The Tectonic Coupling between the Luxi Uplift and the Qikou Depression
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The solid mineral resources in mountain area and the petroleum in basin are two main areas of geological researches, with different emphasis and normally assigned to different department, so that interdisciplinary investigation is scarce to date. The Luxi uplift consists of Nikunshan-Muzishan, Mengshan, Culaishan-Xinfushan-Mengliangang and Taishan-Lushan-Yishan etc. spreading from south to north, furthermore, among these uplift there are distributed four neighboring fault depressions i.e. Siping, Wenmeng, Feicheng and Laiwu fault depressions. Between the fault depressions and the uplift developed the typical listric faults which control the Miocene dustpan-shaped sediments in the fault depressions. In the case of the Qikou depression, there are three subclasses of depressions as Qinan, Qibei and Banqiao with Nandagang and Beidagang buried-hill structure belt as the boundaries and taken on the dissymmetry form with the northern side deep and steep, the southern side shallow and nearly flat. The Qikou depression was faulted in the north and overlapped in the south. Comparative study of the sag and the structure of uplift and depression in the uplift area of Western Shandong becomes an urgent need. From the point of view of mantle branch, the authors propose that both the Luxi uplift and Qikou depression have the main structural features formed through coupling of mountain and basin.Cite
The seismic profile sections and well data of the western Gansu corridor and nearby regions were analyzed. The sedimentary and structural characteristics of the early Cretaceous basins in this area were investigated. A new prototype of basins developed in the early Cretaceous was proposed. It is pointed out that the formerly named as Jiuxi, Huahai, Jiudong and Jinta basins actually belong to one large basin named as Jiuquan Basin now, because the central Kuantaishan-Heishan Uplift and Tianquansi-Helishan Uplift were not developed in the early Cretaceous. The former Huahai Basin and Jiuxi Basin actually belong to a large depression named as Jiuxi Depression composed of Qingxi Sag, Chijin Sag and Shida-Huahai Sag. The later sag is composed of Huahai Sub-Sag,Shibei Sub-Sag and Dahongquan Sub-Sag,and the former Jinta Basin and Jiudong Basin are actually made up of another large depression named as Jiudong Depression including Jinta Sag, Yanchi Sag, Yinger Sag and Maying Sag. The two large depressions are separated by the Jiayuguan uplift, Which is a south-north extending uplift between the two depressions. The southern boundary of the large basin in the early Cretaceous is on the northern Qilianshan and has a distance from 30 to 50 kilometers to the boundary of the present basin.
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Based on the comparison and interpretation of seismic data obtained using an 8×8 km grid,the authors have studied the development of deep fault depressions in the southeastern uplift area of the Songliao basin and think that the fault depressions mainly developed in the Shahezian stage,when eight fault depressions of different sizes occurred.According to the results of seismic interpretation and other related data,the authors have analyzed the difference in distribution of the Huoshiling Formation,Shahezi Formation and Yingcheng Formation during the downfaulting period.Based on the regional geological setting and structures of this area,they think that the deep downfaulting period in the southeastern uplift area of the Songliao basin may be divided into three evolutional stages:the initial rifting stage(Huoshilingian stage),strong downfaulting stage(Shahezian stage) and downfaulting-downwarping transition stage(Yingchengian stage).The reworking of the deep downfaulted strata is also analyzed.
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Intra-sag uplift of Xujiaweizi fault depression in the Songliao basin is significantly different with the surrounding areas in respects of sedimentary-structural features.Based on the comprehensive study of seismic,well and regional geologic data and in combination with the unique geologic features of the intra-sag uplift,it is believed that the intra-sag uplift is a window opened in the shallow part of the early fossil foreland basin.Its formation,development and consumption are systematically discussed in 5 stages by using the theory of normal faults being associated with folds.Although the intra-sag uplift is contemporaneous with the faulted basin on its both sides,they belong to different geologic bodies formed in different geologic time and are the products of basins in two stages.This provides a new understanding for exploration in deep of the Songliao basin and reveals the large deep gas potential in the study area.
Geologic time scale
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The central uplift belt is an oil/gas enrichment zone in the Dongying depression of jiyang geotectogene.It trends nearly E-W and is a dissymmetrical anticline belt with steep dip angle in the north limb and gentle in the south.A rift\|fault system of cabbage style develops on the uplift belt.Because of the characteristics of synsedimentary and reverse drag controlled by the north boundary fault.It was considered as a roll anticline belt in the early exploration time.Due to the accumulation of geological and geophysical data,most of the following investigators have argued the origin of salt\|mud diapir structure since 80s.Based on detailed studying of sesimic and geological data and comparing to previous research results,a sadbox experiment is designed and carried through in this work to search the cause of the central uplift belt.By all the results above,we conclude that the Dongying central uplift belt was formed by extention\|diapirism lead by regional tenso\|shear stress and gravity,and the shape of the local auticlines and the character of the fault system are controlled by the shape of the salt\|mud diapir and the intensity of extension and diapirism.
Anticline
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The southeast upwelling area of Songliao Basin is a fault depression superimposed structure The down-warped stratohorizon is located on the margin of the Songliao Basin,because of the influence by the structure motion in the period of Nenjiang sedimentation ending The Southeast was uplift region uplifted totally and denuded everywhere The residual thickness of hollow depression formation is varied greatly,and the ability of the oil-generation was limited So,it was difficult to form reservoirs The formatin of fault depressions is the main prospecting target stratum They are dismembered by basement uplift,therefore,each one is relatively independent But as they were formed in universal regional structure stress,there was similarity among them:whether or not the oil and gas could gather to become reservoirs,which is restricted by the total resources and the hydrocarbon-born degree of every fault depression
Prospecting
Basement
Stratum
Lithology
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By means of structure-stratigraphy method,through systematic 2 dimension structure-stratigraphy interpretation of several seismic sections,structure-stratigraphy balance recovery,and calculating extension quantity and extension rates,the developing process of Manghan sag is revealed and the tectonic features and forming mechanisms of the basin are analyzed.The results show that Manghan sag is a fault depression superimposed structure.The fault depression is mainly controlled by the faults in the Lower Cretaceous Jiufotang group,Shahai group and Fuxin group periods,and the fault depression turned into depression basin which was not controlled by the faults on both sides of the basin,and its scope of deposition is extended to the both sides,and the strata onlapped to the basin margin from Quantou group to Nenjiang group.The basin structure becomes simple from deep to shallow,and the deep structure is complicated relatively with faults and the shallow structure is simple and flat form of depression structure.Manghan sag structure characteristic fully reveals that the basin developing was controlled by the extension of the sinistral transformation.
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Based on the geological structure interpretation of the 3D and 2D seismic profiles covering the whole study area in the Huanghua depression,the architecture and evolution of the basement and cover of the basin were described and analyzed in detail.The huge Indosinian E-W trending thrust-fold structure and the Yanshanian NNE trending thrust-fold structure were also identified.It is proposed that the main Qikou sag is a rifting basin resulted from negative inversion of the Indosinian uplifting paleo-anticline.The architecture of land in the north and middle part of the Huanghua depression appears as NE striking domino style half graben system,which was faulted at the northwest margin and overlapped at the southeast slope.The offshore part of the basin is characterized by a huge complex graben of nearly W-E striking.The throw of the Cangdong fault,boundary fault of the basin,decreases gradually from south to north,and disappears to the north of the Banqiao sag,and linked with the Chadian fault by the structure transitional zone at the west slope of the Beitang sag.From the quantitative analysis of the activity of the main fault systems and subsidence history of the basin,the Cenozoic synrifting evolution of the Huanghua depression was divided into three episodes.From the episode I to episode II,the depocenter and the subsidence center migrated northwards from the onshore to offshore.Finally,combining analysis of the tectonic stress field involving the migration of the subsidence center and the regional geological features of the Bohai bay basin,the transtensional basin model is preferred to interpret the evolution of the Huanghua depression and the deforming mechanism of the Bohai bay basin during the deposition of the Kongdian Formation(Ek) and Dongying Formation(Ed).
Anticline
Thrust fault
Basement
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Tarim basin
Thrust fault
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Huanghua Depression is one of the most important oil and gas bearing basins in Bohai Bay basin of East China. On the basis of reflection characterisstics, well logging and other geological data, Shahejie Formation and Dongying Formation can be divided into three second-order sequences and eleven third-order sequences. Three system tracts can be recognized in each third-order sequence, which are lowstand system tract, expanding system tract and highstand system tract. Three typical tectonic backgrounds developed in the study area: ①Gentle slope characterized by slope break lies on the west side of Qinan sag, northwest side of Beidagang buried hill and its east-plunging part. Sequence styles of gentle slope break are developed in the above parts. ② Fault-controlled steep slope background can be seen on the south side of Nandagang buried hill and Beidagang buried hill. The above areas form the sequence style of fault-controlled steep slope. ③ The background of multilevel step-fault is Yangerzhuang fault terrace belt and the downthrow wall of Haihe fault. Tectonic activity is the main factor that controls the sequence components, and can be divided into microtectonic and local tectonic activities. Sediment source also mainly controls the sequence pattern.
Sequence (biology)
Sequence Stratigraphy
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The Panyu Uplift is an important oil and gas-bearing district in central south Pearl River Mouth Basin.A series of northwest and east-west striking syndepositional faults were developed during Neogene,and their development and distribution controlled the paleo-structural framework and the sedimentary filling pattern.The main syndepositional faults along the southeastern and northeastern margins of the ancient uplift formed obvious geo-morphologic abrupt zones or fault slope-break zones.The main controlling faults in the southeastern part were formed by the antithetic faults in the hinge gentle slope which were developed during synrifting and formed the boundary between Panyu Uplift and Baiyun deep sag.An analysis of seismic facies and seismic attributes has shown that the lowstand system tract deltaic sandstones in the middle-lower part of Zhuhai and Zhujiang Formations were developed and distributed along the low slope of the fault slope-break zone.Researches indicate that the low slope lowstand system tracts along the fault slope-break zone constitute a favorable condition for the formation of lithostratigraphic or structural-stratigraphic traps.This study hence has offered an important basis for the recent exploration breakthrough in this area.
Growth fault
River mouth
Neogene
Echelon formation
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