Welcome to Journal of Palaeogeography

	· 《Petroleum Science》
	· Periodical Press of CUP
	· China University of Petroleum (Beijing)
	· 《Journal of China University of Petroleum(Edition of Natural Science)》
	· 《ACTA PETROLOGICA SINICA》
	· 《Geology in China》
	· 《China Geology》
	· 《ACTA GEOCHIMICA》
	· 《geochimica》
	· 《GEOTECTONICA ET METALLOGENIA》
	· China Geoscience Journal Portal
	· 《Bulletin of Mineralogy, Petrology and Geochemistry》

	JOPC 2022 Vol.24 Number 2
	2022, Vol.24 Num.2
	Online: 2022-04-01

	REVIEW SPECIAL THEME OF CARBONATE ROCK LITHOFACIES PALAEOGEOGRAPHY AND SEDIMENTOLOGY PALAEOGEOGRAPHY AND MINERAL RESOURCES QUATERNARY PALAEOGEOGRAPHY AND SEDIMENTOLOGY

REVIEW

	190	Feng Zeng-Zhao

		Some new thoughts on definitions of terms of sedimentary facies: based on Miall's paper(1985)
		In recent years,the Journal of Palaeogeography(Chinese Edition and English Edition) continually received some manuscripts. The authors of these manuscripts,according to the viewpoint and method of Miall's paper(1985),selected rocks from each bed in the clastic sections of their study areas and induced some rock types,such as conglomerates,sandstones and fine-grained stones,and considered them as lithofacies. It does not conform to the definition of lithofacies. I wrote some papers,i.e.,Feng(2018,2019,2020),to point out the problems and hope that the authors worldwide,especially Chinese authors,will not continually cite,spread and follow of viewpoint and method of Miall's paper(1985) blindly. Prof. Miall is the first person who considered rocks(in fact,the sediments)as lithofacies and proposed a facies analysis method. His viewpoint and facies analysis method confused the definition of facies and facies analysis method. My current paper is a special article to discuss the principal problems of Miall's paper(1985),i.e.,he considered the sediments as lithofacies and utilized lithofacies to analyze facies,but not to discuss the contributions and less strictness of architectural elements of his paper.Here,I have to declare that the facies in my current paper is the facies of sedimentary petrology,but not of other geological disciplines,such as igneous petrology,metamorphic petrology,palaeontology,stratigraphy,geophysics,geochemistry.Certainly,the definitions of facies and lithofacies are controversial. I will adhere to the policy of “A hundred flowers blossom and a hundred schools of thought contend” and hope that through academic discussions,contends and geological practice,these problems will be solved gradually.
		2022 Vol. 24 (2): 190-190 [Abstract] ( 530 ) [HTML 1KB] [PDF 461KB] ( 504 )

	191	Qiu Long-Wei, Li Xin, Yang Yong-Qiang, Dong Dao-Tao, Fu Jian, Wen Xu, Danish Khan

		Research progresses of the genetic mechanism and architecture characterization on lake bars
		Due to the repeated washing of waves and longshore currents,the bar reservoir has a high maturity,showing great oil and gas exploration potential,and has become the focus of subtle oil and gas reservoir exploration. Based on literature review,we summarize the recent research progresses of bar definitions,sedimentary characteristics,main controlling factors,genetic mechanisms and internal architectures,and propose a new understanding of bar evolution stage and sedimentary architecture. The results show that the bar evolution mainly includes weak wave action stage,turbulent current swash-backwash stage,aeolian stage and swampiness stage. Many factors affect the bar development,in which provenance is the clasts supplier and wind field is the energy engine. Hydrodynamic force induced by the wind strongly affects the development of bar reservoirs. Tectonic movement and sequence evolution control the distribution position and preservation of the bar. The above-mentioned factors work together to determine the morphology,scale,and preservation of the bar. According to the architectural theories,bar architecture is divided into six levels. In this architecture classification,we define composite sand body as level 5,single sand body as level 4 and accretive body as level 3,which are in reservoir scale. We explore the qualitative and quantitative characterization of the bar architecture level 3 to level 5 to provide theoretical support for beach-bar reservoir exploration and development.
		2022 Vol. 24 (2): 191-209 [Abstract] ( 473 ) [HTML 1KB] [PDF 7272KB] ( 384 )

	210	Guo Pei, Li Chang-Zhi

		Genesis of evaporites in petroliferous basins and the sedimentary and climatic significances
		China is rich in saline lakes. Many previous studies were focused on analyzing the water chemistry of saline lakes,salt origins,the development of salt mine resources,but rarely paid attention on sedimentary characteristics and diagenetic processes of evaporites,making it difficult to understand the accumulation processes of hydrocarbon in ancient saline lacustrine basins. In this paper,the classification of saline lakes and the main genetic types of saline minerals in the evaporites are reviewed based on the extensive literature review on a large number of saline lakes. The sedimentary and diagenetic processes of common minerals including sulphates,chlorides,sodium carbonates and borates in lacustrine petroliferous basins and their significance for paleo-climate and paleo-environment were concluded. Meanwhile,the controversial and noteworthy issues in the studies of evaporites in petroliferous basins were discussed based on the latest research findings in saline lakes sedimentology: (1)The hydrothermal fluids can transport large amounts of elements into lakes,but the semi-arid and arid climate and the evaporation and concentration are the pre-conditions for accumulating the massive evaporates in the lakes. (2)The soluble evaporates(e.g.,halite)more easily concentrate in the sedimentary center characterized as a thick single layer,while they are missing in the slope and margins of the lakes,which is controlled by “halite aggregation effect at the center”caused by seasonal temperature and thermocline fluctuation. (3)Temperature affects the solubility,crystal structural morphology and formation depth of salt minerals in evaporites. Some anhydrous salt minerals cannot crystalize under normal temperature and pressure conditions,which are good indicators of paleo-temperature and burial history. (4)The sodium-bearing carbonates are closely related to pCO₂ and paleo-temperature of saline lakes of carbonate subtype.
		2022 Vol. 24 (2): 210-225 [Abstract] ( 493 ) [HTML 1KB] [PDF 15507KB] ( 340 )

SPECIAL THEME OF CARBONATE ROCK

	226	Deng Wei, Tan Xiu-Cheng, Zhang Dao-Feng, Zhong Shou-Kang, Dong Guo-Dong, Xiao Di, Lu Zi-Xing, Yang Meng-Ying, Xiong Ying, Nie Wan-Cai

		Occurrence types and genesis of anhydrite from the Ma5₆ submember of Ordovician Majiagou Formation in central and eastern Ordos Basin
		There are diverse anhydrite in Ma5₆ submember of Ordovician Majiagou Formation in central and eastern Ordos Basin. Based on systematic macroscopic and microscopic petrography analysis,different types of anhydrite were identified and distinguished,such as scattered(A1),laminar(A2),dense massive(A3),nodular or clumpy(A4),squiggly or brecciated(A5).The analysis of high frequency cycles and microfacies of a single well showed that five kinds of high-frequency,shallowing-upward sequences were developed in the Ma5₆ submember,which are respectively related to tidal flat,lagoon,oolitic shoal,Fragmental shoal and microbial mound. It was found that the occurrence type,production position and distribution form of the anhydrite had a good coupling relationship with the shallower sequences.Type A1 and A2 anhydrite occur in the lower and middle part of the high-frequency,shallowing-upward sequence,which is mainly related to the dolomite lagoon or gypsum lagoon,and belongs to the primary chemical sedimentary origin of the lagoon facies. The A3 type anhydrite is distributed in the upper part of the high-frequency,shallowing-upward sequence,which is controlled by the gypsum lagoon,and also belongs to primary chemical sedimentary origin. The classic nodular anhydrite(A4-1)occurs in tidal flat sedimentary sequence in a random distribution form,and is caused by diagenetic metasomatism or gypsification,which is similar to the traditional sabha metasomatism gypsum nodules.A4-2 anhydrite mainly occurs in grainstone and microbialite,and is mainly formed by precipitation of CaSO₄-rich subsurface brine in dissolution pore and small caves.A5 type anhydrite occurs at the upper and top of the shallowing-upward sequence,which is related to high frequency exposure and is caused by karst transformation of dissolution and filling in the syngenetic period.A fully developed single high-frequency cycle has roughly experienced four evolutionary stages: early high-frequency rapid transgression,late high-frequency rapid transgression to early slow regression,late high-frequency slow regression,and exposure at the end of high-frequency regression,which formed a coupled marine carbonate and anhydrite co-occurrence sequence. These understandings will have important referential significance for the re-understanding of the sedimentary paleoenvironment during the deposition of the Majiagou Formation.
		2022 Vol. 24 (2): 226-244 [Abstract] ( 489 ) [HTML 1KB] [PDF 17164KB] ( 270 )

	245	Zhong Shou-Kang, Tan Xiu-Cheng, Nie Wan-Cai, Zhang Dao-Feng, Yang Meng-Ying, Lu Zi-Xing, Zhang Xin-Yue, Xiao Di

		High-frequency cyclic sequence of the Ma5₆ submember of Middle Ordovician Majiagou Formation in Ordos Basin: indication for sea-level change and sedimentary differentiation effect of Hengshan uplift
		Studies in high-frequency cyclic sequence is helpful to reveal much sedimentary information,such as sea-level changes,deposition response and palaeogeographic evolution during depositional stage of shallow carbonate platform,and their impacts on the sedimentary differentiation in the basin. Based on the rich drilling core data,the lithology characteristics and typical fifth-order cyclic sequence of the Ma5₆ submember of Middle Ordovician Majiagou Formation are studied. The results indicate that(1)5 types(Ⅰ~Ⅴ)of typical T-R single cycle have been identified based on the 9 rock types of symbiotic combination of carbonates and evaporites. The cycles of Ⅰ,Ⅱ and Ⅲ are characterized by dolomitic sediments of lagoon-shoal-mud mound,while cycles of Ⅳ and Ⅴ are characterized as gypsum-salt sediments of lagoon. The fifth-order high-frequency cyclic structural sections have been established according to the 5 types of single cycle;(2)Fischer plot established according to the fifth-order high-frequency cyclic sections indicates that the Ma5₆ submember developed in the late stage of the third-order cycle,which comprises 2 fourth-order cycles representing the trend of initial regression-rapid transgression-another regression;(3)the thickness statistics of fifth-order cycles shows that the development of uplift and depression corresponds to the period of the first fourth-order cycle. The Hengshan uplift was the depositional highland,which isolated the seawater between the west and east sides. During the second fourth-order cycle period,filling and leveling up weakened the impact of Hengshan uplift,promoting the seawater circulation and the salinity at the east and west sides of the uplift decreased. The study on the high-frequency cycles of the Ma5₆ submember has been well applied in the analysis of stratigraphy and sedimentology of the Ma5₆ submember in the Hengshan area,which can be further applied in the Majiagou Formation in the Ordos Basin.
		2022 Vol. 24 (2): 245-260 [Abstract] ( 442 ) [HTML 1KB] [PDF 14649KB] ( 274 )

	261	Xu Jie, Xiao Di, Su Wen-Jie, Yan Wei, Zhong Shou-Kang, Yang Ming-Yi, Yang Meng-Ying, Tan Xiu-Cheng

		Characteristics and genesis of leopard-spotted dolomitic limestone in the Member 4 of Ordovician Majiagou Formation: a case study from Guanjiaya section in eastern margin of Ordos Basin
		The leopard-spotted dolomitic limestone are found in the Middle Ordovician Majiagou Formation in the eastern margin of the Ordos Basin. It has been concerned by sedimentologists and reservoir geologists due to the extensive development,complex genesis,and important reservoir significance. This paper takes the top of the Member 4 of the Majiagou Formation in Guanjiaya Section loacted at Xingxian of Shanxi Province as an example. Based on the macroscopic and microscopic petrological characteristics,the geochemical analysis including the stable carbon and oxygen isotopes and in-situ laser ablation of trace rare earth elements,the characteristics and genesis of leopard porphyritic dolomitic limestone are analyzed. The results show that(1)Leopard-spotted dolomitic limestone often develops in granular-bearing micrite limestone,and the degree of dolomitization is enhanced upward. The needle-like or lath-like gypsum pseudocrystals often develop in dolomitic patches;(2)Leopard-spotted dolomitic limestone can be roughly divided into three types based on orientation of rocks: Horizontal,oblique and irregular variegation,corresponding to the lower,middle and up parts of the upward shallowing sedimentary sequence. The near-situ brecciation is often found at the top of the sedimentary sequence;(3)The δ¹³C and δ¹⁸O of the matrix limestone and dolomitic patches are slightly negatively biased compared with the seawater of the same period,and the top irregular dolomitic patches are the most negatively biased;(4)Leopard spot and matrix in limestone both have low contents of Mn,Sr,Ba and other trace elements,and low Mn/Sr ratio;(5)The total REE content of the leopard spotted part is slightly lower than that of the matrix part of limestone,and the REE distribution pattern is characterized as enriched in LREE and depleted in HREE,with the slight negative δCe anomaly and no δEu anomaly. Comprehensive analysis shows that the occurrence of leopard porphyritic dolomitic limestone in the Member 4 is controlled by the coupling of eogenetic karsts driven by biological disturbance and high-frequency in changes of sea level. The coupling modification is from weak to strong level from bottom to top of the sedimentary sequence. The bottom-middle part of the sequence is characterized by horizontal and oblique insect traces that are less affected by the karst,and the upper superimposed karst is strongly transformed to form a vertical sequence combination of irregular mottling. The exposed karst in the early diagenesis period overlaps and transforms the biological burrows. The evaporative and concentrated heavy brine will preferentially replace the areas with high porosity and permeability along the overlapping dominant channels. The dolomitization during the burial period is further strengthened,thus forming various types of leopard porphyritic dolomitic limestone. The research results also indicate that the eogenetic karstification controlled by the micro-topography during the sedimentary period is the key to the formation of the special leopard porphyritic dolomitic limestone or leopard porphyritic dolomite reservoirs of the Member 4 of Majiagou Formation,and this type of reservoir. This understanding also provides new materials for the study of eogenetic karsts driven by high-frequency of exposure periods.
		2022 Vol. 24 (2): 261-277 [Abstract] ( 471 ) [HTML 1KB] [PDF 6178KB] ( 341 )

	278	Luo Yao, Tan Xiu-Cheng, Zhao Dong-Fang, Luo Wen-Jun, Liu Yun, Xiao Di, Qiao Zhan-Feng, Zeng Wei

		Sedimentary characteristics of the Ediacaran microbial carbonates and their geological implications: a case study of the Member 4 of Dengying Formation from Wellblock MX8 in central Sichuan Basin
		The Ediacaran microbial carbonate rocks are widely developed in the Dengying Formation in the Gaoshiti-Moxi area of the Sichuan Basin. This paper takes the Member 4 of the Dengying Formation in Wellblock MX8 as an example. By analyzing the macroscopic and microscopic petrological characteristics of the high-frequency upward shallowing sequence,it is found that the microbial dolomite and sequence construction in the Member 4 of Dengying Formation have the following characteristics: (1)The upward shallowing sequence is mainly composed of thrombolites,stromatolites,microbial dolomicrite and a small amount of microbial bonded granular dolomite. (2)The complete typical upward shallowing sequence is composed of six lithologic units from bottom to top,including microbial dolomicrite(A),flat stromatolite(B),small hummocky stromatolite(C),dispersed thrombolite(D),latticed thrombolite(E),microbial bonded granular dolomite(F). A large number of sequences are composed of incomplete lithologic units such as A-C-E,A-C-D,B-D,B-C-D-E,and the top and bottom of the sequence are distinguished by uneven lithologic mutation surfaces or exposure surfaces such as thrombolites-microbial dolomicrite,stromatolites-microbial dolomicrite. (3)The Ediacaran microbial carbonates were developed in relatively high energy areas above the wave base to near the average sea level,and the environmental energy of the thrombolites are much higher than that of the stromatolites. The results reveal that the high-energy shallow water environment not only controls the distribution of large-scale microbial rocks,but also provides guidance for regional reservoir prediction. Meanwhile,the results are of great sedimentological significance in the establishment of an environmental distribution model that is different from modern microorganisms.
		2022 Vol. 24 (2): 278-291 [Abstract] ( 434 ) [HTML 1KB] [PDF 14821KB] ( 271 )

	292	Deng Cheng-Kun, Li Ting, Yang Wei-Qiang, Zhang Xi-Hua, Cheng Zhong-Zhen, Chen Hao-Ru, Zhu Dan-Cheng, Hu Li-Wen, Zou Hua-Yao

		Characteristics and main controlling factors of shoal reservoirs in the Middle-Upper Cambrian Xixiangchi Formation,central Sichuan Basin
		Within the Middle and Upper Cambrian Xixiangchi Formation,large-scale breakthroughs of the oil and gas exploration never came true and only a small amount of productivity were obtained in the Weiyuan-Ziyang area. Hence,investigating the formation and associated controlling factors of those reservoirs can provide geological basis for the future hydrocargon exploration. Based on outcrops,cores,thin sections,as well as drilling and logging data of the central Sichuan Basin,this study made a detailed description for the characteristics of the Xixiangchi reservoir and then analyzed the influences of the shoal depositional combinations,eogenetic karstification and the telogenetic karstification on the reservoir. The results show that: (1)The Xixiangchi reservoir in the study area is mainly granular dolostone. Based on whether the inner texture of grains can be preserved,the granular dolomite is divided into residual clastic texture dolomite and powder-fine crystal dolomite,whose reservoir spaces come from intergranular dissolved pores,intercrystalline dissolved pores and vugs,and thus,those reservoirs are characterized by low porosity and low permeability as a whole;(2)There are three types of shoal depositional combinations in the Xixiangchi Formation,which are lagoon-shoal(-tidal flat),shoal-tidal flat or mixed tidal flat,and multi-stage shoal vertical overlapping,respectively. The multi-stage shoal vertical overlapping can form a stratal succession with the most grainstone,whose reservoir properties are the best;(3)The eogenetic karstification is crucial for the formation of the reservoir and the telogenetic karstification could also improve the reservoir quality.
		2022 Vol. 24 (2): 292-307 [Abstract] ( 449 ) [HTML 1KB] [PDF 3261KB] ( 244 )

LITHOFACIES PALAEOGEOGRAPHY AND SEDIMENTOLOGY

	308	Lu Lu, Chen Shu-Guang, Li Zhuang-Fu, Qin Yong, Qu Zheng-Hui, Shen Yu-Lin

		Sedimentary evolution and petroleum potential of the Cretaceous to Paleogene in Linhe depression,Hetao Basin
		The study on the sedimentary evolution of the Hetao Basin is relatively insufficient,especially for the Cretaceous and Paleogene strata in the Linhe depression,which has important oil and gas exploration potential. In this article,based on sedimentology,mineralogy,petrology,geochemistry,field and drilling data,we performed a systematic sedimentary research on the Cretaceous to Paleogene strata in the Linhe depression and to explore its petroleum significance. The results show that: (1)From the Cretaceous to Paleogene,the Linhe depression in the Hetao Basin was characterized by sub-tropical arid and semi-arid climate,an overall oxygen-rich water body but locally anaerobic-anaerobic,and alternation of fresh water and brackish water environments. (2)There are five types of sedimentary facies in the Cretaceous to Paleogene strata,including alluvial fan,braided river,braided river delta,fan delta,and lacustrine facies,which are further divided into 12 types of sedimentary subfacies and 22 types of sedimentary microfacies. In the northwestern depression,the alluvial fan-delta-lacustrine sedimentary system was developed due to strong fault activity and high topographic relief. In the southeastern depression,a relatively weak tectonic activity and low topographic relief resulted in a braided river-braided river delta-lacustrine sedimentary system. The sedimentary pattern of each period is similar and only shows the variation of the fan-lacustrine boundary. (3)The Cretaceous to Paleogene Linhe Formation was characterized by arid and semi-arid,shallow water,dual provenances controlled by weak episodic tectonic activity. In the early stage of basin development,the tectonic activity was strong,but the basin was small and shallow. The clastic materials from both sides of basin margin rapidly advanced into and even converged in the center of the basin,forming a basin filled up by sands. With the weakening of tectonic activity and the rapid rise of lake water in the late stage,the clastic materials supply was insufficient to fill the lacustrine basin,thus forming a lake facies. (4)Sedimentary facies distribution in the depression control the macro-scale size,superimposed relationship and vertical evolution of sand bodies,and further determine the spatial distribution of effective reservoirs. Under the dual controlling factors of sedimentary facies and faulting,the favorable reservoirs in the Cretaceous to Paleogene strata are mainly distributed in the central faulted belt,which is dominated by shore-shallow lake and delta front deposits.
		2022 Vol. 24 (2): 308-331 [Abstract] ( 413 ) [HTML 1KB] [PDF 13284KB] ( 513 )

	332	Li Xin, Zhang Xia, Lin Chun-Ming, Deng Cheng-Wen, Li Xu-Long, Feng Xu-Dong, Xia Chang-Fa, Huang Shu-Ya, Zhao Xue-Pei

		Characteristics and its significance of clay minerals in the Holocene deposits of core SE2 in Qiantang River incised valley
		Characteristics of clay minerals in the Holocene Qiantang River incised-valley fill was systematically analyzed by X-ray diffraction. Results show that clay minerals in the Holocene Qiantang River incised-valley fill mainly consist of illite,chlorite,kaolinite,and smectite;Illite has a good degree of crystallization;Chemical index of illite is generally higher than 0.5,indicating clay minerals had undergone strong chemical weathering and the degree decreased gradually from bottom to top. By comparing the clay mineral composition of main rivers in southeastern China,we suggest that the sediments of section Ⅰ(i.e. the paleo-estuary and fluvial)in the Qiantang River incised valley are mainly derived from the Qiantang River drainage basin characteristic of high amount of kaolinite;whereas the sediments of section Ⅱ(present-day estuary and shallow marine)comprise numerous Changjiang sediments with smectite as diagnostic mineral except the Qiantang River deposits. Additionally,kaolinite could act as a good indicator of climate: kaolinite content reached the highest value in the middle Holocene,indicating a humid and hot climate and the highest chemical weathering degree;in the late Holocene,with the decrease of kaolinite content,the climate gradually became colder with a gradually decreasing chemical weathering degree.
		2022 Vol. 24 (2): 332-343 [Abstract] ( 446 ) [HTML 1KB] [PDF 1833KB] ( 264 )

PALAEOGEOGRAPHY AND MINERAL RESOURCES

	344	Mao Qian-Ru, Fan Cai-Wei, Luo Jing-Lan, Cao Jiang-Jun, You Li, Fu Yong, Li Shan-Shan, Shi Xiao-Fan, Wu Shi-Jiu

		Analysis of sedimentary-diagenetic evolution difference on middle-deep buried sandstone reservoirs under overpressure background: a case study of the Miocene Huangliu Formation in Yinggehai Basin,South China Sea
		Overpressured formation is widely developed in Yinggehai Basin. Dongfang and Ledong areas are in the heart of favorable gas accumulation in Yinggehai Basin. The Dongfang area is located in the center of the diapiric zone where the overpressure background formed relatively earlier(9~5 Ma)and the main provenance came from the Kuntum Uplift in the west. The Ledong area is situated in the Yingdong Slope where the overpressure ocurred relatively later(5~2 Ma),and its main provenance was from Hainan Uplift in the east. The comparative analysis of petrology and physical properties,hydrocarbon filling,and diagenetic characteristics of overpressured sandstone reservoirs of Miocene Huangliu Formation in Dongfang and Ledong areas are conducted,based on identification of thin sections under microscope,measurement of fluorescence of hydrocarbon-bearing thin sections and fluid inclusions,scanning electron microscope,electron probe,homogenization temperature of fluid inclusions,X-ray diffraction of clay minerals,etc. The result shows that: (1)Compaction and cementation of the Huangliu Formation in the Dongfang area are relatively weak,which resulted in relatively well physical properties(av. porosity is 17.68% and av. permeability is 11.11×10^-3 μm²)and corresponds to the late mesodiagenetic A. However,the Huangliu Formation in Ledong area is characterized by relatively strong compaction and cementation and lead to poor physical properties(av. porosity is 8.94% and av. permeability is 1.52×10^-3 μm²),corresponding to the diagenetic stage of the mesodiagenetic B. (2)The reservoir physical properties are mainly controlled by the sedimentation,overpressure and the diagenesis. The diagenetic characteristics and diagenetic-pore evolution of reservoirs are jointly affected by the provenance,depositional and subsidence centers,sedimentary facies,the timing of overpressure occurring and the scale of hydrocarbon filling. (3)To some degree,overpressure can minimize the compaction strength,inhibite the cementation and in turn,promote the dissolution.
		2022 Vol. 24 (2): 344-360 [Abstract] ( 393 ) [HTML 1KB] [PDF 9538KB] ( 246 )

	361	Chang Jia, Chen Shi-Yue, Wang Qiong, Pu Xiu-Gang, Yang Huai-Yu

		Sequence stratigraphy and coal accumulation of shallow water delta systems under low accommodation conditions: a case study from the Lower Permian Shanxi Formation in Bohai Bay region
		The Lower Permian Shanxi Formation in the Bohai Bay region was studied to analyze the sequence stratigraphy and coal accumulation of shallow water delta systems under low accommodation conditions. According to the two types of subaerial unconformities(SU)including sedimentary facies transition surface and incised valley scour surface,the Shanxi Formation can be divided into three 3rd order sequences(Sq1,Sq2 and Sq3),each of which represents one stage of delta. Each 3rd order sequence is divided into LST,TST and HST system tracts by maximum flooding surface(MFS)and maximum regression surface(MRS),representing nine 4th order sequences. A series of sequence-specified sedimentary facies diagrams have been constructed based on the contours of lithological parameters. Under the controls of the accommodation space growth rate and peat accumulation rate,flood plain in delta plain and peat swamp in delta front are favorable coal accumulation centers,which are located in the eastern part of Jizhong depression,the middle northern part of Huanghua depression and part of Jiyang depression. Coal seams in the flood plain is thick,and the coal accumulation center tends to move southward with the advance of the shallow water delta. The coal accumulation environment in the delta front is relatively poor,and coal seams are relatively thin,which is easy to be washed by the underwater distributary channel sand bodies. The sequence stratigraphic and sedimentological analysis of the Lower Permian coal-bearing strata of the Bohai Bay region provides a basis for a comprehensive coal accumulation model establishment, which involves a five-period evolution from the LST,early TST,middle TST,late TST to HST. The major coal seams were accumulated in the TST and HST of the sequences Sq1 and Sq2. These results are of practical significance for coal resources exploration and enhance the geological effects of prospecting engineering in the Bohai Bay region.
		2022 Vol. 24 (2): 361-374 [Abstract] ( 387 ) [HTML 1KB] [PDF 10228KB] ( 654 )

	375	Xie Qin, Chen Jia-Sheng, Liu Xiao-Jing, Liu Xiu-Ming

		Detection of climatic precession variability of black shale in the early Aptian of Cretaceous in Zhangye of Gansu Province and its significance
		The earth experienced profound environmental changes at the mid-Cretaceous when a typical representative of the greenhouse climate occurred. In the mid-Cretaceous,studies have shown that black shale in low-latitude(ca.20°~30°N)marine strata in Europe records presents obliquity signals,continental deposits are prevalent in inland China at the same latitude and during the same period,but there are few studies on the orbital-scale periodicity of continental low-latitude black shales. In this study,CaCO₃ content is used as an alternative high-resolution indicator of paleoclimate,and average spectral misfit(ASM)and time scale optimization(TimeOpt)analyses are used to explore the orbital periodicity of the black shale in the Xiagou Formation of the early Aptian of Cretaceous in Nantaizi (palaeoatitude of ca 23°N),Zhangye of Gansu Province, China. The result shows that the climate is dominated by precession and eccentricity cycles,which is significantly different from the result in Europe. The exploration of this climate change not only provides new evidence for the cretaceous orbital-scale climate change in the Northwest China,but also contributes to a more comprehensive understanding of the driving mechanism of climate change in the mid-Cretaceous.
		2022 Vol. 24 (2): 375-388 [Abstract] ( 386 ) [HTML 1KB] [PDF 11696KB] ( 717 )

QUATERNARY PALAEOGEOGRAPHY AND SEDIMENTOLOGY

	389	Ehsan ul Haq, Ji You-Liang, Zhang Sheng-Jiu, Liu Yan-Xin, Khurram Shahzad, Saad Ahmed Mashwani, Liu Xiao-Yu, Jiang Yan

		Analysis on characteristics and formation process of sediment waves on the Pleistocene channel levee backslope of Indus fan
		Architecture of the turbidity current sediment waves exhibit intricate morphologies and patterns on Indus fan channel levee back. The sediment waves are present on the channel levee of Pleistocene age in the study area,and their formation process is poorly understood. Through high-resolution seismic data and seismic interpretation technology, the difference between sediment wave and sediment deformation characteristics is expounded,and the distinguishing mark of the two sediments are summarized;the distribution law of sediment wave on the slope of the channel levee backslope and the regional slope is summarized;on this basis,the formation mechanism of the sediment wave is discussed,and the controlling factors and the formation process of sediment wave are analyzed. At last,the formation mode of sediment wave in Indus fan are established. The research result shows that: (1)The average wave length of the sediment wave in the study area is 486.84 m,and the maximum wavelength is 1473 m;the sediment wave height is between 10 m and 66 m,with an average of 30 m. (2)The morphology of sediment wave is symmetric and asymmetric,and its migration pattern include upslope migration type,aggregative type and downslope migration type. the sediment wave is mainly developed on the channel levee back,a small amount of sediment waves are also developed on the regional slope. The trends of these two types of sediment waves are very different. The sediment waves on the channel levee backslope are mainly distributed on the levee backslope in concave bank of the channel. The farther away from the channel,the smaller the dimension of sediment waves(wave length and wave height),and its trend is close to the NE-SW direction,parallel or oblique to the channel trend. The trend of sediment waves on the regional slope is mostly NW-SE,which is parallel to the trend of the regional slope,and its dimension is larger the farther away from the source area. (3)The sediment waves on the channel levee backslope is formed by the channel-type turbidity current overflowing the levee of the concave bank of the channel under the action of centrifugal force and depositing on the levee backslope outside the bank. The angle of the levee backslope have less effects on the dimension of the sediment waves. The intensity of turbidity current and the amount of sand conveying have a great influence on its dimension. The sediment waves developed on the regional slopes are formed by the non-channelized turbidity currents and are deposited along the slope,and it was considered that the undulating landforms caused by slump deformation,and the existence of early sediment waves all affect the development of later sediment waves.
		2022 Vol. 24 (2): 389-404 [Abstract] ( 365 ) [HTML 1KB] [PDF 9399KB] ( 238 )

JOPC

Dynamic academic

First notice of the 18th National Conference on Palaeogeography and Sedimentology

Together struggle for 20 years

The first 100 cited articles of 20th anniversary of founding of JOPC

more>>

Read Articles

Download Articles

Telephone：010 6239 6246　Email:Jpalaeo1999@163.com