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 show...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.展开更多
Dongsha Island and the adjacent sea area locate at the northern continental margin of the South China Sea (SCS), and is connected to the east by the Manila Trench. Analyses of seismic stratigraphy and gravity, magneti...Dongsha Island and the adjacent sea area locate at the northern continental margin of the South China Sea (SCS), and is connected to the east by the Manila Trench. Analyses of seismic stratigraphy and gravity, magnetic and drilling wells data led to the discovery of three post fault sequences (V, VI, VII). Extensive tectonic uplift, magma activity and erosion occurred in Dongsha Island and the adjacent area, where most of the faults in the northeastern SCS were still active during Pliocene and Quaternary. Two groups of faults trending NEE and NW were developed during Late Cenozoic. We conclude that three important tectonic movements, especially Dongsha movement (4.4-5.2 Ma) and Liuhua movement (1.4-1.89 Ma), controlled the structural framework in the Dongsha rise; whose deformation in the east is stronger than that in the west and whose stress field variation suggests that the tectonic uplift in the study area contributed to magmato tectonic events correlated to the main collision phases between the East China and Taiwan 5-3 and 3-0 Ma ago.展开更多
The north trending rifts in southern Tibet represent the E-W extension of the plateau and confirming the initial rifting age is key to the study of mechanics of these rifts. Pagri-Duoqing Co graben is located at south...The north trending rifts in southern Tibet represent the E-W extension of the plateau and confirming the initial rifting age is key to the study of mechanics of these rifts. Pagri-Duoqing Co graben is located at southern end of Yadong-Gulu rift, where the late Cenozoic sediments is predominately composed of fluvio-lacustrine and moraine. Based on the sedimentary composition and structures, the fluviolacustrine could be divided into three facies, namely, lacustrine, lacustrine fan delta and alluvial fan. The presence of paleo-currents and conglomerate components and the provenance of the strata around the graben indicate that it was Tethys Himalaya and High Himalaya. Electron spin resonance(ESR) dating and paleo-magnetic dating suggest that the age of the strata ranges from ca. 1.2 Ma to ca. 8 Ma. Optically stimulated luminescence(OSL) dating showed that moraine in the graben mainly developed from around181-109 ka(late Middle Pleistocene). Combining previous data about the Late Cenozoic strata in other basins, it is suggested that 8-15 Ma may be the initial rifting time. Together with sediment distribution and drainage system, the sedimentary evolution of Pagri could be divided into four stages. The graben rifted at around 15-8 Ma due to the eastern graben-boundary fault resulting in the appearance of a paleolake.Following by a geologically quiet period about 8-2.5 Ma, the paleolake expanded from east to west at around 8-6 Ma reaching its maximum at ca. 6 Ma. Then, the graben was broken at about 2.5 Ma. At last,the development of the glacier separated the graben into two parts that were Pagri and Duoqing Co since the later stages of the Middle Pleistocene. The evolution process suggested that the former three stages were related to the tectonic movement, which determined the basement of the graben, while the last stage may have been influenced by glacial activity caused by climate change.展开更多
The late Cenozoic geomorphic features and geochronologic data of the Zhingfang River catchment in the Yuntaishan World Geopark are studied. Several quarternary geochronologic methods, including electron spin resonance...The late Cenozoic geomorphic features and geochronologic data of the Zhingfang River catchment in the Yuntaishan World Geopark are studied. Several quarternary geochronologic methods, including electron spin resonance （ESR）, optically stimulated luminescence （OSL）, thermo-luminescence （TL） and U-series are presented in this paper. The results suggest that there are two planation surfaces, named as the Taihang surface which is a peneplain of Taihang stage formed during Oligocene or Oligocene to early-middle Miocene period, and Tang-hien surface which is a mature wide valley of Tang-hien stage formed during late Miocene-Pliocene or Piiocene-early Pleistocene period and probably ended prior to 2.2-2.6 Ma based on ESR dating. After the Tang-hien stage, the incision and aggradation of the river formed six stream terraces with heights of 3-5 m, 8-12 m, 22-24 m, 28-38 m, 50-62 m and 80-85 m above the river bottom, respectively. The dating results of the alluvium sediments suggest that these terraces were formed during Holocene, 20-23 ka B.P., 110-120 ka B.P., 200-240 ka B.P., 840-1200 ka B.P. or ~450 ka B.P. and 1600-1800 ka B.P. or -1100 ka B.P., respectively. These results indicate that episodic incision of the river, which controls the formation of the scenery in the Yuntaishan World Geopark, was mainly influenced by the periodic dry-wet climate change during late Cenozoic mountain uplift.展开更多
The Tianshui Basin,located inside the western Qinling orogenic belt and northeastern margin of the Tibetan Plateau （Fig.1）,is a NE-trending Late Cenozoic basin,which documents the neotectonic response of the northea...The Tianshui Basin,located inside the western Qinling orogenic belt and northeastern margin of the Tibetan Plateau （Fig.1）,is a NE-trending Late Cenozoic basin,which documents the neotectonic response of the northeastward growth of Tibetan Plateau.展开更多
Climate in Eastern Asia is composed of monsoon climate in the east,arid and semi-arid climate in the north and west,and the cold and dry climate of Qinghai-Tibetan Plateau in the southwest.The underlying causes for th...Climate in Eastern Asia is composed of monsoon climate in the east,arid and semi-arid climate in the north and west,and the cold and dry climate of Qinghai-Tibetan Plateau in the southwest.The underlying causes for the evolution of East Asian climate during late Cenozoic have long been investigated and debated,particularly with regards to the role played by the Qinghai-Tibetan Plateau uplift and the global cooling.In this paper,we reviewed major research developments in this area,and summarized the important results.Based on a synthesis of data,we propose that the Qinghai-Tibetan Plateau uplift alone cannot fully explain the formation of monsoon and arid climates in Eastern Asia during the past 22–25 Ma.Other factors such as the global ice volume and high-latitude temperature changes have also played a vital role.Moreover,atmospheric CO2changes may have modulated the monsoon and dry climate changes by affecting the location of the inter-tropical convergence zone(ITCZ),which controls the monsoon precipitation zone and the track of the East Asian winter monsoon during late Cenozoic.The integration of high-resolution geological record and numerical paleoclimate modeling could make new contributions to understanding the climate evolution and variation in eastern Asia in future studies.It could facilitate the investigation of the regional differences in East Asian environmental changes and the asynchronous nature between the uplift of Qinghai-Tibetan Plateau and their climatic effects.These would be the keys to understanding underlying driving forces for the evolution of the East Asian climate.展开更多
In the northern South China Sea, the accumulation of enormous quantities of terrigenous sediment during Cenozoic rendered well-developed polymetallic nodules very rare. In this study, we analyzed a polymetallic nodule...In the northern South China Sea, the accumulation of enormous quantities of terrigenous sediment during Cenozoic rendered well-developed polymetallic nodules very rare. In this study, we analyzed a polymetallic nodule from the northwestern conti- nental margin of the South China Sea using microscopic mineralogical observation, electron probes, X-ray diffraction （XRD）, ICP-MS, and Be isotope dating. We found the nodule＇s shell layers rich in different types of microstructures, including co- lumnar, laminar, stack-like, petal-like, and porphyritic structures. The major mineral components of the nodule are MnO2. Unlike nodules from the eastern Pacific basin, this nodule has high contents in Fe, Si, A1, and REEs but low contents in Mn, Cu, Co, and Ni. The Mn/Fe ratio is also low and the average REEs content is 1370.4 ppm. There is a strong positive anomaly of Ce; and the Be （beryllium） isotope dating shows the initial time of growth of the nodule to be about 3.29 Ma. The inner compact layer formed from 3.29 Ma to about 1.83 Ma. The laminar and stack-like structures and the low contents of the terri- genous elements such as Fe, Si, REE, and A1 indicate the paleoceanographical environment with weak undersea currents and favorable oxidizing conditions. From 1.83 Ma to 0.73 Ma, the growth rate of the nodule increased by about 3%; the micro- structures formed during this period are stack-like and columnar. The contents of Si and A1 are increased by nearly 10%, indi- cating an increase of terrigenous sediment input in the northern South China Sea. The content of Ce is decreased by about 16% indicating a significant weakening of the oxidizing conditions at the seabed. From 0.73 Ma to 0.69 Ma, the growth rate of the nodule rapidly rose up to 8.27 times that of the nodule＇s average growth rate, and the contents of Fe, A1, and REEs in the layer also increased, forming a loose layer characterized by oolitic, granular, porphyritic, and petal-like structures, indicating the paleoceanographical environment with a high sedimemtation rate and abundant supply of terrigenous sediment in the northern South China Sea. From 0.69 Ma to 0.22 Ma, the growth rate of the nodule suddenly slowed and the outer compact layer formed. Contents of Fe, Si, REE, A1, Mn, Cu, Co, and Ni in this layer were significantly lower than in other layers. The main structures of the layer are laminar and fissure filling structures. These reflect the paleoceanographical environment with stable undersea currents, poor oxidizing conditions, and other conditions not conducive to nodule growth. The growth process of nodule S04-1DG-1 was found to respond sensitively to the changes of the paleoceanographical environment of the northern South China Sea during the late Cenozoic.展开更多
In the northwest of the Himalayan-Tibetan Orogen, the ~250 km-long Kongur Shan extensional system in the eastern Pamir was formed during the convergence between the Indian and Asian plates. Tectonic activity of the Ko...In the northwest of the Himalayan-Tibetan Orogen, the ~250 km-long Kongur Shan extensional system in the eastern Pamir was formed during the convergence between the Indian and Asian plates. Tectonic activity of the Kongur Shan normal fault and the Tashkurgan normal fault can help to reveal the origin of east-west extension along the Kongur Shan extensional system. The Kongur Shan fault has been extensively studied, while the Tashkurgan fault calls for systemic research. In this study, low-temperature thermochronology including apatite fission track analysis and apatite and zircon(U-Th)/He analyses is applied to constrain the timing of activity of the Tashkurgan fault. Results indicate that the Tashkurgan fault initiated at 10–5 Ma, and most likely at 6–5 Ma. The footwall of the Tashkurgan fault has been exhumed at an average exhumation rate of 0.6–0.9 mm/a since the initiation of the Tashkurgan fault. Combined with previous research on the Kongur Shan fault, we believe that the origin of east-west extension along the Kongur Shan extensional system was driven by gravitational collapse of over-thickened Pamir crust.展开更多
There is a massive amount of geomorphic evidence for active tectonics in the Longmen Shan at the eastern margin of the Tibetan plateau. We have surveyed some typical geomorphic markers including the Wenchuan-Maowen, B...There is a massive amount of geomorphic evidence for active tectonics in the Longmen Shan at the eastern margin of the Tibetan plateau. We have surveyed some typical geomorphic markers including the Wenchuan-Maowen, Beichuan-Yingxiu and Pengxian-Guanxian faults, terrace offsets, scarps, fault-controlled saddles, dextral shutter ridges, dextral channel offsets, graben, shatter belts, and pull-apart basins. Electron spin resonance （ESR） and thermoluminescence（TL） ages were obtained using silty sand taken from below the surface of the sediments. According to these data, we calculated the rates of thrusting and strike-slip, and the results indicate that Cenozoic tectonic shortening at the plateau margin is minor with the rate of thrusting less than 1.10 mm/a and the rate of strike-slipping less than 1.46 mm/a. The Longmen Shan is a zone of NNE-trending dextral shear with slip-dip ratio of 6：1-1.3：1. From NW to SE, the thrust component becomes smaller, whereas the strike-slip component becomes larger.展开更多
How the Altyn Tagh fault(ATF) extends eastwards is one of the key questions in the study of the growth of the Qinghai–Tibetan Plateau. Detailed fieldwork at the easternmost part of the ATF shows that the ATF extends ...How the Altyn Tagh fault(ATF) extends eastwards is one of the key questions in the study of the growth of the Qinghai–Tibetan Plateau. Detailed fieldwork at the easternmost part of the ATF shows that the ATF extends eastward and bypasses the Kuantan Mountain;it does not stop at the Kuantan Mountain, but connects with the northern Heishan fault in the east. The ATF does not enter the Alxa Block but extends eastward along the southern Alxa Block to the Jintanan Mountain. The Heishan fault is not a thrust fault but a sinistral strike-slip fault with a component of thrusting and is a part of the ATF. Further to the east, the Heishan fault may connect with the Jintananshan fault. A typical strike-slip duplex develops in the easternmost part of the ATF. The cut and deformed Quaternary sediments and displaced present gullies along the easternmost ATF indicate that it is an active fault. The local highest Mountain(i.e., the Kuantan Mountain) in the region forms in a restraining bend of the ATF due to the thrusting and uplifting. The northward growth of the Qinghai–Tibetan Plateau and the active deformation in South Mongolia are realized by sinistral strike-slipping on a series of NE–SW-trending faults and thrusting in restraining bends along the strike-slip faults with the northeastward motion of blocks between these faults.展开更多
The Hezheng area Of Gansu Province produces the most abundant mammal fossils in China as well as the whole Eurasia, and it also produces other Cenozoic fossils of different animals and plants. Therefore, all of them a...The Hezheng area Of Gansu Province produces the most abundant mammal fossils in China as well as the whole Eurasia, and it also produces other Cenozoic fossils of different animals and plants. Therefore, all of them are named the Hezheng Biota. Mammals are very sensitive to environmental changes, and thus the evolution of mammalian faunas in the Hezheng area reflects the strong uplift of the Tibetan Plateau during the Late Cenozoic, which dramatically affects environmental changes. In the Hezheng area, micromammals are not very rich, but some of them still are important. It is relatively uncommon that three primates are found from the Middle Miocene and the Early Pleistocene deposits. Since the Middle Miocene, carnivores have become important components in the ecosystem of the Hezheng area, and dominated in the Early Pleistocene. The Middle Miocene is a time of high diversity for Proboscidea, characterized by shovel-tusked elephants. Perissodactyls in the Hezheng area are very abundant, especially Late Oligocene and Late Miocene rhinoceroses as well as the Late Miocene and Early Pleistocene horses. From the Middle Miocene, artiodactyls became important components of the mammalian faunas, especially bovids.展开更多
The Huang Shui River, a main tributary of the Yellow River, crosses a series of tectonically subsided and uplifted areas that show different patterns of terrace formation. The distribution of fluvial terrace of the Hu...The Huang Shui River, a main tributary of the Yellow River, crosses a series of tectonically subsided and uplifted areas that show different patterns of terrace formation. The distribution of fluvial terrace of the Huang Shui River is studied through topographic and sedimentologic terrace mapping. Three terraces in the Haiyan Basin, four terraces in the Huangyuan Basin, 19 terraces in the Xi＇ning Basin （the four high terraces may belong to another river）, nine terraces in the Ping＇an Basin, five terraces in the Ledu Basin and 12 terraces in the Minhe Basin are recognized. Sedimentology research shows that the geomorphologic and sedimentological pattern of the Huang Shui River, which is located at the margin of Tibet, are different from that of the rivers at other regions. The formation process of the terrace is more complicated at the Huang Shui catchment： both accumulation terrace and erosion terrace were formed in each basin and accumulation terraces were developed in some basins when erosion terraces were formed in other basins, indicating fluvial aggradation may occur in some basins simultaneously with river incision in other basins. A conceptual model of the formation process of these two kinds of fluvial terraces at Huang Shui catchment is brought forward in this paper. First, the equilibrium state of the river is broken because of climatic change and/or tectonic movement, and the river incises in all basins in the whole catchment until reaching a new equilibrium state. Then, the downstream basin subsides quickly and the equilibrium state is broken again, and the river incises at upstream basins while the river accumulates at the subsidence basin quickly until approaching a new equilibrium state again. Finally, the river incises in the whole catchment because of climatic change and/or tectonic movement and the accumulation terrace is formed at the subsidence basin while the erosion terrace is formed at other basins. The existence of the accumulation terrace implied the tectonic subsidence in the sub-basins in Huang Shui catchment. These tectonic subsidence movements gradually developed from the downstream Minhe Basin to the upstream Huangyuan Basin. Dating the terrace sequence has potential to uncover the relationship between the subsidence in the catchment and the regional tectonic at the northeastern Tibetan Plateau.展开更多
Studying the climatic and environmental changes on different time scales in inland arid regions of Asia can greatly im‐prove our understanding of climatic influences for the Qinghai-Tibet Plateau in the context of gl...Studying the climatic and environmental changes on different time scales in inland arid regions of Asia can greatly im‐prove our understanding of climatic influences for the Qinghai-Tibet Plateau in the context of global change. Pollen, as a remnant of seed plants, is sensitive to environmental factors including precipitation, temperature and altitude, and is a clas‐sic proxy in environmental reconstruction. In the last two decades, great progress in the application of palynology to in‐land areas of Asia has highlighted the role of palynology in paleoclimatic and paleoenvironmental research. The main progress is as follows. (1) On the tectonic time scale of the late Cenozoic, the palaeoclimatological sequence has been es‐tablished on the basis of pollen percentage, concentration and taxon. Pollen data have revealed a continuous enhancement of drought in the inland arid region of Asia, in contrast to evidence acquired based on other proxies. (2) In the late Quater‐nary, an increase in herbaceous plants further supports the intensification of drought associated with global cooling. In more detail, the palynological record shows a glacial-interglacial pattern consistent with changes in global ice volume. (3) The Holocene pollen record has been established at a high resolution and across a wide range of inland areas. In general, it presents an arid grassland environment in the early Holocene, followed by the development of woody plants in the mid- to late-Holocene climate optimum. This pattern is related to moisture changes in areas dominated by the westerlies. There are also significant regional differences in the pattern and amplitude of vegetation response to the Holocene environment. (4) Modern pollen studies based on vegetation surveys, meteorological data and statistics show that topsoil palynology can better reflect regional vegetation types (e. g., grassland, meadow, desert). Drier climates yield higher pollen contents of drought-tolerant plants such as Chenopodioideae, Ephedra, and Nitriaria, while contents of Artemisia and Poaceae are greater under humid climates. Besides these achievements, problems remain in palynological research: for example, pol‐len extraction, identification, interpretation, and quantitative reconstruction. In the future, we encourage strengthened inter‐disciplinary cooperation to improve experimental methods and innovation. Firstly, we should strengthen palynological classification and improve the skill of identification;secondly, laboratory experiments are needed to better constrain pol‐len transport dynamics in water and air;thirdly, more rigorous mathematical principles will improve the reliability of re‐constructions and deepen the knowledge of plant geography;and finally, new areas and methods in palynology should be explored, for example DNA, UV-B and isotopic analysis. It is expected that palynology will continue to develop, and we hope it will continue to play an important role in the study of past climatic and environmental changes.展开更多
Genetic type of basement granite from volcanic arc in the north of West Burma Block is S-type granites, which developed in volcanic arc of convergent plate margins. The results yield a group of weighted mean ^206pb/^2...Genetic type of basement granite from volcanic arc in the north of West Burma Block is S-type granites, which developed in volcanic arc of convergent plate margins. The results yield a group of weighted mean ^206pb/^238U ages at 102±0.81 Ma （MSWD=0.23）, which show similarity to 93.7±3.4 Ma in the northern part of sampling points and 105±2 Ma in the southern part of sampling points, indicating continuous development of volcanic arc in the north of West Burma Block and subsequent granitic intrusion of late Early Cretaceous. The apatite fission track age of the samples is 22.72±3 Ma, thermal history modeling reveals that the volcanic arc in the north of West Burma Block went through two main stages in the process of uplift-cooling since Cenozoic： rapid uplifting and cooling from Late Oligocene to Early Miocene （29±1 to 20±1 Ma） and slow uplifting and cooling since Early Pliocene （4.2±1 Ma）.展开更多
As the second largest dust source on the globe,the tectonic and climatic evolution of continental Asia has an important impact on regional and global climate change.The West Pacific is the main sediment sink for eolia...As the second largest dust source on the globe,the tectonic and climatic evolution of continental Asia has an important impact on regional and global climate change.The West Pacific is the main sediment sink for eolian dust transported eastward from the Asian interior.Clay minerals,as the major fine-grained weathering products of continental rocks,can be readily transported by wind or currents over long distances and thus have been widely used in the reconstruction of paleoclimate and weathering history.However,the overall evolutionary tendency and response mechanism of clay mineral records over large spatial and long timescales across Asia remain unclear.Here,two continuous and high-resolution clay mineral records since 30 Ma were reconstructed from sediments at Deep Sea Drilling Program(DSDP)Sites 292 and 296 in the Philippine Sea.Clay minerals and Sr-Nd isotope compositions were used to constrain provenance and reconstruct the drying history of the dust source region since the Oligocene.The results show that the clay-sized detrital sediments in the Philippine Sea are a mixture of Asian eolian dust and volcanic materials from the West Pacific arcs.Based on the clay mineral compositions and eolian flux,we reveal that the Asian interior has been continuously drying since the late Oligocene and that stepwise enhanced aridification occurred at approximately 20,14,7,and 3 Ma.Compared with other regions of the world,the relative contents of illite and chlorite increased more dramatically in Asia during the late Cenozoic,and the inconsistency became more obvious at approximately 20 Ma.Since 3 Ma,illite and chlorite have increased consistently across the globe.Combined with the Asian tectonic and climatic history,we suggest that the increase in illite and chlorite from Asia between 20 and 3 Ma was mainly in response to the uplift of the Himalayan-Tibetan Plateau,whereas after 3 Ma,it was primarily controlled by global cooling driven by the expansion of the Arctic ice sheet.展开更多
基金This study was supported jointly by the National Natural Science Foundation grant 40572134 the Land and Resources Survey project ＂Environmental Evolution Sequence of Tertiary Major Paleolakes on the Qinghai- Tibet Plateau＂ （Ke[2003]007-02）.
文摘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.
文摘Dongsha Island and the adjacent sea area locate at the northern continental margin of the South China Sea (SCS), and is connected to the east by the Manila Trench. Analyses of seismic stratigraphy and gravity, magnetic and drilling wells data led to the discovery of three post fault sequences (V, VI, VII). Extensive tectonic uplift, magma activity and erosion occurred in Dongsha Island and the adjacent area, where most of the faults in the northeastern SCS were still active during Pliocene and Quaternary. Two groups of faults trending NEE and NW were developed during Late Cenozoic. We conclude that three important tectonic movements, especially Dongsha movement (4.4-5.2 Ma) and Liuhua movement (1.4-1.89 Ma), controlled the structural framework in the Dongsha rise; whose deformation in the east is stronger than that in the west and whose stress field variation suggests that the tectonic uplift in the study area contributed to magmato tectonic events correlated to the main collision phases between the East China and Taiwan 5-3 and 3-0 Ma ago.
基金supported by National Natural foundation of China (grants No. 41571013)China Geology Survey project (grants No. DD20160268)
文摘The north trending rifts in southern Tibet represent the E-W extension of the plateau and confirming the initial rifting age is key to the study of mechanics of these rifts. Pagri-Duoqing Co graben is located at southern end of Yadong-Gulu rift, where the late Cenozoic sediments is predominately composed of fluvio-lacustrine and moraine. Based on the sedimentary composition and structures, the fluviolacustrine could be divided into three facies, namely, lacustrine, lacustrine fan delta and alluvial fan. The presence of paleo-currents and conglomerate components and the provenance of the strata around the graben indicate that it was Tethys Himalaya and High Himalaya. Electron spin resonance(ESR) dating and paleo-magnetic dating suggest that the age of the strata ranges from ca. 1.2 Ma to ca. 8 Ma. Optically stimulated luminescence(OSL) dating showed that moraine in the graben mainly developed from around181-109 ka(late Middle Pleistocene). Combining previous data about the Late Cenozoic strata in other basins, it is suggested that 8-15 Ma may be the initial rifting time. Together with sediment distribution and drainage system, the sedimentary evolution of Pagri could be divided into four stages. The graben rifted at around 15-8 Ma due to the eastern graben-boundary fault resulting in the appearance of a paleolake.Following by a geologically quiet period about 8-2.5 Ma, the paleolake expanded from east to west at around 8-6 Ma reaching its maximum at ca. 6 Ma. Then, the graben was broken at about 2.5 Ma. At last,the development of the glacier separated the graben into two parts that were Pagri and Duoqing Co since the later stages of the Middle Pleistocene. The evolution process suggested that the former three stages were related to the tectonic movement, which determined the basement of the graben, while the last stage may have been influenced by glacial activity caused by climate change.
基金the work of "Study of the geo-scientific settings of geo-tourist landscapes in Yuntaishan World Geopark",and supported by the Department of International Cooperation of Ministry of Science and Technology of China. (Grant No. 2006DFA21320)the Science Foundation of institute of geomechanics, CAGS (Grant No. DZLXJK200706) the National Natural Science Foundation of China (Grant No. 40501006)
文摘The late Cenozoic geomorphic features and geochronologic data of the Zhingfang River catchment in the Yuntaishan World Geopark are studied. Several quarternary geochronologic methods, including electron spin resonance （ESR）, optically stimulated luminescence （OSL）, thermo-luminescence （TL） and U-series are presented in this paper. The results suggest that there are two planation surfaces, named as the Taihang surface which is a peneplain of Taihang stage formed during Oligocene or Oligocene to early-middle Miocene period, and Tang-hien surface which is a mature wide valley of Tang-hien stage formed during late Miocene-Pliocene or Piiocene-early Pleistocene period and probably ended prior to 2.2-2.6 Ma based on ESR dating. After the Tang-hien stage, the incision and aggradation of the river formed six stream terraces with heights of 3-5 m, 8-12 m, 22-24 m, 28-38 m, 50-62 m and 80-85 m above the river bottom, respectively. The dating results of the alluvium sediments suggest that these terraces were formed during Holocene, 20-23 ka B.P., 110-120 ka B.P., 200-240 ka B.P., 840-1200 ka B.P. or ~450 ka B.P. and 1600-1800 ka B.P. or -1100 ka B.P., respectively. These results indicate that episodic incision of the river, which controls the formation of the scenery in the Yuntaishan World Geopark, was mainly influenced by the periodic dry-wet climate change during late Cenozoic mountain uplift.
基金supported by the study grants from China Geological Survey (No.1212011120100,1212011120099 and 1212011220259)
文摘The Tianshui Basin,located inside the western Qinling orogenic belt and northeastern margin of the Tibetan Plateau （Fig.1）,is a NE-trending Late Cenozoic basin,which documents the neotectonic response of the northeastward growth of Tibetan Plateau.
基金supported by the Global Change Research Program of Ministry of Science and Technology of China(Grant No.2010CB950200)National Natural Science Foundation of China(Grant No.40930103)
文摘Climate in Eastern Asia is composed of monsoon climate in the east,arid and semi-arid climate in the north and west,and the cold and dry climate of Qinghai-Tibetan Plateau in the southwest.The underlying causes for the evolution of East Asian climate during late Cenozoic have long been investigated and debated,particularly with regards to the role played by the Qinghai-Tibetan Plateau uplift and the global cooling.In this paper,we reviewed major research developments in this area,and summarized the important results.Based on a synthesis of data,we propose that the Qinghai-Tibetan Plateau uplift alone cannot fully explain the formation of monsoon and arid climates in Eastern Asia during the past 22–25 Ma.Other factors such as the global ice volume and high-latitude temperature changes have also played a vital role.Moreover,atmospheric CO2changes may have modulated the monsoon and dry climate changes by affecting the location of the inter-tropical convergence zone(ITCZ),which controls the monsoon precipitation zone and the track of the East Asian winter monsoon during late Cenozoic.The integration of high-resolution geological record and numerical paleoclimate modeling could make new contributions to understanding the climate evolution and variation in eastern Asia in future studies.It could facilitate the investigation of the regional differences in East Asian environmental changes and the asynchronous nature between the uplift of Qinghai-Tibetan Plateau and their climatic effects.These would be the keys to understanding underlying driving forces for the evolution of the East Asian climate.
基金supported by National Natural Science Foundation of China(Grant Nos.40972079,41172015 and 41030853)National Basic Research Program of China(Grant No.2007CB411703)Education Department of Hebei Province(Grant Nos.2009443,2010248)
文摘In the northern South China Sea, the accumulation of enormous quantities of terrigenous sediment during Cenozoic rendered well-developed polymetallic nodules very rare. In this study, we analyzed a polymetallic nodule from the northwestern conti- nental margin of the South China Sea using microscopic mineralogical observation, electron probes, X-ray diffraction （XRD）, ICP-MS, and Be isotope dating. We found the nodule＇s shell layers rich in different types of microstructures, including co- lumnar, laminar, stack-like, petal-like, and porphyritic structures. The major mineral components of the nodule are MnO2. Unlike nodules from the eastern Pacific basin, this nodule has high contents in Fe, Si, A1, and REEs but low contents in Mn, Cu, Co, and Ni. The Mn/Fe ratio is also low and the average REEs content is 1370.4 ppm. There is a strong positive anomaly of Ce; and the Be （beryllium） isotope dating shows the initial time of growth of the nodule to be about 3.29 Ma. The inner compact layer formed from 3.29 Ma to about 1.83 Ma. The laminar and stack-like structures and the low contents of the terri- genous elements such as Fe, Si, REE, and A1 indicate the paleoceanographical environment with weak undersea currents and favorable oxidizing conditions. From 1.83 Ma to 0.73 Ma, the growth rate of the nodule increased by about 3%; the micro- structures formed during this period are stack-like and columnar. The contents of Si and A1 are increased by nearly 10%, indi- cating an increase of terrigenous sediment input in the northern South China Sea. The content of Ce is decreased by about 16% indicating a significant weakening of the oxidizing conditions at the seabed. From 0.73 Ma to 0.69 Ma, the growth rate of the nodule rapidly rose up to 8.27 times that of the nodule＇s average growth rate, and the contents of Fe, A1, and REEs in the layer also increased, forming a loose layer characterized by oolitic, granular, porphyritic, and petal-like structures, indicating the paleoceanographical environment with a high sedimemtation rate and abundant supply of terrigenous sediment in the northern South China Sea. From 0.69 Ma to 0.22 Ma, the growth rate of the nodule suddenly slowed and the outer compact layer formed. Contents of Fe, Si, REE, A1, Mn, Cu, Co, and Ni in this layer were significantly lower than in other layers. The main structures of the layer are laminar and fissure filling structures. These reflect the paleoceanographical environment with stable undersea currents, poor oxidizing conditions, and other conditions not conducive to nodule growth. The growth process of nodule S04-1DG-1 was found to respond sensitively to the changes of the paleoceanographical environment of the northern South China Sea during the late Cenozoic.
基金funded by the National Natural Science Foundation of China (Nos. 41720104003 and 41330207)the National Science and Technology Major Project of China (Nos. 2017ZX05008-001 and 2016ZX05003-001)Chen S Q receives a PhD grant (No. 201706320352) from the China Scholarship Council。
文摘In the northwest of the Himalayan-Tibetan Orogen, the ~250 km-long Kongur Shan extensional system in the eastern Pamir was formed during the convergence between the Indian and Asian plates. Tectonic activity of the Kongur Shan normal fault and the Tashkurgan normal fault can help to reveal the origin of east-west extension along the Kongur Shan extensional system. The Kongur Shan fault has been extensively studied, while the Tashkurgan fault calls for systemic research. In this study, low-temperature thermochronology including apatite fission track analysis and apatite and zircon(U-Th)/He analyses is applied to constrain the timing of activity of the Tashkurgan fault. Results indicate that the Tashkurgan fault initiated at 10–5 Ma, and most likely at 6–5 Ma. The footwall of the Tashkurgan fault has been exhumed at an average exhumation rate of 0.6–0.9 mm/a since the initiation of the Tashkurgan fault. Combined with previous research on the Kongur Shan fault, we believe that the origin of east-west extension along the Kongur Shan extensional system was driven by gravitational collapse of over-thickened Pamir crust.
基金This research was supported by the National Nature Foundation of China （49803031, 40372084） the Seismic Scientific United Fund （95-07-0425）+3 种基金 US National Science Foundation grant EAR-0125565 ETH Forschungskommission grant TH-4/03-01 Key Subject Program of Sichuan province Grant No. SZD0408 and the Program for the Subject of Ph.D. in Higher Education Institute, Grant No.20050616004.
文摘There is a massive amount of geomorphic evidence for active tectonics in the Longmen Shan at the eastern margin of the Tibetan plateau. We have surveyed some typical geomorphic markers including the Wenchuan-Maowen, Beichuan-Yingxiu and Pengxian-Guanxian faults, terrace offsets, scarps, fault-controlled saddles, dextral shutter ridges, dextral channel offsets, graben, shatter belts, and pull-apart basins. Electron spin resonance （ESR） and thermoluminescence（TL） ages were obtained using silty sand taken from below the surface of the sediments. According to these data, we calculated the rates of thrusting and strike-slip, and the results indicate that Cenozoic tectonic shortening at the plateau margin is minor with the rate of thrusting less than 1.10 mm/a and the rate of strike-slipping less than 1.46 mm/a. The Longmen Shan is a zone of NNE-trending dextral shear with slip-dip ratio of 6：1-1.3：1. From NW to SE, the thrust component becomes smaller, whereas the strike-slip component becomes larger.
基金funded by the National Natural Science Foundation of China(Nos.41972224,41572190)the National Key Research and Development Program of China from the Ministry of Science and Technology of China(No.2017YFC0601301)the China Geological Survey(DD20190004)。
文摘How the Altyn Tagh fault(ATF) extends eastwards is one of the key questions in the study of the growth of the Qinghai–Tibetan Plateau. Detailed fieldwork at the easternmost part of the ATF shows that the ATF extends eastward and bypasses the Kuantan Mountain;it does not stop at the Kuantan Mountain, but connects with the northern Heishan fault in the east. The ATF does not enter the Alxa Block but extends eastward along the southern Alxa Block to the Jintanan Mountain. The Heishan fault is not a thrust fault but a sinistral strike-slip fault with a component of thrusting and is a part of the ATF. Further to the east, the Heishan fault may connect with the Jintananshan fault. A typical strike-slip duplex develops in the easternmost part of the ATF. The cut and deformed Quaternary sediments and displaced present gullies along the easternmost ATF indicate that it is an active fault. The local highest Mountain(i.e., the Kuantan Mountain) in the region forms in a restraining bend of the ATF due to the thrusting and uplifting. The northward growth of the Qinghai–Tibetan Plateau and the active deformation in South Mongolia are realized by sinistral strike-slipping on a series of NE–SW-trending faults and thrusting in restraining bends along the strike-slip faults with the northeastward motion of blocks between these faults.
基金This work is supported by the National Natural Science Foundation of China(No.40232023)Chinese Academy of Sciences(No.KZCX2-103 and RJZ2001-105)Ministry of Science and Technology of China(No.G2000077700).|
文摘The Hezheng area Of Gansu Province produces the most abundant mammal fossils in China as well as the whole Eurasia, and it also produces other Cenozoic fossils of different animals and plants. Therefore, all of them are named the Hezheng Biota. Mammals are very sensitive to environmental changes, and thus the evolution of mammalian faunas in the Hezheng area reflects the strong uplift of the Tibetan Plateau during the Late Cenozoic, which dramatically affects environmental changes. In the Hezheng area, micromammals are not very rich, but some of them still are important. It is relatively uncommon that three primates are found from the Middle Miocene and the Early Pleistocene deposits. Since the Middle Miocene, carnivores have become important components in the ecosystem of the Hezheng area, and dominated in the Early Pleistocene. The Middle Miocene is a time of high diversity for Proboscidea, characterized by shovel-tusked elephants. Perissodactyls in the Hezheng area are very abundant, especially Late Oligocene and Late Miocene rhinoceroses as well as the Late Miocene and Early Pleistocene horses. From the Middle Miocene, artiodactyls became important components of the mammalian faunas, especially bovids.
基金supported by the National Natural Science Foundation of China(Grant no.40901002 and 40325007)the 985 project to Nanjing University and the CAS-KNAW PhD project(05-PhD-10)
文摘The Huang Shui River, a main tributary of the Yellow River, crosses a series of tectonically subsided and uplifted areas that show different patterns of terrace formation. The distribution of fluvial terrace of the Huang Shui River is studied through topographic and sedimentologic terrace mapping. Three terraces in the Haiyan Basin, four terraces in the Huangyuan Basin, 19 terraces in the Xi＇ning Basin （the four high terraces may belong to another river）, nine terraces in the Ping＇an Basin, five terraces in the Ledu Basin and 12 terraces in the Minhe Basin are recognized. Sedimentology research shows that the geomorphologic and sedimentological pattern of the Huang Shui River, which is located at the margin of Tibet, are different from that of the rivers at other regions. The formation process of the terrace is more complicated at the Huang Shui catchment： both accumulation terrace and erosion terrace were formed in each basin and accumulation terraces were developed in some basins when erosion terraces were formed in other basins, indicating fluvial aggradation may occur in some basins simultaneously with river incision in other basins. A conceptual model of the formation process of these two kinds of fluvial terraces at Huang Shui catchment is brought forward in this paper. First, the equilibrium state of the river is broken because of climatic change and/or tectonic movement, and the river incises in all basins in the whole catchment until reaching a new equilibrium state. Then, the downstream basin subsides quickly and the equilibrium state is broken again, and the river incises at upstream basins while the river accumulates at the subsidence basin quickly until approaching a new equilibrium state again. Finally, the river incises in the whole catchment because of climatic change and/or tectonic movement and the accumulation terrace is formed at the subsidence basin while the erosion terrace is formed at other basins. The existence of the accumulation terrace implied the tectonic subsidence in the sub-basins in Huang Shui catchment. These tectonic subsidence movements gradually developed from the downstream Minhe Basin to the upstream Huangyuan Basin. Dating the terrace sequence has potential to uncover the relationship between the subsidence in the catchment and the regional tectonic at the northeastern Tibetan Plateau.
基金the NSFC(41772181,41807440 and 41888101)the Strategic Priority Research Program of CAS(No.XDA20070200)+4 种基金Young Top Talents Project of the"Ten Thousand Youth Program"of the Organization Department of the Central Committee of the CPCYouth Innovation Promotion Association,CAS(2014383)"Light of West China"Program,CASand the NSF of Gansu Province(18JR3RA395)We thank Miao's group members and anonymous referees for discussions and their constructive suggestions。
文摘Studying the climatic and environmental changes on different time scales in inland arid regions of Asia can greatly im‐prove our understanding of climatic influences for the Qinghai-Tibet Plateau in the context of global change. Pollen, as a remnant of seed plants, is sensitive to environmental factors including precipitation, temperature and altitude, and is a clas‐sic proxy in environmental reconstruction. In the last two decades, great progress in the application of palynology to in‐land areas of Asia has highlighted the role of palynology in paleoclimatic and paleoenvironmental research. The main progress is as follows. (1) On the tectonic time scale of the late Cenozoic, the palaeoclimatological sequence has been es‐tablished on the basis of pollen percentage, concentration and taxon. Pollen data have revealed a continuous enhancement of drought in the inland arid region of Asia, in contrast to evidence acquired based on other proxies. (2) In the late Quater‐nary, an increase in herbaceous plants further supports the intensification of drought associated with global cooling. In more detail, the palynological record shows a glacial-interglacial pattern consistent with changes in global ice volume. (3) The Holocene pollen record has been established at a high resolution and across a wide range of inland areas. In general, it presents an arid grassland environment in the early Holocene, followed by the development of woody plants in the mid- to late-Holocene climate optimum. This pattern is related to moisture changes in areas dominated by the westerlies. There are also significant regional differences in the pattern and amplitude of vegetation response to the Holocene environment. (4) Modern pollen studies based on vegetation surveys, meteorological data and statistics show that topsoil palynology can better reflect regional vegetation types (e. g., grassland, meadow, desert). Drier climates yield higher pollen contents of drought-tolerant plants such as Chenopodioideae, Ephedra, and Nitriaria, while contents of Artemisia and Poaceae are greater under humid climates. Besides these achievements, problems remain in palynological research: for example, pol‐len extraction, identification, interpretation, and quantitative reconstruction. In the future, we encourage strengthened inter‐disciplinary cooperation to improve experimental methods and innovation. Firstly, we should strengthen palynological classification and improve the skill of identification;secondly, laboratory experiments are needed to better constrain pol‐len transport dynamics in water and air;thirdly, more rigorous mathematical principles will improve the reliability of re‐constructions and deepen the knowledge of plant geography;and finally, new areas and methods in palynology should be explored, for example DNA, UV-B and isotopic analysis. It is expected that palynology will continue to develop, and we hope it will continue to play an important role in the study of past climatic and environmental changes.
基金supported by the Major National Science and Technology Programs in the Twelfth Five-Year Plan Period(No. 2011ZX05030-002-003)the Major National Science and Technology Programs in the Eleventh Five-Year Plan Period(No. 2008ZX05030-02-03-01)the Open Research Fund of Key Laboratory of Tectonics and Petroleum Resources of Min-istry of Education, China (No. TPR-2011-07)
文摘Genetic type of basement granite from volcanic arc in the north of West Burma Block is S-type granites, which developed in volcanic arc of convergent plate margins. The results yield a group of weighted mean ^206pb/^238U ages at 102±0.81 Ma （MSWD=0.23）, which show similarity to 93.7±3.4 Ma in the northern part of sampling points and 105±2 Ma in the southern part of sampling points, indicating continuous development of volcanic arc in the north of West Burma Block and subsequent granitic intrusion of late Early Cretaceous. The apatite fission track age of the samples is 22.72±3 Ma, thermal history modeling reveals that the volcanic arc in the north of West Burma Block went through two main stages in the process of uplift-cooling since Cenozoic： rapid uplifting and cooling from Late Oligocene to Early Miocene （29±1 to 20±1 Ma） and slow uplifting and cooling since Early Pliocene （4.2±1 Ma）.
基金supported by the National Natural Science Foundation of China(Grant Nos.42125602,42076052)the National Key Research and Development Program of China(Grant No.2022YFF0800503)+3 种基金the Strategic Priority Research Program of CAS(Grant No.XDB40010100)the Marine S&T Fund of Shandong Province for QNLM(Grant No.2022QNLM050203)the Innovation Project of QNLM(Grant No.MGQNLM-KF202001)the Taishan and Aoshan Talents Program(Grant No.2017ASTCP-ES01).
文摘As the second largest dust source on the globe,the tectonic and climatic evolution of continental Asia has an important impact on regional and global climate change.The West Pacific is the main sediment sink for eolian dust transported eastward from the Asian interior.Clay minerals,as the major fine-grained weathering products of continental rocks,can be readily transported by wind or currents over long distances and thus have been widely used in the reconstruction of paleoclimate and weathering history.However,the overall evolutionary tendency and response mechanism of clay mineral records over large spatial and long timescales across Asia remain unclear.Here,two continuous and high-resolution clay mineral records since 30 Ma were reconstructed from sediments at Deep Sea Drilling Program(DSDP)Sites 292 and 296 in the Philippine Sea.Clay minerals and Sr-Nd isotope compositions were used to constrain provenance and reconstruct the drying history of the dust source region since the Oligocene.The results show that the clay-sized detrital sediments in the Philippine Sea are a mixture of Asian eolian dust and volcanic materials from the West Pacific arcs.Based on the clay mineral compositions and eolian flux,we reveal that the Asian interior has been continuously drying since the late Oligocene and that stepwise enhanced aridification occurred at approximately 20,14,7,and 3 Ma.Compared with other regions of the world,the relative contents of illite and chlorite increased more dramatically in Asia during the late Cenozoic,and the inconsistency became more obvious at approximately 20 Ma.Since 3 Ma,illite and chlorite have increased consistently across the globe.Combined with the Asian tectonic and climatic history,we suggest that the increase in illite and chlorite from Asia between 20 and 3 Ma was mainly in response to the uplift of the Himalayan-Tibetan Plateau,whereas after 3 Ma,it was primarily controlled by global cooling driven by the expansion of the Arctic ice sheet.
