To reveal the geometry of the seismogenic structure of the Aug. 8, 2017 M_S 7.0 Jiuzhaigou earthquake in northern Sichuan,data from the regional seismic network from the time of the main event to Oct. 31, 2017 were us...To reveal the geometry of the seismogenic structure of the Aug. 8, 2017 M_S 7.0 Jiuzhaigou earthquake in northern Sichuan,data from the regional seismic network from the time of the main event to Oct. 31, 2017 were used to relocate the earthquake sequence by the tomoDD program, and the focal mechanism solutions and centroid depths of the M_L ≥ 3.5 events in the sequence were determined using the CAP waveform inversion method. Further, the segmental tectonic deformation characteristics of the seismogenic faults were analyzed preliminarily by using strain rosettes and areal strains(As). The results indicate:(1) The relocated M_S 7.0 Jiuzhaigou earthquake sequence displays a narrow ～ 38 km long NNW-SSE-trending zone between the NW-striking Tazang Fault and the nearly NSstriking Minjiang Fault, two branches of the East Kunlun Fault Zone. The spatial distribution of the sequence is narrow and deep for the southern segment, and relatively wide and shallow for the northern segment. The initial rupture depth of the mainshock is 12.5 km, the dominant depth range of the aftershock sequence is between 0 and 10 km with an average depth of 6.7 km. The mainshock epicenter is located in the middle of the aftershock region, showing a bilateral rupture behavior. The centroid depths of 32 M_L ≥ 3.5 events range from 3 to 12 km with a mean of about 7.3 km, consistent with the predominant focal depth of the whole sequence.(2) The geometric structure of the seismogenic fault on the southern section of the aftershock area(south of the mainshock) is relatively simple, with overall strike of ～150° and dip angle ～75°, but the dip angle and dip-orientation exhibit some variation along the segment. The seismogenic structure on the northern segment is more complicated; several faults, including the Minjiang Fault, may be responsible for the aftershock activities. The overall strike of this section is ～159° and dip angle is ～59°, illustrating a certain clockwise rotation and a smaller dip angle than the southern segment. The differences between the two segments demonstrate variation of the geometric structure along the seismogenic faults.(3) The focal mechanism solutions of 32 M_L ≥ 3.5 events in the earthquake sequence have obvious segmental characteristics. Strike-slip earthquakes are dominant on the southern segment, while 50% of events on the northern segment are thrusting and oblique thrusting earthquakes, revealing significant differences in the kinematic features of the seismogenic faults between the two segments.(4) The strain rosettes for the mainshock and the entire sequence of 31 M_L ≥ 3.5 aftershocks correspond to strike-slip type with NWW-SEE compressional white lobes and NNE-SSW extensional black lobes of nearly similar size. The strain rosette and As value of the entire sequence of 22 M_L ≥ 3.5 events on the southern segment are the same as those of the M_S 7.0 mainshock,indicating that the tectonic deformation here is strike-slip. However, the strain rosette of the entire sequence of 10 M_L ≥ 3.5 events on the northern segment show prominent white compressional lobes and small black extensional lobes, and the related As value is up to 0.52,indicating that the tectonic deformation of this segment is oblique thrusting with a certain strike-slip component. Differences between the two segments all reveal distinctly obvious segmental characteristics of the tectonic deformation of the seismogenic faults for the Jiuzhaigou earthquake sequence.展开更多
The sequence stratigraphy framework of Paleogene of Qikou Sag has been built in this paper. The evolution law of episodic subsidence in Qikou Sag has been expounded, with the analysis of the characteristic of sequence...The sequence stratigraphy framework of Paleogene of Qikou Sag has been built in this paper. The evolution law of episodic subsidence in Qikou Sag has been expounded, with the analysis of the characteristic of sequence thickness, as well as the study of consedimental tectonic activity, subsidence history, paleogeomorphology and the coupling relationship among them. The faults controlling action was the dominant mechanism during rifting stage I , as the depression was the dominant mechanism during rifting stage III, which embodies a process from intense disparity fault depression to integral subsidence. Meanwhile, under the control of regional faulting and later stage depression, subsidence rate centers and paleogeomorphic concave centers are always corresponding to the sequence thickness centers, and the changes of subsidence centers and paleogeomorphology concave centers are consistent with the migration of thickness centers, which presents the restriction, coupling and response among them and clarifies the law that tectonic activity controls the basin fill by means of controlling the subsidence rate and paleogeomorphology from contributing factor angle. On this basis, the dynamic evolution of the composite pattern of structure-subsidence-deposition in the fault controlling actic region during the three rifting stages and their petroleum geological significance has been discussed.展开更多
Various orders of sequences were recognized in the Tarim Basin from unconformities. Three mega-sequence groups, six mega-sequences, sixteen super-sequences and forty-two sequences were determined from the Sinian to th...Various orders of sequences were recognized in the Tarim Basin from unconformities. Three mega-sequence groups, six mega-sequences, sixteen super-sequences and forty-two sequences were determined from the Sinian to the Quaternary. The mega-sequences and super-sequences were in accordance with the locally tectonic events occurring in both the north and the south margins of the Tarim plate. The global sea level changes only worked to control formations in the tectonically stable periods or in the low order sequences. The sequences had close relationship to the source rocks, reservoirs and cap rocks, and the tectonic events determined the migration, accumulation, and preservation of the hydrocarbon. The three mega-sequence group cycles, including the early cycle-the Sinian-middle Devonian, the middle cycle-the upper Devonian-Triassic, and the late cycle-the Jurassic-Quaternary, corresponded to three reservoir formation cycles. So, it can be concluded that the local tectonic events controlled both the sequences and the distribution of oil and gas in the Tarim Basin.展开更多
The Middle Proterozoic Chartai Group separated by two unconformities consists of three depositional se-quences: the Shujigou Formation-Zenglongchang Formation (DS Ⅰ), the Agulugou Formation (DS Ⅱ), andthe Liuhongwan...The Middle Proterozoic Chartai Group separated by two unconformities consists of three depositional se-quences: the Shujigou Formation-Zenglongchang Formation (DS Ⅰ), the Agulugou Formation (DS Ⅱ), andthe Liuhongwan Formation (DS Ⅲ). The carbonate platform and back-platform basin are the basic environ-ment model of the Chartai Group. The syndepositional faults on the oceanward side of the carbonate platformand large-scale slumping in the soft sediments are important marks of facies tracts. The newly establishedZenglongchan uplifting, an epeirogenetic uplifting, plays an important role in the formation of thepalaeogeographic framework of the Chartai Group. The stratigraphic correlation between the Chartai Groupand the Bayan Obo Group is made for the first time by using sequence stratigraphic principle and model estab-lished by P.R. Vail. The Chartai Group, which was deposited on the northern passive continental margin of theNorth China platfom, represents the platform cover.展开更多
The relationship between deposition and tectonics of sedimentary basins has been a significant subject in recent years.Using typical rift basins such as the Nanpu Sag as an example,combined with the analysis of the te...The relationship between deposition and tectonics of sedimentary basins has been a significant subject in recent years.Using typical rift basins such as the Nanpu Sag as an example,combined with the analysis of the tectonics-palaeogeomorphology of basins,we undertook a detailed study of the differences of the third-order sequences in different basins,the combination of depositional systems within the sequence framework and the distribution of depocenters and subsidence centers.Our results revealed a significant relationship between the tectonics-palaeogeomorphology of rift basins and the filling styles of sedimentary sequences.The basin structure plays a primary role in controlling the development of the third-order sequences and the boundary of these sequences is easily formed in basins with gentle slopes,shallow water and a small area.The characteristics of the tectonics-palaeogeomorphology of rift basins are dominated by half-grabens of extensional faults,which affect the temporal and spatial combination of sedimentary systems within the sequences as well as the distribution of depocenters and subsidence centers.Based on the development rules of the faults dominating the half-grabens of extensional faults,rift basins are classified into two types： the single fault segmented-linkage type and the multi-fault combination type.The main controlling factors of the temporal and spatial combination of sedimentary systems and the distribution of depocenters and subsidence centers in different basins are different.The characteristics of early segmentation and later linkage of the faults play a critical role in controlling the sedimentary system combination within the sequence framework and the temporal and spatial differences of depocenters and subsidence centers of the single fault segmented-linkage rift basins,while the differences in fault activities are the dominating factors of the multi-fault combination rift basins.展开更多
The Jinshajiang belt, located between the Zhongzan and Qamdo massifs, preserves varied sediments representing different tectonic background. Those sediments outcrop in stratigraphic slices,not in continuous stratigrap...The Jinshajiang belt, located between the Zhongzan and Qamdo massifs, preserves varied sediments representing different tectonic background. Those sediments outcrop in stratigraphic slices,not in continuous stratigrapky. The stratigraphic slices of the passive continental margin are investigated by geologic mapping in Tuediug-Xiaruo, Northwestern Yunnan Province, and each of these slices is researched in age and sedimeutary environment. The stratigraphic successions of the passive continental margin are reconstructed. On the basis or new sequence, the evolutional history of the passive continental margin is divided into four stages: rift basin (D,-C,), complex continental margin basin (P1 ), residual hasin (P2-T2) and synorogenic basin (T3).展开更多
To the south of Manzhouli,Hulunbuir,Inner Mongolia,experienced a tectonic regime transformation from compression to extension in the mid-Mesozoic.Based on systematic research of the volcanics,petrology,volcanic facies...To the south of Manzhouli,Hulunbuir,Inner Mongolia,experienced a tectonic regime transformation from compression to extension in the mid-Mesozoic.Based on systematic research of the volcanics,petrology,volcanic facies,chronology and geochemistry of rocks in the Buridun area,two stages of volcanics are identified.The first stage named the trachyte series was formed in the late Middle Jurassic(167-163 Ma),its eruption rhythm is pyroxene trachyandesite-trachyandesite-trachyte,and its origin rock is basic volcanics from thickened lower crust,with a tectonic setting in the collision orogeny after the closure of the Mongolia Okhotsk Ocean(MOO).The second stage is a bimodal volcanic rock,formed in the early Late Jurassic(163-160 Ma).The eruption rhythm of basic volcanics in this stage is basaltic andesite-basalt-olivine basalt,which comes from the metasomatized lithospheric mantle,the acidic volcanics of which being characterized by the eruption rhythm of sedimentary-explosive-overflow facies,which came from the partial melting of newly formed lower crust,and this shows the characteristics of A-type granite;the tectonic setting is extension of the lithosphere after collision and closure of the MOO.The changes in the formation age and tectonic setting of the two stages of volcanics demonstrate that the transition time from the compressive system to the extensional system south of Manzhouli is about 163 Ma.展开更多
Based on 294 earthquake sequences with magnitude greater than or equal to 5.0 occurred in Chinese mainland since 1970, the spatial distribution features of sequence types have been studied. In southwestern China, it t...Based on 294 earthquake sequences with magnitude greater than or equal to 5.0 occurred in Chinese mainland since 1970, the spatial distribution features of sequence types have been studied. In southwestern China, it takes mainshock-aftershock sequence type （MAT） as the major in Chuan-Dian rhombic block and concerned Xianshuihe-Anninghe-Xiaojiang seismic belt, as well as in Jinshajiang-Honghe seismic belt. Multiple mainshock type （MMT） mainly distributes in western Yunnan, and Longlin and Lancang areas in Tengchong-Baoshan block in west of Nujiang-Lancangjiang fault zone. A few isolated earthquake type （IET） mainly occurred in northwestern Sichuan and there is no IET occurred in Yunnan region. In northwestern China, it takes mainshock-aftershock sequence type （MAT） as the major in west segment of South Tianshan in Xinjiang region. Some MMT also occurred in this area in the intersection of Kalpin block and the Puchang fault zone. It takes IET as the major in middle Tianshan in Xinjiang. Along the Qilianshan seismic belt, most of sequences are MAT. In Qinghai region, it takes MAT as the major, but the regional feature of the spatial distribution of sequence types is not very clear. In North China, it takes MAT as the major in Yinshan-Yanshan-Bohai seismic belt, north edge of North China, and in Hebei plain seismic belt, as well as in sub-plate of lower river area of Yangtze River. In intersection of north segment of Shanxi seismic belt and the NW-trending Yinshan-Yanshan-Bohai seismic belt, there are several moderate or strong MMT with magnitude from 5.0 to 6.0 occurred. In south of North China around the latitude line of 35°N, it takes IET as the major. The spatial distribution of sequence types is relevant to the patterns of tectonic movements. MAT is mostly produced by the ruptures of locked units or asperities or the neonatal separating segments inside the fault zones. MMT is generally relevant to the conjugate structures or intersection of many tectonic settings. Further extension of simple fault often produces IET. Spatial distribution of sequence types is also correlative to the regional and deep environment of crustal medium to some extent. MAT mainly distributes in high velocity area in upper crust or in the transition zone between high velocity area and low velocity area, MMT mostly occurred in the low velocity area in upper crust.展开更多
The western Qinling （秦岭） orogenic belt is one of the outermost ranges in the northeas- tern Tibetan Plateau. Its tectonic uplift history is therefore essential to insight on the evolution history of the plateau. H...The western Qinling （秦岭） orogenic belt is one of the outermost ranges in the northeas- tern Tibetan Plateau. Its tectonic uplift history is therefore essential to insight on the evolution history of the plateau. However, the timing of deformation and uplift history is still poorly known. Fortunately, its Cenozoic orogenic history is recorded in an excellent synorogenic sedimentary sequence exposed in the Tianshui （天水）Ba- sin, the northeastern foot of western Qinling. Ac- cording to sedimentary-tectonic analysis of the Yaodian （尧店） and Lamashan （喇嘛山） sections based on the previous magnetostratigraphy stu- dies, we speculated that two stages （occurred at 9.2-7.4 and -3.6 Ma） of variation in depositional facies were attributed to the uplift and deforma- tion of the western Qinling, and the modern structure geomorphic frame of the northeastern Tibet formed after 2.6 Ma. Furthermore, four stages of active processes along the western Qinling occurred at 49--41, 34-27, 25-19 and -13 Ma, are deciphered from an integrated detrital apatite fission-track data of the Ganquan （甘泉）, Yaodian main sections and seven small ones. The former two are represents the exhumation episodes triggered by tectonism and the others attributed to the volcanic signals.展开更多
Based on the case history study of sequence stratigraphic framework,sequence model,and the controlling factors on sequence formation in the southern Junggar foreland basin,a contrasting comparison of the characteristi...Based on the case history study of sequence stratigraphic framework,sequence model,and the controlling factors on sequence formation in the southern Junggar foreland basin,a contrasting comparison of the characteristics among the foreland basin,the faulted basin,and the sag basin is made in the aspects of sequence architecture,filling style,the controlling factors on sequence development,the migrations of basin center and depocenter,etc..The current study results show that there are major differences and these are documented as follows.（1） The accommodation space in foreland basin is mainly created by the subsidence caused by thrusting and napping in the foothill belt,resulting in progradational-dominated parasequence sets in the foothill area and retrogradational parasequence sets in the ramp region.（2） The accommodation space in an open-lake system in faulted basin is mainly created by the activities of the basin margin faults;thus,tectonic sequences are formed.However,in the closed-lake system,the subaqueous accommodation is mainly controlled by climatic-influenced lake-level fluctuations,and climatic sequence is formed.（3） In sag basin,a closed-lake system is easily formed due to its generation often within the cratons and isolation from the sea,and its accommodation space creation is mainly controlled by climatic lake-level fluctuations;thus,the sequence architecture in sag basin is similar to that formed on the passive continental margin.展开更多
The kinematics and dynamics of plate tectonics are frontal subjects in geosciences and the strong earthquake occurred along the plate boundary result directly from plate movement. By analyzing Ibaraki earthquake seque...The kinematics and dynamics of plate tectonics are frontal subjects in geosciences and the strong earthquake occurred along the plate boundary result directly from plate movement. By analyzing Ibaraki earthquake sequence, it has been found that the focal fault plane shows a special image of grading expansion along the direction of strike and adjustment along the dip direction respectively. With the consideration of strike, dip and slip directions of focal mechanism, we have confirmed that Ibaraki earthquake belongs to a thrust fault earthquake occurred under the Japan Trench. The cause of the earthquake sequence is discussed in the paper. The study on the temporal-spatial distribution of the earthquake sequence with a time-scale between the year-scale spatial geodetic data and the second-scale moment tensor of the strong earthquake has indicated the dynamic process of Pacific Plate subduction under the Eurasia Plate. According to the average slip distance of earthquake and the velocity of plate movement, it is predicted that a strong earthquake might occur in recent years.展开更多
The Outangdi Formation in Jiangshan, Zhejiang, is the mixing deposit of terrigenous clastics and carbonates in Weiningian of the late Carboniferous. The mixing deposits include interbeddings, which constitute a series...The Outangdi Formation in Jiangshan, Zhejiang, is the mixing deposit of terrigenous clastics and carbonates in Weiningian of the late Carboniferous. The mixing deposits include interbeddings, which constitute a series of alternated clastic and carbonate beds and mixing within the same bed which forms ＂hunji rock＂. The Outangdi Formation has the features of intercalated marine and terrestrial deposits with the progradational sequences, which are lower fine and upper coarse sedimentary granularity in the section. Hunji rock is formed in a seashore environment. It is a mixed carbonate sediment found in beaches or tideland facies with quartz sand taken from a bayou or beach by coastwise flow and circumfluence. There are two kinds of hunji sequences： （1） interbeds of sandstone and carbonate rock in seashore environments; and （2） interbeds of clastics in river facies and carbonate rock in ocean facies. It is indicated that mixing depositions belong to ＂facies mixing＂, affected mainly by regional tectonic uplift, rise of the global sea level, and the dynamics of water medium in the basin. Regional sea level periodic changes and progradational sequences probably resulted from the intense uplift of the old land called Cathaysia. The classification and name of mixed sediments are also discussed in the present study. Interbeds and alternated beds of clastic and carbonate beds are named ＂hunji sequence＂, a new genetic term. It is suggested that hunji rock means a special sediment event of mixing terrigenous clastics and carbonates instead of a name of a specific rock.展开更多
The Yitong graben is located in the northeastern segment of the Tertiary rift system in East China. The graben is bounded by a steep dipping transform fault on the northwestern side and subparallel normal faults on t...The Yitong graben is located in the northeastern segment of the Tertiary rift system in East China. The graben is bounded by a steep dipping transform fault on the northwestern side and subparallel normal faults on the southeastern side, with very thick marginal fan complexes indicating syntectonic sedimentation. The graben is infilled with Tertiary sediments up to 6 000 m thick, in which a series of different scaled hiatuses and tectonic inversion events have been discerned during hydrocarbon exploration. According to regional and local conformities, the basin infill may be divided into three tectonic sequences, among which the major sequence TS2 is further subdivided into three sequence sets and fourteen subsequences. Based on the sequence stratigraphic framework, depositional system tracts which are characterized by marginal fan complexes on both sides of basin and deep or shallow lacustrine deposits in the central part are reconstructed. The subsidence curves show that the graben had undergone several rapid subsidence episodes, which is interpreted to have been caused by multiple stretching of the lithosphere. Integrative analysis of the depositional structural features shows that the regional tectonic stress system experienced a transformation from dextral transformational shear through thermal subsidence to sinistral compressional shear with a general extensional setting. Extension and wrenching dominated the graben evolution and affected the depositional style in different evolutionary stages, the spatial configuration of depositional system and its relationship with unconformities. The conclusions have been applied with some successes to studying the reservoir and hydrocarbon source rock distribution and lithologic stratigraphic traps in this basin.展开更多
Jurassic deposition was extensively developed in the northern Qaidam basin.According to sequence stratigraphical analysis of outcrops,the Jurassic profile in the Dameigou area can be divided into 6 sequences.Sequences...Jurassic deposition was extensively developed in the northern Qaidam basin.According to sequence stratigraphical analysis of outcrops,the Jurassic profile in the Dameigou area can be divided into 6 sequences.Sequences 1 and 4 consist of lowstand,water transgression and highstand systems tracts,and sequences 2,3 and 5 consist of lowstand and transgression systems tracts.However,sequence 6 only consists of a lowstand systems tract.The development of depositional sequences is controlled by lake level changes and basement faulting,which continued to be active in the Jurassic. The result of sedimentary－ tectonic evolution research indicates that the Qaidam Basin is a fault subsidence.This kind of basin framework determined that the coal－ forming environment would occur on the north side of the northern boundary fault of the Qaidam Basin and on the south side of the Lingjian fault, and the source rock would develop in the central subsidence belt between the two faults.展开更多
The continent of China is grouped into Pan-Cathaysian blocks,Laurasia and Gondwana Continental margins and relics of three oceans-Paleoasian,Tethys,and Pacific as a whole.In detail,the continent of China grew up by co...The continent of China is grouped into Pan-Cathaysian blocks,Laurasia and Gondwana Continental margins and relics of three oceans-Paleoasian,Tethys,and Pacific as a whole.In detail,the continent of China grew up by coalescence of three blocks or platforms (North China,Tarim and Yangtze)and eight orogenic belts (Altay-Inner Mongolia-Daxinganling,Tianshan-Junggar-Beishan,Qinling-Qilian- Kunlun,Qiangtang-Sanjiang,Gangdise,Himalaya,Cathaysia,Eastern Taiwan)during the processes of oceanic crust disappearance and acceretionary-collision of continental crusts.In the orogenic belts,six convergent crustal consumption zones (Ertix-Xar Moron,South Tianshan,Kuanping-Foziling,Bangong co-Shuanghu-Nujiang-Changning-Menglian,Yarlung-Tsangpo,Jiangshao-Chenzhou-Qinfang)have been distinguished.Correspondingly,the strata of the continent of China are subdivided into 17 tectonicstrata superregions,which tectonically belong to three blocks or platforms,six convergent crustal consumption zones and eight orogenic series,respectively.This division is based mainly on differences of tectonic environment and tectonic evolution among blocks,zones and belts,including the timing of when the oceanic crusts transferred into continental crusts,the paleobiogeographic features,and the types of strata.展开更多
Using the moment tensor inversion method, we calculate the focal mechanisms of the aftershock sequence of the Ms=6.1 Lulong earthquake occurred on October 19, 1982 in Hebei Province. We found that the pressure axis in...Using the moment tensor inversion method, we calculate the focal mechanisms of the aftershock sequence of the Ms=6.1 Lulong earthquake occurred on October 19, 1982 in Hebei Province. We found that the pressure axis in Lulong basin is nearly in the east-west direction with an azimuth of N74°E. However, in the north of the basin the stress axis changes to N43°E; and in some places near the center of the basin it changes to the northwest that is almost perpendicular to the P axis obtained by us from those events around the basin. This feature illuminates that in Lulong earthquake sequence, the stress direction is different in different parts of crustal structure, which shows that the tectonic movement in Lulong region is complex. This is because that Lulong is located in the eastern part of Chinese mainland and is subject to the compression of Japanese Sea Basin driven by the Pacific Plate. On the other hand, nipped by the Yanshan and North China blocks, Lulong is obviously restricted by the block boundaries.展开更多
The marine Paleogene at Gangba, south Tibet is characterized by shallow water deposits and in vertical succession shows a clear facies change from fluvial plain through carbonate platform to retro-platform mud flat. F...The marine Paleogene at Gangba, south Tibet is characterized by shallow water deposits and in vertical succession shows a clear facies change from fluvial plain through carbonate platform to retro-platform mud flat. From the bottom of Danian to Upper Priabonian, nine 3rd -order depositional sequences are recognized, which in turn make up four supersequences and constitute two clear transgression-regression cycles. These requences were developed in a tectonic setting of strong compression resulted from the collision between the Indian and Eurasian plates. Between the Paleocene and Eocene, there exists an important hiatus that has consumed at least 5.5 Ma of deposition. This unconformity is thought to be created by the basement uplift coupled with eustatic fall and marks the basin transformation from epicontinental sea to remnant hay. The rapid basement subsidence and relative sea level rise in Late Eocene are thought to be caused by the loading flexure of the Eurasian continent onto the Indian plate, which resulted in the southward migration of depocenter in the epoch.展开更多
Nan'an Basin is a giant hydrocarbon basin,but its tectonic division scheme and associated fault systems has not been well understood.Based on newly acquired seismic data from the southwestern margin of the South C...Nan'an Basin is a giant hydrocarbon basin,but its tectonic division scheme and associated fault systems has not been well understood.Based on newly acquired seismic data from the southwestern margin of the South China Sea,this study analyzed the structural units,tectonic feature and geodynamics of the sedimentary basin.The new data suggests that the Nan0 an Basin is a rift basin oriented in the NE-SW direction,rather than a pull-apart basin induced by strike-slip faults along the western margin.The basin is a continuation of the rifts in the southwest South China Sea since the late Cretaceous.It continued rifting until the middle Miocene,even though oceanic crust occurred in the Southwest Subbasin.However,it had no transfer surface at the end of spreading,where it was characterized by a late middle Miocene unconformity(reflector T3).The Nan'an Basin can be divided into eight structural units by a series of NE-striking faults.This study provides evidences to confirm the relative importance and interplay between regional strike-slips and orthogonal displacement during basin development and deformation.The NE-SW-striking dominant rift basin indicates that the geodynamic drivers of tectonic evolution in the western margin of the South China Sea did not have a large strike-slip mechanism.Therefore,we conclude that a large strike-slip fault system did not exist in the western margin of the South China Sea.展开更多
Studies on outcrop-scale structures have been conducted at the Garba complex. This study aims to add the high-resolution of the South Sumatra region to reconstruct the structural geology and implications of tectonics ...Studies on outcrop-scale structures have been conducted at the Garba complex. This study aims to add the high-resolution of the South Sumatra region to reconstruct the structural geology and implications of tectonics for the region. The study area is commonly referred to as crystalline basement highs forming the southwestern boundary of the Paleogene South Sumatra basin. The structures commonly show the NW-SE, NNW-SSE, and ENE-WSW trends. The methodology used includes field mapping, analysis of Digital Elevation Model (DEM), petrography, and X-ray fluorescence (XRF). The major fractures include wrench slip, reverse, and normal faults, while the observable microstructures comprise pull-apart calcite veins, shear joints, boudins, parasitic folds, and the augens. The earlier structuring episode was probably related to crustal extension, perhaps associated with the Paleogene rifting that occurred along the western margin of Sundaland. In the Late Neogene, tectonic compression took place in the entire region, allowing inversion of the Pre-Tertiary sequence. As compression waned in the Pleistocene, extension commenced, and a number of the ENE-WSW tensional block faulting developed and intersected the older NNW-SSE alignments. It is important to note that the latest tectonic event in conjunction with deep erosional denudation had likely exhumed the terrain and eventually shaped the present-day fractured and rough landforms in the study area.展开更多
This paper deals with indirect effects of major impacting throughout the Early Paleozoic resp. with those of super plume activity during the Early Cretaceous, both applied to the siliciclastic series of Jordan deposit...This paper deals with indirect effects of major impacting throughout the Early Paleozoic resp. with those of super plume activity during the Early Cretaceous, both applied to the siliciclastic series of Jordan deposited on the Arabian Platform, Arabian Plate. Its focus is mainly directed on gases released by both processes (CO2, SO2, NOx, HCl, HF) and the relating acids, challenged by experiments and microscopic analysis of grain mounts and thin sections that reveal chemical instability of quartz and ultrastable heavy minerals (i.e. tourmaline) under high acidity (pH °C - 90°C). According to Lopatin’s Time/Temperatur-Index the Lower Cambrian reached the onset of hydrocarbon generation (liquid window) during the Lower Early Cretaceous. Unstable heavy minerals (apatite, garnet, hornblende, epidote, zoisite/clinozoisite) are generally absent in quartz arenites while in arkosic sandstones of marine environment carbonate cement and primary clay minerals (illite) provide conservation. As known since the eighties, the K/T-event’s indirect effects had global influence on Earth’s surface sediments and atmospheric chemistry by wildfires, hot whirl storms, acidic “sturz rain”, dust, soot, darkness, loss of photosynthesis, toxic metals, gases and relating acids. All of them are here concerned and applied to major impacting throughout the Early Paleozoic using the impact data of Price (2001);while superplume volcanism during Cretaceous led to the opening of the South Atlantic accompanied by the cyclic outflow of the Para?a/Etendeka Flood Basalts and relating gases in a gigantic scale (137 - 127 Ma). Assuming that the gases cause similar global effects on Earth’s surface sediments, an according result may be expected in form of quartz arenites and their sequence-analytical patterns (cyclic SBs, MFSs).*展开更多
基金supported by National Science Foundation of China(41574047)National Key R&D Program of China(2018YFC150330501)
文摘To reveal the geometry of the seismogenic structure of the Aug. 8, 2017 M_S 7.0 Jiuzhaigou earthquake in northern Sichuan,data from the regional seismic network from the time of the main event to Oct. 31, 2017 were used to relocate the earthquake sequence by the tomoDD program, and the focal mechanism solutions and centroid depths of the M_L ≥ 3.5 events in the sequence were determined using the CAP waveform inversion method. Further, the segmental tectonic deformation characteristics of the seismogenic faults were analyzed preliminarily by using strain rosettes and areal strains(As). The results indicate:(1) The relocated M_S 7.0 Jiuzhaigou earthquake sequence displays a narrow ～ 38 km long NNW-SSE-trending zone between the NW-striking Tazang Fault and the nearly NSstriking Minjiang Fault, two branches of the East Kunlun Fault Zone. The spatial distribution of the sequence is narrow and deep for the southern segment, and relatively wide and shallow for the northern segment. The initial rupture depth of the mainshock is 12.5 km, the dominant depth range of the aftershock sequence is between 0 and 10 km with an average depth of 6.7 km. The mainshock epicenter is located in the middle of the aftershock region, showing a bilateral rupture behavior. The centroid depths of 32 M_L ≥ 3.5 events range from 3 to 12 km with a mean of about 7.3 km, consistent with the predominant focal depth of the whole sequence.(2) The geometric structure of the seismogenic fault on the southern section of the aftershock area(south of the mainshock) is relatively simple, with overall strike of ～150° and dip angle ～75°, but the dip angle and dip-orientation exhibit some variation along the segment. The seismogenic structure on the northern segment is more complicated; several faults, including the Minjiang Fault, may be responsible for the aftershock activities. The overall strike of this section is ～159° and dip angle is ～59°, illustrating a certain clockwise rotation and a smaller dip angle than the southern segment. The differences between the two segments demonstrate variation of the geometric structure along the seismogenic faults.(3) The focal mechanism solutions of 32 M_L ≥ 3.5 events in the earthquake sequence have obvious segmental characteristics. Strike-slip earthquakes are dominant on the southern segment, while 50% of events on the northern segment are thrusting and oblique thrusting earthquakes, revealing significant differences in the kinematic features of the seismogenic faults between the two segments.(4) The strain rosettes for the mainshock and the entire sequence of 31 M_L ≥ 3.5 aftershocks correspond to strike-slip type with NWW-SEE compressional white lobes and NNE-SSW extensional black lobes of nearly similar size. The strain rosette and As value of the entire sequence of 22 M_L ≥ 3.5 events on the southern segment are the same as those of the M_S 7.0 mainshock,indicating that the tectonic deformation here is strike-slip. However, the strain rosette of the entire sequence of 10 M_L ≥ 3.5 events on the northern segment show prominent white compressional lobes and small black extensional lobes, and the related As value is up to 0.52,indicating that the tectonic deformation of this segment is oblique thrusting with a certain strike-slip component. Differences between the two segments all reveal distinctly obvious segmental characteristics of the tectonic deformation of the seismogenic faults for the Jiuzhaigou earthquake sequence.
基金support from the National Natural Science Foundation of China (Grant No.40872077)National Major Science and Technology Project of China (Grant No. 2011ZX05009-002)Open Project Foundation of Ministry of Education Key Laboratory of Tectonics and Petroleum Resources (Grant No. TPR-2011-09)
文摘The sequence stratigraphy framework of Paleogene of Qikou Sag has been built in this paper. The evolution law of episodic subsidence in Qikou Sag has been expounded, with the analysis of the characteristic of sequence thickness, as well as the study of consedimental tectonic activity, subsidence history, paleogeomorphology and the coupling relationship among them. The faults controlling action was the dominant mechanism during rifting stage I , as the depression was the dominant mechanism during rifting stage III, which embodies a process from intense disparity fault depression to integral subsidence. Meanwhile, under the control of regional faulting and later stage depression, subsidence rate centers and paleogeomorphic concave centers are always corresponding to the sequence thickness centers, and the changes of subsidence centers and paleogeomorphology concave centers are consistent with the migration of thickness centers, which presents the restriction, coupling and response among them and clarifies the law that tectonic activity controls the basin fill by means of controlling the subsidence rate and paleogeomorphology from contributing factor angle. On this basis, the dynamic evolution of the composite pattern of structure-subsidence-deposition in the fault controlling actic region during the three rifting stages and their petroleum geological significance has been discussed.
文摘Various orders of sequences were recognized in the Tarim Basin from unconformities. Three mega-sequence groups, six mega-sequences, sixteen super-sequences and forty-two sequences were determined from the Sinian to the Quaternary. The mega-sequences and super-sequences were in accordance with the locally tectonic events occurring in both the north and the south margins of the Tarim plate. The global sea level changes only worked to control formations in the tectonically stable periods or in the low order sequences. The sequences had close relationship to the source rocks, reservoirs and cap rocks, and the tectonic events determined the migration, accumulation, and preservation of the hydrocarbon. The three mega-sequence group cycles, including the early cycle-the Sinian-middle Devonian, the middle cycle-the upper Devonian-Triassic, and the late cycle-the Jurassic-Quaternary, corresponded to three reservoir formation cycles. So, it can be concluded that the local tectonic events controlled both the sequences and the distribution of oil and gas in the Tarim Basin.
文摘The Middle Proterozoic Chartai Group separated by two unconformities consists of three depositional se-quences: the Shujigou Formation-Zenglongchang Formation (DS Ⅰ), the Agulugou Formation (DS Ⅱ), andthe Liuhongwan Formation (DS Ⅲ). The carbonate platform and back-platform basin are the basic environ-ment model of the Chartai Group. The syndepositional faults on the oceanward side of the carbonate platformand large-scale slumping in the soft sediments are important marks of facies tracts. The newly establishedZenglongchan uplifting, an epeirogenetic uplifting, plays an important role in the formation of thepalaeogeographic framework of the Chartai Group. The stratigraphic correlation between the Chartai Groupand the Bayan Obo Group is made for the first time by using sequence stratigraphic principle and model estab-lished by P.R. Vail. The Chartai Group, which was deposited on the northern passive continental margin of theNorth China platfom, represents the platform cover.
文摘The relationship between deposition and tectonics of sedimentary basins has been a significant subject in recent years.Using typical rift basins such as the Nanpu Sag as an example,combined with the analysis of the tectonics-palaeogeomorphology of basins,we undertook a detailed study of the differences of the third-order sequences in different basins,the combination of depositional systems within the sequence framework and the distribution of depocenters and subsidence centers.Our results revealed a significant relationship between the tectonics-palaeogeomorphology of rift basins and the filling styles of sedimentary sequences.The basin structure plays a primary role in controlling the development of the third-order sequences and the boundary of these sequences is easily formed in basins with gentle slopes,shallow water and a small area.The characteristics of the tectonics-palaeogeomorphology of rift basins are dominated by half-grabens of extensional faults,which affect the temporal and spatial combination of sedimentary systems within the sequences as well as the distribution of depocenters and subsidence centers.Based on the development rules of the faults dominating the half-grabens of extensional faults,rift basins are classified into two types： the single fault segmented-linkage type and the multi-fault combination type.The main controlling factors of the temporal and spatial combination of sedimentary systems and the distribution of depocenters and subsidence centers in different basins are different.The characteristics of early segmentation and later linkage of the faults play a critical role in controlling the sedimentary system combination within the sequence framework and the temporal and spatial differences of depocenters and subsidence centers of the single fault segmented-linkage rift basins,while the differences in fault activities are the dominating factors of the multi-fault combination rift basins.
文摘The Jinshajiang belt, located between the Zhongzan and Qamdo massifs, preserves varied sediments representing different tectonic background. Those sediments outcrop in stratigraphic slices,not in continuous stratigrapky. The stratigraphic slices of the passive continental margin are investigated by geologic mapping in Tuediug-Xiaruo, Northwestern Yunnan Province, and each of these slices is researched in age and sedimeutary environment. The stratigraphic successions of the passive continental margin are reconstructed. On the basis or new sequence, the evolutional history of the passive continental margin is divided into four stages: rift basin (D,-C,), complex continental margin basin (P1 ), residual hasin (P2-T2) and synorogenic basin (T3).
基金financially supported by the Geological Survey program of China Geological Survey(Grant Nos.DD20189613,12120115031301)National Key Research and Development Program of China(Grant No.2019YFC0605202)。
文摘To the south of Manzhouli,Hulunbuir,Inner Mongolia,experienced a tectonic regime transformation from compression to extension in the mid-Mesozoic.Based on systematic research of the volcanics,petrology,volcanic facies,chronology and geochemistry of rocks in the Buridun area,two stages of volcanics are identified.The first stage named the trachyte series was formed in the late Middle Jurassic(167-163 Ma),its eruption rhythm is pyroxene trachyandesite-trachyandesite-trachyte,and its origin rock is basic volcanics from thickened lower crust,with a tectonic setting in the collision orogeny after the closure of the Mongolia Okhotsk Ocean(MOO).The second stage is a bimodal volcanic rock,formed in the early Late Jurassic(163-160 Ma).The eruption rhythm of basic volcanics in this stage is basaltic andesite-basalt-olivine basalt,which comes from the metasomatized lithospheric mantle,the acidic volcanics of which being characterized by the eruption rhythm of sedimentary-explosive-overflow facies,which came from the partial melting of newly formed lower crust,and this shows the characteristics of A-type granite;the tectonic setting is extension of the lithosphere after collision and closure of the MOO.The changes in the formation age and tectonic setting of the two stages of volcanics demonstrate that the transition time from the compressive system to the extensional system south of Manzhouli is about 163 Ma.
基金Joint Seismological Science Foundation of China (105076) and continued subject ″Statistic Features of Aftershock Sequences and Forecast of the Large Aftershocks″ (2004BA601B01-04-02), Ministry of Science and Technology of China in the 10th Five-Year Plan.
文摘Based on 294 earthquake sequences with magnitude greater than or equal to 5.0 occurred in Chinese mainland since 1970, the spatial distribution features of sequence types have been studied. In southwestern China, it takes mainshock-aftershock sequence type （MAT） as the major in Chuan-Dian rhombic block and concerned Xianshuihe-Anninghe-Xiaojiang seismic belt, as well as in Jinshajiang-Honghe seismic belt. Multiple mainshock type （MMT） mainly distributes in western Yunnan, and Longlin and Lancang areas in Tengchong-Baoshan block in west of Nujiang-Lancangjiang fault zone. A few isolated earthquake type （IET） mainly occurred in northwestern Sichuan and there is no IET occurred in Yunnan region. In northwestern China, it takes mainshock-aftershock sequence type （MAT） as the major in west segment of South Tianshan in Xinjiang region. Some MMT also occurred in this area in the intersection of Kalpin block and the Puchang fault zone. It takes IET as the major in middle Tianshan in Xinjiang. Along the Qilianshan seismic belt, most of sequences are MAT. In Qinghai region, it takes MAT as the major, but the regional feature of the spatial distribution of sequence types is not very clear. In North China, it takes MAT as the major in Yinshan-Yanshan-Bohai seismic belt, north edge of North China, and in Hebei plain seismic belt, as well as in sub-plate of lower river area of Yangtze River. In intersection of north segment of Shanxi seismic belt and the NW-trending Yinshan-Yanshan-Bohai seismic belt, there are several moderate or strong MMT with magnitude from 5.0 to 6.0 occurred. In south of North China around the latitude line of 35°N, it takes IET as the major. The spatial distribution of sequence types is relevant to the patterns of tectonic movements. MAT is mostly produced by the ruptures of locked units or asperities or the neonatal separating segments inside the fault zones. MMT is generally relevant to the conjugate structures or intersection of many tectonic settings. Further extension of simple fault often produces IET. Spatial distribution of sequence types is also correlative to the regional and deep environment of crustal medium to some extent. MAT mainly distributes in high velocity area in upper crust or in the transition zone between high velocity area and low velocity area, MMT mostly occurred in the low velocity area in upper crust.
基金supported by the "Strategic Priority ResearchProgram" of the Chinese Academy of Sciences (No.XDB03020402)the National Basic Research Program (973) of China (No. 2013CB956403)+2 种基金the National Natural Science Foundation of China (Nos. 41201005, 41272128)the Funda-mental Research Funds for the Central Universities (No.lzujbky-2013-122)the NSFC National Innovative ResearchTeam Project (No. 41021091)
文摘The western Qinling （秦岭） orogenic belt is one of the outermost ranges in the northeas- tern Tibetan Plateau. Its tectonic uplift history is therefore essential to insight on the evolution history of the plateau. However, the timing of deformation and uplift history is still poorly known. Fortunately, its Cenozoic orogenic history is recorded in an excellent synorogenic sedimentary sequence exposed in the Tianshui （天水）Ba- sin, the northeastern foot of western Qinling. Ac- cording to sedimentary-tectonic analysis of the Yaodian （尧店） and Lamashan （喇嘛山） sections based on the previous magnetostratigraphy stu- dies, we speculated that two stages （occurred at 9.2-7.4 and -3.6 Ma） of variation in depositional facies were attributed to the uplift and deforma- tion of the western Qinling, and the modern structure geomorphic frame of the northeastern Tibet formed after 2.6 Ma. Furthermore, four stages of active processes along the western Qinling occurred at 49--41, 34-27, 25-19 and -13 Ma, are deciphered from an integrated detrital apatite fission-track data of the Ganquan （甘泉）, Yaodian main sections and seven small ones. The former two are represents the exhumation episodes triggered by tectonism and the others attributed to the volcanic signals.
基金supported by the National Science and Technology Major Project (Nos. 2011ZX05003-002 and 2011ZX05009-003-01)the National Basic Research Program of China (No. 2006CB202302)
文摘Based on the case history study of sequence stratigraphic framework,sequence model,and the controlling factors on sequence formation in the southern Junggar foreland basin,a contrasting comparison of the characteristics among the foreland basin,the faulted basin,and the sag basin is made in the aspects of sequence architecture,filling style,the controlling factors on sequence development,the migrations of basin center and depocenter,etc..The current study results show that there are major differences and these are documented as follows.（1） The accommodation space in foreland basin is mainly created by the subsidence caused by thrusting and napping in the foothill belt,resulting in progradational-dominated parasequence sets in the foothill area and retrogradational parasequence sets in the ramp region.（2） The accommodation space in an open-lake system in faulted basin is mainly created by the activities of the basin margin faults;thus,tectonic sequences are formed.However,in the closed-lake system,the subaqueous accommodation is mainly controlled by climatic-influenced lake-level fluctuations,and climatic sequence is formed.（3） In sag basin,a closed-lake system is easily formed due to its generation often within the cratons and isolation from the sea,and its accommodation space creation is mainly controlled by climatic lake-level fluctuations;thus,the sequence architecture in sag basin is similar to that formed on the passive continental margin.
文摘The kinematics and dynamics of plate tectonics are frontal subjects in geosciences and the strong earthquake occurred along the plate boundary result directly from plate movement. By analyzing Ibaraki earthquake sequence, it has been found that the focal fault plane shows a special image of grading expansion along the direction of strike and adjustment along the dip direction respectively. With the consideration of strike, dip and slip directions of focal mechanism, we have confirmed that Ibaraki earthquake belongs to a thrust fault earthquake occurred under the Japan Trench. The cause of the earthquake sequence is discussed in the paper. The study on the temporal-spatial distribution of the earthquake sequence with a time-scale between the year-scale spatial geodetic data and the second-scale moment tensor of the strong earthquake has indicated the dynamic process of Pacific Plate subduction under the Eurasia Plate. According to the average slip distance of earthquake and the velocity of plate movement, it is predicted that a strong earthquake might occur in recent years.
基金supported by the State Key Laboratory Foundation Project(No.GPMR0508) from the State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences
文摘The Outangdi Formation in Jiangshan, Zhejiang, is the mixing deposit of terrigenous clastics and carbonates in Weiningian of the late Carboniferous. The mixing deposits include interbeddings, which constitute a series of alternated clastic and carbonate beds and mixing within the same bed which forms ＂hunji rock＂. The Outangdi Formation has the features of intercalated marine and terrestrial deposits with the progradational sequences, which are lower fine and upper coarse sedimentary granularity in the section. Hunji rock is formed in a seashore environment. It is a mixed carbonate sediment found in beaches or tideland facies with quartz sand taken from a bayou or beach by coastwise flow and circumfluence. There are two kinds of hunji sequences： （1） interbeds of sandstone and carbonate rock in seashore environments; and （2） interbeds of clastics in river facies and carbonate rock in ocean facies. It is indicated that mixing depositions belong to ＂facies mixing＂, affected mainly by regional tectonic uplift, rise of the global sea level, and the dynamics of water medium in the basin. Regional sea level periodic changes and progradational sequences probably resulted from the intense uplift of the old land called Cathaysia. The classification and name of mixed sediments are also discussed in the present study. Interbeds and alternated beds of clastic and carbonate beds are named ＂hunji sequence＂, a new genetic term. It is suggested that hunji rock means a special sediment event of mixing terrigenous clastics and carbonates instead of a name of a specific rock.
文摘The Yitong graben is located in the northeastern segment of the Tertiary rift system in East China. The graben is bounded by a steep dipping transform fault on the northwestern side and subparallel normal faults on the southeastern side, with very thick marginal fan complexes indicating syntectonic sedimentation. The graben is infilled with Tertiary sediments up to 6 000 m thick, in which a series of different scaled hiatuses and tectonic inversion events have been discerned during hydrocarbon exploration. According to regional and local conformities, the basin infill may be divided into three tectonic sequences, among which the major sequence TS2 is further subdivided into three sequence sets and fourteen subsequences. Based on the sequence stratigraphic framework, depositional system tracts which are characterized by marginal fan complexes on both sides of basin and deep or shallow lacustrine deposits in the central part are reconstructed. The subsidence curves show that the graben had undergone several rapid subsidence episodes, which is interpreted to have been caused by multiple stretching of the lithosphere. Integrative analysis of the depositional structural features shows that the regional tectonic stress system experienced a transformation from dextral transformational shear through thermal subsidence to sinistral compressional shear with a general extensional setting. Extension and wrenching dominated the graben evolution and affected the depositional style in different evolutionary stages, the spatial configuration of depositional system and its relationship with unconformities. The conclusions have been applied with some successes to studying the reservoir and hydrocarbon source rock distribution and lithologic stratigraphic traps in this basin.
文摘Jurassic deposition was extensively developed in the northern Qaidam basin.According to sequence stratigraphical analysis of outcrops,the Jurassic profile in the Dameigou area can be divided into 6 sequences.Sequences 1 and 4 consist of lowstand,water transgression and highstand systems tracts,and sequences 2,3 and 5 consist of lowstand and transgression systems tracts.However,sequence 6 only consists of a lowstand systems tract.The development of depositional sequences is controlled by lake level changes and basement faulting,which continued to be active in the Jurassic. The result of sedimentary－ tectonic evolution research indicates that the Qaidam Basin is a fault subsidence.This kind of basin framework determined that the coal－ forming environment would occur on the north side of the northern boundary fault of the Qaidam Basin and on the south side of the Lingjian fault, and the source rock would develop in the central subsidence belt between the two faults.
基金the Foundation of the Geological Survey of China (DD20160351,121201004000 150013,121201102000150012)the National Key Research and Development Program of China (2016YFC0601005)the National Science Foundation of China (41772107).
文摘The continent of China is grouped into Pan-Cathaysian blocks,Laurasia and Gondwana Continental margins and relics of three oceans-Paleoasian,Tethys,and Pacific as a whole.In detail,the continent of China grew up by coalescence of three blocks or platforms (North China,Tarim and Yangtze)and eight orogenic belts (Altay-Inner Mongolia-Daxinganling,Tianshan-Junggar-Beishan,Qinling-Qilian- Kunlun,Qiangtang-Sanjiang,Gangdise,Himalaya,Cathaysia,Eastern Taiwan)during the processes of oceanic crust disappearance and acceretionary-collision of continental crusts.In the orogenic belts,six convergent crustal consumption zones (Ertix-Xar Moron,South Tianshan,Kuanping-Foziling,Bangong co-Shuanghu-Nujiang-Changning-Menglian,Yarlung-Tsangpo,Jiangshao-Chenzhou-Qinfang)have been distinguished.Correspondingly,the strata of the continent of China are subdivided into 17 tectonicstrata superregions,which tectonically belong to three blocks or platforms,six convergent crustal consumption zones and eight orogenic series,respectively.This division is based mainly on differences of tectonic environment and tectonic evolution among blocks,zones and belts,including the timing of when the oceanic crusts transferred into continental crusts,the paleobiogeographic features,and the types of strata.
基金National Natural Science Foundation of China(40234038)
文摘Using the moment tensor inversion method, we calculate the focal mechanisms of the aftershock sequence of the Ms=6.1 Lulong earthquake occurred on October 19, 1982 in Hebei Province. We found that the pressure axis in Lulong basin is nearly in the east-west direction with an azimuth of N74°E. However, in the north of the basin the stress axis changes to N43°E; and in some places near the center of the basin it changes to the northwest that is almost perpendicular to the P axis obtained by us from those events around the basin. This feature illuminates that in Lulong earthquake sequence, the stress direction is different in different parts of crustal structure, which shows that the tectonic movement in Lulong region is complex. This is because that Lulong is located in the eastern part of Chinese mainland and is subject to the compression of Japanese Sea Basin driven by the Pacific Plate. On the other hand, nipped by the Yanshan and North China blocks, Lulong is obviously restricted by the block boundaries.
文摘The marine Paleogene at Gangba, south Tibet is characterized by shallow water deposits and in vertical succession shows a clear facies change from fluvial plain through carbonate platform to retro-platform mud flat. From the bottom of Danian to Upper Priabonian, nine 3rd -order depositional sequences are recognized, which in turn make up four supersequences and constitute two clear transgression-regression cycles. These requences were developed in a tectonic setting of strong compression resulted from the collision between the Indian and Eurasian plates. Between the Paleocene and Eocene, there exists an important hiatus that has consumed at least 5.5 Ma of deposition. This unconformity is thought to be created by the basement uplift coupled with eustatic fall and marks the basin transformation from epicontinental sea to remnant hay. The rapid basement subsidence and relative sea level rise in Late Eocene are thought to be caused by the loading flexure of the Eurasian continent onto the Indian plate, which resulted in the southward migration of depocenter in the epoch.
基金This research was financially supported by Natural Science Foundation of China(U1701245,No.91228208)CGS project(DD20190213)CNPC project(kt 2021-02-02).
文摘Nan'an Basin is a giant hydrocarbon basin,but its tectonic division scheme and associated fault systems has not been well understood.Based on newly acquired seismic data from the southwestern margin of the South China Sea,this study analyzed the structural units,tectonic feature and geodynamics of the sedimentary basin.The new data suggests that the Nan0 an Basin is a rift basin oriented in the NE-SW direction,rather than a pull-apart basin induced by strike-slip faults along the western margin.The basin is a continuation of the rifts in the southwest South China Sea since the late Cretaceous.It continued rifting until the middle Miocene,even though oceanic crust occurred in the Southwest Subbasin.However,it had no transfer surface at the end of spreading,where it was characterized by a late middle Miocene unconformity(reflector T3).The Nan'an Basin can be divided into eight structural units by a series of NE-striking faults.This study provides evidences to confirm the relative importance and interplay between regional strike-slips and orthogonal displacement during basin development and deformation.The NE-SW-striking dominant rift basin indicates that the geodynamic drivers of tectonic evolution in the western margin of the South China Sea did not have a large strike-slip mechanism.Therefore,we conclude that a large strike-slip fault system did not exist in the western margin of the South China Sea.
文摘Studies on outcrop-scale structures have been conducted at the Garba complex. This study aims to add the high-resolution of the South Sumatra region to reconstruct the structural geology and implications of tectonics for the region. The study area is commonly referred to as crystalline basement highs forming the southwestern boundary of the Paleogene South Sumatra basin. The structures commonly show the NW-SE, NNW-SSE, and ENE-WSW trends. The methodology used includes field mapping, analysis of Digital Elevation Model (DEM), petrography, and X-ray fluorescence (XRF). The major fractures include wrench slip, reverse, and normal faults, while the observable microstructures comprise pull-apart calcite veins, shear joints, boudins, parasitic folds, and the augens. The earlier structuring episode was probably related to crustal extension, perhaps associated with the Paleogene rifting that occurred along the western margin of Sundaland. In the Late Neogene, tectonic compression took place in the entire region, allowing inversion of the Pre-Tertiary sequence. As compression waned in the Pleistocene, extension commenced, and a number of the ENE-WSW tensional block faulting developed and intersected the older NNW-SSE alignments. It is important to note that the latest tectonic event in conjunction with deep erosional denudation had likely exhumed the terrain and eventually shaped the present-day fractured and rough landforms in the study area.
文摘This paper deals with indirect effects of major impacting throughout the Early Paleozoic resp. with those of super plume activity during the Early Cretaceous, both applied to the siliciclastic series of Jordan deposited on the Arabian Platform, Arabian Plate. Its focus is mainly directed on gases released by both processes (CO2, SO2, NOx, HCl, HF) and the relating acids, challenged by experiments and microscopic analysis of grain mounts and thin sections that reveal chemical instability of quartz and ultrastable heavy minerals (i.e. tourmaline) under high acidity (pH °C - 90°C). According to Lopatin’s Time/Temperatur-Index the Lower Cambrian reached the onset of hydrocarbon generation (liquid window) during the Lower Early Cretaceous. Unstable heavy minerals (apatite, garnet, hornblende, epidote, zoisite/clinozoisite) are generally absent in quartz arenites while in arkosic sandstones of marine environment carbonate cement and primary clay minerals (illite) provide conservation. As known since the eighties, the K/T-event’s indirect effects had global influence on Earth’s surface sediments and atmospheric chemistry by wildfires, hot whirl storms, acidic “sturz rain”, dust, soot, darkness, loss of photosynthesis, toxic metals, gases and relating acids. All of them are here concerned and applied to major impacting throughout the Early Paleozoic using the impact data of Price (2001);while superplume volcanism during Cretaceous led to the opening of the South Atlantic accompanied by the cyclic outflow of the Para?a/Etendeka Flood Basalts and relating gases in a gigantic scale (137 - 127 Ma). Assuming that the gases cause similar global effects on Earth’s surface sediments, an according result may be expected in form of quartz arenites and their sequence-analytical patterns (cyclic SBs, MFSs).*
