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《Bulletin of Mineralogy, Petrology and Geochemistry》
JOPC 2017 Vol.19 Number 2
2017, Vol.19 Num.2
Online: 2017-04-01
SPECIAL ISSUE ABOUT “DOLOSTONE”
LITHOFACIES PALAEOGEOGRAPHY AND SEDIMENTOLOGY
NEW TECHNIQUES AND NEW METHODS
PAST AND PRESENT GEOGRAPHIC ENVIRONMENTS AND HUMAN CIVILIZATION
SPECIAL ISSUE ABOUT “DOLOSTONE”
187
Chen Daizhao, Qian Yixiong
Deep or super-deep dolostone reservoirs:Opportunities and challenges
Deep or super-deep dolostone reservoirs tend to be the important exploration field and targets in the future. Resulting from dolomite replacement and dissolution,abundant volumes of secondary porosity were commonly produced,which made the dolostones the potential high-quality petroleum reservoirs. In this context,it is imperative to reveal the mechanisms of dolomitization,porosity generation and preservation,as well as to investigate responsible fluid attributes and evolution pathay,then to establish reliable geological reservoir models. Under documenting the core issues related to “dolomite problems”,this review listed the major dolomitization models,present bandawagons,and main concerns in future dolomite studies,particularly for the deeply-buried dolostones experiencing complicated tectonic and fluid modifications. In China,abundant dolostones occur at great depths of >6500,m in the three largest cratonic sedimentary basins(Sichuan Basin,Tarim Basin and Ordos Basin), which have contributed numerical commercial petroleum reserves and provided favourable opportunities for petroleum exploration in deep or super￣deep formations. However,big challenges would also exist due to the great burial depths,multiple-phase,superimposed tectonic overprinting and complicated history of basin-fluid evolution.
2017 Vol. 19 (2): 187-196 [
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197
Qian Yixiong, He Zhiliang, Li Huili, Chen Yue, Jin Ting, Sha Xuguang, Li Hongquan
Discovery and discussion on origin of botryoidal dolostone in the Upper Sinian in North Tarim Basin
The botryoidal dolostone of a unusual textures features in Qigebulake Formation,in the Upper Sinian developed at Dong'ergou section and Well XH 101 of northern Tarim Basin,has been firstly reported. Constraining its origin based on lithology and geochemical data,the shell-comb or botryoidal dolostone,which consists of shrub fibrous cement,bladed radial as well as granular dolomite crystal with alternately dark and luminescent and zonation,the average of botryoidal dolostone of
δ
13
C
PDB
is 2.50‰(1.80‰~3.16‰),
δ
18
O
PDB
is-3.30‰(-6.40‰~0.86‰),
87
Sr/
86
Sr is 0.7091(0.7089~0.7096),compared with the values of matrix dolostone. The botryoidal dolostone have rather high positive of
δ
18
O
PDB
and
87
Sr/
86
Sr(within the change values of coeval normal sea-water: 0.7087~0.7094)with a similar
δ
13
C
PDB
. The
δ
13
C and
δ
18
O of zonation varies from the dark rimming to the luminescent centre varies slightly decreasing or increasing,while the strong negative deplete of
δ
13
C and
δ
18
O in outer of zonation,shows the tendency of negative deplete of
δ
13
C and
δ
18
O and increasing of
87
Sr/
86
Sr and Mn,decresing of the contents of Al
2
O
3
、Fe
2
O
3
、Na
2
O+K
2
O、P
2
O
5
、Sr/Ba、Fe/Mn. Coupled with a higher dolomitization. The contents of Al
2
O
3
、Fe
2
O
3
、MnO are relatively lower,and Na
2
O+K
2
O,P
2
O
5
,Sr,Hg,Cu,and the ratios of Sr/Ba,Sr/Mn are higher in comparison with the values of matrix dolostone. The contents of REE(10.21×10
-6
~15.75×10
-6
)with the “Left-leaning”distribution pattern of rare earth elements with LREE depletion,heavy REE enrichment,strong negative CE anomaly,indicated that the botryoidal dolostone was formed either in a well-preserved,weak reduction and oversaturated sea water environment with an increasing of pH value and free oxygen contents in sea waters. Or in a residual sea water of pore fluids in the early stage of diagenesis or shallow buried environment,later partly superimposed by a cyclic subaerial-exposed fresh water.
2017 Vol. 19 (2): 197-210 [
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211
Li Hong, Liu Yiqun, Zhang Lixia, Zhou Xin, Niu Yuanzhe, Li Xu, Liu Yongjie
Origin and geological significance of sedimentary exhalative rocks with “porphyritic”structures in the Middle Permian Pingdiquan Formation,eastern Junggar Basin
The Middle Permian Pingdiquan Formation which contains the most important source rocks and hydrocarbon reservoirs in eastern Junggar Basin,a continental rift basin in late Paleozoic, is characterized by interbeded layers of lacustrine sandstones,mudstones,limestones,dolostones,tuffs,and their mixtures with various proportions. One type of special sedimentary rocks was found in Pingdiquan black mudstones and dark grey microcrystalline dolostones in Zhangbei fault-fold zone,Shishugou sag,and Jimsar sag. They are composed of “phenocryst”and “matrix”,which is similar to volcanic “porphyritic”structures. The “phenocrysts”are usually coarse calcite,dolomite,pyrite,and analcime,while the “matrix”is mainly consisted of argillaceous sediments or microcrystalline dolomite,rich in organic matter,with micro-horizontal laminae and small deformation beddings. The “phenocrysts”can be single carbonate mineral and its aggregations or multiple mineral assemblages. “Phenocryst”calcite shows zonal texture under cathode luminescence and back scatter scanning,but “phenocryst”dolomite does not have zonal texture. Analysis of EMPA reveals that “porphyritic”calcite has features of low content of magnesium and iron,and heterogeneous distribution of strontium. Compared with “matrix” microcrystalline dolomite(FeO 1.027%),“porphyritic”dolomite contains higher iron with FeO content ranging from 7.272% to 11.086%. The average homogenization temperature value of fluid inclusions in “porphyritic”calcite is 180.68,℃,lower than that of “porphyritic”dolomite with average value of 320.95,℃. The structures,textures of “phenocrysts”and their geochemical features indicate that the “porphyritic”dolostones and “porphyritic”mudstones were formed by sedimentary hydrothermal exhalation in deep lake environment in the Middle Permian Pingdiquan stage. Lake water penetrated deeply to subsurface along the fractures,heated by underlying strata or magma chamber,exchanged the soluble ions from host rocks,and then circulated upward with the ions. Once the rising hydrothermal fluid was oversaturated,the minerals such as dolomite,calcite,pyrite or analcime would crystallize. They were uplifted by the hydrothermal fluids and finally were broken and exhaled into the fine grained sediments of lake floor. The “porphyritic”dolostones and mudstones in Pingdiquan Formation play an important role to explore the origins of hydrocarbons in research area and also are helpful to better understand the hydrothermal exhalative activities widely distributed in the Middle Permian in North Xingjiang.
2017 Vol. 19 (2): 211-226 [
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227
Tang Dongjie, Shi Xiaoying, Zhang Wenhao, Liu Yun, Wu Jinjian
Mesoproterozoic herringbone calcite from North China Platform:Genesis and paleoenvironmental significance
Herringbone calcite(HC),characterized by the alternation of sub-millimetric light and dark jagged bands,is a special type of carbonate mineral phase that mainly developed during the Archean. Early studies suggest that HC is a kind of inorganic chemical precipitation,formed in anoxic,calcium carbonate supersaturated,and precipitation inhibitor (Fe
2+
,Mn
2+
)￣rich seawater. Therefore,it has been used as an indicator of anoxic seawater conditions,and its abundance decreases over geologic time is thought to have reflected the increasing oxidation of the ocean. However,recent studies suggest that the genesis of HC might have been variable. For the first time,we have found HC in the microbial reef of the Mesoproterozoic Gaoyuzhuang Formation in the North China Platform. Macroscopically,these HCs mainly occurred in the voids of microbial reef as void-filling,distinct from their Archean counterparts which largely occurred as seafloor precipitation. Microscopically,the HC fiber shows a characteristic of rotated distinction along the crystal growth direction,indicating that the internal crystals of each HC fiber was once rotated from the bottom to the top. This is in accordance with the spherulitic growth pattern,therefore,requiring the participation of the calcite precipitation inhibitors. The secular decrease in HC abundance and the changes in their occurrence pattern from seafloor precipitation to void-filling,suggest that HC precipitation inhibitors should be redox-sensitive elements,which have been continuously removed from seawater with the oxidation of the ocean. Thus,we think that the major inhibitors for HC precipitation are Fe
2+
and Mn
2+
,and HC can be used as a mineral indicator for anoxic environment,which is consistent with the Ce anomaly results(without obvious anomalies)in the microbial reef and the presence of strong inhibitor effect of Fe
2+
. In addition,both microscopic and ultramicroscopic observations revealed that there are a large number of bacterial filamentous relics and closely associated organominerals concentrated along the axis of HC fibers,indicating that the microbes have provided favorable sites for the initial nucleation and subsequent growth of HC crystals.
2017 Vol. 19 (2): 227-240 [
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567
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241
Lin Peixian,Lin Chunming,Yao Yue,Wang Bingjie,Li Le,Zhang Xia,Zhang Ni
Characteristics and causes of analcime distributed in dolostone of the Member 3 of Paleogene Shahejie Formation in Beitang sag, Bohai Bay Basin
There are many minerals in the dolostone of the Member 3 of Paleogene Shahejie Formation from Beitang sag of Bohai Bay Basin. X-ray diffraction results show that the dolostone contains dolomite,analcime,quartz,feldspar,clay mineral,pyrite,calcite, etc. and the average content of analcime is about 38.8%. In this paper,based on a vast amount of data from core drilling, thin sections,scanning electron microscope,electron probe and geochemistry characteristics,we study the characteristics and causes of analcime in the Member 3 of Shahejie Formation in detail. Analcime occurs as two types,namely,laminae type and filling type. The former one,mainly laminated and sometimes nodular,is interbedded with dolomite. The other one is formed later and distributed in the crack as a kind of interstitial fillings. These two kinds of analcime are different in many aspects,such as existence form,crystal morphology,and associated minerals, etc. The laminae type is associated with dolostone,and the size of crystal is under 0.04,mm. However,the filling type is associated with pyrite and organic matter,and the size of crystal is above 0.04,mm. Based on the major-trace element and carbon-oxygen isotope analysis,the average salinity is 28.8‰ and the average Sr/Ba value is 2.93. It indicates that the sedimentary environment was alkaline-salty during the depositional period of Member 3 of Paleogene Shahejie Formation in Beitang sag of Bohai Bay Basin,which is beneficial to form analcime. The electron probe chemistry analyses show that the analcime of laminae type and that of filling type have different sources. The source of the analcime of laminae type is clay mineral,and the source of the analcime of filling type is related to hydrothermal fluid. Compared with other similar analcime-bearing dolostone basins in China,such as Jiuxi Basin,Santanghu Basin,we gave analyses on petrology characteristics,REE and formation temperature. The results show that the analcime in the study area has two causes: Analcime of laminae type is formed through deposition process,and analcime of filling type is formed through hydrothermal fluid process.
2017 Vol. 19 (2): 241-256 [
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257
Jiang Qicai, Liu Bo, Guo Rongtao, Gao Xiaoqiao, Li Yang, Zhang Shanming
Microbial mechanism of lacustrine primary dolomite
Recently,with the in-depth research on the microbial dolomite mode,a new perspective on Dolomite Problem has been provided. Previous researches on the origin of microbial dolomite mainly focused on the microbial processes in unconsolidated sediments,which equals to organic penecontemporaneous dolomitization. It differs from bacteria￣induced organic primary dolomite in laboratory in mechanism. This study introduces the formation mechanism of microbial dolomite into lacustrine primary dolomite,concluding that it would also precipitate primary dolomite in the interface between lake water and sediment,organic primary dolomite. There is a distinction between lake water and sediment in microenvironment of interface,which can be generally divided into two subenvironments: Aerobic and anaerobic,living with different microflora. According to the subenvironments' characteristics of different lake types,different microorganism species and their various role in the formation of dolomite,three microbial dolomite modes can be distinguished,which are the aerobic oxidation mode,the sulphate reduction mode and the methanogenesis mode. Different modes of the microbial dolomite correspond to different lake environments: The aerobic oxidation mode mainly develops in aerobic,high Mg/Ca,salt water lake/saline. The sulphate reduction mode mostly develops in anaerobic,high Mg/Ca,salt water lake/saline. The methanogenesis mode primarily develops in anaerobic,low Mg/Ca,freshwater lake/salt water lake. Moreover,some still-controversial issues on the process of dolomite precipitation will be discussed,such as the changing of pH,the effect of S
O
4
2
-
,the impact of sulfide on dehydration of magnesium hydrate and the environmental factors on the precipitation of microbial dolomite. The deep understanding of microbiogenic of primary dolomite model will provide a new theoretical basis and a new insight for lacustrine dolomite.
2017 Vol. 19 (2): 257-269 [
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LITHOFACIES PALAEOGEOGRAPHY AND SEDIMENTOLOGY
271
Chen Shiyue, Zhang Shun, Liu Huimin, Yan Jihua
Discussion on mixing of fine-grained sediments in lacustrine deep water
The mixing of sediments is a common phenomenon in the nature. Fine-grained sedimentary rocks in deep lake are typical peperites. The authors take the example of fine-grained sedimentary rocks in the Lower Member 3 and Upper Member 4 of Shahejie Formation in Dongying Sag. Through core observation in cm-scale,detailed description of small-sized sedimentary structures,thin section identification,analysis of whole rock X-ray diffraction and trace elements test,fine-grained sediments occurrence and their mixed mode were studied,and the effect of basin fluid,climate and water properties on transfer,mixing and sedimentation of fine-grained rocks was analyzed. The mixing sedimentary mechanism of fine-grained rocks was discussed. The results indicate that fine-grained sedimentary rocks in lacustrine deepwater are mixed in both components and structures under macroscopic and microscopic scales. The mixing sedimentation can be classified into homogeneous,lamina-overlapped and heterogeneous mixings with lamina￣overlapped mixing the major type of fine-grained rocks. Based on the lamina contact relations,proportion and mineral occurence,the lamina mixing sedimentation is divided into: Lamina￣overlapped mixing of sand-mud and limestone,lamina￣overlapped mixing of mud and limestone,laminate mixing of mud-sand sequence and limestone,lamina￣overlapped mixing of limestone,mud and dolostone. The types of mixing sedimentation of fine-gained sediments are often influenced by multiple factors at the same time,and the climate and the hydrodynamic conditions are the main factors. The mixing sedimentation of fine-grained sediments varied in different fluids(turbidity current and bottom current). The climate causes changes of physical and chemical properties of water as well as layering of water body,which controls different types of flocculating settling and chemical deposition of fine-grained sediments. The mixing sedimentation types vary in different structural positions and water depths,and are even different vertically in the same structural position.
2017 Vol. 19 (2): 271-284 [
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285
He Jingcong, Zhu Xiaomin, Li Mingrui, Liu Fen, Ye Lei, Xue Mengge
Parent rock types and tectonic setting of the Permian Shanxi and Shihezi Formations in Longdong area,Ordos Basin
Based on petrological and provenance analysis,this paper discusses tectonic property and provenance of the Member 1 of Shanxi Formation and Member 8 of Shihezi Formation of Permian in Longdong Area,Ordos Basin. The results suggest that detrital mode compositions of these two members are similar,which were formed from the same parent rocks and tectonic setting. Microscopic characteristics and CL image of quartz show that the parent rocks are metamorphic rocks and igneous rocks;Light mineral characteristics are associated with collisional suture and fold-thrust belt sources. The plagioclase An and EPMA analysis indicate that the study area and the north Qinling orogenic belt have similar plagioclase type. Tectonic discrimination plots indicate that the provenance was mainly affected by passive continental margin source until the end of Late Paleozoic,then under the influence of active continental margin. Parent rock discrimination plots suggest that the provenance was dominated by felsic rocks. The REE distribution patterns of the sedimentary rock in Shan 1 and He 8 Members are consistently declining to the right,and are very similar to those of Qinling Group and Kuanping Group in the north Qinling orogenic belt. The dating of U-Pb isotope in zircon reveal that they can be divided into two groups according to their ages,which mostly dated from Proterozoic and some from Late Paleozoic. It is concluded that the provenance mainly affected by passive continental margin,others are active continental margin sources. Furthermore,the parent rocks of Shan 1 and He 8 Members are mainly from gneiss and quartzite of Qinling Group and chlorite schist and actinolite schist of Kuanping Group in the north Qinling orogenic belt,a few from igneous rocks of late Paleozoic era in the north Qinling orogenic belt.
2017 Vol. 19 (2): 285-298 [
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299
Sun Ningliang, Zhong Jianhua, Wang Shubao, Liu Shaoguang, Ni Liangtian, Qu Junli, Hao Bing, Liu Chuang
Sedimentary characteristics and petroleum geologic significance of deep-water gravity flow of the Triassic Yanchang Formation in southern Ordos Basin
Through the observation of abundant cores, analysis of drilling and logging data,and outcrop observation,the sedimentary characteristics,triggering mechanisms,sedimentary process and pattern of deep-water gravity flow were analyzed in detail in the Chang 6-7 intervals of the Triassic Yanchang Formation,southern Ordos Basin. The results show that there are five types of gravity flow sediments,which are slipped mass,slump deposits,sandy debris flow deposits,turbidity deposits and muddy debris flow deposits. There are five vertical combination styles of gravity flow deposits in the study area. The sedimentary process of gravity flow can be divided into five stages,which are delta front sedimentary stage,slide stage,slump deformation stage,sandy and muddy debris flow stage and turbidity flow stage. Slide and slump sand bodies are formed in shapes of isolated lens;sandy debris flow sand bodies are formed in fan channel;and turbidity sand body are formed as sheet sand,mainly distributing in the front or sides of the fan channel. Sand bodies of deep-water gravity flow are vertically superposed in large thickness,which could form large scale reservoirs and extremely extends the exploration of deep lake sedimentary facies. In the study area,sand bodies of sandy debris flow in Chang 6-7 intervals are worth of great concern for their preferable physical properties and hydrocarbon potential.
2017 Vol. 19 (2): 299-314 [
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758
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453
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315
Peng Biao, Jin Zhenkui, Zhu Xiao'er, Cui Xuemin, Yang Tianbo, Shi Liang
Discussion about depositional models of fan delta: A case study from the Lower Triassic Baikouquan Formation in Mabei area,Junggar Basin
Fan deltas are important reservoirs for hydrocarbon accumulation. A reliable depositional model of fan deltas is an essential guide for reservoir prediction. The Lower Triassic Baikouquan Formation in Mabei area of Junggar Basin is characterized by the development of fan-delta systems. Although a lot of studies have been done,it is still controversial about the depositional model of fan delta. Based on a comprehensive analysis of modern depositional systems, flume experiment and a subsurface dataset from the Mabei area,it is found that: (1)In fan-delta plain,three types of depositional microfacies,including braided channel,conglomeratic overbank and subaerial outer-fan mud,have been identified,and debris flow deposits exists;in fan-delta front,two types of depositional microfacies,including conglomerate shoal and sandy shoal,have been identified,and subaqueous debris flow deposits exists;(2)In fan-delta plain,channel and inter-channel are dominated by coarse-grained deposits without muddy deposits,and the deposits of channel is better sorted than inter-channel;(3)Fan delta front is dominated by sheet-like,coarse-grained deposits from sheet flow.
2017 Vol. 19 (2): 315-326 [
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347
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327
Wang Jun, Bao Zhidong, Wang Yunlong, Hua Songtao, Yang Yichun, He Lingyuan, Wang Xiaotao, Zhang Yunyi
High-resolution sequence stratigraphy and sedimentary characteristics of the Member 3 of Qingshankou Formation of Upper Cretaceous in Qian'an area, south Songliao Basin
Integrated with core and logging data,the recognition marks of high resolution sequence stratigraphic boundary of the Member 3 of Qingshankou Formation of Upper Cretaceous in Qian'an area of south Songliao Basin is summarized systematically. The high￣resolution sequence is established. Moreover, the stacking pattern of the strata in the framework of high-resolution sequence stratigraphy is discussed and the characteristics of sand distribution and disciplines of sedimentary facies evolution in the sequence framework is analyzed. Several conclusions are made as follows. Three sequence boundaries and two supporting evidences have been recognized in the study area,such as erosion surface,stranded sediments at the bottom of the deposit,slump deposit, switched color of mudstone and differences in petroliferous. Then the Member 3 of Qingshankou Formation is divided into two 3
rd
-order sequences(SQ1,SQ2)and thirteen 4
th
-order sequences(HFSQ1-HFSQ13),and each of the sequence can be divided into lake transgressive system tract(LTST)and lake regressive system tract(LRST). Five types of the 4
th
-order sequence structure have been recognized in the system tract. The process of lake level fluctuation can be divided into four stages,and the combination model of 4
th
-order sequences in each stage is different. Based on the analysis of sand correlation in cross-section and facies distribution, according to the phase division of lake level fluctuation,four types of sedimentary model have been recognized in the framework of high-resolution sequence stratigraphy. Each model has its unique sand distribution feature in vertical direction and shape in horizontal direction.
2017 Vol. 19 (2): 327-340 [
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551
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341
Jin Fengxian, Shao Longyi, Liang Feng, Lin Wen, Li Li, Zhao Qun
Accumulation conditions and strategic selection of favorable areas of shale gas of the Lower Paleozoic in Chongqing area
Chongqing area is the breakthrough area of shale gas exploration and development,and the shale gas is preserved in the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation of the Lower Paleozoic. Based on data from outcrop,drilling core and logging data, using sedimentology,organic geochemistry and other methods, the characteristics of sedimentology of shales,and the shale gas accumulation conditions was analyzed and the favorable areas for shale gas exploration of study area were predicted. The results showed that the dark shale in Chongqing area had a great thickness and a broad distribution, with the content of total organic carbon being more than 2% and the organic matter type being type I. The thermal evolution was in high mature-over mature stage which indicated the shale have a better hydrocarbon￣generating potential. The target dark shale horizon was overlain by a thick sequence of shales and underlain by thick modular limestones and micritic limestones, which provided a deal preservation effect for shale gas. The content of gas was much higher and the average gas content being 1.39,cm
3
/t. The integrated information overlapping method was used to predict favorable areas of shale gas exploration, and two favorable areas were predicted, including the Chengkou-Wuxi area and the Shizhu-Fuling-Wulong-Pengshui-Nanchuan-Qijiang area.
2017 Vol. 19 (2): 341-352 [
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663
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1554KB] (
405
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NEW TECHNIQUES AND NEW METHODS
353
Niu Yongbin, Cui Shengli, Hu Yazhou, Zhong Jianhua, Wang Peijun
Quantitative characterization of bioturbation based on digital image analysis of the Ordovician core from Tahe Oilfield of Tarim Basin
Bioturbation has a great influence on the carbonate reservoir properties of “matrix reservoir” of the Ordovician in Tahe Oilfield of Tarim Basin. With the help of Bioturbated Digital Analysis Images Package of Adobe
®
Photoshop
®
CS6,the study was carried on the core of the Ordovician from Tahe Oilfield to identify and estimate quantitatively the area that was bioturbated in the core digital image. The results show that: (1)Within the methods of Bioturbated Digital Analysis Images Package,“Similar Pixel Selection Method” and “Magic Wand Method” are the most effective to identify and estimate quantitatively bioturbation and have different ranges of application. (2)The Similar Pixel Selection Method is suitable for the samples with high bioturbation,small size and high diversity. When there are considerable differences between the infill of bioturtation and the surrounding rocks,“Select Similar” is the best way to estimate quantitatively the bioturbation. Otherwise,when there are just little differences between the infilling and host rocks,“Color Range” is the best way. (3)Magic Wand Method has an advantage on the samples with large size trace fossils and good continuity as well as different color of infilled material. By modifying “Tolerance”,Magic Wand Method will increase the degree of recognition between the bioturbated area and host rock. This research makes a convincing explanation about heterogeneous and distribution of “matrix reservoir” of carbonate rocks in the perspective of biogenic,and has a great significance on fulfilling the characterization and interpretation of those bioturbation enhanced reservoir capacity in carbonate rocks,enriching geologic theory of carbonate reservoir,guiding the hydrocarbon exploration of the bioturbated reservoir,calculating reserves and selecting the best plan of the development of oil and gas fields.
2017 Vol. 19 (2): 353-363 [
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751
) [
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302
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364
Li Yuan, Lu Xinbian, Cai Zhongxian, Zhang Heng, Liu Xianfeng
Development model of Hercynian cave system in karst canyon area of Tahe Oilfield, Tarim Basin
Giant karst cave reservoir develop in the karst canyon area of Tahe Oilfield,with good explotation result. Through high resolution 3D seismic data,data of drilling and the seismic attributes extracting the karst cave system,palaeo-gemorphology and palaeo-drainage system were rebuilt. The karst development mechanism was discussed and the model of the karst cave were summarized as following: (1)Surface water has strong vertical erosion in upper reaches of the canyon,the canyon lost the drainage function and evolution into dry valley,hydrodynamic conditions in lower reaches of canyon is weaken. (2)Cave types divided into underground water caves,canyon-fault caves,underground water caves development in the upstream of canyon, underground caves and canyon are mapping relationship,canyon-fault caves development on both sides of the canyon,with multilayer characteristics in vertical. (3)With a comprehensive analysis of the karst cave genesis mechanism in the canyon area,we thought that the underground water cave development in an adequate water supply condition and strong vertical erosion of water,canyon-fault caves development in a multiple-stage drop of base level and fault systems. Combined with the characteristics of modern Enshi cave systems. evolutionary model of the karst cave in canyon are proposed,which provides a theoretical reference for further cave reservoir prediction and exploration practice.
2017 Vol. 19 (2): 364-372 [
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593
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267
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PAST AND PRESENT GEOGRAPHIC ENVIRONMENTS AND HUMAN CIVILIZATION
373
Li Fan, Ye Yu, Wan Jinhong
Analysis of drought records of 1920 AD in
Continuation of Disaster Annals in Recent China
(1919
-
1949)
The drought in five provinces of North China during 1920 AD was called “Never Seen in The Past 40 Years”. This paper adopted the related original records of the drought in
The Continuation of Disaster Annals in Recent China
(1919
-
1949) and analyzed the characteristics and difference of the original drought records by dividing them into three social levels and six types. The advantages and limitations of different materials for drought reconstruction were also discussed. Conclusions came as follows: (1)In the aspect of records' contents,the central authorities pay much attention to the severest counties; the statistics from local government and organizations are more detailed; the records of newspapers aren't statistical data but descriptive words. (2)In the aspect of the quantity of statistical information,local government,central authorities and folk level reduce in turn.(3)In the time aspect,the folk level recorded earliest(especially newspapers reported); local government recorded later; central authorities recorded latest.(4)Official documents represented by
Announcement of Relief Work
include abundant information,which helps to reconstruct the drought area; reorganized materials like
the Continuation of Disaster Annals in Recent China
(1919
-
1949) put particular emphasis on the reorganization of the drought conditions so that much more drought influences and responses of 1920 AD need more other historical materials to support.
2017 Vol. 19 (2): 373-382 [
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383
Kong Dongyan, Li Gang, Chen Hai
Spatial-temporal characteristics and environmental background of locust plague in Beijing-Tianjin-Hebei region during Ming and Qing Dynasties
Ming and Qing Dynasties(1368-1911 AD),known as the Chronicles Period of China,belong to the Little Ice Age during which locust plague and other natural disasters were frequently occurring and were well registered in historical documents. The North China Plain is the main source area of locust plague in China's history. It is of special significance to do research on the Beijing-Tianjin-Hebei region of North China plain. Based on historical records in the study area during Ming and Qing Dynasties,this paper reconstructed locust outbreak sequences concerning grades,frequency and counties to disclose the temporal dynamics and spatial pattern,and analyzed the causes and environmental mechanism. The results show that: (1)During Ming and Qing Dynasties,locust plague occurred once every 1.8 a and covered 3 counties per year in Beijing-Tianjin-Hebei region. Locust used to occur from March to August of the summer-half year with the peak in June and July. And September to February of the winter-half year was less. (2)The locust outbreak grades ranged mainly between two and three,and the average grade was 2.17. The decadal locust outbreak frequency and decadal locust outbreak counties presented an overall rising trend with fluctuations. (3)The number of counties of summer locust was more than that of autumn locust. Either warm or cold winters had little impact on the following summer locust outbreak. (4)The result of wavelet analysis indicated that periodicity occurred with primary periods of 100 a and 30 a and secondary periods of 53 a, 17 a and 11 a. (5)The spatial distribution of locusts presented a certain geographic clustering with southeast far more than northwest. It was greatly affected by the topography and water system pattern. (6)The locust plague was insignificantly affected by temperature change but had a strong relationship with drought and a good correspondence with the Nino3 index.
2017 Vol. 19 (2): 383-392 [
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