天水盆地古近纪地层年代及其意义

天水盆地位于青藏高原东北缘六盘山与西秦岭二重要构造带交汇处,该盆地充填的新生代沉积序列记录着该区构造变形历史,因此研究该盆地沉积记录对探讨青藏高原东北缘新生代构造活动事件具有重要意义.通过对天水盆地古近纪砾石层砂质透镜体中碎屑颗粒磷灰石裂变径迹热年代学研究,获得样品地层的最大沉积年龄为24.8士1.5 Ma.结合前人的工作,厘定该套古近纪地层最顶部地层年龄为22～24.8 Ma,并确定天水盆地古近纪沉积物源区在24.8 Ma左右发生了构造冷却事件,推断印度板块与欧亚大陆碰撞的远程效应在古近纪末-新近纪初已传递到青藏高原的最东北缘.     

Magnetostratigraphy of Late Cenozoic fossil mammals in the northeastern margin of the Tibetan Plateau

~~Magnetostratigraphy of Late Cenozoic fossil mammals in the northeastern margin of the Tibetan Plateau~~~~     

平衡剖面反映的柴西新生代变形对青藏高原隆升的响应

柴达木盆地为一中新生代盆地,位于青藏高原北缘,盆内中新生代地层发育很好地记录了印度一欧亚板块自约55Ma以来碰撞传到高原北缘的地质事件.在最新的高精度磁性地层绝对年代控制下,通过盆内西部五条北东-南西向地震大剖面,用平衡剖面方法恢复了新生代以来盆地因两大板块碰撞而引起的地壳收敛缩短量.结果显示:在宏观上柴西地区存在两个相对快速收缩期:早始新世-渐新世和晚中新世或上新世-现今(E_(1+2)末-N_1,43.80～22.00Ma和N~2_2或N_2~3-现今,8.20或2.65～0Ma)和两个相对较弱收缩期:中生代末-早始新世和渐新世-晚中新世(M_z-E_(1+2)初期,65.00～43.80Ma和N_1末-N~2_2,22.00～2.65Ma)以及两个主要的断裂活动期次,早期路乐河组末-下干柴沟组上段时期(E_(1+2)-E_3~2)和晚期上油砂山组至今(N~2_2-Q).在微观上,盆地内部受自身断裂活动的控制,发育了独特的形态.表明在印欧板块碰撞高原隆升的早期,柴西地区就开始变形响应,随后盆地在整个新生代发展过程中,都处于板块碰撞高原隆升的大环境影响下而发生整体的变形缩短,同时自身的断裂活动控制了盆地的微观形态.     

Detrital zircon U-Pb ages of Late Cenozoic sediments from the Yangtze delta: Implication for the evolution of the Yangtze River

Detrital zircon grains of Late Cenozoic sediments dated back to ca.3.6 Ma from core DY03 in the Yangtze delta were dated by LA-ICP-MS,in order to investigate the sedimentary provenance and to find some clue for the evolution of the Yangtze River.Most of the detrital zircon U-Pb ages are distributed at 100 300 Ma,350 550 Ma,600 1000 Ma,1400 2000 Ma and 2200 2800 Ma,which correspond well with the main tectonic and magmatic events in the Yangtze drainage.The detrital zircon age patterns show distinct differenc...     

Northern Tibetan Plateau cooling and aridification linked to Cenozoic global cooling: Evidence from <Emphasis Type="Italic">n</Emphasis>-alkane distributions of Paleogene sedimentary sequences in the Xining Basin

The Xining Basin on the northeastern Tibetan Plateau holds the longest continuous Cenozoic stratigraphic record in China. The sequence record contains considerable information on the history of Tibetan uplift and associated climatic change. In particular, high resolution n-alkane biomarker proxy and pollen records have been obtained from the Paleogene sediments of the Xiejia section of the basin. A combination of the n-alkane and palynological records reveals that the paleoclimate in the Xining Basin experienced a long-term cooling trend from 50.2 to 28.2 Ma with a distinctive ecological event spanning 37.5 to 32.7 Ma. Since this ecological event, a vertical zonation of vegetation from lowland arid grasses, to middle-elevation subtropical broad-leaf plants, to high-elevation coniferous trees was established. We interpret that these changes in climate and vegetation were probably responses to a combination of long term global cooling since the Eocene climatic optimum and uplift of the surrounding mountains on the northern Tibetan Plateau in the early Cenozoic.     

Discovery and character of the Kunlun-Yellow River Movement

Based on geomorphological, tectonic and sedimentary data, a Kunlun Yellow River Tectonic Movement has been recognized in 1 10-0 60 Ma B.P. This tectonic movement, which leads to uplift of the Qinghai_Xizang (Tibet) Plateau from 1 500 to 3 000-3 500 m, is periodic, abrupt and changeable in the movement rate of uplifting and slide slipping.     

苏干湖沉积物纹层计年和~(210)Pb，~(137)Cs测年对比

通过对西北干旱区苏干湖表层沉积物的年纹层计数定年和~(210)Pb,~(137)Cs测年结果对比发现:~(137)Cs测年结果在8.5 cm出现最高蓄积峰,对应1963年世界核爆高峰期,但在同一层位~(210)Pb测年结果则是1972年,存在较大的偏差.年纹层沉积速率达0.31 cm/a,而根据CRS模式建立的~(210)Pb沉积速率为0.30 cm/a.年纹层反映的沉积速率和~(210)Pb测年结果基本一致,互相验证了两者测年的可靠性.~(137)Cs测年则存在蓄积峰向上迁移的现象,在西北干旱区湖泊使用~(137)Cs测年过程中需引起注意.     

青藏高原隆升阶段性

 青藏高原的隆升不仅是印度板块与亚洲板块碰撞导致的地球内部岩石圈地球动力学作用过程的结果,并且对全球和亚洲气候变化、亚洲地貌和地表环境过程及大量地内和地表矿产资源的形成分布产生了深刻影响。因而研究高原隆升的历史不仅对解决上述重大科学问题提供重要途径,而且可为高原区域资源环境的开发和可持续发展提供理论依据。简要回顾和梳理了国内外近年来,围绕青藏高原隆升所取得的主要进展。研究表明新生代青藏高原经历了多阶段、多幕次、准同步异幅且高原南北后期加速隆升的演化过程。具体可划分为55~30、25~10及8~0 Ma 3个主要生长隆升期次。其中55~30 Ma的高原早期隆升,主要集中在高原中南部的拉萨地块和羌塘地块,并且可能隆升到接近3 km高度,或甚至更高,有人称之为“原西藏高原”,但其周缘存在准同步异幅的变形隆升响应;25~10 Ma的中期隆升,“原西藏高原”南北缘的喜马拉雅山和可可西里-昆仑山开始强烈隆升,“原西藏高原”率先隆升到目前高度并开始向东西两侧挤出物质、拉张形成南北向裂谷,高原北缘普遍产生广泛变形隆升但幅度有限;从约8 Ma开始的晚期隆升,高原南、北部边缘的喜马拉雅山和昆仑山-西秦岭以北的高原东北部隆升显著加速,经历一系列短暂快速的多幕次构造变形和生长隆升,最终形成现今高原面貌。     

Early tectonic uplift of the northern Tibetan Plateau

The Hexi Corridor is the northmost foreland basin of the Tibetan Plateau and its formation is controlled by the northern marginal fault of Tibet, Altyn Tagh Fault （ATF）-North Qilian Shan marginal Fault （NQF）, and the southern Kuantan Shan-Longshou Shan Fault （KLF）. So its study is important to understanding the mechanism of Tibet formation and its influence on global climate change. The oldest Cenozoic sediments in the Corridor is the Huoshaogou Formation which consists of terrigenous fine conglomerate, sandstone, sandy mudstone and mudstone, depositing in al- luvial to lacustrine and fan delta sedimentary environments. Detailed paleomagnetic measurements of this sequence at Yumen clearly reveal eleven pairs of normal and reversed polarities. Fossil mammals found around the section support that most of the observed polarities can be well correlated with chrons between 13n and 18r of the standard geomagnetic polarity time scale, yielding ages of 40.2-33.35 Ma. The mean declinations of this sequence and its immediately above stratigraphy indicate an 18.3° rapid clockwise rotation of the Hexi Corridor. Since this sequence has been strongly folded and is capped by an angular unconformity, we think that the presence of the thick alluvial fan conglomeration at the bottom of the foreland basin may indicate the initial deformation and uplift of the northern Qilian Shan. This process could occur at latest at 40.2 Ma, driven by the faults NQF and KLF that thrust onto the Hexi corridor respectively from its southern and northern margins. These faults are in an early response to the collision of India with Asia, while the unconformable termination and rotation of the Huoshaogou Formation at -33.35 Ma indicate other early episode of rapid tectonic deformation and uplift of the northern Tibet.     

"昆仑-黄河运动"与我国自然地理格局的形成

"昆仑-黄河运动"是发生在早、中更新世之交的一次强烈的构造运动.这次构造运动不仅影响到了整个青藏高原,把高原面抬升至3000～3500 m,局部地区的山地上升到4500～5000 m的高度,导致青藏高原进入冰冻圈,而且影响大气环流型式,形成了东亚季风的现代格局.冬季风加强和夏委风减弱使得我国北方干旱化加剧,沙漠面积扩大,湖泊消退,亚热带植物从秦岭以北南撤到南方,而且使得黄土堆积范围得到扩展,黄土堆积速度加快.这次构造运动后基本形成了我国自然地理的现代格局.     

新生代早期南海北部水系演变

珠江在早渐新世仅是涉及华南沿海地区的小河;到晚渐新世,向西延伸到云贵高原前缘地带;到中新世,现代珠江流域格局初步形成。证据显示,南海北部还发育过一条源自南海西部隆起区的大型水系-昆莺琼古河,后淹没在南海之中,但在南海的沉积充填过程中扮演了重要角色。南海北部水系及沉积环境的重建,对于深刻认识南海新生代早期古地理特征以及该地区的油气勘探均具有重要意义。     

青藏高原盆地系统演化与高原形成时间

青藏高原在以时间为坐标的隆升过程中,高原的范围、高度都是呈阶段性递增的.随着青藏高原的构造隆升,在高原的内部和外围发育了众多的沉积盆地,在这些沉积盆地中详细地记录了青藏高原的隆升过程.高原北部盆地的演化显示出向北递进增长的特征,以南北挤压为动力背景的北部前陆盆地演化代表了盆地对高原周缘造山带的响应关系:金沙江缝合带、昆仑山、祁连山的新生代逆冲抬升的时间分别为53 Ma、46 Ma和29.5 Ma.对高原南北盆地-造山带的构造演化对比发现:祁连山和高喜马拉雅的逆冲时间相同,说明青藏高原在渐新世基本定型.     

柴达木盆地成盐期与青藏高原第四纪冰期及构造运动阶段的相关性

 柴达木盆地沉积有巨厚的晚新生代沉积物和丰富的矿产资源,是研究晚新生代以来气候与环境变化、构造运动与盆地演化、成盐成矿规律的理想地区。通过对柴达木盆地钻孔和剖面的含盐地层测年数据进行总结,并与青藏高原第四纪冰川活动和构造运动进行对比,认为柴达木盆地成盐期与青藏高原第四纪冰期及构造运动阶段具有一定的对应关系。柴达木盆地西部盐湖和干盐湖中通常发育有倒数第二次冰期及末次冰期的石盐层,某些盐湖中还有希夏邦玛冰期、望昆冰期、中梁赣冰期的石盐层;迄今为止在柴达木盆地东部的察尔汗盐湖区中仅发现末次冰期以来的石盐层。冰期环境下的干冷气候及冰川扩张,造成盐湖补给水源的减少,有利于盐类物质的沉积。     

Stepwise advance of the Mu Us Desert since late Pliocene: Evidence from a red clay-loess record

Analyses of paleomagnetic polarity reversals, magnetic susceptibility and grain size on the red clay-loess sequence, about 280 m thick, at Jingbian show that this sequence contains most of the stratigraphic units recorded in the standard red clay-loess sections of the Loess Plateau over the past 3.5 Ma. Using sand particle percentage ( > 63 μm%) of the eolian sequence as a proxy indicator of desert extent and aridity in the dust source regions, it is found that during the past 3.5 Ma, there are three important climatic events indicating the advance of the Mu Us Desert. The events occurred at about 2.6, 1.1 and 0.6 MaBP, respectively. The stepwise advance of the Mu Us Desert may be linked closely to increase in global ice volume and uplift of the Tibetan Plateau in the late Cenozoic.     

四川盆地古地温梯度和中-新生代构造热历史

根据27口井的镜质体反射率剖面,恢复了四川盆地早白垩世末—古新世时的古地温梯度.结果表明,古地温梯度介于20~25℃.km-1,总体呈南部略大于北部、东部大于西部的分布特征.根据古今地温梯度的对比,川西坳陷新生代早期以来地温梯度没有明显的变化,川东和川东北地区晚中生代以来地温梯度下降,而川中和川南地区晚中生代以来地温梯度升高.结合构造演化背景分析,盆地中新生代热历史主要受二叠纪末期的构造热事件、中生代晚期以来岩石圈厚度演化以及现今活动构造的影响.其中,二叠纪末期的构造热事件波及盆地大部分地区;现今活动构造对川南地区有明显的影响;中生代晚期以来的岩石圈厚度演化,可能是控制中新生代盆地大部分地区热历史的主要因素.     

Formation of the Yazi Spring Stream and its significance on tectonics-climate on the northern slope of Kunlun Mountains

The sequences of fluvial terraces in the Yazi Spring Stream are signs of the stepwise uplift of the Kunlun Mountains in the northern part of the Tibetan Plateau since the Late Pleistocene. Geomorphic and sedimentary features of the terraces reveal that they have resulted from the phased tectonic uplift and the consequent river incision in the northern plateau. Using the method of Single-aliquot Regenerative-dose （SAR） Protocol and Radiocarbon ^14C dating, the deposit ages of three-grade terraces were obtained, which are 57.5, 12.8 and 5.7 kaBP, respectively. The features and ages of terraces reveal that the incision rate of the stream accelerated at the beginning of the Holocene. The incision rate changed suddenly at 12.8 KaBP, from 0.43±0.07 mm/a to 1.59±0.55 mm/a. This implicates that uplift of the Kunlun Mountains is intensive at the first onset of the Holocene, corresponding to the obvious change of slip-rate on the AItyn Tagh Fault. But its uplift rate is much lower than that of the latter, which suggests that growth of the northern margin of the Tibetan Plateau is stronger than its interior.     

祁连山北缘早中更新世新构造运动的地层记录

巳有研究发现在早、中更新世之交,青藏高原及其领区发生重大的构造隆升事件,并命名为“昆仑-黄河运动”,简称昆黄运动。河西走廊是青藏高原北缘祁连山的山前凹陷。在走廊西端酒西盆地老群庙背斜开展的古地磁和ESR年代学研究发现祁连山在约1.23MaBP发生构造活动,造成玉门砾岩内部出现不整合;第2幕强烈活动发生于0.93-0.84Ma,造成河西走廊地区酒泉砾石层和玉门砾岩区域性角度不整合。这两次构造运动在时间上与昆黄运动吻合。因此,本研究提供了昆黄运动在青藏高原北部表现的新证据。     

Development of a pediment on western slopes of Liupan Mountain related to the Neotectonic Uplift

The late Cenozoic uplift of Qinghai-Xizang Plateau plays an important role in adjacent geomorphic evolution and depositional environments. Liupan Mountain, located at the northeast margin of Qinghai-Xizang Plateau, has different landforms on the east and west sides. Recently, a pediment, which lies above the highest terrace of the Yellow River at the northeast edge of Longzhong Basin, has been described. The paleomagnetic measurements indicate that the pediment had developed at least 1.8 MaBP and its age is in accordance with that of the peneplains near Lanzhou and Linxia, in the southwest of Longzhong Basin. The results suggest that the Longzhong Basin lying to the west of Liupan Mountain had been subject to erosion and developed an extensive pediment; this pediment is named the Gansu Period Peneplain. It also indicates that Qinghai-Xizang Plateau and Liupan Mountain were uplifted strongly at that time, which caused not only the end of pediplanation but also Yellow River appearance and loess accumulation.     

Methoxy n-fatty acids in surface soils from the Gongga and Kunlun Mountains: Ecological implications

GC-MS characteristics of surface soil samples from the eastern and northern Tibetan Plateau provide tentative identification of 8(–14)-Methoxy hexadecanoic acid (iME-16:0) and 9(–17)-methoxy octadecanoic acid (iME-18:0). Sixty surface soil samples were collected from the eastern slope of Gongga Mountain, at elevations ranging from ~1230 to 4500 m (eastern Tibetan Plateau), and from the northern slope of West Kunlun Mountains, ranging from ~1300 to 5500 m (northern Tibetan Plateau). This study also analyzed the methoxy n-fatty acids (MFAs) of Gongga Mountain tree leaves from six common living species, at the elevation of 2900–4200 m. MFAs dominate these samples, with more centrally located methoxy groups eluting earlier than those with methoxy groups located closer to the end of the main carbon chain. MFAs occur prominently in most of the Gongga Mountain soil samples (and from six tree samples) from dominantly coniferous and deciduous broadleaved forests. Other than in two narrow vegetation zones between 4000–4350 m and 2900–3300 m, no MFAs were found in 19 Kunlun Mountains soil samples from areas covered mainly with montane desert and alpine desert steppe vegetation. Based on the inventory of plants and soils from which MFAs have been isolated, we conclude that the MFAs most probably originate from specific woody plants. If we can exclude some particular grasses as sources, MFAs may be specific woody plants-derived biomarkers; thus they would serve as an important additional proxy for comprehensive and precise ecological reconstructions.     

珠江口盆地13.8Ma陆架边缘三角洲与陆坡深水扇的“源-汇”关系

揭示南海北部被动大陆边缘盆地浅海陆架与深水陆坡之间的沉积响应关系,在等时地层格架内对陆架三角洲、上陆坡复合水道和陆坡重力流沉积进行综合分析.研究结果表明:相对海平面变化、陆架多级坡折演化、陆源碎屑供给强度以及陆架海洋水动力作用等四大因素控制着陆架-陆坡体系的发育;珠江口盆地中新统韩江组13.8 Ma形成的界面为三级层序界面,该时期低位域晚期发育陆架边缘三角洲,三角洲前缘带主体分布在白云凹陷北坡的陆架坡折处,随着物源供给,前缘带不断进积,陆架向陆坡方向生长,在多级坡折、坡度变化以及沉积物自身重力影响下,前缘带沉积物由牵引流搬运向重力流搬运转化,在陆坡复合水道搬运通道的作用下向白云凹陷深水区内再沉积,形成低位域晚期多坡度控制的滑塌体、碎屑流-浊流深水扇沉积,构成南海北部珠江口盆地特殊的陆架-陆坡“源-汇”响应系统;该沉积响应具有短暂性、突发性和连续性等特点.