Left-lateral Altyn Tagh Research Articles

The seismicity in the middle section of the Altyn Tagh Fault system revealed by a dense nodal seismic array

The left-lateral Altyn Tagh Fault (ATF) system is the northern boundary of the Qinghai-Xizang Plateau, separating the Tarim Basin and the Qaidam Basin. The middle section of ATF has not recorded any large earthquakes since 1598 AD, so the potential seismic hazard is unclear. We develope an earthquake catalog using continuous waveform data recorded by the Tarim-Altyn-Qaidam dense nodal seismic array from September 17 to November 23, 2021 in the middle section of ATF. With the machine learning-based picker, phase association, location, match and locate workflow, we detecte 233 earthquakes with ML -1-3, far more than 6 earthquakes in the routine catalog. Combining with focal mechanism solutions and the local fault structure, we find that seismic events are clustered along the ATF with strike-slip focal mechanisms and on the southern secondary faults with thrusting focal mechanisms. This overall seismic activity in the middle section of the ATF might be due to the northeastward transpressional motion of the Qinghai-Xizang Plateau block at the western margin of the Qaidam Basin.

Late Quaternary right-lateral slip rates of faults adjacent to the lake Qinghai, northeastern margin of the Tibetan Plateau

By combining terrace riser offsets with terrace ages dated by 14 C, optically stimulated luminescence (OSL), and 10 Be techniques, we determine average slip rates of 1.1 ± 0.3 mm/yr and 1.2 ± 0.4 mm/yr for the Elashan and Riyueshan faults, two north-northwest–trending, right-lateral, strike-slip faults west and east of the lake Qinghai in the northeastern margin of the Tibetan Plateau. These faults are conjugate to the major easterly trending, left-lateral Altyn Tagh, Haiyuan-Qilianshan, and Kunlun faults, and they contribute to the subdivision of the region between the Haiyuan-Qilianshan and Kunlun faults into small blocks tens to ∼100 km in dimension. The relatively low slip rates in this region reflect distributed deformation. The total right-lateral offsets of geological contacts are ∼9–12 km along the Elashan fault and ∼11–12 km for the northern segment of the Riyueshan fault. If long-term slip rates were constant during late Cenozoic time, dates of initiation of dextral movement would be 9 or 10 ± 3 Ma for the two strike-slip faults, concurrent with onsets or acceleration of tectonic deformation in Cenozoic basins nearby. Our study highlights a stage of tectonic deformation in the northeastern margin of the Tibetan Plateau beginning since ca. 8–12 Ma, tens of millions of years after the collision between India and Eurasia began.

Faulted terrace risers place new constraints on the late Quaternary slip rate for the central Altyn Tagh fault, northwest Tibet

The active, left-lateral Altyn Tagh fault defines the northwestern margin of the Tibetan Plateau in western China. To clarify late Quaternary temporal and spatial variations in slip rate along the central portion of this fault system (85°–90°E), we have more than doubled the number of dated offset markers along the central Altyn Tagh fault. In particular, we determined offset-age relations for seven left-laterally faulted terrace risers at three sites (Kelutelage, Yukuang, and Keke Qiapu) spanning a 140-km-long fault reach by integrating surficial geologic mapping, topographic surveys (total station and tripod–light detection and ranging [T-LiDAR]), and geochronology (radiocarbon dating of organic samples, 230 Th/U dating of pedogenic carbonate coatings on buried clasts, and terrestrial cosmogenic radionuclide exposure age dating applied to quartz-rich gravels). At Kelutelage, which is the westernmost site (37.72°N, 86.67°E), two faulted terrace risers are offset 58 ± 3 m and 48 ± 4 m, and formed at 6.2–6.1 ka and 5.9–3.7 ka, respectively. At the Yukuang site (38.00°N, 87.87°E), four faulted terrace risers are offset 92 ± 12 m, 68 ± 6 m, 55 ± 13 m, and 59 ± 9 m and formed at 24.2–9.5 ka, 6.4–5.0 ka, 5.1–3.9 ka, and 24.2–6.4 ka, respectively. At the easternmost site, Keke Qiapu (38.08°N, 88.12°E), a faulted terrace riser is offset 33 ± 6 m and has an age of 17.1–2.2 ka. The displacement-age relationships derived from these markers can be satisfied by an approximately uniform slip rate of 8– 12 mm/yr. However, additional analysis is required to test how much temporal variability in slip rate is permitted by this data set.

Eastward migration of the Qaidam basin and its implications for Cenozoic evolution of the Altyn Tagh fault and associated river systems

Research Article| March 01, 2006 Eastward migration of the Qaidam basin and its implications for Cenozoic evolution of the Altyn Tagh fault and associated river systems Erchie Wang; Erchie Wang 1Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, People's Republic of China and Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100029, People's Republic of China Search for other works by this author on: GSW Google Scholar Feng-Yin Xu; Feng-Yin Xu 2Qinghai Petroleum Sub-corporation of PetroChina Company Limited, Dunhuang 736202, People's Republic of China Search for other works by this author on: GSW Google Scholar Jian-Xun Zhou; Jian-Xun Zhou 3Earth Science Department, University of Petroleum, Beijing 102249, People's Republic of China Search for other works by this author on: GSW Google Scholar Jinglin Wan; Jinglin Wan 4Laboratory of Neotectonic Chronology of Institute of Geology, China Seismological Bureau, Beijing 100029, People's Republic of China Search for other works by this author on: GSW Google Scholar B. Clark Burchfiel B. Clark Burchfiel 5Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2006) 118 (3-4): 349–365. https://doi.org/10.1130/B25778.1 Article history received: 14 Dec 2004 rev-recd: 27 Aug 2005 accepted: 01 Sep 2005 first online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Erchie Wang, Feng-Yin Xu, Jian-Xun Zhou, Jinglin Wan, B. Clark Burchfiel; Eastward migration of the Qaidam basin and its implications for Cenozoic evolution of the Altyn Tagh fault and associated river systems. GSA Bulletin 2006;; 118 (3-4): 349–365. doi: https://doi.org/10.1130/B25778.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Qaidam basin is the largest Cenozoic intermontane basin within the Tibetan plateau, bounded by the Qilian Shan range to the north, the East Kunlun range to the south, the Altyn Tagh range to the west, and the Ela Shan range to the east. Its deposits consist of nonmarine sedimentary rocks, with a maximum thickness exceeding 13,400 m. Modern sedimentation mainly takes place along the marginal areas of the basin, where alluvial fans are formed along a series of rivers that originate from the surrounding mountains. Nevertheless, drilling, sedimentary, and seismic data reveal that the depocenter of the basin during much of Cenozoic time was not developed as foreland basins of the Qilian Shan belt to the north and the East Kunlun belt to the south, but instead the depocenter was in the center of the western part of the basin and had a northwest-southeast trend that shifted eastward ∼380 km during Oligocene to Quaternary time. This indicates that most of the basin sediments were not derived from the surrounding mountain ranges. The results of the fission-track age dating reveal that the rapid uplift of the Yousha Shan anticline bounding the depocenter to the southwest initiated at ca. 31 Ma, indicating that the southeastward shift of the depocenter began at that time, yielding a migration rate for the depocenter of 10.2 mm/yr. The northwestern margin of the depocenter of the Qaidam basin lies to the east of the westward prolongation of the Qaidam basin, the Tula trough, a 300-km-long narrow trough flanked by the Altyn Tagh range along the Altyn Tagh strike-slip fault on the north and the East Kunlun thrust belt on the south. The sedimentary and deformational evidence from this region indicates that the Tula trough was formed as a syncline, along which a paleoriver flowed to the east into the Qaidam basin. To the southwest, this river valley merges with the trace of the Altyn Tagh fault. The latter and its westward continuation are interpreted to have extended to the northern margin of the Pamir folded belt north of the western syntaxis of the Himalaya. We propose that most of the sediments within the depocenter of the Qaidam basin were transported from the northern margin of the Pamir folded belt along a progressively lengthening 2000-km-long longitudinal river that developed along the left-lateral Altyn Tagh fault and its western continuation, as the eastward extrusion of the Tibetan plateau took place in Oligocene time. Both the crustal uplift and continuous southeastward aggradations of the sediments carried by the paleo–Kunlun River are interpreted to be the cause for southeastward migration of the depocenter of the Qaidam basin. The longitudinal river disappeared in late Cenozoic time (2–4 Ma) due to stream capture and climate change. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Late Cenozoic Right-Lateral Movement along the Wenquan Fault and Associated Deformation: Implications for the Kinematic History of the Qaidam Basin, Northeastern Tibetan Plateau

Bounded by the NE-trending Altyn Tagh fault on the northwest, the northeastern margin of the Tibetan Plateau consists of the Qilian Shan belt, Qaidam Basin, west Qinling belt, and east Kunlun belt. In the area where these tectonic units join, the NW-trending Wenquan fault between the Qaidam Basin and west Qinling belt contains clear evidence of active right-lateral movement. At the northern and southern ends of the fault, right-lateral movement has been transferred to NE-SW crustal shortening. Right-lateral movement was initiated in late Miocene to Pliocene time and has ~20 km of total displacement, which yields an average slip rate of ~4 mm/yr. Uplift of the Wahong Shan, bounded by the Wenquan fault on the east, resulted from en echelon thrusting and folding associated with right-lateral movement. The right-lateral movement along the Wenquan fault suggests that displacement occurs between the tectonic units within the northeastern margin of the plateau and that the Qaidam Basin is underlain by a more rigid basement that has moved northward relative to the west Qinling belt to the east. The right-lateral Wenquan fault and left-lateral Altyn Tagh fault can be regarded as conjugate structures, and accommodated the northward indentation of the Qaidam Basin into the Qilian Shan belt. The fact that the Wenquan fault has a slower slip-rate than the Altyn Tagh fault suggests that the northward movement of rigid basement of the Qaidam Basin must have a component of clockwise rotation relative to the Qilian Shan belt. The west Qinling belt pinches out westward between the Wahong Shan and Qilian Shan belt, implying that it may have undergone some eastward extrusion due to the N-S convergence between the Qaidam Basin and Qilian Shan belt.

Danghe area (western Gansu, China) biostratigraphy and implications for depositional history and tectonics of northern Tibetan Plateau

The Danghe area in western Gansu Province is at the focal point of interaction of the northeastern end of the left-lateral Altyn Tagh Fault and growing ramp thrusts of the Danghe Nanshan Mountains along the northern rim of the Qinghai–Tibetan Plateau. With a thick sequence of Tertiary sediments and associated fossil records, the Danghe area is one of few places on the Tibetan Plateau that can offer integrated studies of its tectonic history, depositional environment, and biological records, including vertebrate and plant fossils. Past studies, however, have not been able to capitalize on the paleontological data or were often misguided by an outdated notion of regional chronology. Incorrect age estimates in these studies often have profound effects on tectonic interpretations. We present new stratigraphic and paleontologic evidence from the Danghe area and demonstrate a new chronologic scheme that indicates a much younger age for the majority of the sediments. We recognize three packages of sediments in the Danghe area: (1) Oligocene Paoniuquan (new name) Formation, basal, predominantly fine-grained, dark purple mudstones and siltstones that include the classic Yindirte Fauna, which forms the basis of the Tabenbulukian mammal age; (2) early Miocene to early late Miocene Tiejianggou (new name) Formation that contains a new platybelodont proboscidean in a coarsening-upward sequence terminating in a massive conglomerate; and (3) an unnamed late Neogene formation that contains another coarsening-upward sequence. In light of our new stratigraphic framework, we reinterpret a previously published magnetic column for the middle sequence in Xishuigou as representing chrons C6n through C4Ar corresponding to a span of about 20–9.3 Ma, much younger than has been realized so far. This new chronological framework suggests a depositional history of the Danghe Nanshan that spans at least the early Oligocene through late Miocene, to possibly Pliocene. Early depositions during the Oligocene through middle Miocene are dominated by fine-grained sediments indicating a distant source of sedimentation. Paleontological data suggest a relatively dry environment, as is typical of northern China today. By late Miocene (around 9–12 Ma), the Danghe area began to receive coarse sediments and was much closer to the mountain front. The new stratigraphic framework indicates an earlier onset of sedimentation than has generally been assumed, but also suggests the presence of sediments much younger than many have realized.