Late Oligocene–Early Miocene Birth of the Taklimakan Desert

Late Oligocene–early Miocene birth of the Taklimakan Desert

Hongbo Zhenga,b,1, Xiaochun Weic,1, Ryuji Tadad, Peter D. Clifte, Bin Wangf, Fred Jourdang, Ping Wanga, and Mengying Hea

aSchool of Geography Science, Nanjing Normal University, Nanjing 210023, China; bCenter for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing, 100101, China; cSchool of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China; dDepartment of Earth and Planetary Science, University of Tokyo, Tokyo 113-0033, Japan; eDepartment of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803; fTourism and Environment College, Shaanxi Normal University, Xi’an 710119, China; and gWestern Australian Argon Isotope Facility, Department of Applied Geology and John de Laeter Centre, Curtin University, Perth, WA 6845, Australia

Edited by Zhonghe Zhou, Chinese Academy of Sciences, Beijing, China, and approved May 11, 2015 (received for review December 22, 2014) As the world’s second largest sand sea and one of the most im- along the southwestern margin of the Tarim Basin. Radioiso- portant dust sources to the global aerosol system, the formation topic dating of the volcanic minerals provides a robust age for of the Taklimakan Desert marks a major environmental event in the sections, and therefore we are able to determine the age of central Asia during the Cenozoic. Determining when and how the the Taklimakan Desert more precisely. desert formed holds the key to better understanding the tectonic– climatic linkage in this critical region. However, the age of the Geological Setting and Lithostratigraphy Taklimakan remains controversial, with the dominant view being From latest Cretaceous to early Paleogene, much of the western from ∼3.4 Ma to ∼7 Ma based on magnetostratigraphy of sedi- Tarim Basin was influenced episodically by a shallow sea, which mentary sequences within and along the margins of the desert. In was connected to the Paratethys, an epicontinental marine sea- this study, we applied radioisotopic methods to precisely date a way covering large parts of Europe and southern central Asia volcanic tuff preserved in the stratigraphy. We constrained the (9). Shallow marine strata of this age are observed extensively initial desertification to be late Oligocene to early Miocene, be- along the western and southwestern margins of the Tarim Basin, tween ∼26.7 Ma and 22.6 Ma. We suggest that the Taklimakan extending to Hotan to the east and Ulugqat to the north (Fig. 1). Desert was formed as a response to a combination of widespread Five major marine incursions have been recognized in the broad regional aridification and increased erosion in the surrounding region, with the fourth being the final one at Aertashi, where it is mountain fronts, both of which are closely linked to the tectonic represented by the Wulagen Formation (Fig. 2 A and B and SI uplift of the Tibetan–Pamir Plateau and Tian Shan, which had re- Text). Recent biostratigraphic work at Aertashi has suggested that ached a climatically sensitive threshold at this time. the Paratethys Sea finally retreated from this locality at ∼41 Ma (9, 10), a process that has been attributed to global eustasy coupled Taklimakan Desert | late Oligocene | early Miocene | tectonic uplift | with tectonism associated with the Indo–Asia collision. Together, desertification these have amplified the aridification of the Asian interior (9, 11). Syntectonic foreland basin deposition followed the marine urrounded by the Tian Shan to the north, the Pamir to the regression immediately and led to accumulation of thick conti- Swest, and the West Kunlun to the south, the Taklimakan nental red beds (Fig. 2 A and B). The Bushiblake Formation is Desert is the world’s second largest sand sea (Fig. 1). Located far characterized by red, fine-gained mudstone and fine sandstone, with from any major source of moisture, and shadowed by Tibetan common evaporative gypsum, typical of low-energy, meandering and central Asian mountain ranges, the Taklimakan is deprived river, lacustrine, and playa deposits (SI Text). The overlying of rainfall, with mean annual precipitation not exceeding 50 mm Wuqia Group (SI Text) consists of thickly bedded sandstones with (1). Provenance studies suggest that mineral dust from the Taklimakan Desert contributes substantially to the global aero- Significance sol system, allowing it to play a significant role in modulating global climate on various time scales (2, 3). The formation of the The formation of the Taklimakan Desert marked a major geo- Taklimakan Desert therefore marked a major environmental event logical event in central Asia during the Cenozoic, with far- in central Asia during the Cenozoic, with far-reaching impacts. reaching impacts. Deposition of both eolian sand dunes in the Furthermore, determining when and how the desert formed holds – basin center and the genetically equivalent loessite along the the key to better understanding the nature of tectonic climatic basin margins provide evidence for the birth of the Taklimakan linkage in this critical region. However, the time at which the Desert. This paper resolves a long-standing debate concerning Taklimakan Desert came into existence has been strongly debated, the age of the Taklimakan Desert, specifically whether it dates with estimates ranging from only a few hundreds of thousands to a to ∼3.4–7 Ma, currently the dominant view. Our result shows – few million years ago (1, 4 8). that the desert came into existence during late Oligocene–early In the context of this study, we define desertification to rep- Miocene, between ∼26.7 Ma and 22.6 Ma, as a result of wide- resent not only the formation of a significant sand sea but also spread regional aridification and increased erosion in the sur- the generation of a dynamic eolian system that supplied volu- rounding mountain fronts, both of which are closely linked to minous mineral dust on regional and even global scales. Evi- the tectonic uplift of the Tibetan–Pamir Plateau and Tian Shan. dence of desertification in the geological past is preserved in sedimentary sequences within, and along the margins of, the Author contributions: H.Z. designed research; H.Z., X.W., R.T., P.D.C., B.W., P.W., and M.H. present-day Taklimakan Desert that lies within the Tarim Basin performed research; X.W. and F.J. analyzed data; and H.Z., X.W., and F.J. wrote the paper. (Fig. 1). Recent geochronological work, mostly based on the The authors declare no conflict of interest. magnetostratigraphy of these sedimentary sequences, proposed This article is a PNAS Direct Submission. ∼ – 3.4 Ma to 7 Ma for the initiation of the Taklimakan (4 8). 1To whom correspondence may be addressed. Email: [email protected] or xcwnju@ Precise dating of these terrestrial rocks has largely been ham- gmail.com. pered by lack of dateable material. In this study, we report This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. a newly identified volcanic tuff from two sedimentary sections 1073/pnas.1424487112/-/DCSupplemental.

7662–7667 | PNAS | June 23, 2015 | vol. 112 | no. 25 www.pnas.org/cgi/doi/10.1073/pnas.1424487112 Downloaded by guest on October 6, 2021 N JB A Tian Shan Tian Shan B TB Kalpin Pamir CLP Tibetan Plateau 40 Ulugqat QA

India Kirzlesu River Loess Kashgar Gobi & Desert

Muji Main Pamir Thrust Mazatagh Yarkand River Tarim Basin

Hotan River

Mustagh Aertashi Taklimakan Desert 38 Yecheng Pamir Tashkorgan Kekeya iya River

Ker Yurungkax River Karakorum Fault West Kunlun Shan Karakax RiverHotan 8524m 5000m 3000m Thrust fault Section Mazar Karakax Fault 1000m 36 Nomal fault Town 0m Stike-slip fault Tibetan Pleteau 0km 100km 200km 74 76 78 80

Fig. 1. Location map. (A) Topographic map showing the western portion of the Taklimakan Desert (Tarim Basin) and the surrounding mountain ranges with major active faults. The location of the studied Cenozoic sedimentary sections at Aertashi, Kekeya, and Mazatagh are shown by stars. (B) Map showing the location of the Tarim Basin (TB), Junggar Basin (JB), and Chinese Loess Plateau (CLP). Qin’an loess section (QA) is marked by a red star.

minor mudstone. The overall content of sand increases upward, as source area had become fully arid and desertified, and was does the grain size. supplying dust to the proximal region at that time. Lithofacies change to distal alluvial deposits, consisting of con- Direct evidence of desertification is found in the exposed glomerate, sandstone, and siltstone crossing the boundary from the sedimentary sequence at the Mazatagh Range, in the central Wuqia Group to the Artux Formation (SI Text). The conglomerate Taklimakan Desert (Figs. 1 and 2E). The lithostratigraphy at this layers in the Artux Formation are thin-bedded debris flow deposits, location has been well established and can be generally corre- containing medium-sized, angular to subrounded pebbles, of which lated to the basin margin sequences (Fig. 2G) (5, 6), except that more than half are sedimentary rocks. The overlying Xiyu For- the lithologies are generally finer and sedimentation rates are mation (SI Text) is up to 3 km thick and consists of massive lower. Red cross-bedded eolian sandstone (Fig. 2H and Figs. S1 boulder to cobble-grade conglomerate with increasing volumes C and D and S2) is present in the red bed unit as isolated of igneous and high-grade metamorphic clasts. The Xiyu For- sandstone lenses, likely indicating an initial stage of a desertified mation is typical of proximal diluvial fan deposits derived from environment that was composed of low-energy fluvial, playa EARTH, ATMOSPHERIC,

unroofed mountain belts. Red beds passing upward into upward- lakes and associated lunette dunes. The most prominent sedi- AND PLANETARY SCIENCES coarsening conglomerate and debris flow deposits recorded the mentary unit in the Mazatagh sequence is the well-developed, change in paleoslope and sediment supply related to uplift of the cross-bedded, yellowish sandstone (Fig. 2F). It is about 200 m northern margin of the Tibetan Plateau and Pamir. thick and stratigraphically continuous and is interpreted as typ- Massive siltstone lenses intercalated in the Artux and Xiyu ical desert sand dune deposits. Formations at Kekeya and many other localities are particularly Deposition of both eolian sand dunes in the basin center and noteworthy (Fig. 2 C and D). Previous sedimentological studies, the genetically equivalent loessite along the basin margins pro- including facies investigations and grain size (Fig. S1 A and B) vides two lines of evidence to suggest that the Taklimakan Desert and geochemical analyses, suggest that these siltstone lenses are came into existence around that time. eolian loessite, having been sourced from the desert, deposited, We have identified volcanic ash in the Aertashi and Kekeya and preserved on an intermittent diluvial fan system (4), a pro- sections (Fig. 2C, Fig. S3, and SI Text), where it is intercalated in cess resembling that in the Taklimakan Desert today. the Xiyu Formation, the basal age of which has previously been The modern Taklimakan Desert is surrounded by a series of determined by magnetostratigraphy to be of Plio-Pleistocene age giant diluvial fans that link the uplifting mountain chains with the (12). In this study, 40Ar/39Ar and U–Pb dating of the volcanic ash Tarim Basin. Sediments shed off the mountain fronts have been has provided, for the first time, to our knowledge, an anchor eroded, mostly but not exclusively, by landsliding and glaciation. point to better constrain the strata, and therefore the age of They are then delivered down the slope to the basin through the desertification. Petrologic investigation showed that the com- fan systems, and sorted by eolian and fluvial processes into silt position of the ash includes mainly vitroclastic, sanidine, aegir- and sand fractions, which become the constituents of loess and ine–augite, and biotite, typical of alkaline magmatic rocks (Fig. desert, respectively. These processes of dust and sand production S3). These volcanic minerals are ideal for radioisotopic dating. must have been in operation since the deposition of the Artux In addition, we also carried out field investigations together with and Xiyu formations. We therefore conclude that widespread petrologic studies and found that the volcanic activity associated accumulation of loessite in the Artux and Xiyu formations along with the Tashkorgan alkaline complex (13) is most likely re- the margins of the Taklimakan Desert strongly suggests that the sponsible for providing the Xiyu Formation ash.

Zheng et al. PNAS | June 23, 2015 | vol. 112 | no. 25 | 7663 Downloaded by guest on October 6, 2021 7 Marine A km B Aertashi Kashi G. Aertashi Continental Ash Gypsum ~11 Ma Mudstone + sandstone Marl + limestone + sandstone

C Kekeya Xiyu F. E Mazatagh range E

noitamroF 6 Loess Conglomerate Red eolian sandstone Conglo- merate Volcanic ash Yellowish eolian sandstone uy iX Ma 10 Kekeya Proximal alluvial fan D km Taklimakan Desert GTS2012 (ref. 19) Ma 5 10 F Mazatagh GTS2012 Ash ~11 Ma 4 15 Yellowish eolian sandstone 15 Conglo- 4 merate Xiyu Formation

Sandstone Proximal diluvial fan

noitamroFxutA G Mazatagh 20 Mudstone Loess 3 km 15 2 Conglomerate Ma Yellowish-grey sand, 20 not well exposed GTS2012 Braided +Meandering river 3 20 1 Conglome- Yellowish Conglom- rate eolian sand Atux Formation 25 erate Desert +fluvial Mudstone Sandstone 25 Red eolian sand Sandstone 2 ~26 Ma 25

Distal alluvial fan Loess Mudstone

Distal diluvial fan ~26.7 or Sandstone Brown sandstone

22.6 Ma 30 Group Wuqia Gypsum Fluvial + playa 0 2 Marl

p Mudstone

30 uo Marine rG Gypsum

35 Kashi G ai

q 30 1 Mudstones H Mazatagh uW Mudstone Wuqia Group Wuqia Atux Formation Sandstone Sandstone

35 1 Red eolian sandstone Mudstone

. Sandstone F Delta + playa lake fluvial Delta + playa lake fluvial 35

k Mudstone Gypsum a l 0 ubihsa Sandstone Gypsum Mudstone Gypsum Bashibulak F.

B Siltstone Tuff 40 Final sea retreat 0 Sandstone Shell . ~41 Ma

Gi Marl Marl Conglomerate Eolian loess hs 40 Mudstone Mudstone aK Marine Gypsum Gypsum Marine Marl Eolian sand Kashi G.

Fig. 2. Stratigraphy and magnetostratigraphy of Cenozoic sedimentary sequences within and along the southwestern margin of the Tarim Basin (Takli- makan Desert). The magnetostratigraphy of all sections was correlated to GTS2012 (19). (A) Stratigraphy and magnetostratigraphy of the Aertashi section based on age control from volcanic ash and paleontology (9). (B) Shallow marine deposits and continental red beds at Aertashi. (C) Volcanic ash and loessite intercalated in Xiyu conglomerate at Kekeya section. (D) Stratigraphy and revised magnetostratigraphy for the Kekeya section based on age control of the volcanic ash combined with data from ref. 12. The solid line and dotted line indicate two alternative magnetostratigraphic correlations for this section (see SI Text for more information). (E) Exposed Mazatagh section. (F) Yellowish desert sandstone at Mazatagh section. (G) Stratigraphy and revised magnetostratigraphy based on ref. 6 in the context of regional stratigraphic correlation. (H) Red eolian sandstone within the red beds at Mazatagh. See Fig. 1 for locations.

40Ar/39Ar Dating of Biotite from Volcanic Ash minerals were separated using a Frantz magnetic separator, and We selected three samples (YC10-19, AT10-34, and AT10-35) from then carefully handpicked under a binocular microscope. The se- two locations (Kekeya section and Aertashi section) for 40Ar/39Ar lected biotite crystals of sample AT10-35 were classified according dating and separated unaltered, 200- to 800-μm-size biotite. These to their color, with green, red, and brown populations.

7664 | www.pnas.org/cgi/doi/10.1073/pnas.1424487112 Zheng et al. Downloaded by guest on October 6, 2021 The 40Ar/39Ar analyses were performed at the Western Aus- transmitted, reflected light, as well as cathodeluminescence. The tralian Argon Isotope Facility at Curtin University. Due to the mount was vacuum-coated with high-purity gold before analysis possibility of crystal xenocrysts in the volcanic tuff layers, each with secondary ion mass spectrometry (SIMS). U, Th, and Pb biotite crystal was fused in one step using a 110-W Spectron Laser were measured using a Cameca IMS-1280 SIMS at the Institute System, with a continuous laser rastered over the sample during of Geology and Geophysics, Chinese Academy of Sciences, in 1 min to ensure complete melting (see SI Text for more detail). Beijing. Methods used to obtain the U–Pb analytical data were Ar isotopic data corrected for blank, mass discrimination and similar to those developed by Li et al. (15). The standard zircon radioactive decay are given in Datasets S1–S3. Individual errors Plésovice (14) was used to determine U–Pb ratios and absolute – σ in Datasets S1 S3 are given at the 1 level. Since the crystals in a abundances. The sample was analyzed in a continuous analytical single tuff can yield vastly different ages and we did not step heat session with standards interspersed with every four to five un- the samples, we did not apply the standard plateau age criteria. knowns. Corrections for common Pb in this paper were made Rather, we looked for age convergence of the youngest pop- using measured 204Pb and an age-appropriate Pb isotopic com- ulation with a minimum of four grains yielding indistinguishable position of Stacey and Kramers (16). Data processing was carried age. This procedure is similar to the approach used for individual – out using the Isoplot 4.15 program (17). U Pb zircon age to calculate a magmatic age. All sources of un- Twenty-five spots of 25 zircon grains from sample YC12-13-5 certainties are included in the final age proposed for a given sample. were measured during a single analytical session, and the data Eighteen crystals were analyzed for sample YC10-19. Fig. S4A are reported in Dataset S4, with individual errors given at 1σ shows a continuum of age from ∼11 Ma to 13 Ma. The six level. The analysis results showed relatively high Th/U ratios youngest ages yielded a concordant age population with a ± (0.391–1.903), with U contents ranging from 248 ppm to 2619 weighted average age of 11.17 0.15 Ma (mean square weighted f = P = ppm. Common Pb was low for the majority of analyses, with 206 deviation (MSWD) 1.2, possibility ( ) 0.33), interpreted as 206 206 the age of the youngest eruption bearing the crystals. Those re- values (the proportion of common Pb in total measured Pb) sults also indicate the occurrence of older eruptions, possibly of lower than 4.23%, apart from spot 15, which yielded a value of 28.89%. Since the ages of zircons are quite young, we looked for up to 13 Ma, whose crystals have been entrained during the 206 238 youngest eruption at ∼11.2 Ma; however, since this could be due Pb/ U age convergence of the youngest population as the tuff to minute excess 40Ar* incorporated in the crystal, we refrain eruption age. Twenty out of 25 zircon grains yielded a homog- from making assumptions about the magmatic activity for the enous age population with a weighted mean age of 11.18 ± 0.11 Ma three samples. For sample AT10-34 (from the upper layer), we (95% confidence interval, MSWD = 1.18, P = 0.27; Fig. S5A), analyzed 14 biotite crystals. This sample includes two distinct age while the other five, which could be xenocrystic zircons, pro- groups, with the oldest group (n = 7) having ages ranging from duced 12.4 ± 0.2 Ma, 16.3 ± 0.6 Ma, 28.7 ± 0.6 Ma, 207.0 ± 3.1 Ma, 120 Ma to 180 Ma and whose significance is beyond the scope of this paper. The youngest group (n = 7) shows a range of age B (Fig. S4 ), with the four youngest grains giving a concordant age Detrital contribution (%) population with a weighted mean age of 10.94 ± 0.20 Ma = P = C 0 20 40 60 80 100 (MSWD 0.03, 0.99) (Fig. S4 ). This age is interpreted as 0 the eruption age of the ash layer from which AT10-34 is derived.

(Ma) Plt. The last sample, AT10-35, consists of 21 crystals, and 40Ar/39Ar

results show that this sample also contains crystals from much Pli. older events (Fig. S4D). Apparent ages of the older group (all red or brown crystals) range from 114 Ma to 214 Ma. Five crystals from this group yield a homogenous age population with 10 a weighted mean age of 189.9 ± 1.4 Ma (MSWD = 1.4, P = 0.24) likely to date a Jurassic magmatic event in the region. The n = youngest population ( 13) yields a range of ages from 17 Ma EARTH, ATMOSPHERIC, AND PLANETARY SCIENCES

to 10 Ma, suggesting episodic activity during this period. The 10 Miocene youngest grains belong mostly to the green group and yield a Asian interior concordant age population with a weighted mean age of 11.49 ± 20 = P = E Onset of Chinese loess

0.34 Ma (MSWD 0.70, 0.71) (Fig. S4 ). However, it Onset of desertification should be noted that most of these apparent ages have large age uncertainties due to the fact that the young population consists mostly of small grains that yielded a small argon beam signal. The age of 11.49 Ma is interpreted as the age of the tuff eruption. All three tuff ages are within 0.5 Ma of each other, sug- 30 gesting that explosive volcanism occurred in this region over a wide area at ∼11 Ma. Since the three ages are not concordant Oligocene (MSWD = 4.2), this suggests that the volcanic activity lasted for Detrital a duration of at least several hundred thousands years. Eolian quartz U–Pb Dating of Zircon from Volcanic Ash 40 Sample YC12-13-5 was taken from Kekeya section. It was the Eocene only sample in this study that contained suitable zircon grains for U–Pb dating. Zircon grains were separated using traditional 015 01520 flotation method, and then carefully handpicked under a bin- Eolian quartz (% by weight) ocular microscope to obtain optically clear, colorless grains. Fig. 3. Detrital contribution (blue dots) of core from Site 1215 and aeolian Together with zircon standard Plésovice (337 Ma) (14), the quartz percentage (green dots) of core LL44-GPC3 from the North Pacific zircon grains from sample YC12-13-5 were mounted onto a since the Eocene (22, 24). The arrows on the right side indicate the onset of 2.4-cm-diameter epoxy disk, ground, and then polished for anal- eolian loess at the Chinese Loess Plateau (20, 21) and desertification of Asian ysis. To reveal the internal structure, all zircons were imaged using interior obtained by this study.

Zheng et al. PNAS | June 23, 2015 | vol. 112 | no. 25 | 7665 Downloaded by guest on October 6, 2021 and 707.6 Ma ± 10.3 Ma (spots 20, 17, 08, 10, and 07, respec- modern mineral dust suggest that the Taklimakan Desert is one of tively; Fig. S6 and Dataset S4). Alternatively, to avoid the in- the major dust source areas to the global aerosol system (2, 3), and fluence of common Pb, 14 ages (spots 01, 02, 03, 05, 06, 09, 11, might have been so since the birth of the desert. In this regard, it is 12, 13, 16, 18, 23, 24, and 25; Fig. S6 and Dataset S4)withmea- worth noting that the onset of loess deposition at Qin’an in the sured 206Pb/204Pb > 1,000 were calculated, giving almost the Chinese Loess Plateau (20, 21) (see Fig. 1B for location), and same weighted mean age of 11.18 ± 0.13 Ma (95% confidence change in the dust to the distal north Pacific Ocean (22–24) as interval, MSWD = 1.2, P = 0.26; Fig. S5B). The age of 11.18 Ma shown by a significant increase in the detrital contribution and is interpreted as the eruption age of the tuff layer from which quartz content, occurred at about the same time (Fig. 3). YC12-13-5 is derived. Formation of a desert over tectonic time scales requires two The 206Pb/238U age of 11.18 Ma of sample YC12-13-5 is very integral prerequisite conditions: an arid climate and a sufficient close to the 40Ar/39Ar age of biotite (11.17 Ma) of sample YC10- supply of fine-grained sediments. During much of the Paleogene, 19. The age difference could have resulted from different erup- a roughly zonal region of China between 30°N and 50°N was under tions. However, we believe that this minor discrepancy is more an arid climate, primarily controlled by the northern westerlies likely to have been caused by the difference of closure tempera- (25). The Paleogene aridity of the Tarim Basin, which was part of tures of the two types of minerals or age uncertainties. We there- this arid region, is registered by widespread accumulation of red fore conclude that the volcanic ash was deposited soon after the beds and intercalated evaporite. However, the climatic configu- eruption that occurred at ∼11 Ma in this region. ration changed dramatically during the period from late Oligocene to early Miocene, after which the Asian monsoon set in, prevailing Birth of the Taklimakan Desert: When and How? in southeastern China, and the arid region with greatest severity Constrained by the volcanic ash and regional lithostratigraphic retreated to the northwest. correlations, we are able to reconstruct a magnetostratigraphy Indo–Asia collision likely starting at ∼60 Ma resulted in the for the Cenozoic sequence based on previously published data progressive uplift of the Tibetan Plateau and other mountain from Kekeya (12) and Mazatagh (6), as well as new measure- ranges in Central Asia (26–29). These may have grown to heights A D G ments from Aertashi (Fig. 2 , , and ). All paleomagnetic of more than 3 km by the late Oligocene (30, 31), even if the samples were progressively demagnetized from room tem- extent of uplift has since continued to grow. Generation of such – – perature up to 600 695 °C in 5 100 °C steps. Remanent mag- topography forced major climatic changes during the Cenozoic netizations were measured using a 2G 755-R Superconducting (32–35). Numerous studies suggested that significant uplift of the Rock Magnetometer. The characteristic remnant magnetiza- Tibetan–Pamir Plateau and the Tian Shan occurred around the tion (ChRM) directions were assessed on an orthogonal de- late Oligocene–early Miocene (36–39). The uplifted plateau to- magnetization diagram and calculated by application of principal gether with the possible retreat of the Paratethys (9, 11) forced component analysis to determine the direction of the best least- by uplifting topography could have led to a transition from plan- SI Text squares line fit (18) (Fig. S7 and ). etary climate system to monsoonal climate system (35, 40, 41). At The Aertashi section comprises a relatively complete succes- the same time, the arid zone, with much severity, retreated to the sion of Cenozoic sediments. More importantly, the section is well Asian interior (25). Equally, if not more, important, is the uplift- constrained by the volcanic ash in the upper part and bio- induced erosion and weathering of bedrock, which supplied great stratigraphy at the base (10), and therefore can be used as a ref- volumes of sediments to the mountain fronts in the form of al- erence for regional correlations. The pattern of magnetic polarity luvial and diluvial fans. These sediments would then have been zones of Aertashi can be correlated to the Geologic Time Scale SI Text sorted by fluvial and eolian processes into sand and silt fractions, 2012 (GTS2012) (19) (Fig. S8, ,andDataset S5). Two with the former becoming the constituents of a dynamic desert depositional hiatuses occurred when lithofacies changed to mas- system and the latter being deflated and transported as eolian dust sive sandstone and conglomerate, respectively. Geomagnetic cor- SI Text (4). We suggest that this mechanism has been in operation since relations to GTS2012 of the Kekeya (Fig. S9, ,andDataset the late Oligocene–early Miocene time, and that the resultant S6)andMazatagh(Fig. S10 and SI Text) sections, based on formation of the Taklimakan Desert was a direct response to a stratigraphic correlations to the Aertashi section, yielded age combination of widespread regional aridification and increased ranges from 37.5 Ma to 10 Ma and 34 Ma to 17.5 Ma, respectively. unroofing and erosion in the surrounding mountains, both of Of greatest significance is the timing of the transition from flu- which are closely linked to the uplift of the Tibetan–Pamir Pla- vial deposit to diluvial fan debris flow with eolian silts at Kekeya, teau and the Tian Shan (36–39). and red eolian dunes at Mazatagh, which is, on our updated magnetostratigraphy, dated to be ∼26.7–22.6 Ma (Figs. S9 and S10 SI Text ACKNOWLEDGMENTS. The authors are grateful to the reviewers for their and ). We therefore argue that, by late Oligocene to early constructive comments. H.Z. is indebted to the late Prof. C. Powell and the Miocene time, the Tarim Basin, surrounded by a rising Tibetan– late Prof. X. Wu for their contributions in the field work and analysis of sedi- Pamir Plateau and Tian Shan, had become fully arid and deserti- mentological data. This work was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB03020300), the National fied, supplying dust to the mountain fronts, where it accumulated Science Foundation of China (NSFC 40025207, 90211019, and 41021002), as loess. Desertification of the Asian interior has had far-reaching and the Priority Academic Program Development of Jiangsu Higher Education impacts on regional and even global scales. Provenance studies of Institutions.

1. Zhu ZD, Wu Z, Liu S, Di X (1980) An Outline of Chinese Deserts (Science Press, Beijing). 8. Liu W, et al. (2014) Late Miocene episodic lakes in the arid Tarim Basin, western China. 2. Uno I, et al. (2009) Asian dust transported one full circuit around the globe. Nat Proc Natl Acad Sci USA 111(46):16292–16296. Geosci 2(8):557–560. 9. Bosboom R, et al. (2014) Timing, cause and impact of the late Eocene stepwise sea 3. Shao YP, et al. (2011) Dust cycle: An emerging core theme in Earth system science. retreat from the Tarim Basin (west China). Palaeogeogr Palaeoclimatol Palaeoecol Aeolian Res 2(4):181–204. 403:101–118. 4. Zheng HB, Powell CM, Butcher K, Cao JJ (2003) Late Neogene loess deposition in 10. Bosboom R, et al. (2014) Linking Tarim Basin sea retreat (west China) and Asian ari- southern Tarim Basin: Tectonic and palaeoenvironmental implications. Tectonophy- dification in the late Eocene. Basin Res 26(5):621–640. sics 375(1-4):49–59. 11. Ramstein G, Fluteau F, Besse J, Joussaume S (1997) Effect of orogeny, plate motion 5. Sun J, Liu T (2006) The age of the Taklimakan Desert. Science 312(5780):1621. and land-sea distribution on Eurasian climate change over the past 30 million years. 6. Sun JM, Zhang ZQ, Zhang LY (2009) New evidence on the age of the Taklimakan Nature 386(6627):788–795. Desert. Geology 37(2):159–162. 12. Zheng HB, Powell CM, An ZS, Zhou J, Dong GR (2000) Pliocene uplift of the northern 7. Sun DH, et al. (2011) Palaeomagnetic and palaeoenvironmental study of two parallel Tibetan Plateau. Geology 28(8):715–718. sections of late Cenozoic strata in the central Taklimakan Desert: Implications for the 13. Ke S, et al. (2006) Petrogenesis and geochemistry of Cenozoic Taxkorgan alkalic desertification of the Tarim Basin. Palaeogeogr Palaeoclimatol Palaeoecol 300(1-4):1–10. complex and its geological significance. Acta Petrol Sin 22(4):905–915.

7666 | www.pnas.org/cgi/doi/10.1073/pnas.1424487112 Zheng et al. Downloaded by guest on October 6, 2021 14. Slama J, et al. (2008) Plesovice zircon - A new natural reference material for U-Pb and 35. Kutzbach JE, Prell WL, Ruddiman WF (1993) Sensitivity of Eurasian climate to surface Hf isotopic microanalysis. Chem Geol 249(1-2):1–35. uplift of the Tibetan Plateau. J Geol 101(2):177–190. 15. Li XH, Liu Y, Li QL, Guo CH, Chamberlain KR (2009) Precise determination of Phan- 36. Sobel ER, et al. (2013) Oceanic-style subduction controls late Cenozoic deformation of erozoic zircon Pb/Pb age by multicollector SIMS without external standardization. the northern Pamir orogen. Earth Planet Sci Lett 363:204–218. Geochem Geophys Geosyst 10(4):Q04010. 37. Treloar PRP, Williams M (1991) The role of erosion and extension in unroofing the 16. Stacey JS, Kramers JD (1975) Approximation of terrestrial lead isotope evolution by a Indian Plate thrust stack, Pakistan Himalaya. Geol Mag 128(5):465–478. – two-stage model. Earth Planet Sci Lett 26(2):207 221. 38. Hendrix MS, Dumitru TA, Graham SA (1994) Late Oligocene-early Miocene unroofing 17. Ludwig K (2008) Users Manual for Isoplot 3.7 (Berkeley Geochronol Cent, Berkeley, CA). in the Chinese Tian Shan: An early effect of the India-Asia collision. Geology 22(6): 18. Kirschvink JL (1980) The least-squares line and plane and the analysis of palaeomagnetic 487–490. data. Geophys J R Astron Soc 62(3):699–718. 39. Liu H, et al. (2010) The detrital zircon fission-track ages constraint to tectonic process 19. Gradstein FM, Ogg G, Schmitz M (2012) The Geologic Time Scale 2012 (Elsevier, New – York). in west Kunlun and adjacent regions. Earth Sci Front 17(3):64 78. 20. Guo ZT, et al. (2002) Onset of Asian desertification by 22 Myr ago inferred from loess 40. Prell WL, Kutzbach JE (1992) Sensitivity of the Indian monsoon to forcing parameters deposits in China. Nature 416(6877):159–163. and implications for its evolution. Nature 360(6405):647–652. 21. Qiang X, et al. (2011) New eolian red clay sequence on the western Chinese Loess 41. Ruddiman WF, Kutzbach JE (1990) Late Cenozoic plateau uplift and climate change. Plateau linked to onset of Asian desertification about 25 Ma ago. Sci China Earth Sci Trans R Soc Edinburgh Earth Sci 81(04):301–314. 54(1):136–144. 42. Schwab M, et al. (2004) Assembly of the Pamirs: Age and origin of magmatic belts 22. Pettke T, Halliday AN, Rea DK (2002) Cenozoic evolution of Asian climate and sources from the southern Tien Shan to the southern Pamirs and their relation to Tibet. of Pacific seawater Pb and Nd derived from eolian dust of sediment core LL44-GPC3. Tectonics 23(4):TC4002. Paleoceanography 17(3):3-1–3-13. 43. Robinson AC (2009) Geologic offsets across the northern Karakorum fault: Implica- 23. Rea DK, Leinen M, Janecek TR (1985) Geologic approach to the long-term history of tions for its role and terrane correlations in the western Himalayan-Tibetan orogen. atmospheric circulation. Science 227(4688):721–725. Earth Planet Sci Lett 279(1-2):123–130. 24. Ziegler CL, Murray RW, Hovan SA, Rea DK (2007) Resolving eolian, volcanogenic, and 44. Coutand I, et al. (2002) Late Cenozoic tectonic development of the intramontane Alai authigenic components in pelagic sediment from the Pacific Ocean. Earth Planet Sci Valley, (Pamir-Tien Shan region, central Asia): An example of intracontinental de- Lett 254(3-4):416–432. formation due to the Indo-Eurasia collision. Tectonics 21(6):1053. 25. Sun XJ, Wang PX (2005) How old is the Asian monsoon system? Palaeobotanical re- 45. Cowgill E (2010) Cenozoic right-slip faulting along the eastern margin of the Pamir cords from China. Palaeogeogr Palaeoclimatol Palaeoecol 222(3-4):181–222. – 26. Harrison TM, Copeland P, Kidd WSF, Yin A (1992) Raising Tibet. Science 255(5052): salient, northwestern China. Geol Soc Am Bull 122(1-2):145 161. 1663–1670. 46. Schmidt J, et al. (2011) Cenozoic deep crust in the Pamir. Earth Planet Sci Lett 312(3-4): 27. Tapponnier P, et al. (2001) Oblique stepwise rise and growth of the Tibet plateau. 411–421. Science 294(5547):1671–1677. 47. Arrowsmith JR, Strecker MR (1999) Seismotectonic range-front segmentation and 28. Royden LH, Burchfiel BC, van der Hilst RD (2008) The geological evolution of the Ti- mountain-belt growth in the Pamir-Alai region, Kyrgyzstan (India-Eurasia collision betan Plateau. Science 321(5892):1054–1058. zone). Geol Soc Am Bull 111(11):1665–1683. 29. Molnar P, England P (1990) Late Cenozoic uplift of mountain ranges and global cli- 48. Zhou ZY, ed (2001) Stratigraphy of the Tarim Basin (Science Press, Beijing). mate change: Chicken or egg? Nature 346(6279):29–34. 49. Zheng HB, Tada R, Jia J, Lawrence C, Wang K (2010) Cenozoic sediments in the 30. Sun JM, et al. (2014) Palynological evidence for the latest Oligocene–early Miocene southern Tarim Basin: Implications for the uplift of northern Tibet and evolution of paleoelevation estimate in the Lunpola Basin, central Tibet. Palaeogeogr Palaeoclimatol the Taklimakan Desert. Spec Publ Geol Soc London 342:67–78. – Palaeoecol 399:21 30. 50. Tada R, et al. (2010) Desertification and dust emission history of the Tarim Basin and 31. DeCelles PG, et al. (2007) High and dry in central Tibet during the Late Oligocene. its relation to the uplift of northern Tibet. Spec Publ Geol Soc London 342:45–65. Earth Planet Sci Lett 253(3-4):389–401. 51. Renne PR, Balco G, Ludwig KR, Mundil R, Min K (2011) Response to the comment by 32. Raymo ME, Ruddiman WF (1992) Tectonic forcing of late Cenozoic climate. Nature W. H. Schwarz et al. on “Joint determination of 40K decay constants and 40Ar*/40K 359(6391):117–122. 33. Molnar P, Boos WR, Battisti DS (2010) Orographic controls on climate and caleocli- for the Fish Canyon sanidine standard, and improved accuracy for 40Ar/39Ar geo- ” – mate of Asia: Thermal and mechanical roles for the Tibetan Plateau. Annu Rev Earth chronology by P. R. Renne et al. (2010). Geochim Cosmochim Acta 75(17):5097 5100. Planet Sci 38:77–102. 52. Lee JY, et al. (2006) A redetermination of the isotopic abundances of atmospheric Ar. 34. Zhang ZS, Wang HJ, Guo ZT, Jiang DB (2007) What triggers the transition of palae- Geochim Cosmochim Acta 70(17):4507–4512. oenvironmental patterns in China, the Tibetan Plateau uplift or the Paratethys Sea 53. Koppers AAP (2002) ArArCALC - Software for Ar-40/Ar-39 age calculations. Comput retreat? Palaeogeogr Palaeoclimatol Palaeoecol 245(3-4):317–331. Geosci 28(5):605–619. EARTH, ATMOSPHERIC, AND PLANETARY SCIENCES

Zheng et al. PNAS | June 23, 2015 | vol. 112 | no. 25 | 7667 Downloaded by guest on October 6, 2021