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.     

青藏高原上新世构造岩相古地理

在前人研究成果的基础上,划分出青藏高原及邻区上新世残留盆地共95个,探讨了青藏高原及邻区上新世构造岩相古地理演化。青藏高原上新世总体构造地貌格局主要受控于印度板块与欧亚板块沿雅鲁藏布江缝合带的碰撞及持续挤压,影响着青藏高原广大范围内的构造抬升。东北部昆仑山、祁连山地区是两大构造隆起蚀源区,两大山系夹持的柴达木盆地是高原东北部最大的陆内盆地,祁连山以北和以东地区则以盆山相间的格局接受周围山系的剥蚀物质,直到晚上新世(青藏运动"A"幕)高原东北部进一步强烈隆升,山间盆地抬升成为剥蚀区。新疆塔里木和青藏高原东部羌塘、可可西里地区主体表现为大面积的构造压陷湖盆-冲泛平原沉积区。高原东南部为一系列走滑拉分断裂运动形成的拉分盆地,上新世早期堆积洪冲积相砾岩,中期为湖泊、三角洲沉积,晚期随着山体的进一步抬升,盆地又接受冲洪积扇相砾岩堆积,并被河流侵蚀剥露。高原南部上新世多分布一些近南北向盆地,是响应高原隆升到一定程度垮塌而成的断陷盆地,同东南部拉分盆地类似,上新世沉积相也由早至晚分为3个阶段。恒河地区上新世由于喜马拉雅山的快速抬升,沉积以粗碎屑为主,形成狭长的西瓦利克群堆积。上新世青藏高原总体地势继承了中新世西高东低、南高北低的地貌特征,但地势高差明显较中新世增大。     

青海循化盆地新近纪磁性地层学

青藏高原东北部是研究高原隆升和东亚季风演化的重要地区.通过对青藏高原东北部循化盆地西沟剖面新近纪河湖相沉积的磁性地层学研究, 建立了西沟剖面约14.6~5.0 Ma沉积物的磁极性年代框架.沉积相的分析表明, 循化盆地在约14.6~5.0 Ma期间总体上处于充填萎缩阶段.西沟剖面巨厚层砾岩首次出现的时间约为7.3 Ma前, 应是青藏高原东北部快速隆升的沉积响应.这与青藏高原在约8.0 Ma前快速隆升的时间相近, 进一步说明约8.0 Ma前青藏高原的构造隆升具有准同时性.      

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。     

Detrital apatite fission track analyses of the Subei basin: implications for basin-range structure of the northern Tibetan Plateau

The northern Tibetan Plateau has evolved a unique basin-range structure characterized by alternating elongated mountain ranges and basins over a history of multiple tectonic and fault activities. The Subei basin recorded evolution of this basin-range structure. In this study, detailed detrital apatite fission track (AFT) thermochronological studies in conjunction with previously documented data reveal provenance of the Subei basin, important information about the Indo-Eurasia collision, and two Miocene uplift and exhumation events of the northern Tibetan Plateau. Detrital AFT analyses combined with sedimentary evidences demonstrate that the Danghenanshan Mountains is the major provenance of the Subei basin. In addition, very old age peaks indicate that part sediments in the Subei basin are recycling sediments. Age peak populations of 70–44 Ma and 61–45 Ma from the lower and upper Baiyanghe formations record the tectono-thermal response to the Indo-Eurasia collision. Combined detrital AFT thermochronology, magnetostratigraphy and petrography results demonstrate the middle Miocene uplift and exhumation event initiated 14–12 Ma in the Subei basin, which may resulted from the Miocene east-west extension of the Tibetan Plateau. Another stronger uplift and exhumation event occurred in the late Miocene resulted from strengthened tectonic movement and climate. A much younger AFT grain age, breccia of diluvial facies and boulders of root fan subfacies record the late Miocene unroofing in the Danghenanshan Mountains.     

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。     

中祁连木里盆地古近系ESR年龄及地质意义

对中祁连木里盆地新生代红层进行ESR测年,获得了祁连山地区新生代红层沉积时代及构造变形年代学数据.研究表明,中祁连木里盆地内沉积了巨厚的新生代红层,较好地记录了祁连山隆升历史.盆地最老的新生代地层为始新世由湖相沉积组成的火烧沟组,ESR年龄为40.2～35.3 Ma,与上覆沉积时代为32.6～24.3 Ma的渐新世河湖相沉积组成的白杨河组呈角度不整合接触.构造变形特征与沉积环境的变化说明始新世末与渐新世初木里地区发生了构造变形和山脉的隆升,与祁连山地区新生代早期的隆升有很好的对应关系.     

西藏高原与喜马拉雅的隆升历史和研究方法:回顾与进展

西藏高原和喜马拉雅的隆升历史是新生代以来众多地质事件的边界条件。因此,它对于我们理解新生代全球气候变冷以及亚洲环境变化等许多地质过程都具有深远的意义。尽管各种替代指标已经被广泛应用于研究高原隆升历史,然而,不同方法所得出的高原隆升历史并不一致。这主要归咎于一些替代指标本身存在多解性和不确定性,从而严重阻碍了获取正确的高原隆升历史。在对这些替代指标进行详细的阐述之后,对其指示的高原隆升历史进行重新评估,并结合在高原腹地开展的工作,提出了原西藏高原的隆升模式,即拉萨地体和羌塘地体在始新世就已经达到现在的海拔高度,而此时青藏高原北部还是低地,南部和西部可能还处在海洋环境。在中新世时,高原向北、向东和向南生长并在第四纪时形成现在的高原特征。     

Cenozoic Environmental Changes in the Northern Qaidam Basin Inferred from n-alkane Records

Cenozoic climatic and environmental changes in the arid Asian interior, and their possible relations with global climatic changes and the Tibetan Plateau uplift, have been intensively investigated and debated over past decades. Here we present 40-Myr （million years）-long n-alkane records from a continuous Cenozoic sediment sequence in the Dahonggou Section, Qaidam Basin, northern Tibetan Plateau, to infer environmental changes in the northern basin. A set of n-alkane indexes, including ACL, CPI and Paq, vary substantially and consistently throughout the records, which are interpreted to reflect relative contributions from terrestrial vascular plants vs. aquatic macrophytes, and thus indicate depositional environments. ACL values vary between 21 and 30; CP1 values range from 1.0 to 8.0; and Paq values change from 〈0.1 to 0.8 over the past 40-Myr. We have roughly identified two periods, at 25.8-21.0 Ma （million years ago） and 13.0-17.5 Ma, with higher ACL and CPI and lower Paq values indicating predominant lacustrine environments. Lower ACL and CPI values, together with higher Paq values, occurred at 〉25.8 Ma, 17.5-21.0 Ma, and 〈13.0 Ma, corresponding to alluvial fan/river deltaic deposits and shallow lacustrine settings, consistent with the observed features in sedimentological facies. The inferred Cenozoic environmental changes in the northern Qaidam Basin appear to correspond to global climatic changes.     

西秦岭晚白垩世原型盆地——新生代青藏高原隆起的背景

青藏高原是新生代隆升的构造地貌。本文试图通过对青藏高原东北缘的西秦岭上白垩统的研究,揭示新生代青藏高原隆升之前的晚白垩世原型盆地和构造地貌背景,这对探索青藏高原隆起过程的起始至关重要。西秦岭腹地岷县地区分布着一套角度不整合于下伏不同时代地层之上且沉积序列相近的上白垩统红层地层。该套红层现今呈离散分布,故多被认为是西秦岭陆内造山阶段不同山间盆地或走滑拉分盆地的沉积物。对不同高程和露头上的该套红层与下伏地层之间角度不整合面地质特征对比分析,特别是对不整合面之上含砾砂岩和砂岩的粒度组成和颗粒的显微结构研究表明,该套红层底部的胶结砂砾岩和其上的红色砂岩皆具有沙漠沉积的特征,也就是说西秦岭晚白垩世曾出现过干旱沙漠环境。沙漠环境的出现不仅需要干旱炎热气候条件,而且需要相对平坦的地形地貌空间条件。据此,本文提出了西秦岭在晚白垩世可能处于相对平缓的古地貌状态。现今这套红层不连续分布在相对平坦的山顶面,其下部以洪积砾岩、河床砾岩和砂岩、沙漠相砂岩互层,上部则以河一湖相红色泥岩、粉砂岩和细砂岩等细碎屑沉积为主。经研究分析认为西秦岭在上白垩统红层开始沉积之时,总体已处于地形起伏不大的洪积平原和宽谷型河流地貌,而晚期则演变为平坦湖盆地貌,其原始盆地为统一宽缓的湖相盆地。现今上白垩统红层地层和角度不整合的弥散性分布是在印度板块-欧亚板块碰撞汇聚的动力学背景下,青藏高原崛起和逆冲-走滑作用以及地壳不均匀抬升-侵蚀的结果。西秦岭晚白垩世相对平坦的古地貌状态确定可为研究西秦岭中新生代陆内构造过程和高原隆升与板内变形在东北缘的扩展提供重要线索和参考标志。     

Magnetostratigraphy and Anisotropy of Magnetic Susceptibility of the Lulehe Formation in the Northeastern Qaidam Basin

The timing of onset of deposition of the Lulehe Formation is a significant factor in understanding the genesis of the Qaidam basin and the evolution of the Tibetan Plateau. Here, we describe a detailed magnetostratigraphic and magnetic fabric study of the middle and lower parts of the Lulehe Formation. A total of 234 samples were collected from 117 sites throughout a thickness of almost 460 m of fluvial and lacustrine deposits at the Xitieshan section in the northeastern Qaidam basin. Out of these sites, 94 sites yielded well-defined characteristic remanent magnetization components by stepwise thermal demagnetization and were used to establish the magnetostratigraphy of the studied section. Based on correlation with the geomagnetic polarity timescale, the studied section spans the period from 53.8 Ma to 50.7 Ma. Our results show a three-fold decrease in sedimentation rates as well as marked change in facies from braided river to delta and shore–shallow lake around 52.6 Ma, which suggests tectonic uplift of the northeastern Qaidam basin margin ridge was rapid at the onset of formation of the Qaidam basin and subsequently weakened after 52.6 Ma. The anisotropy of magnetic susceptibility results indicate that tectonic compression stress had reached the northeastern Tibetan Plateau by the early stages of Indo–Eurasian plate collision and that the direction of stress in the study area was NE–SW. Furthermore, a weakening of tectonic compression stress around 52.6 Ma is consistent with sedimentary records. The age of initial deposition of the Qaidam basin (around 53.8 Ma) was almost synchronous with that of the Qiangtang, Hoh Xil, Xining, and Lanzhou basins, which implies that stress was transferred rapidly through the Tibetan Plateau during or immediately after the onset of Indo–Eurasian collision.     

福贡地区石炭系地层可能属于拉萨地块:来自碎屑锆石年龄谱的指示

欧亚与印度大陆的碰撞使得印度大陆的北东角强烈挤入欧亚大陆内部,形成东构造结,其引发的强烈变形将南羌塘地块、北羌塘地块、拉萨地块、保山地块、兰坪-思茅地块以及地块之间的缝合带挤压于很窄的范围内,造成青藏高原腹地与其东南缘之间构造单元划分、对比困难。滇西福贡地区位于青藏高原东南缘,东构造结影响范围内,是三江造山带及青藏高原相关地块的汇聚处。福贡地区石炭系岩石组合表明其形成于较为稳定的浅海相沉积环境中,具有被动大陆边缘沉积特征。三件石炭系二云母石英片岩碎屑锆石表面年龄数据(194个有效分析点)形成五个主要年龄区间:2550~2400Ma、1800~1550Ma、1200~1080Ma、1000~850Ma和600~480Ma,峰值分别为~2502Ma、~1724Ma、~1120Ma、~886Ma和~512Ma。对比其他地块同时代地层的碎屑锆石年龄谱表明,福贡地区石炭系可能是拉萨地块的一部分,与腾冲地块一样,属于其南延部分。结合中新生代岩浆岩带的构造连续性,我们认为,印度板块东北角向北、北东方向的强烈挤压导致拉萨地块及冈底斯岩浆岩带弯曲、缩颈、并发生分离与旋转。     

早更新世以来青藏高原隆升作用在塔里木盆地腹地的响应

自约55Ma印度-欧亚板块碰撞,青藏高原经历持续挤压,发生多次阶段性隆升作用.晚新生代以来强烈隆升作用不仅造就了青藏高原北部强烈的构造变形效应,还引起了大规模的干旱化.位于塔里木盆地腹地(N38° 40.911′,E80°18.484′)的玛扎塔格褶断带东西向延伸约300km,南缘发育出露连续、完全的早更新世地层,岩性主要以灰黄色泥岩、粉砂质泥岩、粉砂岩为主,含有薄层粗砂岩及砾岩.本文延展了原来研究剖面,共采集古地磁样品90块共9个采点.系统热退磁结果揭示出了正反极性,高分辨率的磁性地层学及野外磁化率研究确定研究剖面时代约为2.2～0.1Ma,对玛扎塔格整个剖面地层的年龄控制提供了限定.利用MS2磁化率仪对野外剖面现场测量,采集209米695点数据.通过与深海氧同位素比对分析,说明磁化率结果不仅较好揭示了全球气候变化,还精确记录了约1.8Ma、1.2Ma、0.9Ma、0.65Ma等多期构造活动,并且直接证明年龄约0.05Ma的地层发生了较强构造变形.青藏高原早更新世以来隆升过程具有脉冲特征,约0.9Ma的强烈隆升使主体达到冰冻圈,起到的屏障效应使塔里木盆地开始较快速干旱化,同时为黄土高原提供了更多风尘物质和增强了对粉尘的搬运能力,导致巨厚的粗粒上砂岩层L9形成.     

上新世以来北京平原NBT1孔记录的地层沉积及构造指示

磁性地层学结合宇宙成因核素、AMS 14 C测年为晚新生代可靠的长序地质年代框架建立提供了有效快捷手段。在北京平原东南部钻取的NBT1全取芯钻孔进行了详细的磁性地层学研究,400 m钻孔335 块样品识别出10个正极性和9个负极性时段,记录了布容(Brunhes)、松山(Matuyama)、高斯(Gauss)、吉尔伯特(Gilbert)极性时,孔底进入到4. 2 Ma的Gilbert负极性时。以岩性组合、26 Al/10 Be、AMS 14 C年代学为基础,结合测井沉积〖JP2〗相分析,判断钻孔上新世晚期地层底界位于319. 60 m,第四系下更新统、中更新统、上更新统底界分别位于214. 80 m、〖JP〗70. 60 m、59. 25 m。在上新世约4. 2~3. 5 Ma发育了6期明显的冲洪积扇的快速沉积过程,第四纪早更新世以曲流河沉积体系为主,中更新世以湖沼沉积为主,夹分支河道沉积,沉积厚度相对较薄,晚更新世以分支河道- 湖沼沉积为主,其顶部末次盛冰期浊黄橙色硬质黏土发育。钻孔包含了3个沉积速率较高（>150 m/Ma）的时期,分别为3. 58~3. 33 Ma、1. 945~1. 778 Ma和0. 126~0. 010 Ma,与上新世以来青藏高原隆升扩展及华北地区晚更新世构造活化在时间上具有一致性,揭示了华北地区的沉积构造演化对青藏高原隆升具有一定响应。     

Sedimentary Evolution of the Qinghai–Tibet Plateau in Cenozoic and its Response to the Uplift of the Plateau

We have studied the evolution of the tectonic lithofacies paleogeography of Paleocene–Eocene, Oligocene, Miocene, and Pliocene of the Qinghai–Tibet Plateau by compiling data regarding the type, tectonic setting, and lithostratigraphic sequence of 98 remnant basins in the plateau area. Our results can be summarized as follows. (1) The Paleocene to Eocene is characterized by uplift and erosion in the Songpan–Garzê and Gangdisê belts, depression (lakes and pluvial plains) in eastern Tarim, Qaidam, Qiangtang, and Hoh Xil, and the Neo-Tethys Sea in the western and southern Qinghai–Tibet Plateau. (2) The Oligocene is characterized by uplift in the Gangdisê–Himalaya and Karakorum regions (marked by the absence of sedimentation), fluvial transport (originating eastward and flowing westward) in the Brahmaputra region (marked by the deposition of Dazhuka conglomerate), uplift and erosion in western Kunlun and Songpan–Garzê, and depression (lakes) in the Tarim, Qaidam, Qiangtang, and Hoh Xil. The Oligocene is further characterized by depressional littoral and neritic basins in southwestern Tarim, with marine facies deposition ceasing at the end of the Oligocene. (3) For the Miocene, a widespread regional unconformity (ca. 23 Ma) in and adjacent to the plateau indicates comprehensive uplift of the plateau. This period is characterized by depressions (lakes) in the Tarim, Qaidam, Xining–Nanzhou, Qiangtang, and Hoh Xil. Lacustrine facies deposition expanded to peak in and adjacent to the plateau ca. 18–13 Ma, and north–south fault basins formed in southern Tibet ca. 13–10 Ma. All of these features indicate that the plateau uplifted to its peak and began to collapse. (4) Uplift and erosion occurred during the Pliocene in most parts of the plateau, except in the Hoh Xil–Qiangtang, Tarim, and Qaidam.     

Cenozoic uplift of the Tibetan Plateau: Evidence from the tectonic-sedimentary evolution of the western Qaidam Basin

Geologists agree that the collision of the Indian and Asian plates caused uplift of the Tibet Plateau.However,controversy still exists regarding the modes and mechanisms of the Tibetan Plateau uplift.Geology has recorded this uplift well in the Qaidam Basin.This paper analyzes the tectonic and sedimentary evolution of the western Qaidam Basin using sub-surface seismic and drill data. The Cenozoic intensity and history of deformation in the Qaidam Basin have been reconstructed based on the tectonic developments,faults growth index,sedimentary facies variations,and the migration of the depositional depressions.The changes in the sedimentary facies show that lakes in the western Qaidam Basin had gone from inflow to still water deposition to withdrawal.Tectonic movements controlled deposition in various depressions,and the depressions gradually shifted southeastward.In addition,the morphology of the surface structures in the western Qaidam Basin shows that the Cenozoic tectonic movements controlled the evolution of the Basin and divided it into(a) the southern fault terrace zone, (b) a central Yingxiongling orogenic belt,and(c) the northern fold-thrust belt;divided by the XI fault (Youshi fault) and Youbei fault,respectively.The field data indicate that the western Qaidam Basin formed in a Cenozoic compressive tectonic environment caused by the India—Asia plate collision. Further,the Basin experienced two phases of intensive tectonic deformation.The first phase occurred during the Middle Eocene—Early Miocene(Xia Ganchaigou Fm.and Shang Ganchaigou Fm.,43.8—22 Ma),and peaked in the Early Oligocene(Upper Xia Ganchaigou Fm.,31.5 Ma).The second phase occurred between the Middle Miocene and the Present(Shang Youshashan Fm.and Qigequan Fm., 14.9—0 Ma),and was stronger than the first phase.The tectonic—sedimentary evolution and the orientation of surface structures in the western Qaidam Basin resulted from the Tibetan Plateau uplift,and recorded the periodic northward growth of the Plateau.Recognizing this early tectonic—sedimentary evolution supports the previous conclusion that northern Tibet responded to the collision between India and Asia shortly after its initiation.However,the current results reveal that northern Tibet also experienced another phase of uplift during the late Neogene.The effects of these two stages of tectonic activity combined to produce the current Tibetan Plateau.     

LATE CENOZOIC RAPID UPLIFT OF THE TIBETAN PLATEAU AND FORMATION OF ASIAN MONSOON SYSTEM:EVIDENCE FROM PALEOMAGNETISM AND PALEOBIOLOGY OF RED BED-BOULDER CONGLOMERATE SEQUENCES ALONG THE NORTHERN TIBET PLATEAU

LATE CENOZOIC RAPID UPLIFT OF THE TIBETAN PLATEAU AND FORMATION OF ASIAN MONSOON SYSTEM:EVIDENCE FROM PALEOMAGNETISM AND PALEOBIOLOGY OF RED BED-BOULDER CONGLOMERATE SEQUENCES ALONG THE NORTHERN TIBET PLATEAU     

Cenozoic tectonics and landform evolution in the Qilian Mountains and adjacent areas

ABSTRACT

The formation of the Qilian mountains and the evolution of adjacent basins were controlled by the uplift and northeastward growth of the Tibetan Plateau. In a field survey conducted on the main Cenozoic basin sediments in the Qilian Mountains and adjacent areas, fission track age data of apatite obtained previously were analyzed. Cenozoic tectonics and landform evolution in the area where the Qilian Mountains now stand and its response to the uplift of the Tibetan Plateau were studied. In the Oligocene Epoch, the Tibetan Plateau was initially uplifted and extended northeastward, forming the Guide-Xining-Lanzhou-Linxia foreland basin on the northern margin of the western Qinling Mountains, and the foreland basin in the area where the Qilian Mountains now stand received widespread sediments. In the Miocene, influenced by the enhanced uplift and northeastward thrust of the Tibetan Plateau, a stage of intracontinental squeezing orogeny and foreland basin splitting began in the area where the Qilian Mountains now stand. In the Pliocene Epoch, the Qilian Mountains were continuously uplifted, the basins shrank, large lake basins disappeared gradually, and large-area red-clay-type aeolian sediments appeared. During the Quaternary Period, the uplift of the Tibetan Plateau accelerated, causing a rapid rise in the altitude of the Qilian Mountains. Global climate change occurred and mountain glaciers began to develop. Quaternary moraine deposits appeared for the first time in the area, and very thick loess sediments appeared in the Longzhong area, east of the area where the Qilian Mountains now stand, forming the famous Loess Plateau.     

青藏高原始新世构造岩相古地理

在前人研究成果的基础上,分析青藏高原始新世残留盆地的构造背景、岩石地层序列和青藏高原始新世期间的构造岩相古地理特征。松潘-甘孜和冈底斯带为大面积构造隆起蚀源区,塔里木东部、柴达木、羌塘、可可西里地区主体表现为大面积的构造压陷湖盆-冲泛平原沉积,高原西部和南部为新特提斯海。从构造岩相古地理演化的角度揭示青藏高原始新世构造隆升与沉积响应的耦合关系,划分出2个强隆升期,分别是强隆升期Ⅰ(55-51Ma)和强隆升期Ⅱ(45-34Ma)。     

阿尔金山新生代隆升历史:来自塔东南若羌凹陷的沉积记录

阿尔金山位于青藏高原北部边缘,在高原隆升和演化过程中扮演着重要的角色。但是,关于它的新生代隆升历史现今仍存在较大的争议。阿尔金山北麓若羌凹陷新生代接受来自山脉的剥蚀物质。因此,凹陷内的沉积特征记录了阿尔金山新生代隆升的重要信息。本文利用石油钻井编录资料及地震剖面,通过对盆地区新生代各个地层之间的接触关系、沉积相组合和沉积速率变化进行研究,结果显示阿尔金山34Ma以来的隆升分为两阶段:第一阶段为34~20.4Ma,持续低速隆升;第二阶段为16Ma至现今,急剧快速隆升。结合前人研究成果,认为渐新世—早中新世,阿尔金断裂作为一个局限在中、下地壳的韧性剪切带造成阿尔金山一带产生大范围的地表隆起,控制了山脉在第一阶段的持续低速隆升;中中新世以来,阿尔金断裂大规模左行走滑,青藏高原北缘主要通过地壳缩短的形式释放应力,控制了山脉在第二阶段的急剧快速隆升。