-14‰,δ¹⁸O_PDB of-15‰~-13‰) in the veins and matrices,in contrast,indicate that they would probably have formed in cold climates. All of these observations suggest that the Shennongjia area in the northern margin of the Yangtze Craton was located in the cold periglacial environments before the start of Stuartian Period in the Neoproterozoic Cryogenian. Furthermore,the paper opens up a new research idea and approach for the recognition of the cold climatic conditions in late sedimentary period of the Liantuo Formation,particularly the response on the “Snowball Earth”event in Yangtze Craton. Meanwhile,it also provides a new scientific evidence and sedimentary index for the division of glacial period in Yangtze Craton and correlation at home and abroad.
		2018 Vol. 20 (4): 579-594 [Abstract] ( 691 ) [HTML 1KB] [PDF 36250KB] ( 331 )

	595	Peng Nan, Kuang Hong-Wei, Liu Yong-Qing, Geng Yuan-Sheng, Xia Xiao-Xu, Wang Yu-Chong, Chen Xiao-Shuai, Zheng Hang-Hai

		Recognition of geological age for acanthomorphic acritarchs from the Ruyang Group,southern margin of North China Craton and its implication for evolution of early eukaryotes
		The geological age of eukaryotes represented by large acanthomorphic acritarchs from the Ruyang Group,southern margin of North China Craton,has been controversial. New zircon SHRIMP U-Pb age of tuff(ca. 1639±13Ma)was obtained from the Luoyukou Formation of the Luoyu Group,Yangpo,Ruzhou,west Henan Province. This new age,combined with the ages from the Xiong'er and Ruyang Group,can well constraint the time of these eukaryotes with complex morphology from the Ruyang Group at 1.75-1.64Ga,which belongs to early Mesoproterozoic. Moreover,it shows that some eukaryotes with relatively higher degree of evolution,which were previously thought to be preserved in the Neoproterozoic,may have appeared in the Early Mesoproterozoic. We further suspect that there might be more primitive microfossils preserved in the older strata(>1.6Ga)in the southern margin of the North China Craton,which provides an important window to explore the ancestor of the eukaryote. Thus,caution should be taken when applying these Mesoproterozoic eukaryotes for stratigraphic correlation.
		2018 Vol. 20 (4): 595-608 [Abstract] ( 626 ) [HTML 1KB] [PDF 12325KB] ( 413 )

LITHOFACIES PALAEOGEOGRAPHY AND SEDIMENTOLOGY

	609	Su De-Chen, Qiao Xiu-Fu

		Thixotropic deformation features of cohesive sediments triggered by palaeoearthquakes
		Thixotropy in this article refers to the property exhibited by saturated sludges and clays when with particle sizes less than 0.005mm become liquid upon stir or shake during strong earthquakes. The soft-sediment flow deformation structures triggered by earthquakes include liquefied flow deformation and thixotropic flow deformation. The former refers to the liquefaction and flow deformation of sand layers(including fine carbonate sediments);the latter refers to the flow of saturated argillaceous sediments. Thixotropic structures such as mud,clay,siliceous mud,lime mud, etc. are widely distributed in the stratigraphic record,and they mostly form a composite deformation structure with the liquefied deformation structure of the sand layer. Usually the geologists pay more attention to the features of sand layers or misinterpret the thixotropic structures of argillaceous sediment as the liquefied flow structures of sand. Based on the distribution pattern of saturated argillaceous sediments in the stratum,this paper divides the thixotropic flow deformation into four categories: (1)upward,(2)downward,(3)simultaneous upward and downward, and (4) nearly horizontal flows. In this paper, characteristics of these thixotropic features and their forming processes were described and interpreted in combination with field phenomena. Finally,thixotropic flow deformation structures have been systematically summarized. We hope that the thixotropic features would draw attention from geologists engaged in researches on soft sedimentary deformation and palaeoearthquakes.
		2018 Vol. 20 (4): 609-622 [Abstract] ( 503 ) [HTML 1KB] [PDF 12897KB] ( 349 )

	623	Song Hui-Bo, Li Ya-Nan, Yu Zhen-Feng, Liu Shun-Xi, Hu Bin, Li Zi-Yuan

		Sedimentary succession and environment evolution of the Taiyuan Formation in northeastern Qinshui Basin, Shanxi Province
		The Upper Carboniferous-Lower Permian Taiyuan Formation in northeastern Qinshui Basin of Shanxi Province contains abundant coal and coalbed methane resources,and well outcrops in the area of Heituyan village in Xiyang County. Based on the researches of the outcrop section and some nearby exploration data,this paper detailedly analyzes the lithologic characteristics,sedimentary structures,fossil composition,carbonatite microfacies and sedimentary succession types of the formation and obtains the results as follows: Three kinds of sedimentary systems(including barrier shore,open shore and delta),five kinds of sedimentary facies,three kinds of sedimentary subfacies and five kinds of carbonate microfacies were recognized,and the mixed tidal flat deposits in the middle part of the Taiyuan Formation were found in this area. On this basis,nine types of sedimentary succession and their palaeoenvironment model were suggested. According to the vertical change tendency of sedimentary successions,this paper proposes the sedimentary environment model of the Taiyuan Formation and briefly discusses the evolution process of depositional environments,i.e.,from the bottom to top,ranging from barrier island-lagoon-tidal flat to shallow sea-tidal flat,and then to delta environments.
		2018 Vol. 20 (4): 623-636 [Abstract] ( 631 ) [HTML 1KB] [PDF 20383KB] ( 334 )

	637	Chen Xin-Yi, Huang Chi-Yue, Shao Lei

		Characteristics of heavy minerals in modern sediments of Minjiang and Jiulongjiang Rivers,Fujian Province and their provenance implication
		Analyses of this study revealed that the heavy mineral assemblages in the sediments along the Minjiang River and Jiulongjiang River and the rock types in their adjacent provenance areas are highly correlated. The heavy mineral assemblages in drainage areas of Minjiang and Jiulongjiang Rivers are characterized by opaque Fe oxide minerals,epidote,zircon,tourmaline,and hornblende,with epidote accounting for up to 70% among the primary transparent minerals. Except for the reason of high-grade metamorphism of these rocks,the high epidote content is also associated with the contact metamorphic zone between acid granite intrusion and surrounding rocks. According to the analysis of heavy mineral assemblages,provenance-sensitive index,and U-Pb dating of detrital zircon,heavy minerals in the drainage area of Minjiang River were interpreted to be derived from the Precambrian rocks in the Wuyishan Mountain in northwestern Fujian,Yanshannian magmatite and contact metamorphic rocks in eastern Fujian,and heavy minerals in the drainge area of Jiulongjiang River were derived from Indosinian-Yanshanian granite in southwestern Fujian. Sediments in the upper Minjiang River contain heavy minerals characteristic of high-grade metamorphic parent rocks. Heavy minerals in the sediments in the middle and lower Minjiang River are derived from magmatic rocks,contact metamorphic rocks,and from upper reaches of the river. The heavy minerals in Jiulongjiang River are mainly from Indosinian-Yanshanian granite in southwestern Fujian. This research shows that in rivers with small to medium drainage areas,due to the limited transport distance,the provenance information can be largely preserved in the heavy mineral assemblages. Analysis of heavy minerals can therefore yield crucial information for reconstructions of tectonic evolution and source-to-sink analysis.
		2018 Vol. 20 (4): 637-650 [Abstract] ( 960 ) [HTML 1KB] [PDF 2171KB] ( 322 )

GEOCHEMISTRY AND SEDIMENTARY ENVIRONMENTS

	651	Shang Mo-Han, Tang Dong-Jie, Shi Xiao-Ying, Wei Hao-Ming, Liu An-Qi

		I/(Ca+Mg)as an important redox proxy for carbonate sedimentary environments: Progress and problems
		The redox conditions of seawater play a pivotal role in influencing the origin and early evolution of eukaryotes. However,previous studies regarding ocean redox conditions mainly focus on fine-grained siliciclastic rocks(e.g.,black shale)deposited in relatively deep seawater,rather than carbonates formed in eukaryote-concentrated shallow seawater,due largely to a lack of valid method,significantly limiting our understanding of the mechanisms concerning the origin and early evolution of eukaryotes. In recent years,I/(Ca+Mg)was proposed as a proxy for redox conditions of seawater,and has been widely employed in carbonates to analysis seawater redox conditions. The proposal of this proxy is mainly based on measurements of iodine speciation in modern oceans and experiments of calcite synthesis in laboratory. The measurements demonstrate that marine iodine composition mainly occur in two states, namely, Oxidized-state iodate(IO₃^-)and reduced-state iodide(I^-). With the decrease of oxygen concentration(such as in an oxygen minimum zone,OMZ),the oxidized-state iodate,which is proportional to the oxygen concentration,would be gradually reduced into reduced-state iodide. The experiments confirm that only IO₃^- could be incorporated into the lattices of carbonate minerals with a fixed distribution coefficient,but I^-would be excluded. Because of the high redox potential of IO₃^-/I^-,which is close to that of O₂/H₂O,I/(Ca+Mg) is one of the proxies earliest responding to the decrease of ocean oxygen concentration. I/(Ca+Mg) is therefore sensitive to the variation of oxygen concentrations in weakly oxidized surface seawaters in deep time(e.g.,Precambrian). Furthermore,some scholars attempted to establish semiquantitative relationships of I/(Ca+Mg)values to oxygen concentrations,and two threshold values of I/(Ca+Mg)>0 and 2.5μmol/mol have been proposed as the semiquantitative constraints for the oxygen concentrations in ancient ocean waters. In addition,in the light of the study of iodine speciation and dissolved oxygen concentrations in modern anoxic basins and water columns within OMZs,our results suggest that I/(Ca+Mg)=1.5μmol/mol could be used as the threshold between atmosphere and surface seawater. This threshold value may be used to reflect that the oxygen concentration of surface ocean is up to 10 μM,which is the maximum oxygen concentration increased by the primary productivity,and therefore to distinguish the potential variations of oxygen concentration between atmosphere and surface seawaters. In this paper,some of the recent progress and potential problems in redox analysis using I/(Ca+Mg)in ancient carbonates were briefly reviewed,and some tentative suggestions for future study were also put forward.
		2018 Vol. 20 (4): 651-664 [Abstract] ( 584 ) [HTML 1KB] [PDF 1230KB] ( 348 )

QUATERNARY PALAEOGEOGRAPHY AND SEDIMENTOLOGY

	665	Lu Qing-Wei, Wang Qiang, Zhan Jian, Guo Wei, Li Wen, Wang Xi-Yu

		Middle Pleistocene stratigraphic hiatus on the Cangxian Uplift,the west coast of Bohai Bay
		This study examined core materials of the Borehole CGZ5 with 400m depth in Jinghai County and Borehole TPZ1 with 500m depth in Dagang district of southern Tianjin plain on the west coastal plain of Bohai Bay. Based on analyses of lithology,magnetostratigraphy,¹⁴C dating,micropaleontology,the present paper determined that the bottom of the two boreholes arrived at the upper parts of the Gauss and Gilbert polarity zones dated 3.6Ma and 4.5Ma,respectively. The palaeomagnetotizm boundary of Matuyama/Gauss(M/G)polarity zone dated 2.58Ma occurred at 225m and 208m in the Borehole CGZ5 on the western Cangxian Uplift and in the Borehole TPZ1 on the west slope of the eastern Huanghua Depression,respectively. In the two boreholes mentioned above,the boundary of Brunhes/Matuyama(B/M)polarity zone representing 0.78Ma occurred at 55m and 68.6m,respectively. Combining with analyses of microfossils and determination of three transgression beds,as well as lithological characteristics,the bottom of the Upper Pleistocene series was estimated to be located at depths of 55m and 63.4m in the two studied boreholes. Based on the low waterlevel redoxing clay horizon of LGM(Last Glacial Maximum),the thickness of Holocene series was determined to be 14.8m and 16.5m,respectively. The boundaries of B/M and M/G of the CQJ4 borehole,located between the two boreholes(CGZ5/TPZ1)and at the main Banqiao sag of Huanghua Depression,occurred at 74m and 340m,respectively. The absence of the entire Middle Pleistocene series was observed in the western Borehole CGZ5,whereas the thickness at the eastern Borehole TPZ1 is only 5.3m. It was speculated that this stratal hiatus was caused by the fastly fault-controlled deposition in the preliminary stage of Middle Pleistocene in the Bohai Sea basin. Under the setting of large elevation difference,the significantly high amount of sediments supplied by the rivers flowing into the sea resulted in sediment bypass on the marginal Cangxian Uplift and adjacent coastal plains. For the great east plain of China formed during the palaeogeographic changes of the “Source to Sink”system,the dynamic sedimentary setting during the Middle Pleistocene epoch needs to be further studied.
		2018 Vol. 20 (4): 665-679 [Abstract] ( 635 ) [HTML 1KB] [PDF 33751KB] ( 386 )

	680	Liu Qian, Li Gang, Wang Yu-Xin, Li Wen-Long

		Spatial-temporal evolution, social influence and response of locust plague in Anhui Province during Ming and Qing Dynasties
		Locust plague,flood and drought were the three biggest natural disasters in Chinese history and they had a profound impact on agriculture and social development. Based on the historical records of Locust plague in Anhui Province,this study reconstructed the Locust plague frequency sequence on 10a scale and counties sequence on 1a scale. Locust index spatial distribution of locust outbreak was drawn in Anhui to explore the dynamic changes in temporal and spatial scales. Human social influences and responses affected by the locust plague were explored,involving famine,epidemic disaster and rice price data in Anhui. The results illustrated that 181 locust years occurred in Anhui during this period with an average of 3.2 locust years every 10a,and 653 counties suffered locust plagues during the period with an average of 3.6 counties every 1a. Counties sequence revealed five profound locust outbreak periods related to serious drought events. The locust index north of the Yangtze River was higher than the one in the southern mountainous area,which had spatial differences resulting from terrain,flood/drought and human activities. Locusts would have complicated effects on society. For example,as the primary reason causing famine,the locust plague led to epidemic disaster indirectly,and large-scale locust plague resulted in rice price rising within a short period of time,even social instability. The way and ability that governments handled with the locust plague would affect the survival of people directly,and maintain social stability. Based on comprehensive views,the locust plague had multiple impacts on ancient societies involving agricultural,economic,human and technological subsystems.
		2018 Vol. 20 (4): 680-690 [Abstract] ( 725 ) [HTML 1KB] [PDF 4666KB] ( 285 )

NEW TECHNIQUES AND NEW METHODS

	691	Niu Yong-Bin, Cui Sheng-Li, Hu Ya-Zhou, Zhong Jian-Hua, Pan Jie-Nan

		Three-dimensional reconstruction and their significance of bioturbation-type reservoirs of the Ordovician in Tahe Oilfield
		This paper studied the bioturbation-type reservoirs well-developed in the Ordovician Yingshan and Yijianfang Formations of the Tahe Oilfield based on core observation,cathodoluminescence microscopy,three-dimensional X-ray microscope,and X-ray diffractometer. Two kinds of trace fossils (i.e.,Thalassinoides and Helminthopsis) were identified;the former is most prevalent with the bioturbated volume up to 90%. The burrow infillings are composed mainly of dolomite,accounting for more than 90%. The host rock is micrite. Along with the change of depositional environment during the Early-Middle Ordovician transgression and regression in Tahe Oilfield,burrows also show obvious periodicity. Three-dimensional geological model of the bioturbation-type reservoir in the study area was established using the three-dimensional reconstruction software package by 3ds Max software. This study visualizes the internal structures and microscopic features of the bioturbation reservoir in Tahe Oilfield and provides a solid academic basis for subsequently investigating macro-heterogeneity and micro-anisotropy,quantitatively characterizing the percolation characteristics on the microscopic scale of those bioturbation reservoirs. In addition,it also provides a new idea to improve and perfect the model of Ordovician reservoir of Tahe Oilfield.
		2018 Vol. 20 (4): 691-702 [Abstract] ( 593 ) [HTML 1KB] [PDF 24609KB] ( 258 )

	703	Chen Hao, Huang Ji-Xin, Chang Guang-Fa, Wu Jun-Chang, Sun Tian-Jian

		Ichnology identification and sedimentary enviorment analysis based on CT scanning: A case study from Mackay Ⅲ oil sands,Canada
		Ichnology provides a basis for identification and analysis of depositional environment. Taking the Lower Cretaceous McMurray Formation,Mackay Ⅲ oil sands,Canada as an example,the sedimentary environments of the reservoir were studied with respect to trace fossils' species,size,associations,and facies indicators by high-resolution core photos and CT data. Results indicate that there are 12 species of ten genera in the Middle and Upper McMurray Formation,including Asterosoma isp.,Chondrites isp.,Diplocraterion isp.,Ophiomorpha nodosa,Palaeophycus tubularis,Planolites beverleyensis,Planolites isp.,Rosselia isp.,Skolithos verticalis,Skolithos isp.,Teichichnus isp.,and Thalassinoides isp.. According to the features of these fossils and surrounding lithology,three combinations, including Ophiomorpha-Skolithos,Asterosoma-Chondrites-Rosselia and Teichichnus-Rosselia-Thalassinoides, are established,representing intertidal,subtidal and shallow-marine environments respectively. Sand bodies in reservoir were deposited in the intertidal setting,being the main accumulation of hydrocarbon. This study not only reflects the superiority of CT data,but also provides a reference for recognizing the tidal flat environments.
		2018 Vol. 20 (4): 703-712 [Abstract] ( 720 ) [HTML 1KB] [PDF 3137KB] ( 309 )

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