攀西地区晚新生代沉积研究回顾与问题讨论

攀西地区晚新生代沉积是研究青藏高原东南缘隆升演化历史及其周缘环境响应、中国第一第二阶梯地貌格局演变和高原东南缘水系变迁的天然地质记录，具有重要科学意义。对该区晚新生代河湖相沉积，尤其是昔格达组和大箐梁子组的研究历史、岩性内涵、形成时代、古地理与古气候意义等进行了较全面的回顾。在此基础上对晚新生代冰碛物记录的冰川发育过程、青藏高原东南缘新构造运动和隆升历史、水系格局变迁等过程进行了评述。针对该区晚新生代沉积研究中存在的问题和分歧，提出了今后研究的方向，认为在详细的地层学和地貌学等综合研究基础上开展高精度的年代学研究是当前攀西地区晚新生代沉积研究的重点。     

酒西盆地晚新生代沉积物重矿物分析与高原北部隆升

沉积物的形成是地壳差异升降运动的物质记录.位于青藏高原北缘的酒西盆地晚新生代沉积比较敏感和全面记录了高原北部的构造运动和隆升过程.老君庙剖面晚新生代沉积物重矿物分析表明13 MaBP以来酒西盆地南部沉积物中重矿物具规律性变化;依据重矿物具规律性变化和沉积特征,揭示了青藏高原北缘晚新生代以来地壳运动经历了稳定期(13～8.26 Ma)、逐步阶段性隆升期(8.26～<4.9 Ma)和急剧强烈整体阶段性隆升期(>3.66～0 Ma)三个重大构造演化过程。     

青藏高原30—40ka B.P.暖湿气候事件对川西河谷地质环境的影响

青藏高原在末次冰期晚期(30—40 ka B.P.,相当于MIS3a阶段)出现的暖湿气候事件强烈地影响了川西高原东缘河流地质生态环境。表现在深切河谷中普遍发育大型滑坡、泥石流、冲洪积扇体等灾变事件和古堰塞湖沉积。本文重点剖析了岷江上游、大渡河中游大型堵江事件的地形地貌特点、沉积物发育特征、沉积年代学、新构造背景等,同时分析了黄河上游玛曲段大型冲-洪积扇体的沉积特征与时代。结果表明在川西高原东缘深切河谷普遍存在距今30—40 ka时期的堵江事件,而这一时期在黄河上游发生大型冲-洪积事件和黄河袭夺若尔盖古湖事件,二者均与青藏高原末次冰期暖湿事件同步。研究认为这期急剧气温变化增强了河谷侵蚀和卸载能力,而东缘强烈的地震断层活动又触发了突发事件的发生,暖湿气候事件与新构造运动在时空上的耦合共同塑造了晚更新世晚期川西高原东缘深切河谷系统特殊的地质生态环境及其演变。     

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。     

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。      

祁连山东南缘新生代沉积环境变迁及其意义

祁连山东南缘处于青藏高原东北缘与黄土高原过渡区 ,处于环境变化敏感地带 ,自新生代以来于巴州坳陷、永登坳陷发育了巨厚第三系、第四系 ,为研究祁连山地、青藏高原隆升的良好相关记录。通过系统的地层学、沉积学、地貌学及古气候学研究 ,将研究区自第三纪以来的沉积环境变迁、构造隆升及全球变化分以下几个阶段 :(1)由于燕山运动影响 ,本区缺失了上白垩统 ,至古新世时 ,本区自南而北沉积了一套河控湖相三角洲及冲积扇。反映了区域持续沉降 ,气候炎热 ,降水较丰富 ,推测此时高原抬升缓慢 ,地形起伏不大。(2 )始新世早—中期时 ,本区沉积环…     

祁连山东南缘新生代沉积环境变迁及其意义

祁连山东南缘处于青藏高原东北缘与黄土高原过渡区 ,处于环境变化敏感地带 ,自新生代以来于巴州坳陷、永登坳陷发育了巨厚第三系、第四系 ,为研究祁连山地、青藏高原隆升的良好相关记录。通过系统的地层学、沉积学、地貌学及古气候学研究 ,将研究区自第三纪以来的沉积环境变迁、构造隆升及全球变化分以下几个阶段 :(1)由于燕山运动影响 ,本区缺失了上白垩统 ,至古新世时 ,本区自南而北沉积了一套河控湖相三角洲及冲积扇。反映了区域持续沉降 ,气候炎热 ,降水较丰富 ,推测此时高原抬升缓慢 ,地形起伏不大。(2 )始新世早—中期时 ,本区沉积环…     

西藏纳木错晚更新世以来湖面变化和湖相沉积中粘土矿物显示的环境信息

通过对西藏海拔最高、面积最大湖泊-纳木错周缘湖相沉积、湖岸堤的野外调查和湖岸阶地的水准测量,发现在纳木错沿岸拔湖48m以下,发育有6级湖岸阶地,拔湖48~139.2m发育有高位湖相沉积。湖相沉积物的同位素测年结果表明,纳木错湖泊发育与藏北高原东南部古大湖演化可划分为3个阶段:①116~37kaB.P.间的古大湖期;②37~30kaB.P.间的外流湖期;③30kaB.P.以来的纳木错期。根据纳木错晚更新世以来湖相沉积中粘土矿物的X光衍射分析结果,以及采用比值法、高岭石法和衍射峰法的研究,探讨了粘土矿物所显示的环境变化信息。粘土矿物成分变化表明,该区已具备了寒温带干旱、半干旱区的气候环境特征。为研究青藏高原的湖泊演化、气候变化、古地理变迁及其隆升过程等提供了新资料。      

青藏高原沱沱河盆地中新统五道梁组沉积特征及古环境分析

通过对青藏高原沱沱河盆地五道梁组湖相沉积环境的分析,尝试通过湖相沉积地层记录提取气候变化信息,探索高原腹地中新世古环境变化特点。通过对五道梁组岩石类型及沉积特征研究,识别出了洪积平原、浅湖、滨湖、深湖及盐湖5个沉积相类型。参考现代湖泊特征与古代研究实例,探讨了研究区湖相碳酸盐岩的沉积机制。根据剖面岩相标志及地层叠置样式,证实五道梁组沉积期古湖泊经历了3次由低水位变为高水位的旋回性变化,湖泊最低水位期以石膏层的出现为标志,高水位期发育洪泛泥岩沉积;初步认为五道梁组沉积发育在一个干湿交替的气候期,湖水位变化和湖平面升降主要受气候控制,而构造沉降和湖缘断块隆升是次要控制因素。     

四川攀枝花昔格达组下伏砾石层成因和时代探讨与古金沙江河谷发育

本文主要描述和讨论了四川省攀枝花市沿金沙江分布、并以炳草岗地龙箐剖面为代表的昔格达组湖相沉积下伏的砾石层的沉积特征及其河流相成因.根据前人对昔格达组湖相沉积的磁性地层学研究结果,为4.2/3.28～2.6/2.12/1.78 MaBP的上新世中、晚期或至早更新世早期,表明其下伏厚达50 m的砾石层的形成时代约为4.2～4.5/5 MaBP的上新世早期.早上新世金沙江河流相砾石层在接近金沙江谷底位置的发现,表明金沙江很早就已经从青藏高原主夷平面下切了2000 m以上、已在接近其现今谷底的位置上存在.这对于探讨古金沙江的河谷发育及其与青藏高原隆升的关系,具有重要的指示意义.     

Late Cenozoic Geology and Paleo-environment Change in the Eastern Edge of Qinghai-Xizang Plateau

There are late Cenozoic lacustrine deposits and loess and red clay and moraines in eastern edge of the Qinghai-Xizang Plateau. Various genetic sediments recorded rich information on late Cenozoic paleo-environment changes. Xigeda lacustrine formed during 4.2 Ma B.P.-2.6 Ma B.P. There were 9 periodic warm-cold alternations. Eolian deposition in western Sichuan began at 1.15 Ma B.P. The loess-soil sequences recorded successively 14 paleo-monsoon climate cycles. Laterite in Chengdu plain recorded 5 stages of paleoclimatic stages since 1.13 Ma B.P. There was an old glacial period of 4.3 Ma B.P. in eastern Qinghai-Xizang Plateau. During Quaternary, there are 5 extreme paleoclimatic events corresponding with 5 glaciations.     

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]     

阿尔金山北段阿克塞—当金山口一带新生代山体抬升和剥蚀的裂变径迹证据

阿尔金山北段阿克塞—当金山口一带的裂变径迹测年证据表明,该地区于9～7 Ma以来发生过快速抬升和剥蚀,并且一直持续形成了现今所见的阿尔金山。新生代以来至少经历了三次抬升:早期43.6～24.3Ma、中期19.6～13.6 Ma、晚期9～7 Ma。抬升速率先缓慢、后相对快速,9～7 Ma以来的抬升速率为0.94 mm/a。晚期的构造拾升可能与阿尔金断裂带左行走滑活动有关,而与相邻的柴达木盆地北缘地区的构造抬升并不一致。     

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.     

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。     

共和盆地剖面第四纪孢粉组合特征及环境演化

青藏高原东北缘共和盆地沉积了较厚的第四系,详细地记录了共和盆地第四纪环境变化。通过对共和盆地第四系沉积序列特征和孢粉组合特征的分析,结合热释光测年,本文较详细地研究了共和盆地第四纪以来的环境变迁,并将其分为两大阶段:早期为湖相沉积阶段(中更新世晚期~0.079Ma),气候相对温和。晚期为河流和风成沉积阶段(79.2ka~至今),气候相对干旱。早期阶段又可进一步划分为三个气候期和五个气候亚期。总体上,共和盆地自早更新世以来由偏湿气候逐渐转变为干旱气候,古植被由森林植被逐渐转化为森林草原型植被。其主要原因可能是早更新世以来青藏高原强烈隆升,改变了西南季风气候格局所致。      

中国晚新生代构造-沉积-古气候事件的地质记录

中国区域地质调查工作的重点正在转向大面积覆盖区为主的平原、盆地、草原、荒漠等地区，向深部三维调查拓展.第四纪松散沉积层覆盖区区域地质调查的核心是揭示晚新生代地表过程、圈层相互关系，探讨人与自然的关系，服务于国家生态文明建设与生态环境保护.然而，覆盖区进行地质填图一个很大的难处是第四纪松散沉积层的侧向延伸往往很不稳定，要特别重视重要构造-沉积-古气候和古环境事件，如重要的不整合面、侵蚀面、火山岩层、湖相沉积，重要的海侵层、古气候沉积(如黄土、红土、黑土)，古文化层等.它们可以作为第四纪松散沉积层侧向对比的重要标志，并且往往具有等时性.东亚大陆构造演化及现代地貌特征主要受两大地球动力系统所控制，西部印度-欧亚板块碰撞、高原快速隆升并向北东方向扩展，东部太平洋板块向欧亚大陆俯冲消减并在东亚大陆东缘形成复杂的沟-弧-盆系统.两大构造系统作用奠定了晚新生代以来中国地质演化背景，导致地球深部过程和地表环境发生重大变革.总体表现为青藏高原隆升、东部岩石圈伸展减薄，最终塑造了现今的宏观地貌形态和水系格局.本文针对第四纪松散沉积物覆盖层的这些特点，对中国晚新生代以来重要构造-沉积-古气候事件进行了梳理，总结了晚新生代这些重要事件的地质记录，特别是重要的沉积层、侵蚀面、不整合面、海侵层等，以便在覆盖区区域地质调查时对第四纪松散沉积层进行区域性对比.     

Episodes of Cenozoic Gold Mineralization on the Eastern Margin of the Qinghai-Tibet Plateau:~(40)Ar/~(39)Ar Dating and Implication for Geodynamic Events

A lot of new gold deposits have been found on the eastern margin of the Qinghai-Tibet Plateau during the past two decades. Among them, three main types of gold deposits have been recognized, including quartz-vein-type, shearzone-type and porphyry-type. The former two types of gold deposits are mainly hosted within metamorphic rocks, while the latter is related to Cenozoic magmatism. Although all of these gold deposits are believed to have been formed during the uplift process of the Qinghai-Tibet Plateau in the Cenozoic era (Wang et al., 2002b), precise isotopic age constraints have still been lacking until quite recently. This paper presents new ^40Ar/^39Ar data of some gold deposits on the eastern margin of the Qinghai-Tibet Plateau, which indicate that gold mineralization in the region occurred in response to the episodic stages of the orogenies. Recently obtained ^40Ar/^39Ar data on quartz and feldspars from several gold deposits, such as the Sandiao deposit, the Baijintaizi deposit, the Pusagang deposits, provide new constraints on gold mineralization on the eastern margin of the Qinghai-Tibet Plateau. Geochronological studies of gold deposits along the Daduhe River indicate that there are three stages of gold mineralization. The early two stages occurred as early as 65.1 Ma in the Shuibaiyang deposit and 58.95 Ma in the Ruoji deposit, while the latter stage occurred as late as 25.35 Ma in Baijintaizi and 24.70 Ma in Sandiao. Isotopic dating of three plagioclases from the Beiya deposit, Zhifanggou deposit and Luobodi deposit and a K-feldspar from the Jinchangqing deposit in Yunnan Province indicates that these deposits were formed at two stages. The Zhifanggou and Jinchangqing deposits have early stage records as old as 58.82 Ma in Zhifanggou and 55.49 Ma in Jinchangqing, but all of the above four deposits in Yunnan have late stage records of 23.18 Ma in Jinchangqing, 24.54 Ma in Zhifanggou, 24.60 Ma in Luobodi and 24.56 Ma in Hongnitang. The above results suggest that the gold deposits on the eastern margin of the Qinghai-Tibet Plateau were formed concentratedly at two main episodes, i.e. the end of the Paleocene (about 58 Ma) and the boundary between the Paleogene and the Neogene (about 25 Ma). The later episode appears to be looks like more important and was coupled with the Sichuan movement, which was extensively activated at that period. The beginning of the Cenozoic Era (about 65 Ma) might be another episode of gold mineralization, but only one deposit (Shuibaiyang) in this study has been proved to have been be formed at this stage and might be earlier than the initial collision between the Indian Plate and the Eurasia Plate. In view of geology, the above three episodes of gold mineralization are associated with three events of tectonicmagmatism and/or fluid events. Even though the gold deposits (for example, the Shuibaiyang deposit, Ruoji deposit and Pusagang deposit) were formed at different episodes, all of them are genetically related to tectonic movements in largescale shear zones. It looks like theat tectonic events (including large-scale strike-slip) between Paleogene and Neogene had a wide influence upon gold mineralization, with new deposits formed and old deposits enriched or superimposed to be a higher grade by new stage of mineralization. The above data suggest that gold deposits were not only concentrated in some areas, but also formed mainly at different boundaries of geological times, indicating that there existed some peak stages of gold mineralization (metallogenic episodes), and that the gold deposits were formed mainly by episodic mineralization.     

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。     

Cenozoic Stratigraphy Deformation History in the Central and Eastern of Qaidam Basin by the Balance Section Restoration and its Implication

The Qaidam Basin,located in the northern margin of the Qinghai-Tibet Plateau,is a large Mesozoic-Cenozoic basin,and bears huge thick Cenozoic strata.The geologic events of the Indian-Eurasian plate-plate collision since～55 Ma have been well recorded.Based on the latest progress in high-resolution stratigraphy,a technique of balanced section was applied to six pieces of northeast-southwest geologic seismic profiles in the central and eastern of the Qaidam Basin to reconstruct the crustal shortening deform...