Quaternary extension in southern Tibet: Field observations and tectonic implications

Armijo, Rolando; Tapponnier, Paul; Mercier, J. L.; Han, Tao

doi:10.1029/jb091ib14p13803

Cited by 801 publications

(691 citation statements)

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“…The stress field for these conjugate sets of approximately N-S trending active faults is consistent with widespread observations throughout southern Tibet and the north Himalaya of young E-W expansion (e.g., the graben system of Armijo et al [1986]). We speculate that the occurrence of these strike-slip faults mark an important transition in the geodynamics between the western and the eastern Himalaya, respectively, and strike-slip faulting might be explained by an increasing degree of oblique subduction toward the Eastern Himalaya Syntax as suggested by Drukpa et al [2006].…”

Section: Interpretation Of Deformation Features In the Raphstreng Andsupporting

confidence: 84%

“…The first is the STDS [Burg and Chen, 1984;Burchfiel et al, 1992], a system of shallowly north dipping normal faults, which acted contemporaneously with the Main Central Thrust during the Miocene southward extrusion of the HHC. The second type comprises ESE-WNW directed extension of the Tibetan Plateau and resulted in both normal faulting (N-S trending rift systems) and NW-SE and NE-SW oriented conjugate strike-slip faulting (Figure 1) [Armijo et al, 1986[Armijo et al, , 1989Fielding et al, 1994;Cogan et al, 1998]. Seismic moment tensors for earthquakes within northern and central Tibet suggest that ESE-WNW extensional strain dominates active deformation of the plateau interior, [e.g., Molnar and LyonCaen, 1989;Langin et al, 2003, and references cited therein] which causes an eastward movement of crustal material out of India's path.…”

Section: Introductionmentioning

confidence: 99%

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Active tectonics in Eastern Lunana (NW Bhutan): Implications for the seismic and glacial hazard potential of the Bhutan Himalaya

Meyer

Wiesmayr

Brauner³

et al. 2006

Tectonics

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Paleoseismological investigations, brittle fault analysis, and paleostrain calculations combined with the interpretation of satellite imagery and flood wave modeling were used to investigate the seismic and associated glacial hazard potential in Eastern Lunana, a remote area in NW Bhutan. Seismically induced liquefaction features, cracked pebbles, and a surface rupture of about 6.8 km length constrain the occurrence of M ≥ 6 earthquakes within this high‐altitude periglacial environment, which are the strongest earthquakes ever been reported for the Kingdom of Bhutan. Seismicity occurs along conjugate sets of faults trending NE‐SW to NNW‐SSE by strike‐slip and normal faulting mechanism indicating E‐W extension and N‐S shortening. The strain field for these conjugate sets of active faults is consistent with widespread observations of young E‐W expansion throughout southern Tibet and the north Himalaya. We expect, however, that N‐S trending active strike‐slip faults may even reach much farther to the south, at least into southern Bhutan. Numerous glacial lakes exist in the investigation area, and today more than 100 × 106 m3 of water are stored in moraine‐dammed and supraglacial lakes which are crosscut by active faults. Strong earthquakes may trigger glacial lake outburst floods, and the impact of such flash floods may be worst 80 km downstream where the valley is broad and densely populated. Consequently, tectonic models of active deformation have to be closely linked with glacial hazard evaluation and require rethinking and modification.

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Section: Interpretation Of Deformation Features In the Raphstreng Andsupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Active tectonics in Eastern Lunana (NW Bhutan): Implications for the seismic and glacial hazard potential of the Bhutan Himalaya

Meyer

Wiesmayr

Brauner³

et al. 2006

Tectonics

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“…Although simple geodynamic models linking surface uplift, potential energy increase in the lithosphere, extension, and volcanism are conceptually compelling, a temporal and genetic link between extension, volcanism, and surface uplift remains to be demonstrated. Furthermore, the cause of E-W extension on the high plateau is a matter of active debate; it may be related to a number of processes including strain partitioning during oblique convergence [McCaf-frey and Nabelek, 1998], spreading of the Himalayan arc [Seeber and Pecher, 1998], eastward extrusion of Tibet [Armijo et al, 1986], or thickening of crust with a depth-dependent rheology [Royden, 1996].…”

Section: Introductionmentioning

confidence: 99%

Late Cenozoic evolution of the eastern margin of the Tibetan Plateau: Inferences from⁴⁰Ar/³⁹Ar and (U‐Th)/He thermochronology

et al. 2002

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[1] High topography in central Asia is perhaps the most fundamental expression of the Cenozoic Indo-Asian collision, yet an understanding of the timing and rates of development of the Tibetan Plateau remains elusive. Here we investigate the Cenozoic thermal histories of rocks along the eastern margin of the plateau adjacent to the Sichuan Basin in an effort to determine when the steep topographic escarpment that characterizes this margin developed. Temperaturetime paths inferred from 40 Ar/ 39 Ar thermochronology of biotite, multiple diffusion domain modeling of alkali feldspar 40 Ar release spectra, and (U-Th)/He thermochronology of zircon and apatite imply that rocks at the present-day topographic front of the plateau underwent slow cooling (<1°C/m.y.) from Jurassic times until the late Miocene or early Pliocene. The regional extent and consistency of thermal histories during this time period suggest the presence of a stable thermal structure and imply that regional denudation rates were low (<0.1 mm/yr for nominal continental geotherms). Beginning in the late Miocene or early Pliocene, these samples experienced a pronounced cooling event (>30°-50°C/m.y.) coincident with exhumation from inferred depths of $8 -10 km, at denudation rates of 1 -2 mm/yr. Samples from the interior of the plateau continued to cool relatively slowly during the same time period ($3°C/m.y.), suggesting limited exhumation (1 -2 km). However, these samples record a slight increase in cooling rate (from <1 to $3°C/m.y.) at some time during the middle Tertiary; the tectonic significance of this change remains uncertain. Regardless, late Cenozoic denudation in this region appears to have been markedly heterogeneous, with the highest rates of exhumation focused at the topographic front of the plateau margin. We infer that the onset of rapid cooling at the plateau margin reflects the erosional response to the development of regionally significant topographic gradients between the plateau and the stable Sichuan Basin and thus marks the onset of deformation related to the development of the Tibetan Plateau in this region. The present margin of the plateau adjacent to and north of the Sichuan Basin is apparently no older than the late Miocene or early Pliocene ($5 -12 Ma).

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“…Landsat image interpretation, earthquake fault plane solutions, and a limited number of field studies indicate that the ongoing convergence between India and Siberia (50-55 mm/yr [De Mets et al, 1990]) is absorbed both by crustal thickening and strike-slip extrusion [e.g., Molnar and Tapponnier, 1975;Tapponnier and Molnar, 1977;Molnar and Deng, 1984;Peltzer et al, 1985Armijo et al, 1986]. In the western part of the collision zone, eastward extrusion of Tibet, chiefly between the left-lateral Altyn Tagh and right-lateral Karakorum faults, appears to account for =30% of that convergence Peltzer eta/., 1989;Molnar and Lyon-Caen, 1989], with the rest being absorbed by crustal thickening south and north of these faults, in the Himalayas and in central Asia.…”

Section: Introductionmentioning

confidence: 99%

Active thrusting and folding along the northern Tien Shan and Late Cenozoic rotation of the Tarim relative to Dzungaria and Kazakhstan

Avouac¹,

Tapponnier²,

Bai³

et al. 1993

J. Geophys. Res.

681

604

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We have studied geometries and rates of late Cenozoic thrust faulting and folding along the northern piedmont of the Tien Shan mountain belt, West of Urumqi, where the M=8.3 Manas earthquake occurred on December 23, 1906. The northern range of the Tien Shan, rising above 5000 m, overthrusts a flexural foredeep, filled with up to II ,000 m of sediment, of the Dzungarian basement. Our fieldwork reveals that the active thrust reaches the surface 30 km north of the range front, within a 200-km-long zone of NeogeneQuaternary anticlines. Fault scarps are clearest across inset terraces within narrow valleys incised through the anticlines by large rivers flowing down from the range. In all the valleys, the scarps offset vertically the highest terrace surface by the same amount (10.2±0.7 m). Inferring an early Holocene age (10±2 kyr) for this terrace, which is continuous with the largest recent fans of the piedmont, yields a rate of vertical throw of 1.0±0.3mm/yr on the main active thrust at the surface. A quantitative morphological analysis of the degradation of terrace edf,es that are offset by the thrust corroborates such a rate and yields a mass diffusivity of 5.5±2.5 m /kyr. A rather fresh surface scarp, 0.8±0.15 m high, that is unlikely to result from shallow earthquakes with 6 < M < 7 in the last 230 years, is visible at the extremities of the main fold zone. We associate this scarp with the 1906 Manas earthquake and infer that a structure comprising a deep basement ramp under the range, gently dipping flats in the foreland, and shallow ramps responsible for the formation of the active, fault propagation anticlines could have been activated by that earthquake. If so, the return period of a 1906 type event would be 850 ± 380 years. The small size of the scarp for an earthquake of this magnitude suggests that a large fraction of the slip at depth ( ""2/3) is taken up by incremental folding near the surface. Comparable earthquakes might activate flat detachments and ramp anticlines at a distance from the front of other rising Quaternary ranges such as the San Gabriel mountains in California or the Mont Blanc-Aar massifs in the Alps. We _,:stimate the finite Cenozoic shortening of the folded Dzungarian sediments to be of the order of 30 km and the Cenozoic shortening rate to have been 3 ± 1.5 mrnlyr. Assuming comparable shortening along the Tarim piedmont and minor additional active thrusting within the mountain belt, we infer the rate of shortening across the Tien Shan to be at least 6±3 mm/yr at the longitude of Manas (""85.5°E). A total shortening of 125±30 km is estimated from crustal thickening, assuming local Airy isostatic equilibrium. Under the same assumption, serial N-S sections imply that Cenozoic shortening across the belt increases westwards to 203±50 km at the longitude of Kashgar ( ""76°E), as reflected by the westward increase of the width of the belt. This strain gradient implies a clockwise rotation of Tarim relative to Dzungaria and Kazakhstan of 7 ± 2.5 • around a pole located near the eastern extr...

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Quaternary extension in southern Tibet: Field observations and tectonic implications

Abstract: We summarize evidence for Quaternary and active faulting collected in the field during three

Cited by 801 publications

References 48 publications

Active tectonics in Eastern Lunana (NW Bhutan): Implications for the seismic and glacial hazard potential of the Bhutan Himalaya

Active tectonics in Eastern Lunana (NW Bhutan): Implications for the seismic and glacial hazard potential of the Bhutan Himalaya

Late Cenozoic evolution of the eastern margin of the Tibetan Plateau: Inferences from⁴⁰Ar/³⁹Ar and (U‐Th)/He thermochronology

Active thrusting and folding along the northern Tien Shan and Late Cenozoic rotation of the Tarim relative to Dzungaria and Kazakhstan

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Quaternary extension in southern Tibet: Field observations and tectonic implications

Abstract: We summarize evidence for Quaternary and active faulting collected in the field during three

Cited by 801 publications

References 48 publications

Active tectonics in Eastern Lunana (NW Bhutan): Implications for the seismic and glacial hazard potential of the Bhutan Himalaya

Active tectonics in Eastern Lunana (NW Bhutan): Implications for the seismic and glacial hazard potential of the Bhutan Himalaya

Late Cenozoic evolution of the eastern margin of the Tibetan Plateau: Inferences from40Ar/39Ar and (U‐Th)/He thermochronology

Active thrusting and folding along the northern Tien Shan and Late Cenozoic rotation of the Tarim relative to Dzungaria and Kazakhstan

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Late Cenozoic evolution of the eastern margin of the Tibetan Plateau: Inferences from⁴⁰Ar/³⁹Ar and (U‐Th)/He thermochronology