王斌, 郑洪波, 王平, 何忠. 渭河盆地新生代地层与沉积演化研究: 现状和问题. 地球科学进展, 2013, 28(10): 1126-1135
Wang Bin, Zheng Hongbo, Wang Ping, He Zhong. The Cenozoic Strata and Depositional Evolution of Weihe Basin: Progresses and Problems. Advance in Earth Science, 2013, 28(10): 1126-1135
The Cenozoic Strata and Depositional Evolution of Weihe Basin: Progresses and Problems
Wang Bin1, Zheng Hongbo2, Wang Ping2, He Zhong3
1. School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China
2. School of Geography Science, Nanjing Normal University, Nanjing 210046, China
3. Institute of Soil and Water Conservation, Northwest A&F University, Yangling 712100, China
Abstract
On the basis of the previous stratigraphic research, the Cenozoic strata in the Weihe Basin have been recognized and partially revised. The main regional stratigraphic units in the Weihe Basin are compared with the “China Regional Chronostratigraphic (Geo-chronologic) Scale”, including the Honghe Formation, the Bauluyuan Formation, and the Lengshuigou Formation, the Koujiacun Formation, the Bahe Formation, the Lantian Formation, the Sanmen Formation and the Quaternary loesspaleosol. We found that the conglomerate at the bottom of Lantian Formation should be thought as the upper part of the Bahe Formation. The Sanmen Formation is defined more clearly that it has no vertical relationship with the Lantian Formation. These two formations are the contemporaneous heterotopic facies within the same deposition period, but over different environments, and they have never been found in one section in the Weihe Basin. The “Zhangjiapo Formation” and the “Youhe Formation” were wrongly founded and placed in time before, they should be concealed and belong to the “Sanmen Formation”. The tectonic rifting and sedimentary evolution of the Weihe Basin has been analyzed and reviewed, and the Eocene and late Miocene are found as the two most important developmental stages of the Weihe Basin during the Cenozoic era. The Weihe basin is synergistic and related to the uplifting of the Qinling Mountains and the evolution of the Ordos Plateau in time and motivation.
图1 渭河盆地区域地质图[9, 18](1)渭河盆地北缘断裂带;(2)渭河断裂;(3)秦岭北缘断裂;(4)华山山前断裂;(5)秦岭断裂带;(6)中条山北麓断裂;(7)离石断裂;(8)鄂尔多斯高原西缘断裂;AA′.渭河盆地剖面位置Fig.1 Regional tectonic map of the Weihe Basin[ 9, 18](1)The northern boundary fault of the Weihe Basin; (2) Weihe fault; (3) The northern boundary fault of the Qinling Mountains; (4) Huashan frontal fault; (5) Qinling fault zone; (6) Zhongtiaoshan north frontal fault; (7) Lishi fault;(8) Fault of the western margin of the Ordos Plateau; AA′.The crosssection of Weihe Basin
图3 渭河盆地构造纲要图(图中显示了渭河盆地三大基底分区和主要断裂)[13, 36]1.北部基底:主要为下古生界碳酸岩层;2. 西南部基底:元古界变质岩区;3. 东南部基底:太古界变质岩区; 4. 骊山花岗岩区;5.主要活动断裂, 其中渭河断裂为隐伏断裂, 其余4条为正断裂;A.固市凹陷; B.户县凹陷Fig.3 Tectonic outline map of Weihe Basin[ 13, 36]1. North basement: Most is Lower Paleozoic carbonate; 2. Southwest basement: Proterozoic metamorphic rock area; 3. Southeast basement: Archaeozoic metamorphic rock area; 4. Lishan granite area; 5. Main Faults, Weihe Fault is Buried Fault, the others are Normal Faults; A. Gushi depression; B. Huxian depression
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Institute of Desert Research, Chinese Academy of Sciences, Lanzhou
The Weihe River Basin stands where the four tectonic systems of Qilu,Qin-ling,latitudinal direction,cathaysian and Longxi roll-up intersect,such tectonic characteristics lay a basis for the formation of tectonic landforms of the basin.According to the tectonic structures and formation causes,the tectonic land-forms in the Weihe River Basin can be classified into eight types and each type can be divided further into correspondent based on neotectonic movement characteristics.These geomorphic sequences,which stretch into belts in east-west direction,have lomologous features in north-south direction and possess terracing spatial variations,Under the control of major tectonic systems in the Weihe River Basin,the graben structure with its own features serves as main cause for estabishment of the landform spatial arrangement.The development of tectonic landforms in the Weihe River Basin underwent three stages,namely,preparation stage of Mesozoicera,Tertiary establishment stage and Quaternary completion stage.
Since the beginning of the Cenozoic, north China has been fragmented by intensive intracontinental rifting and extensional tectonics, which resulted in the formation of two extensional domains: the graben systems around the Ordos block in the west and North China Plain in the east. How to link this Cenozoic extensional tectonics to plate kinematics has long been an issue of debate. This paper presents updated results of fault slip data sets collected in different zones in north China and addresses the changes in the direction of extensional stresses over the Cenozoic. A chronology of three successive extensions has been established and provides evidence for constraining the timing and location of either subduction-induced back-arc tectonics along the western Pacific or collision-related extrusion tectonics in Tibet. The oldest NW–SE trending extension occurred concomitantly with the early Tertiary rifting phase, which was initiated in a back-arc setting associated with westward subduction of the Pacific plate under the Asia continent. North China had been subjected, during the Miocene, to regional subsidence with widespread basalt flow, and the direction of extension changed to NE–SW to NNE–SSW, consistent with the spreading direction of the Japan Sea. The dynamic origin of this extension is poorly understood. Since the latest Miocene or earliest Pliocene, north China has been dominated by NW–SE extension resulting in the formation and development of the elongate graben systems around the rigid Ordos block. This extensional phase is accompanied by counterclockwise rotation of blocks such as Ordos, Taihangshan Massif etc., which are bounded to south by the left-lateral strike-slip Qinling fault system. The overall Pliocene-Quaternary deformation in north China accommodates an ESE-ward extrusion of the south China block relative to the Gobi-Mongolia plateau, as the consequence of late-stage India–Eurasia convergence.
Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044
A continuous sedimentary sequence from the Oligocene to the Holocene is well developed and exposed in the Linxia Basin (Gansu, China), in which very abundant mammal fossils are discovered. The Linxia Basin is one of the regions with the richest Late Cenozoic mammal fossils in China as well as the whole Eurasia. The Late Oligocene Dzungariotherium fauna, the Middle Miocene Platybelodon fauna, the Late Miocene Hipparion fauna, and the Early Pleistocene Equus fauna are the most representative in the Linxia Basin. Mammals are very sensitive to climatic and environmental changes. The strong uplift of the Qinghai-Xizang Plateau during the Late Cenozoic greatly influenced climate and environment, which would be reflected from the evolution of mammalian faunas. The Linxia Basin is situated at the transitional zone between the Qinghai-Xizang Plateau and Loess Plateau. During the important period of the uplift of the Qinghai-Xizang Plateau in the Late Cenozoic, the Linxia Basin has the mammal fossil assemblages, which can determine geological ages, and the thick deposits, which can accurately reflect climatic variations. As a result, the Linxia Basin is a best site to study the uplift process of the Qinghai-Xizang Plateau and its influence to climate and environment. For the study to the Qinghai-Xizang Plateau, the Linxia Basin can correspond to or be better than the classical Siwaliks on the south margin of the Qinghai-Xizang Plateau. The ecological features of the distinct faunas indicate that the Linxia Basin came through great climatic and environmental changes: warm and humid forest mixed with some open lands in the Late Oligocene, denser forest with richer water bodies in the Middle Miocene, tropical semiarid savanna with strong seasonal variation in the Late Miocene, to cold and arid climate with high elevation in the Early Pleistocene. The particular geographical position of the Linxia Basin implies that the evolution of its mammalian faunas is tightly related to the uplift of the Qinghai-Xizang Plateau in the Late Cenozoic. The uplift of the Qinghai-Xizang Plateau was not enough to baffle the dispersal of large mammals between north and south of this plateau in the Late Oligocene, but it became an obvious barrier for the mammal migration in the Middle Miocene and more obvious in the Late Miocene. The Linxia Basin reached a relatively high elevation in the Early Pleistocene, so that a plateau or alpine mammalian fauna appeared in this area.
An Zhisheng1, Sun Denghuai1, Chen Mingyang2, Sun Youbin1, Li Li1, Chen Baoqun1
安芷生1, 孙东怀1, 陈明扬2, 孙有斌1, 李立1, 陈宝群1
1. State Key Laboratory of Loess and Quaternary Geology, Chinese Academy of Sciences, Xi'an 710054; 2. Institute of Geology and Geophysics| Chinese Academy of Sciences, Beijing 100029
Based on systematic geological investigation four sections of the Late Tertiary red clay sequence were chosen for the study of stratigraphy, paleomagnetism and paleoclimatology. These sections are Lingtai, Bajiazui, Zhaojiachuan in the central part,Duanjiapo in the southern part of the Loess Plateau. Thermal demagnetizer and cryogenic magnetometer were used to systemahcally measure the magnetic remanence from room temperature up to 500 or 600℃ with 50℃ step in order to establish magnetostrahgraphy of the sections. The results show a consistent polarity structure.Magnetostrahgraphy of the red clay sequence consists of normal polarity Chron of Gauss, reversed Chron of Gilbert. The Chron Gauss is characterized by a long normal polarity with two reversed events at lower part of the Chron. Chron Gilbert can be determined by its polarity structure of two reversed sub-Chron which are separated by 4 small normal events. All complete eolian sequence profile consistently suggest the bottom of red clay is wimin the Chron 3B, and the bottom age of the sequence is about 7.2Ma B. P. The red clay sequence in Chinese Loess Plateau consists of 7 paleosol complex (named RS1 to RS7) interbeded with 7 reddish pedogenic loess complex (named RL1 to RL7),
Wang Shubing1, Jiang Fuchu1,2, Wu Xihao1,3, Wang Sumin2, Tian Guoqiang1
王书兵1, 蒋复初1,2, 吴锡浩1,3, 王苏民2, 田国强1
1. Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081; 2. Open Laboratory of Lake Sediment and Environment, Nanjing Institute of geography and Limnology, Chinese Academy of Sciences, Nanjing 210008; 3. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environ ment, Chinese Academy of Sciences, Xi′an 710075
The lacustrine deposits of the ancient Sanmen Lake have been preserved in good condition in the Huangdigou profile which is located at the north of Sanmenxia Reservoir in Pinglu County of Shannxi Province. From a study of the magnetostratigraphy, the deposition of the ancient Sanmen Lake is known to have started in the middle of Gilbert reversal polarity chron, about 5MaB.P., and ended in the late of Brunhes normal polarity chron, consistent with OSL age, about 150kaB.P. Since the depositions belong to the Ancient Sanmen Lake, and according to the lithostratigraphic principle, it is referred to as Sanmen Formation. Based on the lithological characters, the sequence can be subdivided into three parts, the upper part consisting dominantly of sand layers, the middle part of clay layers and the lower part of basal gravel. The series is now known to have the longest period of deposition that commenced earlier and terminated later than all others ever reported.
Since the beginning of the Cenozoic, north China has been fragmented by intensive intracontinental rifting and extensional tectonics, which resulted in the formation of two extensional domains: the graben systems around the Ordos block in the west and North China Plain in the east. How to link this Cenozoic extensional tectonics to plate kinematics has long been an issue of debate. This paper presents updated results of fault slip data sets collected in different zones in north China and addresses the changes in the direction of extensional stresses over the Cenozoic. A chronology of three successive extensions has been established and provides evidence for constraining the timing and location of either subduction-induced back-arc tectonics along the western Pacific or collision-related extrusion tectonics in Tibet. The oldest NW–SE trending extension occurred concomitantly with the early Tertiary rifting phase, which was initiated in a back-arc setting associated with westward subduction of the Pacific plate under the Asia continent. North China had been subjected, during the Miocene, to regional subsidence with widespread basalt flow, and the direction of extension changed to NE–SW to NNE–SSW, consistent with the spreading direction of the Japan Sea. The dynamic origin of this extension is poorly understood. Since the latest Miocene or earliest Pliocene, north China has been dominated by NW–SE extension resulting in the formation and development of the elongate graben systems around the rigid Ordos block. This extensional phase is accompanied by counterclockwise rotation of blocks such as Ordos, Taihangshan Massif etc., which are bounded to south by the left-lateral strike-slip Qinling fault system. The overall Pliocene-Quaternary deformation in north China accommodates an ESE-ward extrusion of the south China block relative to the Gobi-Mongolia plateau, as the consequence of late-stage India–Eurasia convergence.
Yuan Baoyin①, Tang Guo'an②, Zhou Liping③, Hao Qingzhen①, Li Fayuan②, Lu Zhongchen④
袁宝印①, 汤国安②, 周力平③, 郝青振①, 李发源②, 陆中臣④
① Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029; ② Geography College, Nanjing Normal University, Nanjing 210046; ③ Department of Geography, Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871; ④ Research Center of Ecology, Chinese Academy of Sciences, Beijing 100085
There is tremendous difference in structural characteristics among the different parts of the vast Loess Plateau of China.In this study,three neotectonic regions are defined according to their association with the varying stages of Cenozoic structural evolution in the Loess Plateau: Ordos stable block,Longxi region and Fen-Wei rift valley.The tectonic history and the ancient landform created by the Cenozoic depositional processes have determined the types of loess landform and the sequences of the regional stratigraphy.Geomorphologically,Loess Plateau can be divided into three major geomorphological regions.First,Ordos loess landscape.Here Quaternary loess was mantled on the ancient landform consisting of Neogene red clay Liang,Mao and basin and then eroded,creating the highly diversified and complex landforms.Second,Longxi loess landscape.Its main body consists of red clay landform of Neogene age,covered with thin Quaternary loess.The characteristics of the resent-day landforms are dominated by those of the red clay.Third,loess landscape in the Fen-Wei rift valley.Here Quaternary loess is found to cover the river terraces or lacustrine sediments,forming the so-called Loess Table Yuan.The formation of Cenozoic rift valley around the Ordos block determined the evolution of Yellow River.The rapid development of the Yinhu rift valley and Fen-Wei rift valley during the Neogene caused an abrupt uplift of the Lüliang Mountain and a moderate uplift of the northwestern part of Ordos block.This led to the initial formation of the ancient Yellow River which flowed through Jinshaan Gorge region into ancient Sanmen Lake and finally emptied into Yellow Sea.During the Quaternary period,Yellow River co-existed with lakes for a long time.At the end of Middle Pleistocene,the erosion of Yellow River cut through Sanmen Gorge,leading to the disappearance of the ancient Sanmen Lake and the formation of modern landscape.
This contribution reviews the tectonic structure and evolution of the Qinling orogenic belt, which extends east–west nearly 2500 km across Central China and is a giant orogenic belt formed by the convergence and collision between North China and South China Blocks. The principal tectonic elements including metamorphic basement and its Neoproterozoic to Triassic cover, ophiolitic sutures, nature and ages of granitoid belts, provenance studies and tectonometamorphic studies of metamorphic belts allow tracing the polarity of two stages of plate convergence and collision and the further tectonic history. In this review, we present new distribution maps of the Early Paleozoic ophiolites and associated volcanics in the Shangdan suture zone and the Middle Devonian–Middle Triassic ophiolitic melange in the Mianlue suture zone, as well as the maps of granitoid and metamorphic belts displaying various ages (Silurian–Devonian, Triassic, Late Jurassic–Early Cretaceous). These maps allow better constrain the polarity of subduction and collision. We also discuss the significance of the Early Cretaceous Yanshanian events, which represent a linkage between tectonic events in the Tethyan and East China/Pacific realms.
Two ophiolitic sutures, the Shangdan suture zone in the north and the Mianlue suture in the south, have been intensively studied during the past two decades. The Qinling Orogen is divided into the North Qinling and the South Qinling Belts by the Shangdan suture zone, and this suture zone is thought to represent the major suture separating the North China and South China Blocks. However, the timing and processes of convergence between these two blocks have been disputed for many years, and Silurian–Devonian or Late Triassic collision has been proposed as well. Based on the recent results, a detailed convergent evolutionary history between the North China and South China Blocks along the Shangdan suture is here proposed. The Mianlue suture zone is well documented and represents the Mianlue ocean which separates the South Qinling from the South China Block in Devonian to Mid Triassic times. After the closure of the Mianlue ocean, the South Qinling Belt was emplaced onto the Yangtze Block along the Middle Triassic Mianlue suture zone in Late Triassic–Jurassic times. This suture was overprinted by the south-directed overthrust of the Mianlue–Bashan–Xiangguang thrust fault operative in Late Jurassic-Cretaceous times.
Furthermore, we note that the Yanshanian tectonic events play a major role for rapid Early Cretaceous exhumation of significant portions of the Qinling orogenic belt. In contrast, although high topographic gradients, the Cenozoic tectonism related to lateral extrusion of the Tibet plateau resulted in minor and continuous exhumation and erosion along major transtensional and strike-slip faults were activated.
Highlights
? Ophiolite, volcanic and plutonic rocks indicate two sutures in the Qinling orogen. ? Timing and polarity of two stages of plate subduction and collision are constrained. ? Ages and geochemistry of magmatic rocks reveal a detail evolution of the Qinling Mts.