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82°E 84°E 86°E 88°E 90°E 92°E 94°E 96°E 98°E

Internal Drainage

Three Rivers
32°N Indus

Sutlej

30°N
S1

Yarlung

28°N

T.chron System
Apatite (U-Th)/He
Apatite FT Elevation (km)
Zircon (U-Th)/He
Zircon FT 1 2 3 4 5 6 GPS Station
100 km
West East
400 200 0 200 400
Distance from Center Along Small Circles (km)
Figure 1. Shuttle Radar Topography Mission 90-m color shaded elevation map. Thermochronology data (Laskowski et al., 2018; Thiede and Ehlers, 2013) in
Figure 4 are shown with thermochronometer type. Color scale bar indicates east-west position from swath profile in Figure 4. Open symbols—location in
the hanging wall of a normal fault; white circles—GPS stations from Liang et al. (2013); dashed outlines—areas sampled for Figure 4; solid lines mark topog-
raphy and precipitation in Figure 4A. Thick dotted lines mark centerline for distance measured along small circles in Figure 4A. Individual colored swaths
sample dominant rivers in Figure 4B. Thick black lines are rivers and catchment areas for Sutlej, Indus, Yarlung, and Three Rivers, and zone of Internal
Drainage. Red box shows location of Figure 2. Red symbol shows location of Figure S1 [see text footnote 1].

primarily by understanding the exhumation –directed extension are discussed by the initiation age for one Gangdese Rift is ca.
history of the footwalls of north-striking Blisniuk et al. (2001), Kali et al. (2010), 16 Ma using zircon U-Th/He data (Burke et
normal faults. One example is the northern Langille et al. (2010), Yin and Taylor (2011), al., 2021). The Gangdese Rifts become more
Lunggar Rift that locally has up to 25 km of Sundell et al. (2013), and Styron et al. (2015). northwest striking in the western Lhasa ter-
top-to-the-east displacement and initiated Here we focus on the Gangdese Range of rane, and rift-bounding faults are more linear
in the middle Miocene with uniformly low southern Tibet that locally has nine active in map pattern with the westernmost rifts,
slip rates (<1 mm/yr) (Sundell et al., 2013). NNW-striking normal faults we refer to as suggesting an increase in oblique (i.e., dex-
In the late Miocene, slip rates of rift bound- the Gangdese Rifts, located north of the tral strike-slip) motion (see Fig. S1 in the
ing faults increased up to 5 mm/yr begin- IYS zone and west of Tangra Yum Co (Figs. Supplementary Material ). The Gangdese
1
ning in the southern Lunggar Rift, and 1 and 3). A potential mechanism for their Rifts cut several regional structures, includ-
accelerated northward, perhaps in response formation is discussed in Yin (2000). ing the north-directed Great Counter Thrust
to the northward underthrusting of India (GCT) and the south-directed Gangdese
(Sundell et al., 2013; Styron et al., 2015). GEOLOGY OF THE GANGDESE Thrust (GT) (Yin et al., 1994) (Figs. 1 and 2).
Rift-bounding normal faults in the Yadong RANGE Crosscutting relationships—including the
Gulu section of the Nyainqentanglha initi- Locally, elevations for the Gangdese Range timing of Kailas Formation deposition
ated at ca. 8 Ma based on results using exceed 7500 m, forming the southern bound- between 26 and 23 Ma (Leary et al., 2016),
40 Ar/ Ar thermochronology (Harrison et ary of the internally drained region of the the timing of slip across north-striking nor-
39
al., 1992). In southernmost Tibet near Tibetan plateau (Figs. 1 and 5). The Gangdese mal faults that cut the GCT (Sundell et al.,
Xigaze, a north-trending dike was dated at Rifts are active structures and are shorter in 2013), and the age of a crosscutting pluton
18 Ma and is thought to represent the time length than the seven more well-studied lon- near the town of Lazi at ca. 10 Ma (Laskowski
when east-directed extension initiated (Yin ger rifts cutting the entire Lhasa terrane (e.g., et al., 2018)—are consistent with the GCT
et al., 1994), but whether diking represents a Tangra Yum Co Rift)—along-strike lengths being active between 23 and 16 Ma.
regional extensional event is debated. The of the Gangdese Rifts are between 30 and 50 The south-directed GT (e.g., Yin et al.,
dynamic causes for the development of the km. Detailed studies of the Gangdese Rifts 1994) carries plutonic rocks across a north-
active structures accommodating east-west are lacking, but a recent study concludes that dipping shear zone. Ar/ Ar thermochro-
40
39
1 Supplemental Material. Description of the methodology for projecting various data types onto the swath profiles in Fig. 4 along with Google Earth imagery for evidence
of an increase in the strike-slip component of faulting along the Gangdese Rifts in western Tibet. Go to https://doi.org/10.1130/GSAT.S.14681367 to access the supple-
mental material; contact editing@geosociety.org with any questions.
www.geosociety.org/gsatoday 5