Data Ma

SCIENCE CHINA

Earth Sciences

RESEARCH PAPER January 2011 Vol.54 No.1: 29 44

doi: 10.1007/s11430-010-4110-0

Spatio-temporal framework of tectonic uplift stages of the Tibetan

Plateau in Cenozoic

WANG GuoCan1,2*, CAO Kai2, ZHANG KeXin1,2, WANG An1,2, LIU Chao3,

MENG YanNing2 & XU YaDong2

1

State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China;

2

Faulty of Earth Sciences, China University of Geosciences, Wuhan 430074, China;

3

The Bureau of Non-ferrous Geology of Liaoning Province, Shenyang 110013, China

Received July 6, 2009; accepted August 27, 2010; published online November 24, 2010

Four intensive uplift periods, i.e., 60 35, 25 17 and 12 8 Ma (but 18 13 Ma in the Himalayas of the southern Tibet), and since

about 5 Ma, can be determined on the Tibetan Plateau by synthetical analysis of low-temperature thermo-chronology data,

sedimentary deposit records, and structural deformation records of different areas. The strong tectonic uplift periods in differ-

ent areas on the Tibetan Plateau are penecontemporaneous, except for the Himalayan area of the southern Tibet, where a rapid

uplift and exhumation period, controlled by the activity of the South Tibetan Detachment System faults, occurred during 18 13

Ma. These strong uplift and exhumation periods correspond well to intensive deformation activity periods, suggesting tectoni-

cally-controlled uplift and exhumation. The deposit records, such as the distribution of coarse clastic sediments, the

distribution of tectonically-controlled basins, stratigraphic discontinuousness or unconformity, and fault-controlled geomor-

phologic evolution, also match well with the strong uplift and exhumation periods. Expanding processes of the plateau are also

discussed.

Tibetan Plateau, Cenozoic, intensive tectonic uplift and exhumation periods, plateau growth and expansion

Citation: Wang G C, Cao K, Zhang K X, et al. Spatio-temporal framework of tectonic uplift stages of the Tibetan Plateau in Cenozoic. Sci China Earth Sci,

2011, 54: 29 44, doi: 10.1007/s11430-010-4110-0

Many researches have focused on the uplift processes of the magma evolution. More and more data show that the tec-

Tibetan Plateau because it is the highest and largest plateau tonic processes of the Tibetan Plateau during the Cenozoic

in the world and has a strong influence on the global cli- are characteristic of distinct stages and obvious diversity

matic changes. Researchers have tried to quantitatively con- from area to area. Both tectonic uplift processes and devel-

strain the details of the uplift and exhumation processes in opment of the corresponding deposition and structural de-

different parts of the plateau by using multidisciplinary ap- formation exhibit the spatial-temporal diversity of the uplift

proaches, including low-temperature thermo-chronology, and exhumation. This paper will review and analyze the

paleontology, climatology, paleogeography, paleogeo- spatial-temporal framework of tectonic uplift stages of the

barometry, and stable isotope, etc. They have also tried to Tibetan Plateau in the Cenozoic based on low-temperature

study the dynamics of the tectonic uplift of the plateau by thermo-chronology data, sedimentary deposit records, and

analyzing the Cenozoic structural deformation pattern and structural deformation records of different areas on the pla-

teau.

*Corresponding author (email: *****@***.***.**)

Science China Press and Springer-Verlag Berlin Heidelberg 2010 earth.scichina.com www.springerlink.com

30 Wang G C, et al. Sci China Earth Sci January (2011) Vol.54 No.1

1 Intensive uplift and exhumation stages of key Mountains was initiated at about 46 Ma based on magneto-

stratigraphy and deposit analysis at the Cenozoic sediment

areas of the Tibetan Plateau and their deposi-

section in the northern front of the West Kunlun Mountains.

tional and tectonic responses

However, an obvious surface uplift had not occurred be-

cause there were still marine deposits in the Paleogene in

The marginal mountains surrounding the Tibetan Plateau the West Kunlun Mountains [10].

are the most sensitive to the uplift and exhumation proc- The three younger peaks of Neogene ages from the bed-

esses during the Cenozoic. Many low-temperature thermo- rocks of the West Kunlun Mountains coincide well with the

chronologic studies have been focused on those areas. For DZFT peaks and the DAFT peaks from current clastic de-

comparison, we systematically collected 572 published apa- posits of the Wusiteng and Yarkant rivers, indicating three

tite fission-track (AFT) ages of the marginal mountains of intensive tectonic uplift and exhumation events in the West

the Tibetan Plateau, and divided them into six key areas, i.e., Kunlun Mountains. The AFT ages at 23 18 Ma are widely

the West Kunlun Mountains, Altyn Tagh Mountains, north- distributed in the bedrocks of the West Kunlun Mountains,

eastern margin of the plateau, Himalayas, Gangdese, and roughly coinciding with the strongest peak of the DZFT at

eastern margin of the plateau (eastern Tibet-western Si- 18 Ma and stronger DAFT peak at 22 Ma. The AFT ages at

chuan-western Yunnan). The analysis of activity of a series 10 8 Ma are distributed mainly in the Muztag-Pulu [2] and

of main faults and deposition of the concerned basins in the Kudi-Sanju [4], but the AFT ages since 5 Ma are concen-

Cenozoic was combined with those AFT ages to explore the trated in the Muztag-Pulu [2, 5] and Kongur-Muztag Ata

spatial-temporal framework of tectonic uplift and exhuma- areas [1, 3]. Different fission-track age components in dif-

tion stages of the Tibetan Plateau (Figures 1 and 2). ferent areas reveal differential uplift and exhumation among

different fault-controlled blocks [1]. Except the Kongur-

Muztag Ata block, surrounded by normal faults, with un-

1.1 West Kunlun Mountains

usually young fission-track ages, the other blocks with dif-

Statistic analysis of 42 AFT ages from bedrocks of the West ferent fission-track age components mainly exhibit a series

Kunlun Mountains exhibits 3 distinct peaks, i.e., 23 18, of thrust faults surrounding them. The wide distribution of

10 7, and since 5 Ma (Figure 2(a)) [1 6]. Fifty-two detrital 23 18 Ma fission-track ages suggest an extensively thrust-

apatite fission track (DAFT) ages from current clastic de- controlled uplift in this period. However, the rapid uplift

posits of the Wusiteng River and Yarkant River, the northern since 5 Ma mainly happened in two areas. One is the

front of the West Kunlun Mountains, show two peaks at 22 Kongur-Muztag Ata area close to the Pamir Syntaxis [1, 3],

and 4.5 Ma, and one sub-peak at 11.8 Ma, similar to the AFT and the other is the Muztag-Pulu area close to the connection

age components of bedrocks of the West Kunlun Mountains area of the West Kunlun Mountains and Altyn Tagh Moun-

(Figures 2(a) and 3(a)). The peak-fitting to 313 detrital zircon tains [5], suggesting that the strong strain concentration of the

fission track (DZFT) ages from these two rivers shows more eastern and western syntaxis of the West Kunlun Mountains

complex age components, which have six main peaks at controlled the rapid uplift since 5 Ma. Other geochronologic

223.1, 112.1, 41.1, 18, 7.7, and 1.3 Ma respectively (Figure data revealed more details about the strong tectonic uplift of

3(b)). The three younger peaks (18, 7.7, and 1.3 Ma) of the the West Kunlun Mountains. For example, the monazite dat-

DZFT ages are similar to the DAFT peaks and the AFT peaks ing of the Konggur gneisses revealed a crustal thickening and

of the bedrocks of the West Kunlun Mountains, but the other amphibolite-facies metamorphism event at about 9 Ma [7].

three older peaks (223.1, 112.1, and 41.1 Ma) have no signal Ar-Ar dating of K-feldspar multiple diffusion domains re-

vealed that the normal fault-controlled rapid uplift and exhu-

in the DAFT and the bedrocks.

mation of the Kongur Shan mainly began at about 5 Ma and

The three older peak ages of the DZFT probably re-

accelerated since about 2 Ma [1, 11].

corded the thermal events or rapid tectonic uplift and ex-

Based on above geochronological data, the tectonic uplift

humation events that had happened at deeper crust level of

and exhumation in the West Kunlun Mountains during the

the West Kunlun Mountains or southern adjacent areas be-

Cenozoic can be divided into four strong stages, i.e., >41,

cause of higher closure temperature of zircon fission-track

23 18, 12 7, and since 5 Ma. The deposition also corre-

(ZFT). The peak ages of 223.1 and 112.1 Ma correspond to

sponds to these rapid uplift and exhumation periods. During

two tectonic thermal events in the Mesozoic, coinciding

the Paleocene-Eocene, deposits are mainly littoral-neritic

with the peak magma-metamorphic event in 230 200 Ma,

clastic in the West Kunlun Mountains, and changed to mesa

which is related to the subduction of the Paleo-Tethyan

carbonate in the southwestern Tarim Basin [10], implying a

oceanic basin [7] and strong fault activity or crustal thick-

southern eroding area, most probably the Tianshuihai ter-

ening event between 125 and 101 Ma [7, 8]. The peak age

rane. Therefore, the 41 Ma peak age of the DZFT might

of 41.1 Ma corresponds to a rapid uplift and exhumation

mainly record the intensive uplift and exhumation in the

event due to thrusting caused by the India-Eurasia collision

Tianshuihai terrane, although thrusting-controlled rock up-

at a deeper crustal level. Yin et al. [9] also suggested that

lift in deep crustal level also occurred in the West Kunlun

the thrust system with top to the north in the West Kunlun

Wang G C, et al.

Sci China Earth Sci

January (2011) Vol.54 No.1

Figure 1 Cenozoic geological sketch map of the Tibetan Plateau and adjacent areas. 1. Quaternary; 2. Pliocene-early Pleistocene (N2Qp1x: Xiyu Fm., N2Qp1y: Yanyuan Fm.); 3. Miocene-early Pleisto-

cene (NQp1X: Siwalik Gr., NQp1Z: Zhada Gr.); 4. Pliocene (N2a:Atushi Fm., N2qs: Quanshuigou Fm., N2s: Shizigou Fm., N2l: Linxia Fm., N2q: Quguo Fm., N2W: Wuyu Gr., N2cy: Ciying Fm., N2m:

Mangbang Fm.); 5. Miocene (N1GS: Gansu Gr., N1c: Chabaoma Fm., N1w: Wudaoliang Fm.); 6. Miocene-Pliocene (Ns: Suonahu Fm., Nsp: Shipingding Fm., Nwm: Woma Fm.); 7. Oligocene-Miocene

(E3N1G: Guide Gr., E3N1k: Kangtuo Fm., E3N1y: Yulinshan Fm., E3N1d: Dazhuka Fm.); 8. undivided Paleocene-Miocene (including Lulehe Fm. (E1-2l), Ganchaigou Fm. (ENg) and Youshashan Fm (N1y)

on the northern margin of the Qaidam Basin, and Kashi Gr. (EK) and Wuqia Gr. (N1W) in the southwestern Tarim Basin); 9. Oligocene (E3n: Nadingcuo Fm., E3by: Baiyanghe Fm.); 10. Eocene-Oligocene

(western Yunnan); 11. Eocene Zhaojiadian Fm. (western Yunnan); 12. Paleocene-Eocene (E1-2L: Linzizong Gr., E1-2LQ: Liuqu Gr., E1-2n: Niubao Fm.); 13. Paleocene-Eocene (E1-2dgm: Denggang m -

lange); 14. Paleogene (including Tuotuohe Fm. (E1-2t) and Yaxicuo Fm. (E3y) in Hoh Xil-Yushu area; EX: Xining Gr., EK: Kashi Gr.), 15. undivided Cretaceous-Paleogene (Pamir); 16. Miocene monzo-

nitic granite; 17. Miocene granite; 18. Oligocene granite; 19. Eocene granite; 20. Eocene monzonitic granite; 21. Paleocene granite; 22. Paleogene granite; 23. Paleogene monzonitic granite; 24. Paleogene

granodiorite; 25. thrust fault; 26. detachment fault; 27. reverse fault; 28. normal fault; 29. strike-slip fault; 30. other general fault; 31. regional fault: ATF-Altyn tagh fault; ANF-Anninghe-Zemuhe fault;

BNF-Bangong-Nujiang fault; GLF-Garz -Litang fault; HYF-Haiyuan fault; JLF-Jiali fault; XJHF-Xijinwulan-Jinsha River-Red River fault; KDF-Kudi fault; KKF-Karakorum fault; KXF-Kangxiwa fault;

LCF-Lancangjiang fault; LMF-Longmen Shan fault; LSF-Longmucuo-Shuanghu fault; MBT-Main Bountary Thrust fault; MCT-Main Central Thrust fault; MKF-Muztag-South Kunlun fault;

STDS-South Tibetan Detachment System; XSF-Xianshuihe fault; YZF-Yarlung Zangbo fault.

31

32 Wang G C, et al. Sci China Earth Sci January (2011) Vol.54 No.1

Figure 2 Histogram of apatite fission track ages in six key areas of the Tibetan Plateau. (a) West Kunlun Mountains; (b) Altyn Tagh Mountains; (c) north-

eastern margin of the Tibetan Plateau; (d) Himalaya; (e) Gangdese; (f) eastern Tibet-western Sichuan-western Yunnan.

stones and conglomerates in the southern Tarim Basin. In

Mountains. During late Oligocene-early Miocene (about

Pliocene, especially since 3.5 Ma, the rapid uplift and ex-

25 17 Ma), the denudation area expanded northward from

humation were marked by the famous molasse of the Xiyu

the Tianshuihai to the West Kunlun Mountains, and con-

Formation (N2-Qp1x). The deposit characteristics showing

trolled the development of the foreland basin of the south-

the rapid uplift and exhumation in this period are: (1)

western Tarim Basin. A coarsening-up tendency occurs

northward and up-decreasing dip angle of the Xiyu Forma-

from the late Oligocene Bashibulake Formation to the early

tion (4.5 1.1 Ma), suggesting a typical growth strata char-

Miocene Kezinoyi Formation. The sedimentary facies

acter [13, 14]; (2) a change of sedimentary facies in 4.5 3.5

changed from a marine environment with purplish-red fine

Ma from distal alluvial plains to proximal alluvial fans [15];

sandstones and mudstones in early Oligocene to littoral,

(3) a rapid increase in deposition rate from 0.15 mm yr 1

salt-water lacustrine, fluvial and alluvial environments with

mainly purplish-red sandstones intercalated with mudstones before 4.5 Ma (early Oligocene-early Pliocene) to 0.95

mm yr 1 during 4.5 2 Ma, especially 1.4 mm yr 1 during

and siltstones in late Oligocene, then to terrestrial lacustrine

deposits in early Miocene. These are corresponded to a ma- 3.6 2.6 Ma [15].

rine regression from east to west in the southwestern Tarim

area during late Oligocene-early Miocene [12], indicating a 1.2 Altyn Tagh Mountains

sedimentary sequence of a foreland basin, and a northwest-

ward expanding and uplifting of the Tibetan Plateau during Bounding the northern boundary of the Tibetan Plateau, the

Altyn Tagh strike-slip fault played an important role in the

late Oligocene-early Miocene. The deposition correspond-

uplifting and related deformation in the Altyn Tagh Moun-

ing to the intensive uplift and exhumation period in mid-

tains. There are a series of thermochronological data to ex-

dle-late Miocene (13 7 Ma) was shown mainly by a coars-

plore the development of the Altyn Tagh strike-slip fault.

ening-up and accelerative deposition and increased sand-

33

Wang G C, et al. Sci China Earth Sci January (2011) Vol.54 No.1

Figure 3 Histogram and Gaussian distribution of best-fit peaks for detrital apatite and zircon fission track ages for the current river deposits in northern

front of the West Kunlun Mountains. (a) Detrial apatite fission track ages; (b) detrial zircon fission track ages.

By summarizing 85 AFT ages from the bedrocks of the Tagh Mountains can be roughly divided into four periods,

Altyn Tagh Mountains [16 23], we can distinguish five i.e., 61 32, 22 17, 10 7, and since 5 Ma, similar to the peak

distinct peak ranges, i.e., 34 32, 22 17, 10 7, 5.5 4.5, and ages of the AFT in the West Kunlun Mountains as a whole.

2.11 1.18 Ma (Figure 2(b)). There also occur some older This indicates similar period s response to strong tectonic

Paleocene-Eocene AFT ages. They are distributed mainly in uplift in the northern Tibetan Plateau. However, the fault-

the northern and southeastern edges away from the Altyn controlled spatial difference is also obvious, e.g., the rapid

Tagh strike-slip fault. For example, the AFT ages of 61 34 uplift events in 10 7 Ma and since 5 Ma were directly re-

Ma are concentrated at the Lapeiquan-Hongliugou in the lated to the strong sinistral strike-slip movement of the

northern Altyn Tagh area [18], implying an earlier uplift Altyn Tagh fault.

and exhumation here than the other areas. The AFT ages in

the NE-trending Qiemo-Mangai areas between the

1.3 Northeastern margin of the Tibetan Plateau

Lapeiquan-Hongliugou area and the Altyn Tagh strike-slip

fault are mostly between 22 and 17 Ma [18]. Sobel et al. [23] The 51 AFT ages from the areas including the East Kunlun

also supported that an intensive exhumation and cooling Mountains, Qilian Mountains and the headwaters of the

event happened between 26 and 19 Ma in this area based on Yellow River are mostly between 57 and 45 Ma, generally

their thermochronological data. The AFT ages of 22 17 Ma older than that from the West Kunlun and the Altyn Tagh

are also concentrated in Qiman area, the south of the Altyn mountains. The younger AFT ages have a scattered distri-

Tagh strike-slip fault [17], implying intensive exhumation bution with no obvious peak (Figure 2(c)) [24 27]. How-

and cooling in this area. The younger AFT ages of 10 7 Ma

ever, Yuan et al. [24] revealed that in the East Kunlun

are widely distributed along the Altyn Tagh strike-slip fault

Mountains the exhumation rate was about 100 150 m Ma 1

and formed the strongest peak (Figure 2(b)), indicating the

in average and gradually accelerated during 20 10 Ma by

strong activity period of the fault. Closer to the Altyn Tagh

the AFT length thermal history modeling. Using the AFT

strike-slip fault, there are mainly AFT ages of 10 7 Ma,

length thermal history modeling method, Jolivet et al. [25]

whereas older ages occur in areas away from the fault [19,

revealed that in the Qilian Mountains, a rapid exhumation

21, 22], indicating that a tilting led to a rapid uplift and ex-

cooling event occurred at about 40 Ma, a tectonic heating

humation near the Altyn Tagh strike-slip fault when it was

event at about 22 18 Ma, and a rapid exhumation cooling

active. The rapid uplift and exhumation event during the

event at 9 5 Ma. Through the DAFT study of the Cenozoic

late Pliocene-early Pleistocene mainly occurred in Aqiang

detrital sediments from the Linxia Basin, Zheng et al. [28]

area of the middle Altyn Tagh strike-slip fault. Here the

suggested that there were two rapid exhumation events at

AFT ages suggest that rapid exhumation occurred during

about 14 and about 8 5.4 Ma respectively in the source

5.15 4.15 and 2.11 1.18 Ma [19], implying that rapid

areas, mostly in the Laji Mountains and the East Kunlun

strike-slip movement along the Altyn Tagh fault happened

Mountains.

in the late Pliocene-early Pleistocene along with the rapid

Four stages of strong tectonic uplift and exhumation can

uplift and exhumation in the nearby areas.

be distinguished in the eastern segment of the East Kunlun

To sum up, rapid uplift and exhumation in the Altyn

34 Wang G C, et al. Sci China Earth Sci January (2011) Vol.54 No.1

Mountains and Laji Mountains, i.e., 50 40, 23 21, ~8 and and stronger contrast in relief. The deposition of a suite of

since about 3.6 Ma, based on analysis of sediment se- coarse conglomerates at the northern front of the Qilian

Mountains represents rapid uplift of the Qilian Mountains

quences, growth strata and depositional facies of the Xining,

since 3.66 Ma.

Linxia and Guide-Xunhua Basins on the northeastern mar-

Deposition analysis suggests that tectonic uplift and ex-

gin of the Tibetan Plateau [29 32]. During the Eocene, the

humation of the west-middle segment of the East Kunlun

Xining-Lanzhou Basin and the Guide Basin seemed to be an

Mountains during the Cenozoic are quite different from

uniform intra-continental foreland basin or flexural basin

those in the eastern segment of the East Kunlun Mountains.

that were controlled by northward thrusting of the Eastern

During the Paleocene-Eocene, the representative deposition

Kunlun fault and intensive uplift of the eastern segment of

of the Qaidam Basin in the north of the west-middle seg-

the East Kunlun Mountains [29]. The Laji Mountains,

ment of the East Kunlun Mountains was a sequence of

which now separates the Xining-Lanzhou Basin and the

coarse alluvial sandstones and conglomerates, known as the

Guide Basin, did not exist at that time, and the southern

Lulehe Formation (E1-2l), very similar to the Tuotuohe For-

boundary of this uniform basin must be located in the front

mation (E1-2t) of the Hoh Xil Basin in time and petrology,

of the eastern segment of the East Kunlun Mountains. In the

which is located to the south of the west-middle segment of

early Miocene (about 23 21 Ma), the unconformity between

the East Kunlun Mountains, indicating a possible good-

the Guidemen Formation and the underlying Xining Group

sized uniform basin at that time. Yin et al. [33] found that

imply a period of strong tectonic movement. Closer to the

the folds of the Cenozoic strata in the Qaidam Basin formed

East Kunlun Mountains, the Xining Group was strongly

first (65 50.5 Ma) at the western Qaidam Basin near the

folded at the southern margin of the Guide Basin, indicating

Altyn Tagh fault and then expanded to eastern Qaidam Ba-

northward compression and uplift of the East Kunlun

sin at about 23.3 Ma, indicating that deposition and defor-

Mountains. The Haiyan-Tongren fault at the east side of the

Guide Basin and the Laji Shan back-thrusting system began mation of the Lulehe Formation E1-2l were controlled by a

to be strongly active at this time. The outline of a series of southward thrusting system of the northern margin of the

mountains including the Laji Mountains and the Zhamazari Qaidam Basin. The source regions were located to the north

Mountains began to form. The previous uniform intra- or northwest of the Qaidam Basin, but not from the East

continental foreland basin was separated into several small Kunlun Mountains to the south. Through studies of a series

fault-controlled intramountain basins. The Xining-Linxia, of seismic transects across the Qandam Basin, Yin et al. [33]

Guide and Xunhua basins began to develop independently. concluded that the thrust system at the southern margin of

Since about 8 Ma, deposition at the northern margin of the the Qaidam Basin or the East Kunlun thrust system had be-

Guide Basin changed rapidly from lacustrine facies to gun to control the deposition and folding of the Qaidam

alluvial-pluvial facies at the piedmont, and to braided allu- Basin by 35.5 23.3 Ma. This means that the western-middle

vial river facies in the basin center, forming conglomerate segment of the East Kunlun Mountains, which now sepa-

fans extending from the basin margin to the center. The rate rates the Qaidam Basin from the Hoh Xil Basin, did not

of deposition increased, accompanied by tilting and folding exist during the Paleocene-Eocene and began to uplift in the

of strata. These indicated that the Laji Mountains, separat- Oligocene. Strong compression and uplift must have oc-

ing the Guide Basin from the Xining Basin, was strongly curred in the late Oligocene. This caused extensive folding

uplifted and rapidly expanded towards the basins. At about and faulting of the Tuotuohe Formation (56 32 Ma) and the

3.6 Ma the rate of deposition rapidly increased and allu- Yaxicuo Formation (32 30 Ma) and a regional unconformity

vial-pluvial conglomerates of the Ganjia Formation spread between the underlying folded Tuotuohe Formation (56 32

right across the Guide Basin. At the margin of the Basin, the Ma) and the Yaxicuo Formation and the overlying horizontal

Ganjia Formation was deposited unconformably on the de- Wudaoliang Formation (23 16 Ma) in the Hoh Xil-Tong-

formed underlying strata, indicating an episode of Laji tianhe area. However, the deposition sequence in the Qaidam

Mountains sharp uplift, thrusting and folding of the previ- Basin was continually developed in this process.

ous strata. In summary, the strong tectonic uplift on the northeastern

Deposition of the Jiuquan-Zhangye Basin records three margin of the Tibetan Plateau can be divided into four

stages of strong tectonic uplift in the Qilian Mountains: stages: 57 45, 23 21, ~8 and since 3.6 Ma. AFT ages

23 21, 8.26 and since 3.66 Ma [29, 32]. In the early Mio- suggest that the strong exhumation mainly happened during

cene, northward compression of the Qilan Mountains 57 45 Ma in the eastern segment of the East Kunlun

caused a break in deposition in the Jiuquan-Zhangye Basin Mountains, whereas no strong exhumation occurred since

so that early-middle Miocene deposits are absent. At 8.26 the Miocene on the northeastern margin of the Tibetan Pla-

Ma, massive delta conglomerates were widely deposited. teau. The intensive uplift since the Miocene is mainly

The deposition rate abruptly increased from a previous 0.16 shown as the development of fault-controlled basin-range

to 0.3 mm yr 1 during the interval of 8.26 8.23 Ma, indi- structures, surface uplift, and plateau expansion. Total

exhumation since the Miocene is usually less than 3 4 km.

cating the intensive tectonic uplift of the Qilian Mountains

35

Wang G C, et al. Sci China Earth Sci January (2011) Vol.54 No.1

three earlier stages, but extensional and normal fault col-

1.4 Eastern margin of the Tibetan Plateau (eastern

lapse at the last stage. Thermochronology data in the west-

Tibet-western Sichuan-western Yunnan)

ern Yunnan area show similar deformation stages to the

Zhong et al. [34] systemically summarized the FT data from eastern Himalayan syntaxis. For example, Ar-Ar age dating

the eastern Himalayan syntaxis and discovered three distinct along the Ailaoshan-Red River fault shows that four periods

peaks (25 17, 13 8, and since 3 Ma) and a few ages >35 of strong strike-slip movememt happened at 58 56, 24 22,

Ma. By comparing the tectonic events of the whole Tibetan 13 12, and since 5.5 4.7 Ma. In the three earlier stages,

Plateau and related surrounding regions, they distinguished movements were sinistral strike-slip, but at the last stage it

four stages of strong tectonic uplift of the Tibetan Plateau: was reversed to dextral strike-slip. The Gaoligong fault,

45 38, 25 17, 13 8, and since 3 Ma. In recent years, more Lancangjiang fault, and Nujiang fault also have similar his-

and more thermochronological data from western Sichuan tories of tectonic activity [39, 40, 44 ]. In western Sichuan,

and western Yunnan have also allowed us to portray the structural deformation in the Cenozoic is represented by the

tectonic uplift processes of these areas in detail. For exam- Longmenshan fault, Xianshuihe fault, and Garz -Litang

ple, using AFT age dating and AFT length thermal history fault. The strong activity during Paleocene-Eocene is repre-

modeling of granites along the Garz -Litang fault and the sented mainly by the sinistral strike-slip movement along

Longmenshan fault, Lai et al. [35] found two periods of the Longmenshan fault [45]. The interval of 20 16 Ma was

rapid exhumation cooling, 20 16 and since about 5 Ma. By an intensive thrusting period along the Garz -Litang fault

apatite U-Th/He and fission-track age dating of a series of [35]. The most significant, strongest, and most extensive

granites along the gorges of the Dadu River, Anning River structure deformation periods on the eastern margin of the

and Yalong River, Clark et al. [36] demonstrated a rapid Tibetan Plateau were 13 8 and since 5 Ma. The deformation

uplift stage of 13 9 Ma on the eastern margin of the Tibetan at 13 8 Ma formed a series of pull-apart basins within a

Plateau. Rapid uplift and exhumation at 13 9 Ma were also series of sinistral strike-slip fault zones. The Xianshuihe

detected by AFT age records from the Longmen Mountains fault was mainly formed at this stage [44, 46]; faulting since

and Gongga Mountains in the western Sichuan [35, 37], 5Ma on the eastern margin of the Tibetan Plateau became

Zayu in the eastern Tibet [38], and the Gaoligong Moun- more intensive and extensive; for instance, strong eastward

tains in the western Yunnan [39], suggesting widespread thrusting in the Longmen Mountains led to Dayu conglom-

uplift effects on the eastern margin of the Tibetan Plateau erates formed in front of the Longmen Mountains, and

throughout this period of rapid uplift. There are more AFT strong sinistral strike-slip movement occurred along the

ages since 5 Ma, and they have been determined along the Xianshuihe fault.

Dulong River and the Red River in western Yunnan as well

as in the areas mentioned above [40, 41]. A histogram of

1.5 Himalayan area

108 AFT ages (Figure 2(f)) from the eastern margin of the

Tibetan Plateau shows five peaks at 48 40, 26 21, 17 15, With the greatest altitude and relief in the world, the Hima-

13 10, and since 7 Ma respectively. Except for the peak at layas along the south margin of southern Tibet is a fasci-

17 15 Ma, most peaks are roughly coincident with the nating area for researching tectonic uplift and related sur-

stages mentioned above. The ages of 17 15 Ma mostly have face processes. Both Chinese and foreign geologists have

short fission-track lengths [35, 42] normally 9.3 10.8 m. devoted great efforts to obtain a wealth of thermochro-

The AFT length thermal history modeling to these ages in- nologic data in this area [47 55]. A total of 265 published

dicated that a period of the rapid uplift and exhumation oc- AFT ages are mostly younger than 17 Ma. There are more

curred during 20 16 Ma but not 17 15 Ma [35]. young cooling ages than the older ones (Figure 2(d)), sug-

In summary, there were four periods of intensive uplift gesting an accelerated cooling and exhumation at the Hi-

and exhumation on the eastern margin of the Tibetan Pla- malayas. Older rock exhumation information was obtained

teau at 45 38, 25 17, 13 8, and since about 5 Ma. The most mainly by ZFT or DZFT dating in Cenozoic sedimentary

intensive and extensive uplift and cooling events were at basins. On the basis of thermochronologic data, four major

13 8 and since about 5 Ma. intensive rock cooling and exhumation periods in the Ce-

These periods of intensive uplift and exhumation match nozoic are identified at 55 36, 25 20, 17 12, and 3 0 Ma at

well with the periods of intensive structural deformation. In the Himalayas.

the eastern Himalayan syntaxis, Ar-Ar age dating shows The 55 36 Ma cooling event was mainly obtained by

that four periods of strong deformation happened at 60, 23, ZFT dating [53, 56]. Our DZFT dating of six sandstone

13, and since 7 Ma [43]. Through structural analysis, Zhang samples in Miocene-Pliocene sediments in the Gyirong Ba-

et al. [43] suggested that the deformation took the form of sin indicates a static peak at 43 36 Ma, which implies syn-

chronous fast cooling and exhumation in its source area1). It

northward-wedging thrusts at different crustal levels in the

1) Wang G C, Garver J I, Liu C, et al. Cenozoic tectonic history in the Gyirong-Nyalam area, south Tibet: Evidence from fission-track thermochronology.

In: Garver J I, Montario M, eds. Proceedings from the 11th International Conference on Thermochronometry, Anchorage Alaska, Sept. 2008

36 Wang G C, et al. Sci China Earth Sci January (2011) Vol.54 No.1

is worth noting that the present Himalayas to the south of Range began to form at that time [57].

the Yarlung Zangbo suture zone did not exist in the Paleo- Rapid uplift and cooling between 17 and 12 Ma were

gene when the Gangdese terrane to the north was exhumed mainly related to the activation of the South Tibetan De-

[57], implying that the static peak at 43 36 Ma reflects fast tachment System (STDS) accompanied by doming in the

rock cooling and exhumation of the Gangdese area. How- northern Himalayan belt. In general, the timing of STDS

ever, thermochronological study in the northern Himalayan activation is constrained in the range of 22 14 Ma [72 74].

region in northwest India indicates that the Tso Morari However, most geochronologic data tend to support a major

Nappe was initiated and extruded upwards at 55 47 Ma, range of 17 12 Ma when extension gave rise to a series of

and ceased at 45 40 Ma, when its root zone deformed as a domes in the northern Himalayan belt and exhumation of

dome and was exhumed to a depth of ~10 km [53]. This the Greater Himalayan sequences. Thermochronologic data

indicates the uplift and exhumation occurred at deep crustal have revealed that rapid exhumation periods were coupled

levels in the northern Himalayan region dominated by with major activation of the STDS between 17 and 12 Ma

thrusting in depth. Although thrust stacking dominated rock [51, 52, 73, 75 80]. Our unpublished FT work in the Nya-

uplift and exhumation at deep crust level existed in the lam and Gyirong areas indicates an average cooling rate of

50 55 C Ma 1; accompanied by a rapid exhumation rate of

northern Himalayan region, no significant denudation areas

1.4 1.6 mm yr 1 assuming a geothermal gradient of 35 C

occurred on the surface. During this period, there was still a

remnant of the Neo-Tethys Ocean along the Yarlung km 1 for the Greater Himalayan sequences at 17 12 Ma.

Zangbo suture zone and the northern Himalayan region lay Geochronologic studies on the deformed leucogranites

to its south [58 62]. Recent field geologic surveys in south- within the STDS also tend to indicate that ductile extension

ern Tibet have provided some new insights into the Paleo- postdated 19 18 Ma [71]. We link the activity of the STDS

cene-Eocene remnant ocean. Abundant abyssal-hypabyssal and the series of domes in the northern Himalayan belt to

shales, sandstones, radiolaria-bearing siliceous rocks, and isostatic rebound induced by stress removal after crustal

basalts of Paleocene-Eocene age have been identified, for compressional thickening at 25 20 Ma. Significant surface

example, the Denggang Formation (E1-2d), Yanduo Forma- uplift in the southern Tibet was induced in this period and

tion (E2y) and Guoyala Formation (E2g) to the south of the reached to present altitude mostly at about 12 Ma1). Signifi-

Yarlung Zangbo suture zone (Figure 1). Some formations cant surface uplift caused gravitational instability which

are m langes e.g., the Denggang M lange (E1-2dgm), Sang- created a series of N-S trending grabens in southern Tibet,

mai M lange (E2sm), and Yanduo M lange (E2ym). such as Musitang Basin, Pulan Basin, Gyirong Basin, Zada

Intensive tectonic uplift from 25 20 Ma is recorded in Basin and Yangbajing-Dangxiong Basin, at 13 7 Ma post-

ZFT chronologic data in a few places. For example, the Tso dating the activation of the STDS. The occurrence of these

Morari nappe in the northern Himalayan belt in northwest fault-basins in southern Tibet indicates that the development

India had undergone further upward thrusting at ~20 Ma of the Tibetan Plateau had entered a new tectonic stage,

[53]. In regional scale, this period corresponded to a sig- when NS shortening changed to EW extension and/or east-

nificant crustal thickening indicated by a series of thrusting ward creep-dispersion.

structures in the Himalayan orogen. For instance, the Main The intensive exhumation since 3 Ma has been widely

Central Thrust (MCT) fault was developed during this pe- recorded by AFT and ZFT thermochronology in the Greater

riod and dominated the formation of the Siwalik foreland Himalayan sequences and the southern Himalayan front.

basin in the Himalayan foothills [34] when depositional AFT and ZFT chronologies in the Greater Himalayan se-

conditions changed from marine to terrestrial facies quences in the Gyirong and Nyalam areas indicate slow

[63 67]. exhumation between 13 and 3 Ma and a clear acceleration

since ~3 Ma1). Differences between ZFT and AFT ages in

Major southward thrusting of the Gangdese belt also

originated mainly in the late Oligocene (30 24 Ma) and the Greater Himalayan sequences along the Gyirong and

lasted until the Miocene [68, 69], dominating the formation Nyalam transects diminish southwards, indicating a south-

of molasse of the Dazuka Formation along the Yarlung ward increase in exhumation rate after 13 Ma. Two aspects

Zangbo River. The latest chronologic data reveal that sig- might give rise to this trend: one is the southward thrusting

nificant dextral shearing of the Karakorum Fault at high on the major boundary thrust faults; the other is the south-

temperature occurred between 27 and 20 Ma [70], accom- wardly increase of the rate of erosion at the Himalayan front.

panied by a syn-tectonic leucogranite intrusion. Significant The rapid rock uplift and exhumation at the southern Hima-

crustal thickening by thrusting in the Himalayan orogen layan front and its elevation to high altitude were controlled

induced partial melting of the lower crust and produced the by tectonics and climate. In the northern Himalayan belt,

widely distributed leucogranites with U-Pb ages of mostly structures post-dating 3 Ma are mainly found in N-S graben,

22 19 Ma [71]. The Himalayan Range became a geographic while E-W faults show less activity. The intensive tectonic

barrier of the southern Tibetan Plateau by this period of uplift since 3 Ma and the relief contrasts are indicated by

tectonic uplift. The incipience of the present Yarlung widespread molasses deposited under accelerated sedimenta-

Zangbo valley between the Himalayas and the Gangdese tion rates. In the Ganges plain to the south of the Himalayan

37

Wang G C, et al. Sci China Earth Sci January (2011) Vol.54 No.1

front, the Siwalik Group changed into coarse gravel sedi- south of the Bangong-Nujiang fault, while extensive Ceno-

ments at ~3.6 Ma. Deposits in the series of N-S grabens in zoic basin deposits occur to the north. This implies that the

the northern Himalayan belt also changed into coarse gravel Bangong-Nujiang fault controlled the development of the

sediments, e.g., the Gongba molasses in the Gyirong Basin. basin to the north of the fault, especially the molasse depos-

its of the Kangtuo Formation (E3N1k). Wang et al. [88] also

emphasized that a protoplateau with a present elevation at

1.6 Gangdese area

~40 Ma had formed in the Gangdese-Qiangtang areas.

A number of thermochronologic data have also been ob- However, the study of the paleogeography suggested that

tained in recent years in the Gangdese area [81 86]. 96 AFT there was still an extensive alluvial and flooding plain in the

dates collected from the Gangdese belt indicate three cool- Qiangtang and Hoh Xil areas during the Paleocene-Eocene

ing age peaks at 22 15, 10 7, and 5 0 Ma, along with scat- [89]. In the Ali area of the western Gangdese, Paleocene-

tered Paleogene ages (Figure 2(e)). Eocene marine strata occur, indicating a paralic character at

Although the dates of Paleogene tectonic uplift and ex- that time [67]. In Zongba and the Linzhou counties of the

humation rates in the Gangdese area cannot be obtained middle segment of the Gangdese, there are also marine

from AFT data, several related studies on the thermochro- limestone interlayers with Eocene fossils [90 92]. There-

nology, basin infilling sequences, and fault structure do in- fore, we suggest that the Gangdes-Qiangtang area in the

dicate an intensive tectonic uplift and exhumation period Paleocene-Eocene was a paralic area with low altitude, not

between ~60 and 35 Ma. Wang et al. [85] used AFT age as high as at present.

dating to reveal a fast cooling and exhumation episode at There are relatively abundant AFT data concentrated at

45 35 Ma in the Gangdese belt. Wu et al. [87] determined 22 15 Ma. In a thermal evolution study of the Gangdese

that the Namcuo thrust was activated at ~44 Ma and had granite batholith, Copeland et al. [93] suggested a fast cool-

induced rock uplift and cooling. ing period between 26 and 20 Ma with an acceleration at 20

Wang et al. [88] suggested that a protoplateau composed Ma, and Harrison et al. [68] detected a fast cooling episode

of both the Gangdese and the Qiangtang terranes was at 20 18 Ma with exhumation rates over 2 mm yr 1 in the

formed at ~40 Ma from the studies on magnetostratigraphy, Qushui pluton by thermochronological study. An AFT study

sedimentology, and paleocurrent measurements in the Hoh by Yuan et al. [82] in the Lhasa-Yangbajing area suggested

Xil Basin, fission-track studies in the Tanglha Mountains, fast cooling and exhumation between 21 and 15 Ma. The

and 40Ar/39Ar age dating of volcanic rocks in the central- rapid cooling and exhumation in the Gangdese area between

northern Tibetan Plateau. They explained the Tuotuohe

22 and 15 Ma coincided with large-scale southward thrust-

Formation (E1-2t) in the Hoh Xil Basin as a foreland basin

ing along the southern margin of the Gangdese belt and

deposit controlled by northward thrusting of the northern

northward thrusting along the Banggong-Nujiang fault to

Tanglha fault, the northern boundary of the protoplateau.

the north. Southward thrusting along the southern margin of

However, the Tanglha fault seems not a facies-controlling

the Gangdese belt dominated the deposition of the coarse-

fault in the Paleocene-Eocene. The sedimentary characters

grained Dazuka Formation along the Yarlung Zangbo River

of both side of the fault are very similar. In the Paleo-

[68, 69] and the formation of the incipient of the present

cene-Eocene, the Niubao Formation represents the deposits

Yarlung Zangbo valley [57]. Northward thrusting along the

in the Southern Qiangtang to the south of the Tanglha fault

Banggong-Nujiang fault dominated the development of a

(E1-2n) (Figure 1), which is characteristic of sandstone and

foreland basin containing molasse of the Kangtuo Forma-

conglomerate of braided river delta facies at the bottom and

tion (E3N1k). The total thickness of the Kangtuo Formation

sandstone/siltstone, limestone and gypsum of lacustrine

is over 1400 m in the south and decreases to 300 400 m in

facies on the top. The Tuotuohe Formation (E1-2t) represents

the north, consistent with that of the foreland basin deposit

the deposits in the northern Qiangtang to the north of the

dominated by the Bangong-Nujiang fault.

Tanglha fault. Similar to the Niubao Formation, the Tuo-

AFT data show a sub-peak of cooling ages between 10

tuohe Formation is characterized by conglomerate, sand-

and 7 Ma. This period of cooling is probably related to rapid

stone imbedded with siltstone and mudstone of alluvial fan

exhumation of the footwalls of a series of NS-trending gra-

facies at the bottom, and sandstone and siltstone of lacus-

bens (Figure 2(e)). For example, the Nianqingtangglha duc-

trine facies on the top. So, we agree that distinct tectonic

tile shear zone, which dominated the development of the

uplift and exhumation existed somewhere in the Qiangtang

Yangbajing graben, was initiated at ~8 Ma [74] and induced

terrane during the Paleocene-Eocene, for example the Tan-

intensive uplift and exhumation of the footwall, i.e., the

glha Mountains areas [88], but the Gangdese terrane and the

Nianqingtangglha Mountains by shearing and tilting.

Qiangtang terrane could not have been a uniform uplift sys-

AFT data concentrated after ~6 Ma imply significant

tem during the Cenozoic. Instead of the Tanglha fault, the

tectonic uplift in the Gangdese area. This is supported by

Banggong-Nujiang fault in fact played a more important

AFT length thermal history modeling from the Nanmulin

role during Paleocene-Eocene. It constructed the southern

area of the Gangdese belt, which indicates that intensive

boundary of the Cenozoic basin as a whole. Figure 1 shows

tectonic uplift and exhumation occurred since 6 Ma [82].

that Paleogene volcanic rocks are mainly distributed to the

38 Wang G C, et al. Sci China Earth Sci January (2011) Vol.54 No.1

Rapid tectonic uplift induced high contrast of relief in the lift. In N-S direction perpendicular to the Himalayas, AFT

Gangdese belt and in turn resulted in the sediment coarsen- ages in the Northern Himalayan belt to the north of STDS

ing upwards in adjacent basins. are mainly older than 8 Ma with a lower average exhuma-

tion rate of 0.38 mm yr 1 since 8 Ma but those in the

Thus, we have identified four relatively intensive tec-

tonic uplift episodes during the Cenozoic in the Gangdese Greater Himalayan belt to the south

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