青藏高原东缘晚新生代地质特征与古环境变化

青藏高原东缘地区发育了完整的晚新生代湖相、黄土、红土和冰川沉积系列,不同成因的沉积物记录了晚新生代以来古环境时空变迁的信息。上新世昔格达湖相沉积发育于4.2～2.6MaBP,具有9个冷—暖气候环境变化阶段。川西风尘堆积始于1.15MaBP,连续记录了14个古季风变化旋回,成都平原红土记录了1.13Ma来的5个古环境演化阶段。青藏高原东缘发育了约4.3MaBP的老冰期,第四纪时期出现了5次极端古气候事件,对应为5期冰期。     

Geological characteristics and evolution of the eastern Qinghai-Tibetan plateau since the late Cenozoic

The eastern edge of the Qinghai-Tibetan plateau developed an integrated series of late Cenozoic lacustrine, loess, red and moraines deposits. Various genetic sediments recorded rich information of Quaternary palaeoenvironment changes. Xigeda Pliocene lacustrine deposits, formed during 4.2 Ma B.P.–2.6 Ma B.P., experienced nine periodic warm-cold stages. Eolian deposition in western Sichuan began at 1.15 Ma B.P., and the loess-soil sequences successively record fourteen palaeomonsoon change cycles. Red clay in the Chengdu plain record five stages of paleoclimatic change stages since 1.13 Ma B.P.. There was an old glacial period of 4.3 Ma B.P. in the eastern Qinghai-Tibetan plateau. During the Quaternary, there were five extreme paleoclimatic events corresponding to five glaciations. __________ Translated from Geological Bulletin of China, 2007, 26(12): 1620–1626 [译自: 地质通报]     

关于晚新生代准1.2Ma周期构造气候旋回

构造气候旋回的理论要点是构造作用驱动气候变化,因而不同于Milankovitch冰期气候旋回,但两者又都是受地球轨道要素控制的。本文主要根据青藏高原和黄土高原的晚新生代地质记录,以磁性地层为时间标尺,以黄道倾斜(ε)最大变幅位置为模式年龄,划分最近8Ma的准1.2Ma周期构造气候旋回的主旋回层,即MTC₇、MTC₆、MTC₅、MTC₄、MTC₃、MTC₂、MTC₁、MTC₀,它们的界线年龄分别为7.3、6.1、4.9、3.7、2.5、1.3和0.2MaBP。在此基础上,分析了青藏高原构造隆升和黄土高原风尘沉积各自显示的准1.2Ma周期的演变特征,表明它们之间具有构造驱动气候的因果关系。文中还探讨了最近7.3MaBP的古环境变迁,获得了有关晚新生代东亚季风形成演变和环境分异是在轨道气候旋回背景下受构造气候旋回控制的新认识。      

Late Cenozoic orogenic history of Western Qinling inferred from sedimentation of Tianshui basin, northeastern margin of Tibetan Plateau

The Western Qinling orogenic belt marks the northeastern margin of the Tibetan Plateau. Its late Cenozoic orogenic history is recorded in an excellent sedimentary sequence exposed in the Tianshui sub-basin of the Longzhong basin. According to the magnetostratigraphic analysis from the Yaodian and Lamashan sections, we speculate that the late Cenozoic Tianshui basin accumulated lacustrine/floodplain deposits from ~14.8 to ~2.6?Ma. In addition, detrital apatite fission-track thermochronologic and paleocurrent data reveal that the detritus of the Tianshui basin mostly derived from the Western Qinling and that the youngest population age represents a ~14?Ma volcanic intrusion, which can be related to the lithospheric deformation and uplift of the Tibetan Plateau. Furthermore, two stages of variations in depositional facies and average accumulation rates were attributed to the pulse uplift and deformation of the Western Qinling at 9.2–7.4 and ~3.6?Ma.     

青藏高原北部温泉活动沉积盆地的沉积特征及其地质意义

晚新生代温泉沉积盆地,是青藏高原腹地在南北向挤压、东西向伸展的构造背景下,沿南北向边界走滑断层,经边界正断层和内部张剪断层的进一步发展而形成的近南北向单断单剪楔形半地堑活动沉积盆地。它可能代表了晚新生代青藏高原第三期强烈挤压隆升事件,是侧向向东剪切挤出的结果。笔者以盆地充填序列和TL、ESR测年资料为主要依据,推测唐古拉山在30 0～2 5 0ka前后全面进入冰冻圈;而以温泉活动沉积盆地为代表的中更新世晚期(2 2 4 .0～1 5 0 .2ka)的冰碛 冰水堆积则对应于青藏高原第三期隆升的断陷盆地发育阶段;中更新世晚期—晚更新世中期(1 4 4 .0～5 6ka)为湖相沉积;晚更新世中期至今(35～0ka)对应于高原缓慢隆升与夷平发育阶段。长江溯源在35ka切割通天河盆地,形成通天河;而在1 6ka侵蚀切穿雁石坪 温泉兵站峡谷,形成布曲河。     

可可西里东部地区的夷平面与火山年代

青藏高原夷平面及其年代是高原隆升、时代和幅度研究中的一个关键问题。可可西里东部地区通过1∶100000航测地形图所示的山顶面形态特征分析表明,本区广泛分布的山顶平坦地形面为青藏高原主夷平面的一部分,其海拔高度大多在4900～5200m。本区平坦顶面的熔岩方山常与夷平面交叉分布,也为高原主夷平面一部分,其同位素年代19.6～6.95MaB.P.之间的有39个(9.9～6.95MaB.P.有17个)。又据本区相邻的山间盆地内的火山地貌年龄推论,夷平面形成于9.9～6.95MaB.P.之后,3MaB.P.之前已形成     

贵州碳酸盐岩红色风化壳次生石英的裂变径迹测年研究

贵州位于青藏高原东南缘,由于缺乏沉积记录其新生代的地质演化历史还不很明晰,而广泛分布于云贵高原的碳酸盐岩红色风化壳可能蕴涵着重要的地质演化信息.本文对贵州多个原位碳酸盐岩红色风化壳中产出的晶体形态较好的石英进行了裂变径迹方法测年.结果显示,石英的裂变径迹年龄数据呈现出较大的变化范围,从 1 Ma到 25 Ma,且远远地小于其三叠纪和寒武纪的母岩年龄;结合贵州 25 Ma到 1 Ma的区域地质演化历史,裂变径迹年龄值可以排除石英来源于母岩碎屑、成岩过程的次生形成以及火山活动产生的热水沉淀或交代形成的可能性,而只能推断为该晶体形态较好的石英于碳酸盐岩风化作用产生的富硅流体中沉淀形成;各剖面石英的年龄值与新生代的青藏高原夷平期、华南红土期、贵州构造稳定期乃至世界范围内的风化气候期有着良好的对应关系,说明次生石英裂变径迹测年具有很好的可行性和可靠性.     

青藏高原的冰碛层与环境

最近3.4 Ma青藏高原尤其是南部可见七套冰碛层（自新至老M₀—M₆）,M₁—M₆上对应发育古土壤MS₀—MS₅,除M₀和MS₀外,形成于六次冰期和五次间冰期。通过与黄土高原对比,除M₆外,可用黄土-古土壤序列确定它们的年代。分别以M₀—M₅上的古土壤为标志,算出高原于1.56—1.23 Ma B.P.、平均高程约2500m开始整体隆升、经历时约0.4 Ma的三个阶段,在0.075 MaB.P.已升到4300m,上升速率从2.0、2.5、2.8增至8.7 mm/a,导致冰期雪线升高,冰进范围缩小。冰期和季风气候变化及阶段性隆升共同决定了高原的环境变迁。     

青藏高原隆起与黄河地文期

青藏高原隆起与黄河发育历史有密切关系，黄河地文期既反映黄河发育的各个阶段，也与青藏高原隆起的阶段性相对应。根据最近对黄河阶地及地文期的研究，将黄河发育历史划分为三个阶段：１)黄河雏形期，时代为上新世，黄河至少已达到河套地区；２)河湖并存期，早更新世至中更新世，黄河已达到共和盆地，沿黄河及大的支流出现若干湖泊；３)大黄河期，晚更新世至今，沿黄河的湖泊消失，现今黄河的基本面貌形成。     

青藏高原东北部贵德盆地上新世沉积环境分析及其意义

青海贵德盆地发育巨厚的新生代地层,在青藏高原北部具有很好的代表性,其中含较丰富的重要哺乳动物化石,对确定盆地及周边相似地层的年代、高原隆升过程具有重要的科学意义.结合哺乳动物采用典型剖面精确古地磁测年为基础的时间框架,通过盆地沉积层序、沉积相和沉积演化以及其对构造和气候变化响应的研究表明:6.5～约1.8MaB.P.期间盆地沉积环境变化经历了8个阶段的演化,反映在此期间青藏高原北部经历了＞5.4MaB.P.、3.6MaB.P.、2.6MaB.P.和1.8MaB.P.4次明显的构造挤压隆升运动,其中约1.8MaB.P.的构造运动可能使黄河向上游溯源侵蚀,同时切穿积石峡、李家峡和松巴峡而到达贵德盆地.研究时段内气候以干旱为主,但在6.2～4MaB.P.和2.1～1.85MaB.P.的两个时期气候明显湿润.     

青藏高原古大湖与夷平面的关系及高原面形成演化过程

青藏高原经过古近纪挤压缩短和增厚地壳均衡隆升,晚新生代形成了以走滑和伸展为主的相对稳定构造环境。中新世早期与晚更新世分别发育巨型古大湖,上新世-早更新世发育很多规模较大的古湖泊,古大湖对夷平面形成演化具有重要的控制作用。中新世早期(（24.1±0.6） ~（14.5±0.5）Ma)以古大湖的湖面为侵蚀基准面,经过隆起区剥蚀夷平和长期湖相沉积,在高海拔环境下形成早期夷平面。中新世晚期-第四纪以湖面与五道梁群湖相沉积顶面为基准,在高海拔环境下继续发生剥蚀夷平和准平原化,逐步形成主夷平面或高原面。第四纪河流溯源侵蚀导致内外流水系分界线自东向西迁移,在青藏高原东部形成高山峡谷地貌。     

Late Cenozoic Sedimentary Evolution of Pagri‐Duoqing Co graben,Southern End of Yadong‐Gulu Rift,Southern Tibet

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 fluvio-lacustrine 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 around 181–109 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.     

阿尔金-祁连山晚新生代隆升-剥露过程——来自岩屑磷灰石裂变径迹热年代学的制约

阿尔金-祁连山位于青藏高原北缘, 其新生代的隆升-剥露过程记录了高原变形和向北扩展的历史, 对探讨高原隆升动力学具有重要意义。本文采用岩屑磷灰石裂变径迹测年分析, 利用岩屑的统计特征限定阿尔金-祁连山新生代的隆升-剥露过程。磷灰石裂变径迹测试结果表明, 阿尔金-祁连山地区存在4个阶段的抬升冷却: 21.1~19.4 Ma、13.5~10.5 Ma、9.0~7.3 Ma、4.3~3.8 Ma。其中, 4.3~3.8 Ma抬升冷却事件仅体现在祁连山地区, 9.0~7.3 Ma抬升冷却事件在区内普遍存在, 且9.0~7.3 Ma隆升-剥露造就了现代阿尔金-祁连山的地貌。区域资料分析表明, 9~7 Ma(或者8~6 Ma)期间, 青藏高原北缘、东缘, 甚至整个中国西部地区发生了大规模、区域性的抬升, 中国现今"西高"的构造地貌形态可能于当时开始形成。阿尔金-祁连山地区4期抬升冷却事件与青藏高原的隆升阶段有很好的对应关系, 应该是对印度-欧亚板块碰撞的响应。     

New paleomagnetic constraints on rift basin evolution in the northern Himalaya mountains

The late Cenozoic sediments in the rift basins in the northern Himalaya Mountains document important information about the uplift and deformation of the most active tectonic region in the Tibetan Plateau. However, these sediments have not been precisely dated, hindering our ability to address the basin development and termination associated with a series of uplifts in the southern Tibetan Plateau. Here, we report a detailed magnetostratigraphic study on the fluvio - lacustrine sedimentary sequence of the Dati Formation bearing abundant Hipparion forstenae fossils in the Dati Basin in the northern frontal region of the Himalaya Mountains. The 195 m – thick section yielded six normal and seven reversed polarity zones that correlate well with Chrons C3An.1r to C4r.2r of the geomagnetic polarity time scale, constraining the section age to ~8.6 – ~6.2 Ma. Together with the magnetostratigraphic results from other rift basins in the region, these results indicate that the horizons bearing the Hipparion fossils were deposited during the age interval of 7.1–6.5 Ma in the northern Himalaya Mountains. The regional tectonic activity and comprehensive magnetostratigraphic and sedimentologic comparisons suggest that the evolution of the rift basins in the northern Himalaya Mountains has involved three major stages since the late Cenozoic, i.e., (1) ~10.0–8.0 Ma, onset of the basins with fan delta facies; (2) ~8.0–3.0 Ma, expansion of the basins with mainly lacustrine facies; (3) ~3.0–1.7 Ma, shrinking and termination of the basins with alluvial fans. The basin evolutionary history indicates an accelerated tectonic uplift of the Himalaya Mountains at ~10.0 Ma, and two deformational events at ~3.0 Ma and at ~1.7 Ma.     

青藏高原东部雀儿山地区新近纪隆升速率探讨——来自雀儿山花岗岩体磷灰石裂变径迹证据

通过青藏高原东部川西地区雀儿山花岗岩体磷灰石裂变径迹分析,新获得了4个磷灰石裂变径迹年龄值,分别为4. 9±0. 3Ma、6. 2±0. 5 Ma、7. 2±0. 4 Ma和7. 3±0. 7 Ma。运用径迹年龄-地形高差法计算出雀儿山花岗岩体新近纪的隆升速率,为0. 15～2 mm/a,平均隆升速率为0. 78mm/a。隆升速率在每个阶段有所不同,但呈现出一种快速隆升→缓慢隆升的过程,为整个青藏高原东缘的隆升过程提供了约束条件。     

临夏盆地晚新生代沉积物元素特征与古气候变迁

青藏高原东北临夏盆地发育较完整的晚新生代地层,特别13～4.34 Ma段以稳定低能细粒湖相沉积为主、发育的不同尺度和各种形式沉积韵律旋回记录着古气候变化信息。本文通过对临夏盆地稳定细粒湖相沉积物元素地球化学特征及其变化序列研究,结合其它气候指标,揭示13～4.4 Ma时段气候演化经历了四个阶段:13～12 Ma期间气候湿润、12~7.8Ma期间气候以湿润为主夹短暂干旱事件、7.8～6.2 Ma期间气候以干旱为主、6.2～4.4 Ma期间气候进一步干旱加剧,并认为7. 8 Ma左右的气候转型可能与冬季风加强有关,而6.2 Ma以来的有规律的高频气候波动可能与现代季风形成有关。     

东南季风区及青藏高原东部湖泊沉积研究与古环境重建

本文根据青藏高原东部若尔盖盆地ＲＨ孔的全面分析，讨论了青藏高原８２．６万年以来的长期气候变化，共划分为２３个阶段。基本特征为冷期持续时间要远远超过暖期，内部结构相对比较稳定，而暖期的内部次级波动要频繁得多。通过呼伦湖和固城湖岩芯研究，重建晚冰期以来的气候变化历史，新仙女木事件及全新世几次降温事件在两个湖泊中均有反映。统计了中国东部２７个湖泊湖面波动资料，讨论了季风区环境变化的穿时性。     

青藏高原新生代隆升研究现状

新生代青藏高原的隆升过程倍受世界关注。国内外学者从不同角度围绕青藏高原成为统一整体(印度-欧亚碰撞)的时限、隆升阶段性和空间差异性、青藏高原作为高海拔高原形成的时间、青藏高原隆升的动力机制等重大事件进行了深入的研究。对印度板块-欧亚板块的碰撞时间存在70Ma、65Ma、55Ma、50Ma、45Ma和40～34Ma等多种观点。印度板块与欧亚板块碰撞不是在某个时间点完成的,其碰撞持续时间约10～15Ma。碰撞方式存在由西向东迁移、由东向西迁移等多种观点。青藏高原的隆升过程具有强烈的时空差异性。青藏高原新生代隆升阶段存在多种划分方案,流行的有3阶段、4阶段和5阶段强隆升过程。青藏高原作为高海拔高原形成的时间可归纳为约3.6Ma以来、13～8Ma、26～20Ma、40～35Ma和55～45Ma 5类观点。青藏高原的形成机制模型存在较大分歧,流行的模式可分为碰撞、俯冲、挤出和拆沉-板片断离4类。青藏高原多阶段隆升及构造-岩浆演化造就了高原复杂多样的大陆成矿作用。高原隆升与环境和气候演变具耦合关系。     

中国风尘堆积与全球干旱化

通过极地冰盖增长、中国风尘堆积(包括西风带下太平洋的风尘沉积)、青藏高原隆起以及现代表面洋流形成过程等资料的分析,初步认为,影响全球干旱化的重要因素之一是极地冷源的作用,山地隆起幅度和洋流变异是干旱化不可忽视的重要因素。据此本文对建立全球干旱化环境序列做一初步尝试。     

三万年来可可西里地区湖泊环境演化序列

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