Tectonic Setting and Nature of the Provenance of Sedimentary Rocks in Lanping Mesozoic-Cenozoic Basin: Evidence from Geochemistry of Sandstones

The geochemical composition of sandstones in the sedimentary basin is controlled mainly by the tectonic setting of the provenance, and it is therefore possible to reveal the tectonic setting of the provenance and the nature of source rocks in terms of the geochemical composition of sandstones. The major elements, rare\|earth elements and trace elements of the Mesozoic\|Cenozoic sandstones in the Lanping Basin are studied in this paper, revealing that the tectonic settings of the provenance for Mesozoic\|Cenozoic sedimentary rocks in the Lanping Basin belong to a passive continental margin and a continental island arc. Combined with the data on sedimentary facies and palaeogeography, it is referred that the eastern part of the basin is located mainly at the tectonic setting of the passive continental margin before Mesozoic, whereas the western part may be represented by a continental island arc. This is compatible with the regional geology data. The protoliths of sedimentary rocks should be derived from the upper continental crust, and are composed mainly of felsic rocks, mixed with some andesitic rocks and old sediment components. Therefore, the Lanping Mesozoic\|Cenozoic Basin is a typical continental\|type basin. This provides strong geochemical evidence for the evolution of the paleo\|Tethys and the basin\|range transition.

Meso-Cenozoic Evolution of the Tanlu Fault and Formation of Sedimentary Basins

Abstract: There are a group of large and medium-scale Meso-Cenozoic petroliferous basins along both sides of the Tanlu fault or within the fault zone, e.g., the Songliao basin, the Bohai Bay basin and the Subei-Yellow Sea basin. As shown by studies of the structural types, sedimentary formations, volcanic activities, tectonic evolution as well as the time-space relationship between the Tanlu fault zone and the basins, the formation and distribution of the basins are controlled by the movement of the Tanlu fault. This paper presents an analysis of the tectono-geometric, kinematic and geodynamic features of the basins on the basis of integrated geological-geophysical data, and an exploration into the internal relations between the fault and the basins as well as the formation mechanism and geodynamic processes of the basins.

Petrochemical Characteristics of the Mesozoic-Cenozoic Volcanic Rock in Huanghua Basin

Based on the data from typical core sampling, combined with K Ar dating, petrochemistry ,trace elemental geochemistry and isotopic compositions of the Mesozoic Cenozoic volcanic rock in the Huanghua basin, Bohai region, the geochemical features of the volcanic rock were studied. The rocks fall into four groups: Cenozoic basalt,Mesozoic late Cretaceous basaltic trachy andesite, Mesozoic late Cretaceous trachy dacite and liparite,and Mesozoic early Triassic dacite. The distribution pattern of the main elemental abundance of late Mesozoic shows a typical bimodal.Chronologically,for the volcanic rock,the amount of SiO 2 decreases gradually,the contents of Fe 2O 3,FeO,CaO,MgO,TiO 2,P 2O 5 and MnO increase little by little.The Cenozoic basalt is derived from the asthenospheric mantle.The late Cretaceous basaltic trachy andesite is derived from the enriched lithospheric mantle.In late Cretaceous and early Palaeogene,the felsic volcanic rock may be derived from fractional melting of the crust.

Mesozoic-Cenozoic Basin Features and Evolution of Southeast China

The Late Triassic to Paleogene （T3-E） basin occupies an area of 143100 km^2, being the sixth area of the whole of SE China; the total area of synchronous granitoid is about 127300 km^2; it provides a key for understanding the tectonic evolution of South China. From a new 1：1500000 geological map of the Mesozoic-Cenozoic basins of SE China, combined with analysis of geometrical and petrological features, some new insights of basin tectonics are obtained. Advances include petrotectonic assemblages, basin classification of geodynamics, geometric features, relations of basin and range. According to basin-forming geodynamical mechanisms, the Mesozoic-Cenozoic basin of SE China can be divided into three types, namely： 1） para-foreland basin formed from Late Triassic to Early Jurassic （T3-J1） under compressional conditions; 2） rift basins formed during the Middle Jurassic （J2） under a strongly extensional setting; and 3） a faulted depression formed during Early Cretaceous to Paleogene （K1-E） under back-arc extension action. From the rock assemblages of the basin, the faulted depression can be subdivided into a volcanic-sedimentary type formed mainly during the Early Cretaceous （K1） and a red -bed type formed from Late Cretaceous to Paleogene （K2-E）. Statistical data suggest that the area of all para-foreland basins （T3-J1） is 15120 km^2, one of rift basins （J2） occupies 4640 km^2, and all faulted depressions equal to 124330 km^2 including the K2-E red-bed basins of 37850 km^2. The Early Mesozoic （T3-J1） basin and granite were mostly co-generated under a post-collision compression background, while the basins from Middle Jurassic to Paleogene （J2-E） were mainly constrained by regional extensional tectonics. Three geological and geographical zones were surveyed, namely： 1） the Wuyishan separating zone of paleogeography and climate from Middle Jurassic to Tertiary; 2） the Middle Jurassic rift zone; and 3） the Ganjiang separating zone of Late Mesozoic volcanism. Three types of basin-granite relationships have been identified, including compressional （a few）, strike-slip （a few）, and extensional （common）. A three-stage geodynamical evolution of the SE-China basin is mooted： an Early Mesozoic basin-granite framework; a transitional Middle Jurassic tectonic regime; intracontinental extension and red-bed faulted depressions since the Late Cretaceous.

Successor Characteristics of the Mesozoic and Cenozoic Songliao Basins

The Songliao basin is a complex successor basin that was initiated in the Mesozoic and experienced multiple periods of reactivation. Based on seismic and drilling data, as well as regional geologic research, we suggest that the Songliao basin contains several different successor basins resting on top of Carboniferous-Permian folded strata forming the basement to the Songliao basin. These basins include the Triassic-Mid Jurassic Paleo-foreland basin, the Late Jurassic-Early Cretaceous downfaulted basin, and an early Cretaceous depressed basin （since the Denglouku Group）. This paper presents a systematic study of the basin-mountain interactions, and reveals that there are different types of prototype basin at different geologic times. These prototype basins sequentially superimposed and formed the large Songliao basin. Discovery of the Triassic-early Middle Jurassic paleo-foreland basin fills a Triassic-early Middle Jurassic gap in the geologic history of the Songliao basin. The paleo- foreland basin, downfaulted basin, and depressed thermal subsidence basin all together represent the whole Mesozoic-Cenozoic geologic history and deformation of the Songliao basin. Discovery of the Triassic-early Middle Jurassic paleo-foreland basin plays an important role both for deep natural gas exploration and the study of basin-mountain coupling in north China and eastern China in general. This example gives dramatic evidence that we should give much more attention to the polyphase tectonic evolution of related basins for the next phase of exploration and study.

Geothermal Regime of Meso-Cenozoic Basins and Their Tectonic Background in East China

? This paper presents a brief analysis of the geothermal fields of Meso-Cenozoic basins and their evolution in East China by means of heat flow, geotemperature gradient, vitrinite reflectence and its gradient in the basins, and reveals a basic framework of the geothermal regime of the basins. The geothermal regime of Meso-Cenozioc basins in East China is mainly dominated by tectonic conditions. The important factor determining the geothermal state of basins is the thickness of lithosphere—burial depth of asthenospheric top, which is related to geodynamic type of basins. Basins in the western zone, represented by Sichuan and Ordos, belong to the flexure basins on the basement of continental block, with thick lithosphere, generally 120-150 km. All basins in this zone fall into middle heat basin type in the light of their lower ancient and present geotemperature gradient. While the middle zone is represented by Songliao and Bohaiwan basins, the continental margin zone is represented by East China Sea shelf basin and northern continental shelf basins of South China Sea. They belong to the extensional basins with thinning lithosphere, the smallest burial depth of paleoasthenospheric top, being 55-60 km. Therefore they should belong to heat basin type. The geothermal state of the basins is correlated positively with extension degree in the majority of basins controlled by dynamic mechanism of extension and transtension.

Stratigraphic Succession,Source-Rock Distribution and Paleoclimatic Zone in Meso-Cenozoic Basins,Eastern China

?The unequal spacetime distribution of the source rocks resulted from the mutual superimposition of the biota evolution, basin type, and paleoclimatic change. The basin type is the most important in controlling the distribution of source rocks. The effect of the paleoclimate on the source rocks varied with different basins. In the rift basin, the source rocks were accumulated in the humid, semihumid and semiarid climates; however, in the flexural basin, only in the humid and semihumid climates. The biota features may control, to a great extent, the distribution pattern and the sourcerock quality. The abundance of the terrestrial flora and lacustrine phytoplankton was essential for the generation of the Meso-Cenozoic source rocks on a large scale.

Evaluation of the Hydrocarbon Potential in the Meso－Cenozoic Basins of South China

The blocks opening to foreign investors for iointly exploring and developing oil and gas involve Jiangsu.Anhui,Zhejiang.Fujian.Hunan.Jiangxi.Yunnan.Guizhuo.Guangxi.Guangdong and Hainan provinces,where the non-marine sedimentary basins each with an area over 200 km'amount to 167 and the total coverage is more than 400 thousand km*.They were formed respectively in early Indosinian.early Y enshanian,late Ye-.nshanian and Himalayan.

Logging interpretation method for reservoirs with complex pore structure in Mesozoic-Cenozoic faulted basin around Daqing exploration area

In Mesozoic-Cenozoic faulted basin in the periphery of Daqing exploration area, the clastic reservoirs mainly consist of siltstone and gravel-bearing sandstone. The electrical conductivity of the reservoirs is complicated due to the complex pore structures, which cannot be accurately interpreted with commonly used model. In order to solve the problem, a three-water model has been applied in this study based on in-depth analysis of the conductive mechanism of rocks in the explored area, and favorable application results are achieved.

Sequence of the Cenozoic Mammalian Faunas of the Linxia Basin in Gansu, China

In the Linxia Basin on the northeast margin of the Tibetan Plateau, the Cenozoic strata are very thick and well exposed. Abundant mammalian fossils are discovered in the deposits from the Late Oligocene to the Early Pleistocene. The Dzungariotherium fauna comes from the sandstones of the Jiaozigou Formation, including many representative Late Oligocene taxa. The Platybelodon fauna comes from the sandstones of the Dongxiang Formation and the conglomerates of the Laogou Formation, and its fossils are typical Middle Miocene forms, such as Hemicyon, Amphicyon, Platybelodon, Choerolophodon, Anchitherium, and Hispanotherium. The Hipparion fauna comes from the red clay of the Liushu and Hewangjia Formations, and its fossils can be distinctly divided into four levels, including three Late Miocene levels and one Early Pliocene level. In the Linxia Basin, the Hipparion fauna has the richest mammalian fossils. The Equus fauna comes from the Wucheng Loess, and it is slightly older than that of the classical Early Pleistocene Nihewan Fauna. The mammalian faunas from the Linxia Basin provide the reliable evidence to divide the Cenozoic strata of this basin and correlate them with European mammalian sequence.

The Cenozoic activities of Yangjiang-Yitongdong Fault: insights from analysis of the tectonic characteristics and evolution processes in western Zhujiang(Pearl) River Mouth Basin

The Yangjiang-Yitongdong Fault (YJF) is an important NW-trending regional fault, which divides the Zhujiang (Pearl) River Mouth Basin (ZRMB) into western and eastern segments. In Cenozoic, the northern continental margin of the South China Sea (SCS) underwent continental rifting, breakup, seafloor spreading and thermal subsidence processes, and the Cenozoic activities of YJF is one part of this series of complex processes. Two long NW-trending multichannel seismic profiles located on both sides of the YJF extending from the continental shelf to Continent-Ocean Boundary (COB) were used to study the tectonic and sedimentary characteristics of western ZRMB. Using the 2D-Move software and back-stripping method, we constructed the balance cross-section model and calculated the fault activity rate. Through the comprehensive consideration of tectonic position, tectonic evolution history, featured structure, and stress analysis, we deduced the activity history of the YJF in Cenozoic. The results showed that the YJF can be divided into two segments by the central uplift belt. From 65 Ma to 32 Ma, the YJF was in sinistral motion as a whole, inherited the preexisting sinistral motion of Mesozoic YJF, in which, the southern part of YJF was mainly in extension activity, controlling the formation and evolution of Yunkai Low Uplift, coupled with slight sinistral motion. From 32 Ma to 23.8 Ma, the sinistral motion in northern part of YJF continued, while the sinistral motion in southern part began to stop or shifted to a slightly dextral motion. After 23.8 Ma, the dextral motion in southern part of YJF continued, while the sinistral motion in northern part of YJF gradually stopped, or shifted to the slightly dextral motion. The shift of the YJF strike-slip direction may be related to the magmatic underplating in continent-ocean transition, southeastern ZRMB. According to the analysis of tectonic activity intensity and rift sedimentary structure, the activities of YJF in Cenozoic played a regulating role in the rift extension process of ZRMB.

Cenozoic Environmental Changes in the Northern Qaidam Basin Inferred from n-alkane Records

Cenozoic climatic and environmental changes in the arid Asian interior, and their possible relations with global climatic changes and the Tibetan Plateau uplift, have been intensively investigated and debated over past decades. Here we present 40-Myr （million years）-long n-alkane records from a continuous Cenozoic sediment sequence in the Dahonggou Section, Qaidam Basin, northern Tibetan Plateau, to infer environmental changes in the northern basin. A set of n-alkane indexes, including ACL, CPI and Paq, vary substantially and consistently throughout the records, which are interpreted to reflect relative contributions from terrestrial vascular plants vs. aquatic macrophytes, and thus indicate depositional environments. ACL values vary between 21 and 30; CP1 values range from 1.0 to 8.0; and Paq values change from 〈0.1 to 0.8 over the past 40-Myr. We have roughly identified two periods, at 25.8-21.0 Ma （million years ago） and 13.0-17.5 Ma, with higher ACL and CPI and lower Paq values indicating predominant lacustrine environments. Lower ACL and CPI values, together with higher Paq values, occurred at 〉25.8 Ma, 17.5-21.0 Ma, and 〈13.0 Ma, corresponding to alluvial fan/river deltaic deposits and shallow lacustrine settings, consistent with the observed features in sedimentological facies. The inferred Cenozoic environmental changes in the northern Qaidam Basin appear to correspond to global climatic changes.

Late Cenozoic Stratigraphy and Paleomagnetic Chronology of the Zanda Basin,Tibet, and Records of the Uplift of the Qinghai-Tibet Plateau

The characteristics of Late Cenozoic tectonic uplift of the southern margin of the Qinghai- Tibet Plateau may be inferred from fluvio-lacustrine strata in the Zanda basin, Ngari, Tibet. Magnetostratigraphic study shows that the very thick fluvio-lacustrine strata in the basin are 5.89- 0.78 Ma old and that their deposition persisted for 5.11 Ma, i.e. starting at the end of the Miocene and ending at the end of the early Pleistocene, with the Quaternary glacial stage starting in the area no later than 1.58 Ma. Analysis of the sedimentary environment indicates that the Zanda basin on the southern Qinghai-Tibet Plateau began uplift at -5.89 Ma, later than the northern Qinghai-Tibet Plateau. Presence of gravel beds in the Guge and Qangze Formations reflects that strong uplift took place at -5.15 and -2.71 Ma, with the uplift peaking at -2.71 Ma.

Plate tectonic control on the formation and tectonic migration of Cenozoic basins in northern margin of the South China Sea

The tectonic evolution history of the South China Sea(SCS) is important for understanding the interaction between the Pacific Tectonic Domain and the Tethyan Tectonic Domain,as well as the regional tectonics and geodynamics during the multi-plate convergence in the Cenozoic.Several Cenozoic basins formed in the northern margin of the SCS,which preserve the sedimentary tectonic records of the opening of the SCS.Due to the spatial non-uniformity among different basins,a systematic study on the various basins in the northern margin of the SCS constituting the Northern Cenozoic Basin Group(NCBG) is essential.Here we present results from a detailed evaluation of the spatial-temporal migration of the boundary faults and primary unconformities to unravel the mechanism of formation of the NCBG.The NCBG is composed of the Beibu Gulf Basin(BBGB),Qiongdongnan Basin(QDNB),Pearl River Mouth Basin(PRMB) and Taixinan Basin(TXNB).Based on seismic profiles and gravity-magnetic anomalies,we confirm that the NE-striking onshore boundary faults propagated into the northern margin of the SCS.Combining the fault slip rate,fault combination and a comparison of the unconformities in different basins,we identify NE-striking rift composed of two-stage rifting events in the NCBG:an early-stage rifting(from the Paleocene to the Early Oligocene) and a late-stage rifting(from the Late Eocene to the beginning of the Miocene).Spatially only the late-stage faults occurs in the western part of the NCBG(the BBGB,the QDNB and the western PRMB),but the early-stage rifting is distributed in the whole NCBG.Temporally,the early-stage rifting can be subdivided into three phases which show an eastward migration,resulting in the same trend of the primary unconformities and peak faulting within the NCBG.The late-stage rifting is subdivided into two phases,which took place simultaneously in different basins.The first and second phase of the early-stage rifting is related to back-arc extension of the Pacific subduction retreat system.The third phase of the earlystage rifting resulted from the joint effect of slab-pull force due to southward subduction of the proto-SCS and the back-arc extension of the Pacific subduction retreat system.In addition,the first phase of the late-stage faulting corresponds with the combined effect of the post-collision extension along the Red River Fault and slab-pull force of the proto-SCS subduction.The second phase of the late-stage faulting fits well with the sinistral faulting of the Red River Fault in response to the Indochina Block escape tectonics and the slab-pull force of the proto-SCS.

MASS ACCUMULATION IN THE CENOZOIC HOH XIL BASIN,NORTHERN TIBET

Sedimentary basins are where the products or erosion of the related reliefs accumulate.The sedimentary records preserved in the basins offer the possibility of quantifying the paleotopography z(x,y,t) at each point( x,y )of a given region at any time t in the past by using methods of mass balanced reconstruction(Hay et al.,1989,Métivier and Gaudemer,1997),The importance of paleotopography is on that atmospheric circulation models and the ocean circulation models which depend on them require knowledge of the topography of the land as an important input boundary condition which strongly affects the model output(Barron and Washington,1984,Ruddiman et al.,1997).Thus,a first step towards establishing paleoelevations is to reconstitute the history of sedimentary basins in terms of mass accumulation(Hay et al.,1989).This work reconstructs the space\|time depositional history and estimates the mass stored in the Hoh Xil basin,northern Tibet.The Hoh Xil basin,with an area of 101000km\+2 and an average elevation of over 5000m,is the largest Cenozoic sedimentary basin in the hinterland of the Tibetan plateau.From the Early Eocene to the Early Miocene,a sediment pile of approximately 5 4km thick of fluvial mudstone,sandstone,and conglomerate and 0 3km thick of limestone was formed in the basin (Liu and Wang,2000;Liu et al.,2000).the mass estimate is derived from 21 measured field cross\|sections,with total thickness of 13479 3m.The results show that the Hoh Xil basin has undergone 7 stages of evolution from the Early Eocene to the Early Oligocene,with a period of no sedimentation during the Late Oligocene.The Fenghuoshan Group was formed from the first four stages as 56 0～52 0,52 0～46 7,46 7～39 7,and 39 7～33 2Ma ago,with the depocenter moving eastward and northward.The Yaxicuo Group was formed from the two next stages as 33 2～32 2 and 33 2～30 2Ma ago.The Wudaoliang Group spread the entire basin during the last stage of ca.23 0～16 0Ma ago,with its depocenter in the northern part.The strata of the Fenghuoshan and Yaxicuo Groups have undergone strong deformation mainly during 30 0 to ca.23 0Ma,whereas only minor tilting has occurred in the Wudaoliang Group later.The space\|time evolution indicates that the Hoh Xil basin could be formed by the collision between Indi and Asia during the Early Eocene,and that its filling processes were controlled by early uplift and crustal shortening of the Tibetan plateau.The sedimentation budget is estimated as 297 15×10 12 t for the Cenozoic sediments deposited in the Hoh Xil basin.The accumulation rate curve shows that the value rises suddenly to around 800t/(m\+2 Ma -1 )during 32 2～30 0Ma ago from around 400t/(m\+2·Ma -1 )during 56～32 2Ma ago.The sudden increase of accumulation rate could be produced by early uplift of the Tibetan plateau.

Cenozoic Vertical-Axis Rotations of the Hoh Xil Basin, Central–Northern Tibet

Understanding the Cenozoic vertical-axis rotation in the Tibetan Plateau is crucial for continental dynamic evolution. Paleomagnetic and rock magnetic investigations were carried out for the Oligocene and Miocene continental rocks of the Hoh Xii basin in order to better understand the tectonic rotations of central Tibet. The study area was located in the Tongtianhe area located in the southern part of the Hoh Xil basin and northern margin of the Tanggula thrust system in central-northern Tibet. A total of 160 independently oriented paleomagnetic samples were drilled from the Tongtianhe section for this study. The magnetic properties of magnetite and hematite have been recognized by measurements of magnetic susceptibility vs. temperature curves and unbiocking temperatures. The mean directions of the Oligocene Yaxicuo Group in stratigraphic coordinates （Declination/Inclination = 354.9°/29.3°, k = 33.0, a9s = 13.5°, N =5 Sites） and of the Miocene Wudaoliang Group in stratigraphic coordinates （Declination/Inclination = 3.60/36.4°, k = 161.0, a9s = 9.7°, N =3 Sites） pass reversal tests, indicating the primary nature of the characteristic magnetizations. Our results suggested that the sampled areas in the Tuotuohe depression of the Hoh Xil basin have undergone no paleomagnetically detectable rotations under single thrusting from the Tanggula thrust system. Our findings, together with constraints from other tectonic characteristics reported by previous paleomagnetic studies, suggest tectonic rotations in the Cuoredejia and Wudaoliang depressions of the Hoh Xil basin were affected by strike-slip faulting of the Fenghuo Shan-Nangqian thrust systems. A closer examination of geological data and different vertical-axis rotation magnitudes suggest the tectonic history of the Hoh Xil basin may be controlled by thrust and strike-slip faulting since the Eocene.

Meso-Cenozoic Evolution of Earth Surface System under the East Asian Tectonic Superconvergence

The East Asian geological setting has a long duration related to the superconvergence of the Paleo-Asian, Tethyan and Paleo-Pacific tectonic domains. The Triassic Indosinian Movement contributed to an unified passive continental margin in East Asia. The later ophiolites and I-type granites associated with subduction of the Paleo-Pacific Plate in the Late Triassic, suggest a transition from passive to active continental margins. With the presence of the ongoing westward migration of the Paleo-Pacific Subduction Zone, the sinistral transpressional stress field could play an important role in the intraplate deformation in East Asia during the Late Triassic to Middle Jurassic, being characterized by the transition from the E-W-trending structural system controlled by the Tethys and Paleo-Asian oceans to the NE-trending structural system caused by the Paleo-Pacific Ocean subduction. The continuously westward migration of the subduction zones resulted in the transpressional stress field in East Asia marked by the emergence of the Eastern North China Plateau and the formation of the Andean-type active continental margin from late Late Jurassic to Early Cretaceous （160-135 Ma）, accompanied by the development of a small amount of adakites. In the Late Cretaceous （135-90 Ma）, due to the eastward retreat of the Paleo-Pacific Subduction Zone, the regional stress field was replaced from sinistral transpression to transtension. Since a large amount of late-stage adakites and metamorphic core complexes developed, the Andean-type active continental margin was destroyed and the Eastern North China Plateau started to collapse. In the Late Cretaceous, the extension in East Asia gradually decreased the eastward retreat of the Paleo-Pacific subduction zones. Futhermore, a significant topographic inversion had taken place during the Cenozoic that resulted from a rapid uplift of the Tibet Plateau resulting from the India-Eurasian collision and the formation of the Bohai Bay Basin and other basins in the East Asian continental margin. The inversion caused a remarkable eastward migration of deformation, basin formation and magmatism. Meanwhile, the basins that mainly developed in the Paleogene resulted in a three-step topography which typically appears to drop eastward in altitude. In the Neogene, the basins underwent a rapid subsidence in some depressions after basin-controlled faulting, as well as the intracontinental extensional events in East Asia, and are likely to be a contribution to the uplift of the Tibetan Plateau.

LATE CENOZOIC TECTONICS ALONG THE NORTHWESTERN MARGIN OF THE TARIM BASIN: INTERACTIONS BETWEEN THE TARIM BASIN AND THE SOUTHERN TIAN SHAN, WEST CHINA

The Late Cenozoic fold\|and\|thrust zone along the northwestern margin of the Tarim Basin and the adjacent Tian Shan of Central Asia is an actively deforming part of the India\|Asia collision system. This deformation zone has two remarkable oppositely vergence arcuate fold\|and\|thrust systems (Kepingtage and Kashi\|Atushi fold\|and\|thrust belts) reaching from east of Keping to west of Kashi. This shape is manifested by structure, topography and seismicity. From north to south, this deformation zone is characterized by four main kinematic elements: (1) a hanging\|wall block (Maidan fault and Tuotegongbaizi\|Muziduke thrust system) that represents the Cenozoic reactivation of a late Paleozoic thrust system; (2) an imbricated thrust stack (Kepingtage\|Tashipeshake thrust system) where slices of Tarim platform sediments are thrust south toward the basin; (3) the Kashi\|Atushi fold\|and\|thrust system where thrusting and folding verge toward the Tian Shan; (4) a foot\|wall block (Tarim craton) that dips gently northwest below the sediment\|filled southern Tian Shan basin and generally has little internal deformation.

SEDIMENTARY PROCESS OF THE CENOZOIC BASIN AND ITS RESPONSE TO THE SLIP-HISTORY OF THE ALTYN TAGH FAULT, NW CHINA

The NEE\|striking Altyn Tagh Fault (ATF) has been well known as one major point to know the growth history of the Tibetan plateau. Lots of investigations done since 1970’s were mostly focus on active features, particularly on determining slip, slip rate and their distribution along the fault. However, Cenozoic slip\|history of this fault remains poorly understood, and the age of initiation and total offset are controversial. Several Cenozoic sedimentary basins develop in Suo’erkulinan to Mangya regions (Fig.1). Their sedimentary processes are closely related with the ATF. The studies of the Neogene sedimentary sequences and the reconstruction of the paleo\|geography are essential to establish the displacement history of the fault during Late Cenozoic.Located at the southern side of the ATF, the Suo’erkulinan basin consists of more than 600\|meter\|thick Pliocene Shizigou Formation below and about 120\|meter\|thick Early to Middle Pleistocene Qigequan Formation above according to the 1∶200000 geological map by Xinjiang Province. An obvious erosional surface can be seen on the top of the lower sequence. Sediments in the Shizigou Formation are characterized by 400\|meter\|thick yellow to red cobble\|sized conglomerates in the bottom, up\|grading to sandstones and grey\|green mudstones. This indicated that the sedimentary facies changed from alluvial fan to fluvial fan and sediments became more and more mature. The upper sequence, the Qigequan Formation, corresponds to an alluvial facies series composed of yellow to white cobble\|sized conglomerates intercalated with lenticular sandstones. Paleo\|current indicators showed that the Shizhigou conglomeratic series were sourced from northwest. Well\|developed syn\|sedimentary faults, normal faults mostly inherited from syn\|sedimentary faults, and some striation lineations on the surface indicated transtensional tectonic environment of the strike\|slip faulting.

Meso-Cenozoic Tectonic Events Recorded by Apatite Fission Track in the Northern Longmen-Micang Mountains Region

There is a cross-cutting relationship between the E-W trending structures and the NE- trending structures in the northern Longmen-Micang Mountains region, which reflects possible regional tectonic transition and migration. Apatite fission track （AFT） analyses of 15 samples collected from this area yield apparent ages varying from 30.3±4.2 Ma to 111.7±9.0 Ma and confined-track-lengths ranging from 10.6±0.3 pm to 12.4±0.1 μm. Four specific groups were identified on the basis of the Track Age Spectrum Calculation （TASC） patterns, i.e., 143-112 Ma, 93.6-88 Ma, 42-40 Ma and -25.6 Ma. These age groups correspond to the spatial distributions of datasets and may represent four tectonic events. Together with the regional deformation patterns, the four age groups are interpreted to indicate tectonic superposition, transition and migration during the Meso-Cenozoic with the following possible order： （1） the Micang Mountains belt was dominated by the E-W trending structure during 143-112 Ma; （2） the contraction of the Longmen Mountains belt from the NW to the SE during 93.6-88 Ma led to the superposition of the NE-trending structures over the E-W trendinding structures; （3） dextral strike-slip shear dominated the Longmen Mountains belt at 42-40 Ma; （4） westward migration of the active tectonic belt occurred from 93.6-25.6 Ma in a break-back sequence in the northern Longmen Mountains belt. The Late Cenozoic tectonics in the northern Longmen Mountains belt are characterized by the dextral strike-slip shear and the occurrence of westward break-back sequence of deformations. As a result, north-south differences in deformations along the Longmen Mountains belt were intensified since the Miocene time and strains were mainly accumulated in the hinterland of the Longmen Mountains instead of being propagated to the foreland basin.