This document is downloaded from DR‑NTU (https://dr.ntu.edu.sg) Nanyang Technological University, Singapore. The Pingding segment of the Altyn Tagh Fault (91°E) : holocene slip‑rate determination from cosmogenic radionuclide dating of offset fluvial terraces Lasserre, C.; Xu, X.; Ryerson, Frederick J.; Finkel, Robert C.; Mériaux, Anne‑Sophie; Van der Woerd, Jérôme; Tapponnier, Paul 2012 Mériaux, A.‑S., Van der Woerd, J., Tapponnier, P., Ryerson, F. J., Finkel, R. C., Lasserre, C.,& Xu, X. (2012). The Pingding segment of the Altyn Tagh Fault (91°E): Holocene slip‑rate determination from cosmogenic radionuclide dating of offset fluvial terraces. Journal of geophysical research : solid earth, 117(B9). https://hdl.handle.net/10356/99204 https://doi.org/10.1029/2012JB009289 © 2012 American Geophysical Union. This paper was published in Journal of geophysical research : solid Earth and is made available as an electronic reprint (preprint) with permission of American Geophysical Union. The paper can be found at the following official OpenURL: [http://dx.doi.org/10.1029/2012JB009289]. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law. Downloaded on 04 Oct 2021 07:42:33 SGT JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 117, B09406, doi:10.1029/2012JB009289, 2012 The Pingding segment of the Altyn Tagh Fault (91E): Holocene slip-rate determination from cosmogenic radionuclide dating of offset fluvial terraces A.-S. Mériaux,1 J. Van der Woerd,2 P. Tapponnier,3,4 F. J. Ryerson,5 R. C. Finkel,6 C. Lasserre,7 and X. Xu8 Received 6 March 2012; revised 1 August 2012; accepted 10 August 2012; published 25 September 2012. [1] Morphochronologic slip-rates on the Altyn Tagh Fault (ATF) along the southern front of the Pingding Shan at 90.5E are determined by cosmogenic radionuclide (CRN) dating of seven offset terraces at two sites. The terraces are defined based upon morphology, elevation and dating, together with fieldwork and high-resolution satellite analysis. The majority of the CRN model ages fall within narrow ranges (<2 ka) on the four main terraces (T1, T2, T3 and T3′), and allow a detailed terrace chronology. Bounds on the terrace ages and offsets of 5 independent terraces yield consistent slip-rate estimates. The long-term slip-rate of 13.9 Æ 1.1 mm/yr is defined at the 95% confidence level, as the joint rate probability distribution of the rate derived from each independent terrace. It falls within the bounds of all the rates defined on the central Altyn Tagh Fault between the Cherchen He (86.4E) and Akato Tagh (88E) sites. This rate is 10 mm/yr less than the upper rate determined near Tura at 87E, in keeping with the inference of an eastward decreasing rate due to progressive loss of slip to thrusts branching off the fault southwards but it is greater than the 9 Æ 4 mm/yr rate determined at 90E by GPS surveys and other geodetic short-term rates defined elsewhere along the ATF. Whether such disparate rates will ultimately be reconciled by a better understanding of fault mechanics, resolved transient deformations during the seismic cycle or by more accurate measurements made with either approach remains an important issue. Citation: Mériaux, A.-S., J. Van der Woerd, P. Tapponnier, F. J. Ryerson, R. C. Finkel, C. Lasserre, and X. Xu (2012), The Pingding segment of the Altyn Tagh Fault (91E): Holocene slip-rate determination from cosmogenic radionuclide dating of offset fluvial terraces, J. Geophys. Res., 117, B09406, doi:10.1029/2012JB009289. 1. Introduction (1000 m a.s.l.), the Altyn Tagh Fault (ATF) is usually considered to be the largest active strike-slip fault of Eurasia. [2] Given its great length (1800 km between 78 E and Slip-rate and seismic behavior of the fault are keys to the 97E) and topographic prominence as a limit between the present-day kinematics of collision tectonics in Asia, and Tibetan highlands (3000–5000 m a.s.l.) and the Tarim basin viewed as an important factor in evaluating whether conti- nental deformation can be approximated by block tectonics or not, a topic that remains the subject of debate [Avouac et al., 1993; Calais et al.,2006;Dayem et al.,2009;England and 1 Houseman,1986;England and Molnar, 1997; Hilley et al., School of Geography, Politics and Sociology, Newcastle University, 2009; Holt et al.,2000;Loveless and Meade,2011;Meade, Newcastle upon Tyne, UK. 2IPGS-EOST, UMR 7516, CNRS, Université de Strasbourg, Strasbourg, 2007; Peltzer and Saucier, 1996; Thatcher,2007;Vergnolle France. et al., 2007]. Recent slip-rate estimates based on comple- 3EOS, Nanyang Technological University, Singapore. mentary and/or similar techniques currently yield disparate 4 Institut de Physique du Globe de Paris, UMR 7154, CNRS, Paris, results along the Altyn Tagh Fault. Near Tura (86.4E) France. 5Lawrence Livermore National Laboratory, Livermore, California, USA. radiocarbon and CRN dating of offset features at two sites - 6Earth and Planetary Science Department, University of California, Cherchen He and Sulamu Tagh - yields left-lateral slip rate of Berkeley, California, USA. 27 Æ 7 mm/yr [Mériaux et al., 2004]. Reinterpretation of the 7Maison des Géosciences, ISTerre, Grenoble, France. Æ 8 Cherchen He site by Cowgill [2007] yield a rate of 9.4 Central Earthquake Administration, Beijing, China. 2.3 mm/y. Recently, studies by Gold et al. [2009, 2011] on Corresponding author: A.-S. Mériaux, School of Geography, Politics the same Cherchen fault segment yield estimates from 7 to and Sociology, Newcastle University, Claremont Road, Newcastle upon 17 mm/yr for the late Holocene at Kelutelage (86.67E) and Tyne NE1 7RU, UK. ([email protected]) Tuzidun (86.72E). About 100 km further East at Yukuang ©2012. American Geophysical Union. All Rights Reserved. (87.87 E), Keke Qiapu (88.12 E) and Yuemake (88.51 E), 0148-0227/12/2012JB009289 B09406 1of26 B09406 MÉRIAUX ET AL.: THE PINGDING SHAN SEGMENT OF THE ATF B09406 Figure 1. Map of topography and active faulting along Altyn Tagh Fault (ATF) system between 86 and 94E. Mapping is based on field observations complemented by satellite imagery analysis and earlier work [e.g., Cowgill et al., 2004a, 2004b; Mériaux,2002;Meyer et al., 1998; Peltzer et al., 1989; Tapponnier and Molnar,1977;Tapponnier et al., 2001]. SATF: South Altyn Tagh Fault, NATF: North Altyn Tagh Fault. Grey and purple dots are GPS stations from Bendick et al. [2000] and Wang et al. [2001], respectively. White dots are earthquakes from USGS/NEIC (PDE), with Harvard focal mechanisms for Mb ≥ 6. Thick green lines indicate published morphological sites at Cherchen He (C [Mériaux et al., 2004; Cowgill, 2007]), Kelutelage (K [Gold et al., 2011]), Tuzidun (T [Gold et al., 2009]), Sulamu Tagh (S [Mériaux et al., 2004]), Yukuang (Yu [Gold et al., 2011]), Keke Qiapu (Ke [Gold et al., 2011]) and Yuemake (Y [Cowgill et al., 2009]). Thick red lines indicate trench locations of Washburn et al. [2003, 2001] (Kulesayi at 90EandXorKolat 91.25E). A: Annamba, T: Tura, H: Huatugou and M: Mangnai Zhen. QTF: Qiman Tagh Fault [Tapponnier and Molnar, 1977], also named Kadzi Fault in Cowgill et al. [2004a]. HMA: Huatugou- Mangnai Anticlinorium. PPU and APU are Pingding Push-Up and Altyn Push-Up (gray lines), respec- tively. Lakes are in dark blue and salt flats are in pale blue. Studied sites are located along the main branch of the ATF in the Pingding Shan area between 90Eand91E. Dashed rectangle outlines area of Figure 2. studies lead to estimates of 2–17.5 mm/yr, 1.5–17.8 mm/yr et al.,2004;Van der Woerd et al., 2006]. Indeed, GPS and [Gold and Cowgill,2011]and8.5–15 mm/yr [Cowgill et al., InSAR measurements yield far-field, decadal averages, 2009], respectively, on the main strand of the Altyn Tagh while morphochronology and trenching address the near- fault between the Sulamu Tagh and Akato Tagh restraining field, centennial and millennial behavior of the fault. In bends. At 94.3E, on the eastern Aksay segment of the addition, the results of some studies [Ge et al., 1992; north Altyn Tagh Fault (NATF), a slip-rate of 18 Æ 4mm/ Washburn et al., 2001] are constrained by very few absolute yr [Mériaux et al., 2004] has been estimated. Three-epoch- ages. Other morphological studies have used only one dated campaign GPS results along a profile crossing the fault at offset riser to derive the slip-rate [Cowgill et al.,2009;Gold Mangnai Zhen (90E) imply a rate of 9 Æ 5 mm/yr [Bendick et al., 2009], that do not allow the derivation of an averaged et al.,2000;Wallace et al., 2004], compatible with broader long-term slip-rate or to test the variability of the slip rate based, regional campaign GPS studies (9 Æ 2mm/yr[Shen over time and space. As importantly however, the rather et al., 2001]) (Figure 1). Paleoseismic interpretations of complex geometry of the ATF fault system, related to its trenches at Kulesayi (89.9E) and Xorkol (91.25E) propagation toward the NE, along with the growth of the suggest a record of only two to three earthquakes with Mw Tibet plateau [Métivier et al., 1998; Meyer et al., 1998; of7to7.6inthelast2–3 ka, consistent with a slip-rate of Tapponnier et al., 2001], requires that the three different about 10 mm/yr [Washburn et al., 2003; Washburn et al., types of approaches be applied to the same segment of the 2001] (Figure 1).