Abrupt uplift of Tibetan Plateau a t the end of early Pleistocene and Australasian impact event

The latest sharp uplift of the Tibetan Plateau and adjacent mountains occurred at the end of the early Pleistocene. The uplift of the Plateau resulted from Late Mesozoic－Cenozoic comp ressional structure due to the subduction of the Indian Plate beneath the Asian continent. This event definitively effected the formation of basin-mountain relief, Cenozoic basin deformation, large scale aridity and desertification of western China. The Australasian meteorites impact event happened ca. 0.8 Ma ago, located in the triangle area of the Indian Ocean ridge (20°S/67°E) . The impact may have resulted in an acceleration of speeding of the Indian Ocean ridge pushing the Indian Plate to subduct rapidly northward. Thus, the impact event can give reasonable explanation for the dynamic background of the latest rapid uplift of the Tibetan Plateau and the continental deformation of western China and even of the Middle Asia.     

Red Clay Sediment in the Central Chinese Loess Plateau and Its Implication for the Uplift of the Tibetan Plateau

Introduction A set of reddish clay-silt-sized sediments named red clay underlying the Quaternary loess-paleosol sequence widely distribute in the Chinese Loess Plateau. The thickness of the red clay sediments ranges from decades of meters to over 100 m (Evan et al.1991,Mo and Derbyshire 1991, SUN et al. 1997&1998, DING et al. 1999, GUO et al. 2001, QIANG et al. 2001). Previous studies show that not only loess-paleosol (e.g.LIU et al.1985,AN et al.1990,DING et al.1992),but also red …     

大陆岩石圈的增厚及对流剥离对青藏高原隆升的影响

伴随着印度板块对欧亚板块南缘的碰撞、挤压,青藏高原地壳及下伏地幔岩石圈的厚度增加了１倍。增厚岩石圈热结构的变化可导致高原海拨下降约１５００ｍ。其对流剥离并被较热的软流圈物质替代可用以解释青藏高原自８百万年或３百万年前开始的快速隆升。大陆岩石圈的增厚及热结构变化和对流剥离可能是青藏高原自９百万年前开始的夷平—快速隆升过程的主导控制因素。     

青藏高原挠曲均衡重力异常特征及其地质意义

自新生代印度板块的块持续碰撞与俯冲作用下,青藏高原经历了快速隆升与复杂的岩石圈改造过程,但高原现今的垂向动力学机制和地壳形变特征仍然存在争议。基于非均一有效弹性厚度的挠曲模型,利用地形和地球重力场模型数据,计算了青藏高原及邻区的挠曲均衡重力异常。结果显示,青藏高原的均衡重力异常在-120~90 mGal之间,高原中部为明显的正异常特征,边缘为显著的均衡负异常。极小值出现在青藏高原西北部及其相邻的帕米尔高原,极大值则出现在与之紧邻的喜马拉雅块体西北部。此外,在青藏高原北面和东面,塔里木盆地和四川盆地显示出大片的均衡正异常。这些特征说明青藏高原及邻区地壳现今处于非均衡的状态,在板块碰撞挤压作用下,老的块体地壳整体发生抬升,导致了均衡正异常特征;而年轻的造山区域,地壳形变主要表现为地表抬升与下地壳强烈增厚,形成了均衡负异常。在高原中部和北部,均衡调整方向与地壳垂向运动趋势相一致;但在高原南面（喜马拉雅块体）和东面（四川盆地）,均衡调整方向与地表形变观测结果相反。这说明印度板块碰撞与俯冲仍然控制着青藏高原南部、东部及其相邻块体的地壳形变过程,然而在更北的区域,地壳正通过均衡调整恢复均衡状态。      

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四川盆地北缘大巴山前陆构造中—新生代构造隆升史

大巴山前陆构造的抬升剥蚀与保存条件对其矿床和油气藏勘探潜力评价极为重要。应用磷灰石裂变径迹热年代学方法,通过研究大巴山前陆构造热演化史,恢复构造隆升过程,确定其中—新生代构造抬升剥蚀量,探讨大巴山前陆晚期构造隆升对矿床和油气资源的影响。结果表明:大巴山前陆构造在152Ma以前快速沉降,沉降速率平均高达150m·Ma-1,此后便长期处于隆升过程;136~152Ma时期为快速隆升阶段,隆升速率平均为56.3m·Ma-1,隆升量约为900m,是燕山运动导致秦岭造山期后的一次陆内挤压;70~136Ma时期为较缓慢隆升阶段,隆升速率平均为39.4m·Ma-1,隆升量约为2 600m,是秦岭造山晚期挤压的结果;0~70Ma时期的隆升速率为42.8m·Ma-1,持续时间较长,隆升幅度约3 000m,是喜马拉雅构造运动的结果。中生代构造隆升对本区低温热液矿体和油气保存极为不利;上新统以来(8Ma或5Ma),青藏高原快速隆升向东扩展的远程效应对大巴山前陆构造的影响不明显。     

Paleosols and their reflection of the environmental changes in the northeast region of the Qinghai-Xizang Plateau

Based on field investigations, laboratory analyses and ¹⁴C dating, this paper discusses the laws of the formation and development of the paleosols in the northeast region of the Qinghai-Xizang Plateau since Late Pleistocene. The authors reconstruct basic conditions of climate, vegetation, soil and natural zones during the three periods in which the paleosols were formed, i.e. the last interglacial of the Late Pleistocene, warm stage of Late Glacial and the Optimum of Holocene. Finally, this paper discusses the relationship between the paleosols and the uplift of the Qinghai-Xizang Plateau.     

PALEOSOLS AND THEIR REFLECTION OF THE ENVIRONMENTAL CHANGES IN THE NORTHEAST REGION OF THE QINGHAI－XIZANG PLATEAU

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Quartz grain surface microtextural evidence for provenance of the Quaternary aggradation red earth deposit,southern China

The Quaternary aggradation red earth(QARE) deposit in the middle reaches of the Yangtze River(MRYR) in southern China provides important evidence for understanding the paleoenvironment. However, its provenance remains controversial. In this study, the surface microtextures of grains from the QARE were observed, and compared with those of grains from the loess deposit on the Loess Plateau in northern China. The results show that the surface microtextures and morphologies of the quartz grains in the QARE are distinctly different from those in the northern loess, indicating that the deposits in the two regions have different provenances. The Gobi and deserts in inland northwestern China are not considered as the primary provenance for the QARE in southern China. It is suggested that the large areas of dry and bare river and lake beds and floodplains in the MRYR, which became exposed during glacial periods, provided the dominant source for materials in the QARE. We suggest that against the background of the middle-Pleistocene climate transition(MPT), regional aridification and a strengthened east Asian winter monsoon(driven by global cooling and the rapid uplift of the Tibetan Plateau) were primary drivers for the initiation of the QARE deposit in the MRYR region in southern China. The development of large areas of aeolian red earth deposit is direct evidence of environmental deterioration in the MRYR, indicating a cold and dry environment with frequent aeolian activity, in an area that now experiences a warm and humid subtropical monsoon climate. The results are also evidence of a regional response in the mid-subtropics of southern China to the MPT global cooling event around 1.2 Ma.     

Progress in studies on geographical environments of the Qinghai-Xiang plateau

The Qinghai-Xizang (Tibet) Plateau area was subjected to twice uplift and planation in the Tertiary. Intense uplifting of the plateau area has given rise to drastic changes and differentiation of physical environment on the plateau and the surrounding area since 3.4 Ma B.P. Significant environmental changes with dry tendency in interior of the plateau had occurred during the last 150 ka B.P. By comparative study on several mountains of the plateau, two systems of the structure-type of the altitudinal belt are identified and nine groups are subdivided. A distribution model with close relevance to highland uplift effect has been generalized. A number of striking geo-ecological phenomen and their spatial pattern such as moisture corridor, dry valleys, high-cold meadow zone, and high-cold arid core area are investigated and discussed. Based on the thermal conditions, moisture regimes and variation in landforms of the plateau is sequentially demarcated. A tentative scheme of 2 temperature belts, 10 natural zones and 28 physical districts has been proposed not including southern slopes of the East Himalayas. The Qinghai-Xizang Plateau is sensitive to “green house effect”, showing close relation with global change. Characteristics of temperature and precipitation on the plateau during the last 2000 years, and response of glaciers, snow deposit and permafrost on the plateau to global change are dealt with in the present paper. Under the auspices of Chinese National Key Project for Basic Research (G1998040800) and CAS project on the Qinghai-Xizang Plateau (KZ951 - A1 - 204, KZ95T - 06)     

RECENT DEVELOPMENT OF RESEARCH ON ENVIRONMENTAL EVOLUTION IN CHINA

Recent achievements of the research on Chinese environmental evolution are brieny summarized in this paper. Following aspects are touched upon: relationship between Chinese environmental evolution and global change, the influence of the swift uplift of the Qinghai-Xizang Plateau, time sequence and the reconstruction of environment in characteristic stages, trend towards dryness in north and northwestern China, sea level change and regional studies.     

Critical Approach to Methods of Glacier Reconstruction in High Asia and Discussion of the Probability of a Qinghai-Xizang （Tibetan） Inland Ice

This overview discusses old and new results as to the controversy on the past glacier extension in High Asia, which has been debated for 35 years now. This paper makes an attempt to come closer to a solution. H.v. Wissmann's interpretation (1959) of a small-scale glaciation contrasts with M. Kuhle's reconstruction (1974) of a large-scale glaciation with a 2.4 million km2 extended Qinghai-Xizang (Tibetan) inland glaciation and a Himalaya-Karakorum icestream network. Both opinions find support but also contradiction in the International and Chinese literature (Academia Sinica). The solution of this question is of supraregional importance because of the subtropical position of the concerned areas. In case of large albedo-intensive ice surfaces, a global cooling would be the energetical consequence and, furthermore, a breakdown of the summer monsoon. The current and interglacial heat-low above the very effective heating panel of the Qinghai-Xizang (Tibetan) Plateau exceeding 4000 m, which gives rise to this monsoon circulation, would be replaced by the cold-high of an inland ice. In addition, the plate-tectonically created Pleistocene history of the uplift of High Asia — should the occasion arise up to beyond the snowline (ELA) —would attain a paleoclimatically great, perhaps global importance. In case of a heavy superimposed ice load, the question would come up as to the glacio-isostatic interruption of this primary uplift. The production of the loesses sedimentated in NE-China and their very probable glacial genesis as well as an eustatic lowering of the sea-level by 5 to 7 m in the maximum case of glaciation are immediately tied up with the question of glaciation we want to discuss. Not the least, the problems of biotopes of the sanctuary-centres of flora and fauna, i.e., interglacial re-settlement, are also dependent on it. On the basis of this Quaternary- geomorphological-glaciological connection, future contributions are requested on the past glaciation, the current and glacial permafrost table and periglacial development, the history of uplift, and the development of Ice Age lakes and loess, but also on the development of vegetation and fauna in High Asia.     

基于填充海拔的金沙江南流泄口位置

长江的发育演化尤其是东西贯通的时限问题,是百余年来地学界的焦点问题,金沙江水系的演化重组是长江演化中的关键一环。基于填充海拔的模型模拟以及物源示踪的梳理结果,讨论了金沙江在夷平面上南流汇入红河的可能性。结果显示当海拔填充至2 000~2 200 m时,金沙江水系格局发生重大变化,表现为金沙江在金江街一改东流之势,沿宾川盆地汇入古红河;古雅砻江在攀枝花附近转而向西,沿金沙江河谷经宾川盆地流入古红河,形成古红河的一级支流。推断哀牢山-红河断裂带、程海-宾川断裂带的活动及山体隆升特别是鸡足山的隆升可能阻断了上述南流泄口,切断了金沙江与红河的联系,从而形成今日江水东流的水系格局,这为古金沙江南流路径的研究提供了新的思路和方向。     

Sediment Delivery across Multiple Spatio-temporal Scales in an Agriculture Watershed of the Chinese Loess Plateau

There is a consensus that sediment delivery ratio in the Chinese Loess Plateau is close to 1at the inter-annual timescale. However, little information is available about the sediment delivery at finer timescales. We evaluated the sediment delivery from plots to watersheds at the event or intra-annual, annual, and inter-annual timescales within the Wudinghe river basin, a 30,261 km2 basin in the Loess Plateau. We calculated the ratio of sediment output to sediment input and presented the temporal change of the channel morphology to determine whether sediment deposition occurs.Although a single flood event frequently has a sediment yield exceeding 10,000 t km-2, sediment deposition rarely occurs except during some small runoff events(sediment yield 5000 t km-2) or dry years(sediment yield 10,000 t km-2) when moving from slopes up to the main channels of the Wudinghe River. This observation suggests a sediment delivery ratio close to 1 even at the event or intra-annual and the annual timescales, but not necessarily at the interannual timescale. Such a high sediment delivery ratio can be related to hyper-concentrated flows, which have very strong sediment transport capacity even at low flow strength. Because hyper-concentrated flows are well-developed in the whole Loess Plateau, a sediment delivery ratio close to 1 below the interannual timescale possibly remains true for other rivers in the Loess Plateau.     

托克妥环形构造与铜的成矿关系及今后找矿方向

托克妥环形构造处于昆中断裂的次级构造带上,形成于三叠纪,为一火山构造,属于火山颈相。随着青藏高原的抬升,其一直处于剥蚀阶段,至目前最有利于铜成矿的火山口构造已被剥蚀,只留下了火山颈的部分。经研究认为找铜的方向应在火山构造与围岩的接触带上,特别是接触带产状较缓的部位。     

The anisotropy of loess magnetic susceptibility in the northeastern fringe of Qinghai-Xizang Plateau as an indicator of palaeowind direction

Estimates of the palaeo-subaerial wind direction were studied systematically for the first time by using the anisotropy of loess magnetic susceptibility (AMS) measurements in the northwestern China. One hundred and forty undisturbed oriented aeolian loess samples were collected from Lanzhou, Linxia and Wudu areas for AMS measurements, which indicated the subaerial wind directions were not the same while the loess deposited. From the Early Pleistocene to Middle Pleistocene till Late Pleistocene, the wind direction experienced an anticlockwise rotation in the studied area. We suggested this change was related to the uplift of the Qinghai-Xizang Plateau and the adjustment of current and landform effects.     

倒刺鲃属鱼类物种分化的研究

依据倒刺属内部骨骼和外部形态特征，结合其地理分布．首次探讨了该属鱼的物种分化与区域地理演变历史的关系。研究结果表明，倒刺属鱼类共有３个共同离征。其一级姐妹群的分布范围在中国东南沿海地区有较大的重叠。二级姐妹群的分化与云贵高原的抬升和相应的水系分流有密切的关系。三级和四级姐妹群的分化主要是由于生活环境的差异所致。     

The anisotropy of loess magnetic susceptibility in the northeastern fringe of Qinghai-Xizang Plateau as an indicator of palaeowind direction

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Analysis of longitudinal profiles along the eastern margin of the Qinghai-Tibetan Plateau

Resulting from the collision of the Eurasian and Indian plates, the Qinghai-Tibetan Plateau is commonly known as the ’roof of the world’. Collectively the Yarlung Tsangpo, Nu, Lancang, Yangtze, Yalong, and Yellow River basins drain the eastern margin of the plateau. In this paper, we utilize Shuttle Radar Topography Mission elevation data to examine morphometric and relief attributes of these basins to reveal insights into tectonic activity and rates of incision. A robust technique using Matlab is proposed to alleviate errors associated with SRTM data in the derivation of river longitudinal profiles. Convex longitudinal profiles are interpreted to be a product of uplift rates that exceed rates of channel incision along the entire margin of the Qinghai-Tibetan Plateau. Highest relief towards the south reflects extensive fluvial incision. High relief is also prominent along major active faults. Erosion patterns are related to distance from knickpoints. Highest rates of erosion and incision are evident towards the south, with decreasing values towards the north, suggesting a link between tectonic activity and erosion.     

基于D-InSAR的樱岛火山喷发形变场解算与反演分析

采用D-InSAR技术对覆盖2020年日本鹿儿岛市樱岛火山喷发前后时段的2景降轨Sentinel-1A数据进行处理,获取日本鹿儿岛市樱岛火山南岳火山口喷发事件引起的地表形变场,并在此基础上结合点源Mogi模型对樱岛火山喷发时的岩浆源进行反演分析。结果表明,2020-07-28~08-09期间沉降主要集中在火山中心地区,最大沉降区域为火山中心地带,最大沉降量与平均沉降量分别为5.5 cm与2.85 cm;抬升主要发生在火山边缘区域,最大抬升量与平均抬升量分别为5 cm与2.24 cm,抬升可能与艾拉火山口下方的岩浆活动有关。根据点源Mogi模型反演得到岩浆源深度和体积变化量分别为1.016 km和-0.139×10⁶ m³,岩浆源位于南岳下方,与南岳火山口的喷发活动有关。