Tectonic and Erosional History of Southern Tibet Recorded by Detrital Chronological Signatures Along the Yarlung River Drainage

Home , Transhimalaya, Yarlung Valley

Tectonic and erosional history of southern Tibet from rivers Tectonic and erosional history of southern Tibet recorded by detrital chronological signatures along the Yarlung River drainage

Barbara Carrapa†, Mohd Faiz bin Hassim, Paul A. Kapp, Peter G. DeCelles, and George Gehrels Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, Arizona 85721, USA

ABSTRACT INTRODUCTION zone provides an opportunity to broadly sample source rocks in the region and to study the tim- The Indus-Yarlung suture zone, within the The Indus-Yarlung suture zone in southern ing of regional cooling and inferred erosion larger Indo-Asia collision zone in southern Tibet (Fig. 1A) is part of the larger Indo-Asia related to processes following India-Asia col- Tibet, is characterized by a central depres- collision zone, which represents the modern lision (e.g., Hoang et al., 2009; Zhang et al., sion with two oppositely directed axial rivers: surface expression of the contact between the 2012; Saylor et al., 2013). Whereas previous the eastward-flowing Yarlung River and the Indian and Eurasian continental plates as a result work focused on detrital zircon U-Pb geochro- westward-flowing Indus River. The axial of Paleocene collision (e.g., Garzanti et al., 1987; nology of modern rivers from the main Yarlung valley is flanked by high-elevation ranges Najman et al., 2010; DeCelles et al., 2014; Hu River and the eastern part of its drainage system of the southern Lhasa terrane to the north et al., 2015). The Indus-Yarlung suture zone is (Zhang et al., 2012; Cina et al., 2009), this study and the Tethyan Himalaya to the south. This characterized today by a depression occupied by includes the poorly studied western portion of study analyzes the detrital geochronological the eastward-flowing Yarlung River, with tribu- the Yarlung drainage system and two rivers and thermochronological signatures of rivers taries that drain the Gangdese magmatic arc, draining the Kailas and Xiao Gurla ranges into draining into the Indus-Yarlung suture zone Xigaze forearc, and Cenozoic strata to the north, La’nga and Mapan Yum lakes respectively. as a proxy for the timing of tectonic, mag- and Paleozoic–Mesozoic Tethyan Himalayan Detrital studies commonly assume that the matic, and erosional processes in southern strata to the south (Fig. 1). The Yarlung drainage sample age distributions from sedimentary ba- Tibet. Zircon U-Pb ages reflect source area includes several large nonmarine Cenozoic sedi- sin strata and modern river sand samples closely crystallization ages, and their distribu- mentary basins, such as the Oligocene–Miocene match the age spectra within the drainage catch- tion is proportional to the relative area of Kailas basin (Aitchison et al., 2002; DeCelles ments of the eroding source region. For ex- source rocks exposed in the catchment areas. et al., 2011), and the Miocene Liuqu basin (Li ample, the degree of mixing of different source Rivers draining the northern side of the colli et al., 2015a; Leary et al., 2016a). Formation of signals, as recorded by detrital zircon U-Pb sion zone are dominated by ages between the Kailas basin has been associated with ex detrital ages in modern river sands, has been ca. 40 Ma and ca. 60 Ma, similar to ages of tension possibly related to slab rollback or trans- shown to be proportional to the exposed source rocks in the Gangdese arc, whereas one river tension along the Karakoram fault (DeCelles area within the catchment (Saylor et al., 2013). sample draining the southern side records et al., 2011). Thermochronological studies show This approach is based on the assumption that a Tethyan Himalayan signature character- cooling of the Kailas (Carrapa et al., 2014) fertility of source rocks is the same in all of the ized by age clusters at ca. 500 Ma and ca. and Liuqu basins (Li et al., 2015a; Leary et al., drained lithological units. This assumption may 1050 Ma. U-Pb zircon ages from the modern 2016a) at ca. 17 Ma and ca. 12–10 Ma respec- not be valid if significant volumes of ultramafic drainages are similar to signals preserved in tively, which is consistent with >4 km of basin rocks and limestone are present in the drainage the Oligocene−Miocene Liuqu and Kailas exhumation. Cooling of the Gangdese arc and of area. Our study area does not contain significant basins, suggesting that the geology of the the Tethyan Himalaya near Lhasa between ca. limestone and ultramafic rocks, and therefore Cenozoic drainages was similar to modern, 20 Ma and 10 Ma has been associated with ac- we consider this assumption to be valid. albeit with significant erosion in the Miocene. celerated upper-crustal exhumation (Fig. 1; e.g., Other studies have documented that zircon New apatite fission-track (AFT) ages from Dai et al., 2013; Li et al., 2015b). An early Mio- U-Pb ages of modern samples not only reflect some of the same rivers show an early Mio- cene pulse of at least local rapid exhumation in- mixing of upstream bedrock sources, but are also cene regional exhumation signature, which is ferred from rock cooling was detected by Cope influenced by a dilution effect owing to progres- interpreted to record regional uplift-induced land et al. (1987) and Harrison et al. (1992) in sive downstream mixing, topographic relief, and erosion coupled with efficient river incision some of the earliest thermochronological work precipitation (Zhang et al., 2012). Although this by the Indus-Yarlung fluvial system as a re- in southern Tibet. However, the regional extent, is an important issue to consider when sampling sult of renewed underthrusting (following timing, and magnitude of such Cenozoic cooling progressively downstream along a main trunk rollback) of India under Asia. Late Miocene in southern Tibet and underlying mechanisms river, it should not be an issue when sampling (ca. 8 Ma) apatite (U-Th)/He (AHe) ages are remain poorly constrained. Another feature that tributaries with smaller drainage basins. consistent with cooling and exhumation asso is not well understood is the timing of establish- The goal of this study was to test the follow- ciated with E-W extension followed by a de- ment of the modern Yarlung drainage. ing hypotheses. (1) Detrital minerals from the crease in erosion after ca. 6 Ma. Detritus from modern rivers, mostly includ- Yarlung drainage, including the Indus-Yarlung ing tributaries of the Yarlung River, draining suture zone within the larger Indo-Asia collision †bcarrapa@email.arizona.edu southern Tibet and the Indus-Yarlung suture zone (Fig. 1), directly reflect cooling due to ero-

GSA Bulletin; Month/Month 2016; v. 128; no. X/X; p. 1–12; doi: 10.1130/B31587.1; 6 figures; 1 table; Data Repository item 2016356.; published online XX Month 2016.

1A 72o E 80o E 88o E 96o E

36o N Indus Rive

Ladakh r TIBET Zhang et al. (2012) batholith Li et al. (2016) 1B 32o N Li et al. (2015) Mt. Kailas Dai et al. (2013) Lhasa Yarlung RiLopu Range Namche ver g R Leary et al. (2016) Satlej Ri Ganges Ri rnali ive S Barwa i r Xigaze a Ka n Kailas basin River g R. o ve Mt. Everest 28 N r r

200 km Brahmaputra Rive

Indus River Karakoram Faul India-Asia 1B 1C A′ A suture zone o Main Central Thrust Xigaze 32 N Forearc Kailas Fm. Tethyan Thrust Belt Liuqu Fm. Gangdese Arc t Lesser Him. Sequence subduction complex Asian plate Indian plate Mt. Kailas ~25 km Greater Himalayan Lhasa terrane Sequence 0~100 km o River 7 River 6 31 N La'nga Lake subduction complex Xiao Gurla A Mapam Yarlung drainage Yum Lake

Lopukangri 30oN Range River 5 River 3 Geydo Jiada Yarlung River River 2 Dogxhun River 4 Xigaze Karnali River 1 29oN River Shab Chu Kaligandaki River A'

28oN

0 200 km

81oE83oE 85oE87oE89oE 91oE 1D River 7 River 6 River 5 River 1 2% 9% 3%

10% 2% 2% 72%

39% 53% 39% 4% 58% 8% 13% 3% 48% 17% 5km

River 4 RiverRiv 2 4% 18% 9%

23% 9% River 3 14% 21% 17% 20% 35%

1% 20% 28% 9% 33% 12%

14% 31% Gangdese arc plutonic rocks Gneiss domes Tethyan Himalaya rocks Ophiolites Cenozoic sedimentary rocks Xigaze Fm. Kailas Formation and Melanges Linzizong volcanics Figure 1. (A–B) Digital topographic maps of the southern Tibetan Plateau and the Himalayan orogen based on Global Multi-Resolution Topography (GMRT) data. Main streams of the rivers are marked by blue lines; their tributaries are marked by red lines. Rivers 1–7 mark locations of sand samples collected from tributaries of the Yarlung River in this study. (C) Simplified cross section across southern Tibet and the Himalaya, modified after Murphy (2007). (D) Diagrammatic maps of the bedrock geology (from 1:1,500,000 geological map of Tibet; Pan et al., 2004) in each of the analyzed river catchment areas; pie charts indicate relative proportions of different rock types.

2 Geological Society of America Bulletin, v. 1XX, no. XX/XX Tectonic and erosional history of southern Tibet from rivers sion of the source area and therefore are repre- rocks and Cenozoic sedimentary strata. Most of cons and apatites were separated from river sentative of regional tectono-thermal signatures. the sampled rivers drain into the Yarlung River sand samples using standard techniques. The (2) Miocene exhumation in southern Tibet (except for Rivers 6 and 7), which in turn flows interpreted zircon U-Pb ages and main popu- was widespread and had tectono-climatic sig- eastward to the eastern Himalayan syntaxis, lations are shown on relative age-probability nificance. (3) The modern longitudinal Yarlung veers abruptly south-southwestward (taking on diagrams (Fig. 2) using Isoplot (Ludwig, 2008). drainage system developed in the middle Mio- the name Siang River), and connects with the Data tables for zircon U-Pb analyses are avail- cene. We applied detrital zircon U-Pb geochro- Brahmaputra River, which ultimately joins able in the Data Repository (Table DR2 [see nology, apatite fission-track (AFT), and apatite the Ganges River and flows into the Bay of footnote 1]). (U-Th)/He (AHe) thermochronology to river Bengal; the total length of the drainage system Of the seven samples collected, four (River 3, sand samples from tributaries of the Yarlung exceeds 2500 km. River 6 drains into Mapam River 4, River 5, and River 7) yielded enough River and from two rivers from the western, Yum Lake, and River 7 drains into La’nga quality apatite grains to conduct AFT analyses, internally drained, portion of the Indus-Yarlung Lake (Fig. 1). Within the study area, ophiolitic and five (including River 1) contained enough collision zone near Mount Kailas in order to rocks and sedimentary- and serpentinite-matrix quality apatites for AHe analyses. Ten to 15 constrain the timing of crystallization and exhu- mélanges are structurally juxtaposed against apatite grains per sample were targeted for AHe mation of the different sediment sources within Tethyan Himalayan strata in the south and Gang- analyses (Table DR4 [see footnote 1]) to assess the catchment areas. The study area covers an dese arc and Xigaze forearc and younger rocks the youngest cooling component. Additional along-strike distance of ~800 km from Mount in the north (Burg and Chen, 1984; Yin et al., analytical information is available in Data Re- Kailas in the west to Xigaze in the east (Fig. 1999; Murphy and Yin, 2003; Ding et al., 2005). pository (see footnote 1). 1B). In order to assess how well the detrital zir- The Gangdese arc is a complex of calc-alkaline For AFT and AHe data, kernel density esti con U-Pb age spectra represent the ages of rocks batholiths and related volcanic and volcaniclas- mates (KDEs) and probability density plots within the respective catchments, we analyzed tic rocks that formed as a Cordilleran-style mag- (PDPs) were produced using the program Den- and compared the geology of the catchment matic arc along the southern flank of the Lhasa sity Plotter (Fig. 3); PDPs were calculated by area, and zircon U-Pb ages typical of different terrane in response to subduction of Tethyan oce- summing Gaussian distributions in which the geological units within the catchment, to zir- anic lithosphere, Indian continental lithosphere, means and standard deviations correspond to con populations derived from each of the river and possibly island arcs, from at least Creta- the individual ages and their respective analyti- samples (Fig. 1D). ceous to Eocene time (e.g., Schärer et al., 1984; cal uncertainties, whereas KDEs also involve U-Pb geochronology of zircon provides in- Coulon et al., 1986; Chung et al., 2005; Hébert summing a set of Gaussian distributions without formation on cooling through the ~>900 °C et al., 2012). The Gangdese arc is characterized explicitly taking into account the analytical un- isotherm (Lee et al., 1997; Cherniak and Wat- by zircon U-Pb ages of ca. 120–40 Ma (e.g., certainties (Vermeesch, 2012). Forward thermal son, 2001), thus constraining the age of crystal- Harris et al., 1988; Copeland et al., 1995; Chung modeling of the main AHe and AFT age com- lization of the mineral, which, in turn, can be et al., 2005; Wen et al., 2008; Ji et al., 2009; Jiang ponents was performed using HeFty (Ketcham, used as a provenance proxy and to interpret tec et al., 2012). For a more complete set of refer- 2005) in order to test continuous versus episodic tonics (e.g., Gehrels et al., 2008; Gehrels, 2014). ences, refer to Figure 2. Thermochronological cooling and inferred exhumation. Average apa- AFT and AHe provide information on cooling data from the Gangdese arc show cooling epi- tite chemical values were used with the anneal- through the ~40–110 °C temperature window sodes at ca. 48–42, ca. 26–17, and ca. 11–8 Ma, ing model of Flowers et al. (2009) for AHe age (e.g., Gleadow and Duddy, 1981; Wolf et al., which have been interpreted to be the result of modeling. 1996), which is often associated with shallow- accelerated exhumation (Copeland et al., 1987; crustal deformation and erosion. The applica- Pan et al., 1993; Harrison et al., 2000; He et al., RESULTS tion of these different techniques to the same 2007; Yuan et al., 2009; Dai et al., 2013). The river detritus provides information on the prov- Tethyan Himalayan Sequence, exposed south Zircon U-Pb Geochronology enance, crustal evolution, and erosion history of of the Indus-Yarlung suture zone, produces sig- the source regions (e.g., Carrapa, 2010). nificant detrital zircon age clusters at 500 Ma Results are described in geographical order and 1100 Ma (e.g., DeCelles et al., 2000, 2004; from east to west (Fig. 3). The catchment area GEOLOGICAL SETTING Tobgay et al., 2010; Gehrels et al., 2003, 2011). for River 1 is ~4840 km2 (Fig. 1D), and its bed- The geology of southern Tibet includes four rock is composed of 72% Tethyan Himalayan METHODS major tectonic features: the Gangdese magmatic strata, 10% undifferentiated Cenozoic sedi- arc, the Indus-Yarlung suture zone within the We collected seven sand samples, five from mentary rocks, 9% North Himalayan gneiss larger India-Asia collision zone, the right-lateral tributaries of the Yarlung River draining south- domes, 3% Xigaze forearc basin fill, and 2% Karakoram fault, and the Tethyan Himalayan ern Tibet between Xigaze and Mount Kailas and Gangdese arc plutonic rocks, ophiolite, and thrust belt (e.g., Burg and Chen, 1984; Burg two from the western, internally drained, portion mélange (Table DR1 [see footnote 1]). In this et al., 1984, 1987; Yin et al., 1999; Murphy and of the Indus-Yarlung suture zone; these samples sample, 96% of the U-Pb ages are older than Yin, 2003; Aikman et al., 2008; Fig. 1C). The were analyzed for detrital zircon U-Pb geochro- 120 Ma, with a significant age cluster between geology of southern Tibet drained by the Yar- nology, and AFT and AHe thermochronology 1200 Ma and 450 Ma and two significant age lung River and its tributaries includes the Lower (Fig. 1; Table 1). We refer the reader to the GSA components at ca. 500 Ma and ca. 1100 Ma Cretaceous Xigaze ophiolite and Cretaceous– Data Repository for a detailed description of (Fig. 2). Although ages up to ca. 3.6 Ga are Eocene Xigaze forearc basin, as well as Ceno- the methods used in this paper.1 Detrital zir- present (Table DR2 [see footnote 1]), for the zoic nonmarine basins. scope of this paper, we plot ages younger than 1GSA Data Repository item 2016356, analyti- River catchments along and to the west of the cal description and data tables, is available at http:// 3 Ga (Fig. 2). Within the young age range Yarlung drainage are composed of Gangdese www.geosociety.org/pubs/ft2016.htm or by request (younger than 120 Ma), only four grains (4%) arc, Xigaze forearc, and Tethyan Himalayan to editing@geosociety.org. are younger than ca. 120 Ma (Fig. 2).

Geological Society of America Bulletin, v. 1XX, no. XX/XX 3 Carrapa et al.

AB 700 Kailas (n = 813) KailasFm.

500 Liuqu (n = 1659) Liuqu Fm.

100 Gangdese (n = 331) Gangdese

2500 Forearc (n = 3429) Forearc

40 River 7 River 7 (n = 93)

River 6 40 River 6 (n = 88)

40 River 5 (n = 92) River 5

40 River 4 (n = 81) River 4

40 River 3 (n = 81) River 3

40 River 2 (n = 86) River 2 y

40 River 1 (n = 184) River 1 (composite) y Relative probabilit 40 050100 150200 River 1 (n = 88) Age (Ma) r Re-worked Tethyan signature Numbe Tethyan signature 0 Relative probabilit 0 500 1000 1500 2000 2500 3000 Gandese arc signature Age (Ma) Figure 2. (A) U-Pb ages of detrital zircons from sand samples collected in this study and from literature data from Xigaze, Kailas, Liuqu sedimentary rocks, and Gangdese arc (Aitchison et al., 2009, 2011; Aoya et al., 2005; Chiu et al., 2009; Chu et al., 2006; Copeland et al., 1995; Coulon et al., 1986; Ding et al., 2003, 2005; Guo et al., 2011; Harrison et al., 1997, 2000; He et al., 2007, 2011; Hou et al., 2004; Kapp et al., 2005; Ji et al., 2009, 2012; Kawakami et al., 2007; King et al., 2007, 2011; Larson et al., 2010; Leary et al., 2016a; Lee et al., 2006, 2009, 2011; Lee and Whitehouse, 2007; Liang et al., 2008; Mahéo et al., 2007; McDermid et al., 2002; Mo et al., 2003, 2005; Nomade et al., 2004; Pan et al., 2004; Quidelleur et al., 1997; Ratschbacher et al., 1994; Schärer et al., 1986; Harris et al., 1988; Spicer et al., 2003; Guan et al., 2012; Orme et al., 2014; DeCelles et al., 2011; Wu et al., 2014). (B) 0–120 Ma U-Pb ages for the same samples in Figure 1A. The ages are represented using relative probability distribution plots (PDPs) generated using the routines in Isoplot (Ludwig, 2008); numbers in brackets are the number of grains analyzed for each sample.

4 Geological Society of America Bulletin, v. 1XX, no. XX/XX Tectonic and erosional history of southern Tibet from rivers

TABLE 1. SAMPLE INFORMATION AND COORDINATES Coordinates Sample name Latitude Longitude Modern river sand (°N) (°E) Description River 1 29.21275 88.36983 Shab Chu River, S tributary of the Ya rlung draining N; sample collected under bridge between Zadacun and Jidingzhen River 2 29.45555 86.68974 Dogxung River, N tributary of Ya rlung draining south; sample collected W of Ban Tanghairu River 3 29.46957 85.9174 N tributary of Ya rlung draining south; NE of Dasangcun River 4 29.34012 85.13931 Jiada River, N tributary of Ya rlung draining south; W of Xigaze River 5 29.55813 84.60146N tributary of Ya rlung draining south; N of Lazangxiang River 6 30.72953 81.84457 N tributary of Ya rlung draining south; E of Mapam Yum Lake River 7 30.95678 81.27789 N tributary of Ya rlung draining south; N of La’nga Lake

The sample from River 2 is derived from a River 6 drains into the Mapam Yum Lake. detrital AFT populations in these two samples catchment area of ~1350 km2 (Fig. 1B). The geol The catchment area for this sample covers suggest that these signals are significant. The ogy of the catchment area is composed primarily ~4840 km2 (Fig. 1B) and consists of 58% Kailas sample from River 5, which is mainly derived of Xigaze forearc deposits (35%), Gangdese arc Formation, 39% Gangdese arc plutonic rocks, from Cenozoic sedimentary strata, shows one plutonic rocks (28%), Linzizong volcanic rocks and only 3% mélange (Table DR1 [see foot- AFT population at ca. 22 Ma, and River 7 shows (20%), and undifferentiated Cenozoic sedimen- note 1]). Zircon ages between ca. 120 Ma and one population at ca. 18 Ma. River 1 is the only tary rocks (17%; Table DR1 [see footnote 1]). ca. 1200 Ma account for 43% of the total dated river draining the Tethyan Himalaya to the south Zircon ages are distributed mainly between grains, with significant age signals between of the main Yarlung River; AHe ages from this 40 Ma and 136 Ma, with a significant Cenozoic ca. 470 Ma and ca. 1100 Ma; 45% of the total sample are similar to ages from rivers draining age signature between ca. 40 Ma and ca. 50 Ma; dated zircon grains are younger than ca. 120 Ma the Gangdese arc and Cenozoic rocks (Fig. 3). grains younger than ca. 120 Ma account for 42% (Fig. 2). Age signals between ca. 50 Ma and ca. Unfortunately, not enough apatites were avail- of the total grains (Fig. 3). 15 Ma are also present (Fig. 2). able for detrital AFT from River 1. AHe ages for The bedrock of the ~1720 km2 River 3 drain- River 7 drains into the La’nga Lake; our sam- five of the samples analyzed for AFT are consis- age area consists of 33% Kailas Formation, 31% ple from this river was derived from a drainage tent with AFT ages (i.e., the AHe ages are simi- Xigaze forearc basin, 14% mélange, 12% Gang- area of ~1.72 km2 (Fig. 1B). The geology of the lar but generally younger than AFT ages) and dese arc plutonic rocks, 9% Linzizong volcanic drainage area is composed of 53% Gangdese arc show significant age signals between ca. 20 and rocks, and only 1% Tethyan Himalayan strata rocks, 39% Kailas Formation, and 8% Cenozoic 8 Ma (Fig. 3). (Fig. 1B; Table DR1 [see footnote 1]). Results undifferentiated sedimentary rocks (Fig. 1D; AFT and AHe ages from all rivers, when show 68% of the zircon U-Pb ages are distrib- Table DR1 [see footnote 1]). In this sample, zir- combined (Fig. 4), show two prominent popula- uted between ca. 420 Ma and ca. 1860 Ma, con U-Pb ages younger than ca. 120 Ma account tions with a mean value at ca. 19 Ma for AFT with dominant age clusters at ca. 500 Ma and for 86% of the total dated grains, with a signifi- and at ca. 8.3 Ma for AHe. These ages are con- ca. 1000 Ma; 32% of the zircon U-Pb ages are cant age signal at ca. 50 Ma (Figs. 2 and 3). The sistent with major tectonic and erosional events younger than ca. 120 Ma, with significant Ceno remaining ages are between ca. 480 Ma and ca. documented by other studies in southern Tibet zoic age signals between ca. 36 Ma and ca. 3.3 Ga (Fig. 2; Table DR2 [see footnote 1]). and suggest that these ages represent regional 46 Ma (Fig. 2). cooling and erosional signatures. The catchment area of River 4 is ~5293 km2 Detrital AFT and AHe Thermochronology and includes the Lopu Range (Fig. 1B). The INTERPRETATIONS drainage is composed of 23% Xigaze forearc Only four of the seven river samples provided basin, 20% Kailas Formation, 21% other undif- enough apatites to be analyzed for AFT and five Detrital Zircon U-Pb Geochronology ferentiated Cenozoic sedimentary rocks, 14% provided enough for AHe thermochronology Linzizong volcanic rocks, 9% mélange, 9% (Tables DR3 and DR4 [see footnote 1]; Fig. 3). Detrital zircon U-Pb ages from the sampled Gangdese arc plutonic rocks, and 4% ophiolite Whereas single-grain U-Pb and AHe ages can be rivers range between ca. 15 Ma and ca. 3568 Ma. (Table DR1 [see footnote 1]). Results show 52% considered significant, AFT single-grain ages, Age clusters at ca. 500 Ma and ca. 1100 Ma are of zircon U-Pb ages are between ca. 150 Ma and because of their large errors, should not. For this typical of the Tethyan Himalaya (Gehrels et al., ca. 1200 Ma, with significant age components at reason, AFT requires several ages (e.g., 20 for 2003, 2011) preserved in either Tethyan Hima ca. 500 Ma and ca. 1000 Ma; 32% of the ages basement and 100 for detrital) to be analyzed layan sources for River 1 or in the Kailas For- are younger than ca. 120 Ma, and dominated by and statistically treated as populations (Gal- mation and other Cenozoic strata, which contain age signals between ca. 37 Ma and ca. 50 Ma braith and Laslett, 1993); accordingly, for river reworked Tethyan grains (e.g., Aitchison et al., (Fig. 2). samples, only AFT detrital populations (calcu- 2011; DeCelles et al., 2011). Samples from The drainage area for River 5 is ~565 km2 lated here using Density Plotter; Vermeesch, rivers draining the northern side of the Yarlung (Fig. 1B); it consists of 48% undifferentiated 2012) are here interpreted as significant. drainage (River 2, 3, 4, and 5) and its western Cenozoic sedimentary rocks, 13% Kailas For- River 3 and River 4 samples, which are termination (Rivers 6 and 7) mainly yield ages mation, 18% mélange, 17% Gangdese plutonic mainly derived from Cenozoic sedimentary between ca. 40 and ca. 60 Ma, similar to ages of rocks, and 4% Xigaze forearc basin (Table DR1 rocks (Kailas and Liuqu Formations) and the Gangdese arc (Fig. 2). Cretaceous ages be- [see footnote 1]). Zircon ages from 120 Ma to Xigaze forearc basin strata, have AFT popula- tween ca. 75 and ca. 120 Ma are interpreted to 1000 Ma account for 20% of the total dated tions at ca. 88 Ma and ca. 12 Ma and at ca. 91 be derived from plutonic and volcanic/volcani grains; 65% of the zircon U-Pb ages are younger and 32 Ma, respectively (Fig. 3). Although the clastic rocks of the Gangdese arc and from than 120 Ma, with significant age signals be- apatite yield and number of grains analyzed Xigaze forearc strata, which record similar sig- tween ca. 37 Ma and ca. 60 Ma (Fig. 2). were low for River 3, the similarities between natures (Fig. 5; e.g., Lee et al., 2009; Orme et al.,

Geological Society of America Bulletin, v. 1XX, no. XX/XX 5 Carrapa et al. 100

100 2014). Miocene ages (ca. 25–20 Ma) in sample 90

90 River 1 are consistent with Miocene granites cor- 80

80 ing the north Himalayan gneiss domes (e.g., Lee 70

70 et al., 2000, 2006; Lee and Whitehouse, 2007); 60

60 Miocene ages in River 6 sample are consistent 50

50 with widespread Miocene igneous rocks in the N.A. 40

40 southwestern Lhasa terrane (e.g., Miller et al., AHe (n=13) U-Pb (n=6) 30

30 1999; Nomade et al., 2004). 20

20 Our analyses indicate that ~85% of the zir- 10 10

River 1 con ages are younger than 120 Ma in the west- 0 0 Southern drainage 6 5 4 3 2 1 0 ernmost River 7 sample (near Mount Kailas), 2 1 0 whereas only ~5% of zircons are younger than

100 120 Ma in the easternmost River 1 sample (near 100 100 )

90 Xigaze). This is consistent with the fact that 90

90 88.4±8.8 (91.9±5.5%) 80 53% of the catchment area of River 7 consists of 80 80 70 U-Pb (n=31 Gangdese arc rocks, whereas the River 1 catch- 70 70

60 ment contains only 2% Gangdese arc rocks. To 60 60

46.82±0.21 50 test whether the detrital zircon U-Pb age distri- 50 50 (33.3±5.2%) 40 Age (Ma) butions closely match the zircon age signatures 40 40 AHe (n=10)

30 of the source region (e.g., Saylor et al., 2013), 30 30 20 AFT (n=30) we plotted the percentage of detrital zircon ages 20 20 12.4±4.1 10

10 from 40 to 120 Ma, typical of Gangdese arc

10 (8.1±5.5%) River 3 0

0 rocks, against the percentage of Gangdese arc 0 11 8 5 2 0

4 3 2 1 0 4 3 2 1 0 rocks exposed in the drainage catchments for

100 each river (Fig. 6). This analysis shows a linear 100 100

91±30 90 relationship, supporting the interpretation that 90 90

(11.2 ± 9.1%) ) 80 the Gangdese arc is the main contributor of 40– 80 80

70 120 Ma ages, even for samples where Xigaze 70 70

60 forearc and early Cenozoic strata, partially de- U-Pb (n=81 60 60

46.04±0.19 50 rived from the Gangdese arc and containing ca. AHe (n=9 ) AFT (n=100) 50 50

(34.6±5.3%) ge (Ma) 40 120–54 Ma ages (Orme et al., 2014), are present 40 40

32.9±2.9 30 in the drainage. (88.8 ± 9.1%) 30 30 20 20 20

10 Detrital Thermochronology 10 10 0 River 4 0 0 18 13 9 4 0 Lopu Range

6 5 4 3 2 1 0 The four samples (River 3, 4, 5, and 7) ana- 24 18 12 6 0

10 0 lyzed for both detrital AFT and AHe thermochro- 10 0 10 0

90 nology show significant Cretaceous and Mio- 90 90 80 Northern drainages cene detrital populations (Fig. 3). Cretaceous 80 80

70 AFT cooling signals, albeit small, are consistent 70 70 60

U-Pb (n=92) with exhumation of the Gangdese retroarc thrust 60 60

50 belt (Kapp et al., 2007) as recorded by the Upper 50 50 41.57±0.12

(65.8±5%) 40 AFT (n=101) Cretaceous Takena Formation deposited within AHe (n=10) 40 40 Age (Ma )A

30 a retro-arc foreland basin in southern Tibet 30 22.4±1.4 30 100% 20 (Leier et al., 2007) and with early exhumation 20 20

10 of the Gangdese arc. In order to be able to inter- River 5 10 10

0 pret the Cenozoic cooling ages as representative 0 0 5 0 23 17 11 0 4 3 2 1 0 of exhumation rather than magmatic activity, a 54 40 27 13 e

10 0 comparison between AFT ages and U-Pb ages is 10 0 10 0

90 necessary. AFT ages representative of magmatic 90 80

80 activity match crystallization (zircon U-Pb) 80 Probability Density Plot Histogram 70

70 ages. Figure 3 shows that the youngest detrital 70 U-Pb (n=93) 60 46.72±0.12 Kernel Density Estimat

60 AFT populations are significantly younger (on 60 (84.9 ± 3.7%) 50 Figure 3. Kernel density estimate and probability density plots of detrital apatite fission-track (AFT), (U-Th)/He (AHe), and U-Pb ages density estimate and probability 3. Kernel Figure 2012). in Density Plotter (Vermeesch, 7 using the routines 5, and River 4, River 3, River 1, River River (0–100 Ma) from

50 average >10 m.y.) than the zircon U-Pb ages for 50 Age (Ma) 40 AHe (n=10)

40 the same sample. Hence, we interpret the AFT 40 AFT (n=100) River 7 30

30 and the AHe cooling signals to reflect cooling 30 Kailas Range 18.68±0.94 20 20 by exhumation, rather than cooling following 20 (100%) 10

10 magmatic heating. This is supported by the fact 10 0

0 that no Miocene igneous bodies directly intrude 0 38 28 19 9 0 8 7 6 5 4 3 2 1 0 0 69 51 34 17 the Kailas Formation or the Eocene Gangdese

6 Geological Society of America Bulletin, v. 1XX, no. XX/XX Tectonic and erosional history of southern Tibet from rivers 19.06 ±0 (100± Forward thermal modeling

A 0% ) 0 C Modeled AHe age: 8.9 Ma .5 1 20 Modeled AFT age: 16.3–18.1 Ma 40 60 80 all AFT data rivers (n=330) 100 120 Temperature (°C) 140 160 180 200 30 28 26 24 22 20 18 16 14 12 10 86420 Time (Ma)

D 0 Modeled AHe age: 8.7 Ma 20 Modeled AFT age: 16.2–18.2 Ma 40

0 10 20 30 40 50 60 70 80 90 100 110120 60 Age (Ma) 80

(100 ±0 8.3 ± 100 B 120 0.02 Temperature (°C) %) 140

160 180 all AHe data rivers (n=52) 200 30 28 26 24 22 20 18 16 14 12 10 86420 Time (Ma) E 0 Modeled AHe age: 13.1 Ma 20 Modeled AFT age: 17.2–18.2 Ma 40

60 80

100

120

Temperature (°C) 140

160 0 10 20 30 40 50 60 70 80 90 100 110 120 180 Age (Ma) 200 30 28 26 24 22 20 18 16 14 12 10 86420 Time (Ma) Figure 4. (A) Apatite fission-track (AFT) and (B) (U-Th)/He (AHe) ages and main populations calculated using Density Plotter (Vermeesch, 2012). (B and C) Forward modeling of AFT and AHe populations showing episodic cooling history in the Miocene using HeFty (Ketcham, 2005). (D) Forward modeling of AFT and AHe age assuming continuous accelerated cooling between 18 Ma and Present. (E) Forward modeling of AFT and AHe populations showing continuous cooling after ca. 19 Ma. arc rocks exposed in drainage catchments that has not significantly affected AFT ages. Also, by the overlying Kailas Formation (Carrapa produced our samples. Small-volume Miocene if erosion were responsible for cooling, we et al., 2014), supporting cooling by erosion/ leucogranites were emplaced at depth in the would expect a younging downward trend, from incision. The detrital cooling signatures at ca. Lopu Range (Murphy et al., 2010; Laskowski, higher- to lower-elevation stratigraphic level, in 33 Ma, 22–18 Ma, and 12 Ma are in agreement et al., 2016); however, the fact that the AFT response to progressive incision. Cooling ages with Oligocene–Miocene exhumation ages re- population for River 4, which drains this range, from Gangdese arc rocks below the Kailas For- corded in the Gangdese arc, Tethyan Himalaya, is ca. 33 Ma shows that thermal overprinting mation are younger than cooling ages recorded and Cenozoic deposits of the Liuqu and Kailas

Geological Society of America Bulletin, v. 1XX, no. XX/XX 7 Carrapa et al.

population from the River 4 sample, which is Modern River zircon U-Pb ages <120 Ma derived from the Lopu Range, is in agreement

(17.2± 35.23± (69.1± 47.985 ±0 (13.7± 89.63± with previous interpretations of Oligocene exhumation of granites and Tethyan Himalaya 2.4% ) 2.9% ) 3.7% ) 0.11 0.37

.0 9 rocks within this range (Sanchez et al., 2013; Laskowski et al., 2016). River 3 shows an AFT 82 (n=263) population at ca. 12 Ma, which may reflect late Miocene exhumation of the Gangdese arc in response to E-W extension, in agreement with 61 cooling ages from the Xiao Gurla Range (Pullen et al., 2011; Carrapa et al., 2014). AHe ages are generally younger than AFT 41 ages, as expected, and suggest exhumation of southern Tibet during the late Miocene. The following question remains: Is cooling representative of exhumation, and if it is, was it continuous 20 or episodic with rapid cooling at ca. 19 and 8 Ma? Because most of the AFT cooling ages pre- date the time of extension, are younger than the 0 age of crystallization, and are consistent with periods of active tectonics and or incision of the 0 10 20 30 40 50 60 70 80 90 100 110 120 Yarlung drainage basin, we generally interpret Age (Ma) cooling recorded by the AFT system to represent erosion. AHe cooling ages at ca. 8 Ma may represent both tectonic exhumation and erosion. Gangdese arc zircon U-Pb ages from literature Forward modeling of the ca. 19 Ma AFT signal and ca. 8 Ma AHe signal shows that a good (31.1± 13.175± (41± 49.348± (13.6± 80.07 match between predicted model ages and mea- 2.7%) ±0 2.5% ) 1.9% ) sured ages is obtained with an episodic exhuma- 0.021 0.082 .3 6 tion history characterized by two rapid cooling 30 events between ca. 20 and 17 Ma and between 8 Ma and 6 Ma, followed by periods of slow (n=331) cooling (Fig. 4B). We also note that a similar match is obtained by continuous rapid cooling 22 between 8 and Present (Fig. D). Relatively slow erosion between ca. 17 and 8 Ma is consistent with the absence of major upper-crustal short- 15 ening within the plateau at this time (Kapp and Guynn, 2004). Continuous cooling following the accelerated early to mid-Miocene cooling 7 event, which has been widely documented in southern Tibet (e.g., Carrapa et al., 2014), would instead predict ca. 14 Ma AHe ages (Fig. 4E). 0 DISCUSSION 0 10 20 30 40 50 60 70 80 90 100 110 120 Age (Ma) Overall the detrital zircon U-Pb signatures recorded in river detritus from southern Tibet indicate that both the ages and their relative Figure 5. Probability density plots (black line) and kernel density estimates (blue lines) of proportions directly reflect the ages and relative zircon U-Pb ages from literature (refer to captions of Fig. 2 for references) and from rivers areas of source rocks present in the respective analyzed in this study. catchment basins. In particular, our study suggests that zircon U-Pb ages between ca. 40 and Formations (Pan et al., 1993; Copeland et al., basin during the Miocene (Carrapa et al., 2014). 120 Ma typical of the Gangdese arc are prefer- 1995; Yuan et al., 2009, 2009; Dai et al., 2013; The sample from River 5 shows a slightly older entially derived from first-cycle material off the Carrapa et al., 2014; Li et al., 2015a, 2015b, signal at ca. 22 Ma, which may reflect cooling Gangdese arc, rather than from reworked Creta- 2016; Leary et al., 2016a, 2016b). The sample and exhumation of the Gangdese arc and/or a ceous and Cenozoic strata. This is indicated by from River 7 draining the Kailas Range shows a mixed population recording both fully reset and the linear relationships described in Figure 6. ca. 18 Ma detrital signal coeval with cooling as- partially reset ages in the source region and thus When the age spectra for all detrital samples sociated with regional exhumation of the Kailas variable levels of erosion. The ca. 33 Ma AFT are compared against the signature from the

8 Geological Society of America Bulletin, v. 1XX, no. XX/XX Tectonic and erosional history of southern Tibet from rivers

50 lift and erosion in the eastern Himalayan syn- River 7 taxis (Namche Barwa) since late Miocene time 40 Figure 6. Correlation between (Burg et al., 1997; Zeitler et al., 2014). Geo- percentage of detrital zircon 1:1 morphological analysis of the eastern Yarlung 30 R2 = 0.80867 (DZ) ages between 120 and River indicates 500–2000 m of incision prior to River 5 River 6 40 Ma and percentage of Gang- 10 Ma, which has been associated with uplift of 20 River 4 River 3 dese arc rocks exposed within southern Tibet (Schmidt et al., 2015). A greater River 2 each catchment. High R2 value 10 discharge and, by inference, a more humid cli- of >0.8 indicates that a positive River 1 mate and/or lower elevation, allowing for pre- % of DZ ages 12 0– 40 Ma 0 linear correlation model fits the cipitation to penetrate deeper into the Yarlung 01020304050 observed data. valley, may have existed in the early to middle % of Gangdese arc rocks exposed in drainage catchment area Miocene in southern Tibet. This is supported by sedimentological and geochemical analyses of the Kailas and Liuqu Formations, which indicate Gangdese arc from the literature, it is clear regions, including the Yarlung drainage. The more humid conditions consistent with lower that the detrital zircon U-Pb data presented in early Miocene cooling event, which was origi- elevations in the early Miocene in southern Tibet this study directly record magmatic activity in nally noted by Copeland et al. (1987), postdates (Leary, 2015; DeCelles et al., 2011, 2016). the Gangdese arc (Fig. 5). The near absence of the Kailas basin, which has been interpreted to In general, the similarities between U-Pb ages zircons younger than 35 Ma in our data is con- represent possible Asian plate extension in re- from modern rivers and detrital zircon U-Pb ages sistent with the data from the literature show- sponse to southward retreat (or rollback) fol- from the Kailas and Liuqu Formations suggest ing a magmatic lull between ca. 40 Ma and ca. lowed by break-off of part of the subducting that sediment provenance in the Indus-Yarlung 20 Ma. The age signal at ca. 48 Ma is consis- Indian plate (DeCelles et al., 2011). If this is suture zone and neighboring regions has not tent with peak magmatism of the Gangdese arc, correct, and considering that geophysical data changed much since late Oligocene time (ca. which has been interpreted as a result of break- suggest that India is underthrusted under central 25–16 Ma); as it is today, the region was char- off of the Tethyan slab (Wen et al., 2008; Wei- Tibet today (Capitanio and Replumaz, 2013), a acterized by short-stem rivers flowing off of the Qiang et al., 2016). A few ages around 25– plausible mechanism to drive the early Miocene Gangdese arc to the north and Tethyan rocks to 17 Ma suggest sporadic activity of the Gangdese cooling event would be uplift-induced erosion- the south into an axial valley. However, the val- arc into Miocene time. incision driven by northward underthrusting of ley was also occupied by large, deep lakes in a In general, AFT ages are younger than ca. the Indian plate after the slab break-off event. rapidly subsiding basin, and there is no evidence 40 Ma, and AHe ages are younger than ca. However, if India underthrusting was the only for a large through-going axial river during the 25 Ma, with significant Miocene age signals cause for uplift and erosion, we would expect early Miocene in the region (Wang et al., 2010, at ca. 19 and 8 Ma (Fig. 4). The presence of a the area north of the Gangdese arc to record the 2013; DeCelles et al., 2011; Leary et al., 2016a, few Cretaceous AFT ages (ca. 90 Ma) to the same Miocene signature, whereas AFT and AHe 2016b). There is also no evidence of a southeast (Rivers 3 and 4) may represent exhuma- ages from central Tibet are overall much older ward-flowing transverse drainage system at that tion related to the development of the Creta- (Rohrmann et al., 2012) than ages documented time between the suture zone, the Himalaya, ceous Gangdese retroarc thrust belt associated in this study. This indicates younger cooling and its foreland basin to the south (as suggested with the Takena Formation retroarc foreland and a higher magnitude of erosion in southern by Tremblay et al., 2015). Instead, the major basin and/or early exhumation of the Gangdese Tibet compared with central Tibet and suggests through-going axial river system similar to today arc. AFT ages show two strong signals at ca. that Miocene exhumation in southern Tibet and in southern Tibet was most likely established 22–18 Ma and 12 Ma, which are in agreement along the Indus-Yarlung suture zone was likely in the mid-Miocene as river response to uplift with accelerated cooling and exhumation of the the combined result of Indian underthrusting through incision (Carrapa et al., 2014; Bracciali Gangdese arc (Dai et al., 2013; Li et al., 2016). coupled with efficient sediment export from the et al., 2015; Lang and Huntington, 2014; Robin- The 22–18 Ma ages indicate regional cool- region by the paleo–Yarlung River system. son et al., 2014). ing in the early Miocene. AFT ages between Efficient river incision and evacuation of ma- A different mechanism other than growth ca. 20 and ca. 15 Ma in the Tethyan Himalaya terial from southern Tibet by the paleo–Yarlung of the Himalaya to the south is thus required have been attributed to activity along the Great River, and possibly the Indus River, during the to produce the ca. 8 Ma signal recorded re- Counter thrust (Li et al., 2015b). Similar cool- early to mid-Miocene suggest higher discharge, gionally in southern Tibet and to explain the ing ages at ca. 17 Ma recorded in the Kailas which implies different climatic-geomorphic possible decrease in erosion after ca. 11 Ma Formation, which rests unconformably upon conditions than observed today. For example, documented by Tremblay et al. (2015). The ca. Gangdese arc rocks, suggest that this signal is today the Yarlung River drops off the edge of 8–6 Ma rapid cooling event (Fig. 4E) is consis- related to regional cooling and exhumation of the Tibetan Plateau through the steep, narrow tent with tectonic exhumation associated with southern Tibet and the Indus-Yarlung suture Tsangpo Gorge; evacuation of material through E-W extension affecting southern Tibet in the zone (Carrapa et al., 2014). The fact that Mio- the gorge is limited to the edge of the plateau Miocene (e.g., Murphy et al., 2002, 2009; Pul- cene exhumation is also recorded in the Indus where it is cut by the gorge. Episodic damming len et al., 2011). For example, exhumation of Basin (the northwestward continuation of the followed by flooding and upstream sediment ac- Gurla Mandhata occurred mainly between ca. Kailas basin; Sinclair and Jaffey, 2001) and in cumulation characterize the Yarlung River above 8 and 2 Ma (McCallister et al., 2014) and has the Ladakh batholith (Kirstein et al., 2006) in- the gorge (Lang et al., 2013; Wang et al., 2014). been associated with arc-parallel extension. Al- dicates that the early Miocene signal is regional Exhumation ages near the Tsangpo Gorge and though the timing of E-W extension can explain and affected an ~1500 km along-strike length of eastern syntaxes are generally younger than ca. the accelerated cooling between ca. 8 and 6 Ma, the Indus-Yarlung suture zone and neighboring 10 Ma and have been interpreted to reflect up- the decrease in cooling after ca. 6 Ma cannot be

Geological Society of America Bulletin, v. 1XX, no. XX/XX 9 Carrapa et al.

explained by extension, which seems to have Tsangpo suture zone, SE Tibet: Journal of Asian Earth the Neogene evolution of the Yarlung-Brahmaputra Sciences, v. 21, p. 251–263, doi:10 .1016 /S1367 -9120 River system: Earth and Planetary Science Letters, continued until at least 2 Ma (McCallister et al., (02)00037-8 . v. 285, p. 150–162, doi:10.1016/j.epsl.2009.06.005. 2014). Instead, a possible decrease in erosion Aitchison, J.C., Ali, J.R., Chan, A., Davis, A.M., and Lo, Copeland, P., Harrison, T.M., Kidd, W.S.F., Xu, R., and after ca. 6 Ma (Fig. 4E) can be associated with C.‑H., 2009, Tectonic implications of felsic tuffs within Zhang, Y., 1987, Rapid early Miocene acceleration of the Lower Miocene Gangrinboche conglomerates, uplift in the Gangdese Belt, Xizang-southern Tibet, the uplift of the eastern syntaxis, which began southern Tibet: Journal of Asian Earth Sciences, v. 34, and its bearing on accommodation mechanisms of at ca. 7 Ma, with intense exhumation after ca. p. 287–297, doi:10.1016/j.jseaes.2008.05.008. the India-Asia collision: Earth and Planetary Science Aitchison, J.C., Xia, X., Baxter, A.T., and Ali, J.R., 2011, Letters, v. 86, p. 240–252, doi:10.1016/0012-821X 5 Ma (Seward and Burg, 2008; Zeitler et al., Detrital zircon U-Pb ages along the Yarlung-Tsangpo (87)90224-X. 2014; Lang et al., 2016), likely blocking mois- suture zone, Tibet: Implications for oblique conver- Copeland, P., Harrison, M.T., Yun, P., Kidd, W.S.F., Roden, ture from the southeast and leading to a decrease gence and collision between India and Asia: Gondwana M., and Yuquan, Z., 1995, Thermal evolution of the Research, v. 20, p. 691–709, doi:10.1016/j.gr.2011.04 Gangdese batholith, southern Tibet: A history of epi- in fluvial erosion rates in southern Tibet. .002. sodic unroofing: Tectonics, v. 14, no. 2, p. 223–236, Aoya, M., Wallis, S.R., Terada, K., Lee, J., Kawakami, T., doi:10.1029/94TC01676. CONCLUSIONS Wang, Y., and Heizler, M., 2005, North-south exten- Coulon, C., Maluski, H., Bollinger, C., and Wang, S., 1986, sion in the Tibetan crust triggered by granite emplace- Mesozoic and Cenozoic volcanic rocks from central ment: Geology, v. 33, no. 11, p. 853–856, doi:10.1130 and southern Tibet: 40Ar-39Ar dating, petrological char- Detrital zircon U-Pb ages from rivers drain- /G21806.1. acteristics and geodynamical significance: Earth and ing southern Tibet, including the Indus-Yarlung Bracciali, L., Najman, Y., Parrisha, R.R., Akhterd, S.H., and Planetary Science Letters, v. 79, no. 3-4, p. 281–302, Millar, I., 2015, The Brahmaputra tale of tectonics and doi:10.1016/0012-821X(86)90186-X. suture zone, directly reflect ages present in the erosion: Early Miocene river capture in the Eastern Dai, J., Wang, C., Hourigan, J., Li, Z., and Zhuang, G., 2013, drainage basin and thus preserve an accurate Himalaya: Earth and Planetary Science Letters, v. 415, Exhumation history of the Gangdese batholith, south- p. 25–37, doi:10.1016/j.epsl.2015.01.022. ern Tibetan Plateau: Evidence from apatite and zircon record of regional tectonic and erosional pro- Burg, J., and Chen, G., 1984, Tectonics and structural zona- (U-Th)/He thermochronology: The Journal of Geol- cesses. Extensive early to mid-Miocene cooling tion of southern Tibet, China: Nature, v. 311, p. 219– ogy, v. 121, no. 2, p. 155–172, doi:10.1086/669250. supports the interpretation of regional uplift of 223, doi:10.1038/311219a0. DeCelles, P., Gehrels, G., Quade, J., LaReau, B., and Spur- Burg, J.P., Brunel, M., Gapais, D., Chen, G.M., and Liu, lin, M., 2000, Tectonic implications of U-Pb zircon southern Tibet at this time, combined with effi- G.H., 1984, Deformation of leucogranites of the crys- ages of the Himalayan orogenic belt in Nepal: Science, cient exhumation by river incision of the Yarlung talline Main Central Sheet in southern Tibet (China): v. 288, no. 5465, p. 497–499, doi:10.1126/science.288 drainage system. The similarities between the Journal of Structural Geology, v. 6, no. 5, p. 535–542, .5465.497. doi:10.1016/0191-8141(84)90063-4. DeCelles, P.G., Gehrels, G.E., Najman, Y., Martin, A.J., modern detrital signatures and the geochronolog- Burg, J.-P., Leyreloup, A., Girardeau, J., and Chen, G.-M., Carter, A., and Garzanti, E., 2004, Detrital geochronol- ical signatures preserved in the Kailas and Liuqu 1987, Structure and metamorphism of a tectonically ogy and geochemistry of Cretaceous–early Miocene thickened continental crust: The Yalu Tsangpo suture strata of Nepal: Implications for timing and diachro- basin strata indicate that the modern longitudinal zone (Tibet): Philosophical Transactions of the Royal neity of initial Himalayan orogenesis: Earth and Plan- drainage system developed no later than middle Society of London, ser. A, Mathematical and Physical etary Science Letters, v. 227, p. 313–330, doi:10 .1016 Miocene time. Sciences, v. 321, no. 1557, p. 67–86, doi:10 .1098/rsta /j.epsl.2004.08.019. .1987.0005. DeCelles, P.G., Kapp, P., Quade, J., and Gehrels, G., 2011, Drainage reorganization of southern Tibet in Burg, J.-P., Davy, P., Nievergelt, P., Oberli, F., Seward, D., Oligocene–Miocene Kailas basin, southwestern Tibet: the Miocene by capture of the Yarlung by the Diao, Z., and Meier, M., 1997, Exhumation during Record of postcollisional upper-plate extension in Brahmaputra River may have enhanced river crustal folding in the Namche-Barwa syntaxis: Terra the Indus-Yarlung suture zone: Geological Society of Nova, v. 9, no. 2, p. 53–56, doi:10.1111/j.1365-3121 America Bulletin, v. 123, p. 1337–1362, doi:10 .1130 incision. An overall greater discharge of the .1997.tb00001.x. /B30258.1. Indus-Yarlung River during the early Miocene Capitanio, F., and Replumaz, A., 2013, Subduction and slab DeCelles, P.G., Kapp, P., Gehrels, G., and Ding, L., 2014, than that observed today, and by inference a breakoff controls on Asian indentation tectonics and Paleocene–Eocene foreland basin evolution in the Himalayan western syntaxis formation: Geochemistry Himalaya of southern Tibet and Nepal: Implications wetter climate and or higher relief and lower Geophysics Geosystems, v. 14, no. 9, p. 3515–3531, for the age of initial India-Asia collision: Tectonics, elevation of the Indus-Yarlung valley during doi:10.1002/ggge.20171. v. 33, p. 824–849, doi:10.1002/2014TC003522. Carrapa, B., 2010, Resolving tectonic problems by dating DeCelles, P.G., Castañeda, I.S., Carrapa, B., Liu, J., Quade, Kailas and Liuqu basins deposition, could have detrital minerals: Geology, v. 38, no. 2, p. 191–192, J., and Zhang, L., 2016, Oligocene–Miocene Great also contributed to regional Miocene erosion. doi:10.1130/focus022010.1. Lakes in the India-Asia collision zone: Basin Research, Late Miocene accelerated cooling can be ex- Carrapa, B., Orme, D.A., DeCelles, P.G., Kapp, P., Cosca, doi:10.1111/bre.12217. M.A., and Waldrip, R., 2014, Miocene burial and ex- Ding, L., Kapp, P., Zhong, D., and Deng, W., 2003, Ceno plained by tectonic exhumation associated with humation of the India-Asia collision zone in southern zoic volcanism in Tibet: Evidence for a transition regional arc-parallel extension in response to Tibet: Response to slab dynamics and erosion: Geol- from oceanic to continental subduction: Journal of outward expansion of the Tibet-Himalaya oro- ogy, v. 42, p. 443–446, doi:10.1130/G35350.1. Petrology, v. 44, no. 10, p. 1833–1865, doi:10 .1093 Cherniak, D.J., and Watson, E.B., 2001, Pb diffusion in zir- /petrology/egg061. genic system. con: Chemical Geology, v. 172, p. 5–24, doi:10 .1016 Ding, L., Kapp, P., and Wan, X.Q., 2005, Paleocene–Eocene /S0009-2541(00)00233-3. record of ophiolite obduction and initial India-Asia ACKNOWLEDGMENTS Chiu, H.-Y., Chung, S.-L., Wu, F.-Y., Liu, D., Liang, Y.-H., collision, south central Tibet: Tectonics, v. 24, no. 3, Lin, I.J., Iizuka, Y., Xie, L.-W., Wang, Y., and Chu, p. TC3001, doi:10.1029/2004TC001729. This research was supported by U.S. National M.‑F., 2009, Zircon U-Pb and Hf isotopic constraints Flowers, R.M., Ketcham, R.A., Shuster, D.L., and Farley, Science Foundation Continental Dynamics grant from eastern Transhimalayan batholiths on the pre K.A., 2009, Apatite (U-Th)/He thermochronometry EAR-1008527 awarded to the University of Arizona collisional magmatic and tectonic evolution in south- using a radiation damage accumulation and anneal- Tectonics Group and grant EAR-1338583 for support ern Tibet: Tectonophysics, v. 477, p. 3–19, doi:10.1016 ing model: Geochimica et Cosmochimica Acta, v. 73, /j.tecto.2009.02.034. p. 2347–2365, doi:10.1016/j.gca.2009.01.015. of the Arizona LaserChron Center. We thank Peter Chu, M.-F., Chung, S.-L., Song, B., Liu, D., O’Reilly, S.Y., Galbraith, R.F., and Laslett, G.M., 1993, Statistical models Reiners for help with (U-Th)/He analyses, and Jean- Pearson, N.J., Ji, J., and Wen, D.-J., 2006, Zircon U-Pb for mixed fission track ages: Nuclear Tracks and Radia Pierre Burg, Eduardo Garzanti, and Stefano Mazzoli and Hf isotope constraints on the Mesozoic tectonics tion Measurements, v. 21, no. 4, p. 459–470, doi:10 for constructive reviews. and crustal evolution of southern Tibet: Geology, v. 34, .1016/1359 -0189 (93)90185 -C . p. 745–748, doi:10.1130/G22725.1. Garzanti, E., Baud, A., and Mascle, G., 1987, Sedimentary REFERENCES CITED Chung, S.-L., Chu, M.-F., Zhang, Y., Xie, Y., Lo, C.-H., record of the northward flight of India and its collision Lee, T.-Y., Lan, C.-Y., Li, X., Zhang, Q., and Wang, Y., with Eurasia (Ladakh Himalaya, India): Geodinamica Aikman, A.B., Harrison, T.M., and Lin, D., 2008, Evidence 2005, Tibetan tectonic evolution inferred from spatial Acta, v. 1, no. 4–5, p. 297–312, doi:10 .1080/09853111 for early (>44 Ma) Himalayan crustal thickening, and temporal variations in post-collisional magmatism: .1987.11105147. Tethyan Himalaya, southeastern Tibet: Earth and Plan- Earth-Science Reviews, v. 68, p. 173–196, doi:10.1016 Gehrels, G.E., 2014, Detrital zircon U-Pb geochronology etary Science Letters, v. 274, p. 14–23, doi:10.1016/j /j.earscirev.2004.05.001. applied to tectonics: Annual Review of Earth and Plan- .epsl.2008.06.038. Cina, S., Yin, A., Grove, M., Dubey, C.S., Shukla, D.P., etary Sciences, v. 42, p. 127–149, doi:10.1146/annurev Aitchison, J.C., Davis, A.M., Badengzhu, and Luo, H., Lovera, O.M., Kelty, T.K., Gehrels, G.E., and Foster, -earth-050212-124012. 2002, New constraints on the India-Asia collision: The D.A., 2009, Gangdese arc detritus within the eastern Gehrels, G.E., Yin, A., and Wang, X.-F., 2003, Detrital zir- Lower Miocene Gangrinboche conglomerates, Yarlung- Himalayan Neogene foreland basin: Implications for con geochronology of the northeastern Tibetan Pla-

10 Geological Society of America Bulletin, v. 1XX, no. XX/XX Tectonic and erosional history of southern Tibet from rivers

teau: Geological Society of America Bulletin, v. 115, Jiang, Z.-Q., Wang, Q., Li, Z.-X., Wyman, D.A., Tang, G.‑J., Lee, H.-Y., Ching, S.-L., Lo, C.-H., Ji, J., Lee, T.-Y., Qiang, p. 881–896, doi:10.1130/0016-7606(2003)115<0881: Jia, X.-H., and Yang, Y.-H., 2012, Late Cretaceous (ca. Q., and Zhang, Q., 2009, Eocene Neotethyan slab DGOTNT>2.0.CO;2. 90 Ma) adakitic intrusive rocks in the Kelu area, Gang- breakoff in southern Tibet inferred from the Linzizong Gehrels, G.E., Valencia, V.A., and Ruiz, J., 2008, Enhanced dese belt (southern Tibet): Slab melting and implica- volcanic record: Tectonophysics, v. 477, p. 20–35, doi: precision, accuracy, efficiency, and spatial resolution tions for Cu-Au mineralization: Journal of Asian Earth 10.1016/j.tecto.2009.02.031. of U-Pb ages by laser ablation–multicollector–induc- Sciences, v. 53, p. 67–81, doi:10.1016/j.jseaes.2012.02 Lee, J., and Whitehouse, M.J., 2007, Onset of mid-crustal tively coupled plasma–mass spectrometry: Geochem- .010. extensional flow in southern Tibet: Evidence from istry Geophysics Geosystems, v. 9, no. 3, p. Q03017, Kapp, P., and Guynn, J.H., 2004, Indian punch rifts Tibet: U/Pb zircon ages: Geology, v. 35, p. 45–48, doi:10 doi:10.1029/2007GC001805. Geology, v. 32, no. 11, p. 993–996, doi:10.1130 .1130/G22842A.1. Gehrels, G., Kapp, P., DeCelles, P., Pullen, A., Blakey, R., /G20689.1. Lee, J., Dinklage, W.S., Hacker, B.R., Wang, Y., Gans, P.B., Weislogel, A., Ding, L., Guynn, J., Martin, A., Mc- Kapp, P., Yin, A., Harrison, T.M., and Ding, L., 2005, Cre- Calvert, A., Wan, J., Chen, W., Blythe, A., and Mc- Quarrie, N., and Yin, A., 2011, Detrital zircon geochro- taceous–Tertiary shortening, basin development, and Clelland, W., 2000, Evolution of the Kangmar Dome, nology of pre-Tertiary strata in the Tibetan-Himalayan volcanism in central Tibet: Geological Society of southern Tibet: Structural, petrologic, and thermo orogeny: Tectonics, v. 30, p. TC5016, doi:10.1029 America Bulletin, v. 117, p. 865–878, doi:10.1130 chronologic constraints: Tectonics, v. 19, p. 872–895, /2011TC002868. /B25595.1. doi:10.1029/1999TC001147. Gleadow, A.J.W., and Duddy, I.R., 1981, A natural long- Kapp, P., DeCelles, P.G., Leier, A.L., Fabijanic, J.M., He, Lee, J., McClelland, W., Wang, Y., Blythe, A., and McWil- term annealing experiment for apatite: Nuclear Tracks S., Pullen, A., Gehrels, G.E., and Ding, L., 2007, The liams, M., 2006, Oligocene–Miocene middle crustal and Radiation Measurements, v. 5, p. 169–174, doi:10 Gangdese retroarc thrust belt revealed: GSA Today, flow in southern Tibet: Geochronology of Mabja .1016/0191-278X(81)90039-1. v. 17, no. 7, p. 4–9, doi:10.1130/GSAT01707A.1. Dome, in Law, R.D., Searle, M.P., and Godin, L., eds., Guan, Q., Zhu, D., Zhao, Z., Dong, G., Zhang, L., Li, X., Kawakami, T., Aoya, M., Wallis, S.R., Lee, J., Terada, K., Channel Flow, Ductile Extrusion and Exhumation in Liu, M., Mo, X., Liu, Y., and Yuan, H., 2012, Crustal Wang, Y., and Heizler, M., 2007, Contact metamor- Continental Collision Zones: Geological Society of thickening prior to 38 Ma in southern Tibet: Evidence phism in the Malashan dome, North Himalayan gneiss London Special Publication 268, p. 445–469, doi:10 from lower crust–derived adakitic magmatism in the domes, southern Tibet: An example of shallow exten- .1144/GSL.SP.2006.268.01.21. Gangdese Batholith: Gondwana Research, v. 21, p. 88– sional tectonics in the Tethys Himalaya: Journal of Lee, J., Hager, C., Wallis, S.R., Stockli, D.F., Whitehouse, 99, doi:10.1016/j.gr.2011.07.004. Metamorphic Geology, v. 25, p. 831–853, doi:10 .1111 M.J., Aoya, M., and Wang, Y., 2011, Middle to late Guo, L., Zhang, H.-F., Harris, N., Pan, F.-B., and Xu, W.-C., /j.1525-1314.2007.00731.x. Miocene extremely rapid exhumation and thermal re- 2011, Origin and evolution of multi-stage felsic melts Ketcham, R.A., 2005, Forward and inverse modeling of equilibration in the Kung Co rift, southern Tibet: Tec- in eastern Gangdese belt: Constraints from U-Pb zir- low-temperature thermochronometry data: Reviews in tonics, v. 30, p. TC2007, doi:10.1029/2010TC002745. con dating and Hf isotopic composition: Lithos, v. 127, Mineralogy and Geochemistry, v. 58, p. 275–314, doi: Lee, J.K.W., Williams, I.S., and Ellis, D.J., 1997, Pb, U and p. 54–67, doi:10.1016/j.lithos.2011.08.005. 10.2138/rmg.2005.58.11. Th diffusion in natural zircon: Nature, v. 390, p. 159– Harris, N.B.W., Xu, R., Lewis, C.L., and Jin, C., 1988, Plu- King, J., Harris, N., Argles, T., Parrish, R., Charlier, B., 162, doi:10.1038/36554. tonic rocks of the 1985 Tibet geotraverse, Lhasa to Sherlock, S., and Zhang, H.F., 2007, First field evi- Leier, A.L., DeCelles, P.G., Kapp, P., and Gehrels, G.E., Golmud: Philosophical Transactions of the Royal So- dence of southward ductile flow of Asian crust beneath 2007, Lower Cretaceous strata in the Lhasa terrane, ciety of London, ser. A, v. 327, p. 145–168. southern Tibet: Geology, v. 35, p. 727–730, doi:10 Tibet, with implications for understanding the early Harrison, T.M., Copeland, P., Kidd, W.S.F., and Yin, A., .1130/G23630A.1. tectonic history of the Tibetan Plateau: Journal of Sedi- 1992, Raising Tibet: Science New Series, v. 255, King, J., Harris, N., Argles, T., Parrish, R., and Zhang, H.F., mentary Research, v. 77, no. 9–10, p. 809–825, doi:10 no. 5052, p. 1663–1670. 2011, Contribution of crustal anatexis to the tectonic .2110/jsr.2007.078. Harrison, T.M., Lovera, O.M., and Grove, M., 1997, New evolution of Indian crust beneath southern Tibet: Geo- Li, G., Kohn, B., Sandiford, M., Xu, Z., and Wei, L., 2015a, insights into the origin of two contrasting Himalayan logical Society of America Bulletin, v. 123, p. 218– Constraining the age of Liuqu Conglomerate, southern granite belts: Geology, v. 25, no. 10, p. 899–902, doi:10 239, doi:10.1130/B30085.1. Tibet: Implications for evolution of the India–Asia .1130/0091-7613(1997)025<0899:NIITOO>2.3.CO;2. Kirstein, L.A., Sinclair, H., Stuart, F.M., and Dobson, K., collision zone: Earth and Planetary Science Letters, Harrison, T.M., Yin, A., Grove, M., Lovera, O.M., Ryerson, 2006, Rapid early Miocene exhumation of the Ladakh v. 426, p. 259–266, doi:10.1016/j.epsl.2015.06.010. F.J., and Zhou, X., 2000, The Zedong Window: A rec batholith, western Himalaya: Geology, v. 34, no. 12, Li, G., Tian, Y., Kohn, B.P., Sandiford, M., Xu, Z., and Cai, ord of superposed convergence in south-eastern Tibet: p. 1049–1052, doi:10.1130/G22857A.1. Z., 2015b, Cenozoic low temperature cooling history Journal of Geophysical Research, v. 105, p. 19,211– Lang, K.A., and Huntington, K.W., 2014, Antecedence of of the Northern Tethyan Himalaya in Zedang, SE Tibet, 19,230, doi:10.1029/2000JB900078. the Yarlung–Siang–Brahmaputra River, eastern Hima and its implications: Tectonophysics, v. 42, p. 29–35, He, S., Kapp, P., DeCelles, P.G., Gehrels, G.E., and Heizler, laya: Earth and Planetary Science Letters, v. 397, doi:10.1016/j.tecto.2014.12.014. M., 2007, Cretaceous–Tertiary geology of the Gangdese p. 145–158, doi:10.1016/j.epsl.2014.04.026. Li, G., Kohn, B., Sandiford, M., Xu, Z., Tian, Y., and Seiler, arc in the Linzhou area, southern Tibet: Tectonophysics, Lang, K.A., Huntington, K.A., and Montgomery, D.R., C., 2016, Synorogenic morphotectonic evolution of the v. 433, p. 15–37, doi:10.1016/j.tecto.2007.01.005. 2013, Erosion of the Tsangpo Gorge by megafloods, Gangdese batholith, south Tibet: Insights from low- Hébert, R., Bezard, R., Guilmette, C., Dostal, J., Wang, C.S., Eastern Himalaya: Geology, v. 41, p. 1003–1006, doi: temperature thermochronology: Geochemistry Geo- and Liu, Z.F., 2012, The Indus–Yarlung Zangbo ophio- 10.1130/G34693.1. physics Geosystems, v. 17, p. 101–112, doi:10.1002 lites from Nanga Parbat to Namche Barwa syntaxes, Lang, K.A., Huntington, K.W., Burmester, R., and Housen, /2015GC006047. southern Tibet: First synthesis of petrology, geochemis- B., 2016, Rapid exhumation of the eastern Himalayan Liang, Y.H., Chung, S.L., Liu, D.Y., Xu, Y.G., Wu, F.Y., try, and geochronology with incidences on geodynamic syntaxis since the late Miocene: Geological Society of Yang, J.H., Wang, Y., and Lo, C.H., 2008, Detrital reconstructions of Neo-Tethys: Gondwana Research, America Bulletin, v. 128, no. 9-10, p. 1403–1422, doi: zircon evidence from Burma for reorganization of the v. 22, p. 377–397, doi:10.1016/j.gr.2011.10.013. 10.1130/B31419.1. eastern Himalayan river system: American Journal of Hoang, L.v., Wu, F.Y., Clift, P.D., Wysocka, A., and Swierc- Larson, K.P., Godin, L., Davis, W.J., and Davis, D.W., 2010, Science, v. 308, p. 618–638, doi:10.2475/04.2008.08. zewska, A., 2009, Evaluating the evolution of the Out-of-sequence deformation and expansion of the Ludwig, K.R., 2008, Manual for Isoplot 3.7: Berkeley Geo- Red River system based on in situ U-Pb dating and Himalayan orogenic wedge: Insight from the Changgo chronology Center Special Publication 4, 77 p. Hf isotope analysis of zircons: Geochemistry Geo- culmination, south central Tibet: Tectonics, v. 29, Mahéo, G., Leloup, P.H., Valli, F., Lacassin, R., Arnaud, physics Geosystems, v. 10, p. Q11008, doi:10.1029 p. TC4013, doi:10.1029/2008TC002393. N., Paquette, J.L., Fernandez, A., Haibing, L., Farley, /2009GC002819. Laskowski, A.K., Kapp, P., Vervoort, J.D., and Ding, L., K.A., and Tapponnier, P., 2007, Post–4 Ma initiation Hou, Z.Q., Gao, Y.F., Qu, X.M., Rui, Z.Y., and Mo, X., 2004, 2016, High-pressure Tethyan Himalaya rocks along the of normal faulting in southern Tibet. Constraints from Origin of adakitic intrusives generated during mid- India-Asia suture zone in southern Tibet: Lithosphere, the Kung Co half graben: Earth and Planetary Science Miocene east-west extension in southern Tibet: Earth v. 8, no. 5, p. 574–582, doi:10.1130/L544.1. Letters, v. 256, p. 233–243, doi:10.1016/j.epsl.2007.01 and Planetary Science Letters, v. 220, p. 139–155, doi: Leary, R., 2015, Post-collisional Evolution of the India-Asia .029. 10.1016/S0012-821X(04)00007-X. Suture Zone: Basin Development, Paleogeography, McCallister, A.T., Taylor, M.H., Murphy, M.A., Styron, Hu, X., Garzanti, E., Moore, T., and Raffi, I., 2015, Direct Paleoaltimetry, and Paleoclimate [Ph.D. thesis]: Tucson, R.H., and Stockli, D.F., 2014, Thermochronologic con- stratigraphic dating of India-Asia collision onset at the Arizona, University of Arizona, http://hdl.handle.net straints on the late Cenozoic exhumation history of the Selandian (middle Paleocene, 59 ± 1 Ma): Geology, /10150/594960. Gurla Mandhata metamorphic core complex, south- v. 43, p. 859–862, doi:10.1130/G36872.1. Leary, R., DeCelles, P., Quade, J., Gehrels, G., and Wan- western Tibet: Tectonics, v. 33, no. 2, p. 27–52, doi:10 Ji, W.-Q., Wu, F.-Y., Chung, S.-L., Li, J.-X., and Liu, C.‑Z., deers, G., 2016a, The Liuqu Conglomerate, southern .1002/2013TC003302. 2009, Zircon U-Pb geochronology and Hf isotopic Tibet: Early Miocene basin development related to McDermid, I.R.C., Aitchison, J.C., Davis, A.M., Harrison, constraints on petrogenesis of the Gangdese batholith: deformation within the Great Counter thrust system: T.M., and Grove, M., 2002, The Zedong terrane: A Chemical Geology, v. 262, p. 229–245, doi:10 .1016/j Lithosphere, v. 8, p. 427–450, doi:10.1130/L542.1. Late Jurassic intra-oceanic magmatic arc within the .chemgeo.2009.01.020. Leary, R., Orme, D., Laskowski, A., DeCelles, P.G., Kapp, Yarlung-Zangbo suture zone, southeastern Tibet: Ji, W.-Q., Wu, F.-Y., Liu, C.-Z., and Chung, S.-L., 2012, P., Carrapa, B., and Dettinger, M., 2016b, Along-strike Chemical Geology, v. 187, p. 267–277, doi:10.1016 Early Eocene crustal thickening in southern Tibet: diachroneity in the deposition of the Kailas Formation /S0009-2541(02)00040-2. New age and geochemical constraints from the Gang- in central southern Tibet: Implications for Indian slab Miller, C., Schuster, R., Klotzli, U., Frank, W., and dese batholith: Journal of Asian Earth Sciences, v. 53, dynamics: Geosphere, v. 12, no. 4, p. 1198–1223, doi: Purtscheller, F., 1999, Post-collisional potassic and p. 82–95, doi:10.1016/j.jseaes.2011.08.020. 10.1130/GES01325.1. ultrapotassic magmatism in SW Tibet: Geochemical

Geological Society of America Bulletin, v. 1XX, no. XX/XX 11 Carrapa et al.

and Sr-Nd-Pb-O isotopic constraints for mantle source Quidelleur, X., Grove, M., Lovera, O.M., Harrison, T.M., Vermeesch, P., 2012, On the visualisation of detrital age dis- characteristics and petrogenesis: Journal of Petrology, Yia, A., and Ryerson, R.J., 1997, Thermal evolution tributions: Chemical Geology, v. 312–313, p. 190–194, v. 40, no. 9, p. 1399–1424, doi:10.1093/petroj/40.9 and slip history of the Renbu Zedong thrust, south- doi:10.1016/j.chemgeo.2012.04.021. .1399. eastern Tibet: Journal of Geophysical Research, v. 102, Wang, J., Hu, X., Wu, F., and Jansa, L., 2010, Provenance of Mo, X.X., Zhao, Z.D., Deng, J.F., Dong, G.C., Zhou, S., no. B2, p. 2659–2679. the Liuqu Conglomerate in southern Tibet: A Paleogene Guo, T.Y., Zhang, S.Q., and Wang, L.L., 2003, Re- Ratschbacher, L., Frisch, W., Liu, G., and Chen, C., 1994, erosional record of the Himalayan-Tibetan orogen: sponse of volcanism to the India-Asia collision: Earth Distributed deformation in southern and western Tibet Sedimentary Geology, v. 231, p. 74–84, doi:10 .1016/j Science Frontiers, v. 10, p. 135–148. during and after the India-Asia collision: Journal of .sedgeo.2010.09.004. Mo, X.X., Dong, G.C., Zhao, Z.D., Zhou, S., Wang, L.L., Geophysical Research–Solid Earth (1978–2012), v. 99, Wang, J., Hu, X., Garzanti, E., and Wu, F., 2013, Upper Qiu, R.Z., and Zhang, F.Q., 2005, Spatial and tempo- no. B10, p. 19,917–19,945. Oligocene–Lower Miocene Gangrinboche Conglom- ral distribution and characteristics of granitoids in the Robinson, R.A.J., Brezina, C.A., Parrish, R.R., Horstwood, erate in the Xigaze area, southern Tibet: Implications Gangdese, Tibet, and implication for crustal growth M.S.A., Oo, N.W., Bird, M.I., Thein, M., Walters, for Himalayan uplift and paleo–Yarlung-Zangbo initia- and evolution: Geological Journal of China Univer- A.S., Oliver, G.J.H., and Zaw, K., 2014, Large rivers tion: The Journal of Geology, v. 121, p. 425–444, doi: sities, v. 11, p. 281–290 [in Chinese with English and orogens: The evolution of the Yarlung Tsangpo– 10.1086/670722. abstract]. Irrawaddy system and the eastern Himalayan syntaxis: Wang, P., Scherler, D., Liu-Zheng, J., Mey, J., Avouac, J.‑P., Murphy, M., 2007, Isotopic characteristics of the Gurla Gondwana Research, v. 26, p. 112–121, doi:10 .1016/j Zhang, Y., and Shi, D., 2014, Tectonic control of Yar- Mandhata metamorphic core complex: Implications .gr.2013.07.002. lung Tsangpo Gorge revealed by a buried canyon in for the architecture of the Himalayan orogeny: Geol- Rohrmann, A., Kapp, P., Carrapa, B., Reiners, P.W., Guynn, southern Tibet: Science, v. 346, p. 978–981, doi:10 ogy, v. 35, p. 983–986, doi:10.1130/G23774A.1. J., Ding, L., and Heizler, M., 2012, Thermochrono- .1126/science.1259041. Murphy, M.A., and Yin, A., 2003, Structural evolution and logic evidence for plateau formation in central Tibet Wei-Qiang, J., Fu-Yuan, W., Sun-Lin, C., Xuan-Ce, W., sequence of thrusting in the Tethyan fold-thrust belt by 45 Ma: Geology, v. 40, p. 187–190, doi:10 .1130 Chuan-Zhou, L., Qiu-Li, L., Zhi-Chao, L., Xiao-Chi, and Indus-Yalu suture zone, southwest Tibet: Geologi- /G32530.1. L., and Jian-Gang, W., 2016, Eocene Neo-Tethyan slab cal Society of America Bulletin, v. 115, p. 21–34, doi: Sanchez, V.I., Murphy, M.A., Robinson, A.C., Lapen, T.J., breakoff constrained by 45 Ma oceanic island basalt– 10.1130/0016-7606(2003)115<0021:SEASOT>2.0 and Heizler, M.T., 2013, Tectonic evolution of the type magmatism in southern Tibet: Geology, v. 44, .CO;2. India-Asia suture zone since middle Eocene time, no. 4, p. 283–286, doi:10.1130/G37612.1. Murphy, M.A., Yin, A., Kapp, P., Harrison, T.M., Manning, Lopukangri area, south-central Tibet: Journal of Asian Wen, D.-R., Liu, D., Chung, S.-L., Chu, M.F., Ji, J., Zhangd, C.E., Ryerson, F.J., Ding, L., and Guo, J., 2002, Struc- Earth Sciences, v. 62, p. 205–220, doi:10.1016/j.jseaes Q., Song, B., Lee, T.Y., Yeh, M.-W., and Lo, C.-H., tural and thermal evolution of the Gurla Mandhata .2012.09.004. 2008, Zircon SHRIMP U-Pb ages of the Gangdese detachment system, southwest Tibet: Implications Saylor, J.E., Knowles, J.N., Horton, B.K., Nie, J., and Mora, Batholith and implications for Neotethyan subduction for the eastward extent of the Karakoram fault sys- A., 2013, Mixing of source populations recorded in de- in southern Tibet: Chemical Geology, v. 252, no. 3–4, tem: Geological Society of America Bulletin, v. 114, trital zircon U-Pb age spectra of modern river sands: p. 191–201, doi:10.1016/j.chemgeo.2008.03.003. p. 428–447, doi:10.1130/0016-7606(2002)114<0428: The Journal of Geology, v. 121, p. 17–33, doi:10.1086 Wolf, R.A., Farley, K.A., and Silver, L.T., 1996, Helium dif- SEOTGM>2.0.CO;2. /668683. fusion and low-temperature thermochronometry of apa Murphy, M.A., Saylor, J.E., and Ding, L., 2009, Late Mio- Schärer, U., Xu, R.H., and Allègre, C.J., 1984, U-Pb geo- tite: Geochimica et Cosmochimica Acta, v. 60, no. 21, cene topographic inversion in southwest Tibet based chronology of Gangdese (Transhimalaya) plutonism p. 4231–4240, doi:10.1016/S0016-7037(96)00192-5. on integrated paleoelevation reconstructions and struc- in the Lhasa-Xigaze region Tibet: Earth and Planetary Wu, F.-Y., Ji, W.Q., Wang, J.-G., Liu, C.-Z., Chung, S.-L., tural history: Earth and Planetary Science Letters, Science Letters, v. 69, p. 311–320, doi:10 .1016/0012 and Clift, P.D., 2014, Zircon U-Pb and Hf isotopic v. 282, p. 1–9, doi:10.1016/j.epsl.2009.01.006. -821X(84)90190-0. constraints on the onset time of India-Asia collision: Murphy, M.A., Sanchez, V., and Taylor, M.H., 2010, Syn- Schärer, U., Xu, R.-H., and Allègre, C.J., 1986, U-(Th) American Journal of Science, v. 314, p. 548–579, doi: collisional extension along the India-Asia suture Pb systematics and ages of Himalayan leucogran- 10.2475/02.2014.04. zone, south-central Tibet: Implications for crustal ites, south Tibet: Earth and Planetary Science Let- Yin, A., Harrison, T.M., Murphy, M., Grove, M., Nie, S., deformation of Tibet: Earth and Planetary Science ters, v. 77, no. 1, p. 35–48, doi:10.1016/0012-821X Ryerson, F., Feng, W.X., and Le, C.Z., 1999, Tertiary Letters, v. 290, p. 233–243, doi:10.1016/j.epsl.2009 (86)90130-5. deformation history of southeastern and southwestern .11.046. Schmidt, J.L., Zeitler, P.K., Pazzaglia, K.J., Tremblay, M.M., Tibet during the Indo-Asian collision: Geological Soci- Najman, Y., Appel, E., Boudagher–Fadel, M., Bown, P., Shuster, D.L., and Fox, M., 2015, Knickpoint evolution ety of America Bulletin, v. 111, no. 11, p. 1644–1664, Carter, A., Garzanti, E., Godin, L., Han, J., Liebke, U., on the Yarlung River: Evidence for late Cenozoic uplift doi:10.1130/0016-7606(1999)111<1644:TDHOSA>2 Oliver, G., Parrish, P., and Vezzoli, G., 2010, Timing of the southeastern Tibetan Plateau margin: Earth and .3.CO;2. of India-Asia collision: Geological, biostratigraphic, Planetary Science Letters, v. 430, p. 448–457, doi:10 Yuan, W., Deng, J., Zheng, Q., Dong, J., Bao, Z., Eizen- and palaeomagnetic constraints: Journal of Geo- .1016/j.epsl.2015.08.041. hoefer, P.R., Xu, X., and Huang, Z., 2009, Apatite fis- physical Research, v. 115, p. B12416, doi:10.1029 Seward, D., and Burg, J.P., 2008, Growth of the Namche sion track constraints on the Neogene tectonothermal /2010JB007673. Barwa syntaxis and associated evolution of the Tsangpo history of Nimu area, southern Gangdese terrane, Tibet Nomade, S., Renne, P.R., Mo, X., Zhao, Z., and Zhou, S., Gorge: Constraints from structural and thermo Plateau: The Island Arc, v. 18, p. 488–495, doi:10 .1111 2004, Miocene volcanism in the Lhasa block, Tibet: chronological data: Tectonophysics, v. 451, p. 282–289, /j.1440-1738.2009.00669.x. Spatial trends and geodynamic implications: Earth and doi:10 .1016 /j .tecto .2007 .11 .057 . Zeitler, P.K., Meltzer, A.S., Brown, L., Kidd, W.S.F., and Planetary Science Letters, v. 221, p. 227–243, doi:10 Sinclair, H.D., and Jaffey, N., 2001, Sedimentology of the Lim, C., 2014, Tectonics and topographic evolution .1016/S0012-821X(04)00072-X. Indus Group, Ladakh, northern India: Implications of Namche Barwa and the easternmost Lhasa block, Orme, D.A., Carrapa, B., and Kapp, P., 2014, Sedimentol- for the timing of initiation of the paleo–-Indus River: Tibet, in Nie, J., Horton, B.K., and Hoke, G.D., Toward ogy, provenance and geochronology of the Upper Cre- Journal of the Geological Society of London, v. 158, an Improved Understanding of Uplift Mechanisms and taceous–Lower Eocene western Xigaze forearc basin, p. 151–162, doi:10.1144/jgs.158.1.151. the Elevation History of the Tibetan Plateau: Geologi- southern Tibet: Basin Research, v. 27, no. 4, p. 1–25, Spicer, R.A., Harris, N.B.W., and Widdowson, M., 2003, cal Society of America Special Paper 507, p. 23–58, doi:10.1111/bre.12080. Constant elevation of southern Tibet over the past 15 doi:10.1130/2014.2507(02). Pan, G., Ding, J., Yao, D., and Wang, L., 2004, Geological million years: Nature, v. 421, p. 622–624, doi:10 .1038 Zhang, J.Y., Yin, A., Liu, W.C., Wu, F.Y., Lin, D., and Grove, Map of the Qinghai-Xizang (Tibet) Plateau and Adja- /nature01356. M., 2012, Coupled U-Pb dating and Hf isotopic analy- cent Areas with Guidebook: Chengdu, Chengdu Carto- Tobgay, T., Long, S., McQuarrie, N., Ducea, M.N., and sis of detrital zircon of modern river sand from the Yalu graphic Publishing House, scale 1:1,500,000. Gehrels, G., 2010, Using isotopic and chronologic data River (Yarlung Tsangpo) drainage system in south- Pan, Y., Copeland, P., Roden, M.K., Kidd, W.S.F., and Har- to fingerprint strata: Challenges and benefits of vari- ern Tibet: Constraints on the transport processes and rison, M.T., 1993, Thermal and unroofing history of able sources to tectonic interpretations, the Paro For- evolution of Himalayan rivers: Geological Society of the Lhasa area, southern Tibet—Evidence from apatite mation, Bhutan Himalaya: Tectonics, v. 29, p. TC6023, America Bulletin, v. 124, no. 9–10, p. 1449–1473, doi: fission track thermochronology: International Jour- doi:10.1029/2009TC002637. 10.1130/B30592.1. nal of Radiation Applications and Instrumentation, Tremblay, M.M., Fox, M., Schmidt, J.L., Tripathy-Langa, Nuclear Tracks and Radiation Measurements, v. 21, A., Wielickid, M.M., Harrison, M.T., Zeitler, P.K., and Science Editor: Bradley S. Singer p. 543–554. Shuster, D.L., 2015, Erosion in southern Tibet shut Associate Editor: Stefano Mazzoli Pullen, A., Kapp, P., DeCelles, P.G., Gehrels, G.E., and Ding, down at ~10 Ma due to enhanced rock uplift within L., 2011, Cenozoic anatexis and exhumation of Tethyan the Himalaya: Proceedings of the National Acad- Manuscript Received 2 June 2016 Revised Manuscript Received 30 September 2016 sequence rocks in the Xiao Gurla Range, southwest emy of Sciences of the United States of America, Manuscript Accepted 17 November 2016 Tibet: Tectonophysics, v. 501, p. 28–40, doi:10.1016/j v. 112, no. 39, p. 12,030–12,035, doi:10.1073/pnas .tecto.2011.01.008. .1515652112. Printed in the USA

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