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The WNW-trending Guanggaishan–Dieshan fault (GDF) is located in the West Qinling Range at a site of tectonic junction between the Tibetan plateau, the Sichuan basin and the Ordos block. Tectonically, this region is bounded by the East Kunlun fault to the southwest, the West Qinling fault to the north, and the Longmenshan fault to the southeast. The activity of the GDF is essentially related with the northeastward expansion of the Tibetan Plateau and associated strain partition between the East Kunlun fault and the West Qinling fault. This study reported the sense of fault movement, rate of fault slip, and the timing of three paleoseismic events on the east segment of the Guanggaishan–Dieshan fault (EGDF) with which no historical earthquake has been documented before. We focused our investigation on three branch faults in the central part of the EGDF using a range of study methods, e.g. structural mapping, paleoseismological trenching, unmanned aircraft vehicle photogrammetry, differential GPS survey, as well as radiocarbon and optically stimulated luminescence dating. Our new results highlighted: (1) the EGDF is dominated by the left-lateral sense of movement with a minor component of dip slip, (2) the range-bounding branch is characterized by a maximum left-lateral slip rate of 0.72 ± 0.34 mm/year and a maximum vertical-slip rate of 0.13 ± 0.03 mm/year, respectively. Kinematics of the EGDF is similar to many other active faults in the West Qinling Range, together they play a joint role in accommodating and transferring the residual left-lateral slip of the East Kunlun Fault. Three paleoseismic events were identified on the range-bounding fault based on two types of event markers: cut-cover relation and colluvial deposition. The ages of the most recent two events are estimated to be 2765–3320 cal. year BP and 12,775–13,005 cal. year BP and the age of the oldest event is as early as 18,495–32,950 cal. year BP. In contrast, there is no compelling evidence to show paleoseismic event along the rest two branches, and further work is needed to demonstrate this.

The Yinwashan and Xinminpu faults are located in the Jiuxi Basin in the western end of the Hexi Corridor. The determination of their activity and slip rates is of great significance for understanding the eastward extension of the Altyn Tagh fault. Based on geological and geomorphologic field survey, trench excavation, optically stimulated luminescence dating, we define the fault geometry and kinematic properties of the two faults. Based on fault scarps measurement using differential GPS and 10Be surface exposure dating, we determined vertical slip rate of 0.09±0.01 mm/yr for the Yinwashan fault and 0.1±0.02 mm/yr for the Xinminpu fault. Using the dips observed in trenches and natural sections, we estimated horizontal shortening rates of 0.05±0.03 and 0.23±0.06 mm/yr, respectively. No significant strike slip motion is observed on these two faults, and we infer that this region was dominated by horizontal shortening in the Late Quaternary. Although the shortening rate is quite low on each individual fault, together with other faults in this area, these two faults have an essential role in transferring slip from the eastern end of the Altyn Tagh fault and in accommodating the northeastward growth of Tibetan Plateau.

The eastern Qilian Shan is a tectonically-active region consisting of a series of faults with bounded intermountain basins and is located within the transition zone between the mainland Tibetan Plateau and the Alax Block. Active deformation affecting the topography in this region can be quantified based on geomorphic indices. Therefore, we applied the geomorphic indices (hypsometry and stream-power incision model) to evaluate the tectonic deformation pattern of the eastern Qilian Shan. Hypsometric curves and S-A plots of the selected seven rivers were determined. HI values of every single sub-basins were also calculated. The results show that the local topographic evolution of the eastern Qilian Shan is in pre-steady state and will soon reach its equilibrium state. According to the analysis of regional climate condition (e.g., rainfall and glaciers distribution) and fault characteristics, it is suggested that abundant glacial snowmelt water sustains fluvial incision, and tectonic deformation from sustained northeastward expansion of the Tibetan Plateau is the main reason for the landscape growth. Combining the research of the deep electric structure beneath the Gulang Boundary Zone, we claimed that the eastern Qilian Shan (even the northeastern Tibet) has been growing and expanding northeastward since the middle Miocene, and its leading edge now is the Hexibao-Sidaoshan Fault. On the premise of synthetically considering the western and middle parts of the Qilian Shan, it is suggested that the Hexibao-Sidaoshan Fault area will rise into a mountain in 1–2 Ma.

The late Pleistocene deformation pattern in the eastern Qilian Shan remains controversial. Study of the geometry and slip rate of the fault holds crucial value for better understanding the regional deformation pattern. The active E-W trending Gulang and Tianjing Shan Fault Zone is located in the southern boundary of the Tengger Desert which plays a significant role in tectonic deformation and slip transfer in the NE Tibetan Plateau. Geomorphic mapping of the active fault traces reveal that the Gulang fault is composed of two segments, separated by the Guanjia Tai pull-apart basin. Offset geomorphic features indicate that the Gulang fault appears to be primarily sinistral strike-slip with no reverse component. Based on offset gullies/terraces and optically stimulated luminescence dating of offset-related sediments, we obtain a consistent late Pleistocene slip rate of ~2.5 mm/a along the western and eastern segments of the Gulang Fault. Meanwhile, the slip vectors indicate the Gulang fault redistributes strain and transforms displacement along the Haiyuan fault, accommodating the westward motion of the Gobi-Alashan block. Moreover, a devastating earthquake of Ms 8.0 struck Gulang on 23rd May 1927. Geomorphically fresh fault scarps and surface rupture zone are observed at Gulang Fault, we modify the Modified Mercalli Intensities (MMI) and revise the isoseismal map for the Gulang earthquake. Combining with the high-resolution deep seismic-reflection data, the Gulang fault may be the source of the earthquake. Regionally, GPS velocities indicate that faulting, crustal shortening, and basin/block rotation accommodate deformation of the plateau's northern margin. In conclusion, the fault geometry, kinematics, and regional GPS velocities reflect that this region experiences eastward movement of the northeastern Tibetan Plateau relative to the Gobi-Alashan.

The Tibetan plateau is prone to destructive earthquakes. A number of strong thrust events occurred in the recent past, seeming to migrate from south to north, to the Qilian Mountains area. Many active thrust faults are known in the Qilian Mountains, and most of them are capable of producing large earthquakes. Here we study the southern Zongwulong Shan (shan means mountain) fault that lacks any paleoseismology studies so far. This fault is the eastern boundary of the Qaidam and Qilian blocks, posing a threat to the populated area of Delingha in western China. In this paper, we document its Holocene rupture history based on paleoseismic trenches, and we assess the seismic risk in this area. We excavated two trenches across 4.5 ± 0.5 m high fault scarps in alluvial fans. We found ruptures that affect young alluvial units and almost penetrate the top thick loess unit. We show that four paleoearthquakes occurred in the Holocene with an average recurrence interval of 2300 ± 500 years. The most recent event happened between 272 BCE and 572 CE. Three older events probably occurred in the past 9.5 ± 0.8 ka.

The Minle-Yongchang fault is an active reverse fault-related fold structural belt developed in the Hexi Corridor Basin on the northeastern edge of the Tibetan Plateau. An earthquake of Ms6.1 occurred near the Minle-Yongchang fault zone in 2003. The deformation pattern of the Minle-Yongchang fault and its relationship with this strong earthquake, however, are still not well known. In this study, we used the methods of HYPOINVERSE absolute location and double-difference location with waveform cross-correlation technology to relocate the 2003 Minle earthquake sequence. In total, 383 earthquakes are precisely relocated. Based on the results of precise seismic relocation, using the method of determining fault planes by small earthquakes, the seismogenic fault is found to be a low-angle thrust with a strike of 311°, a dip of NE, and a dip angle of 14°. It does not rupture the surface, extends to 19–20 km depth, and is hidden beneath the Yonggu Anticline. We also employed the cut-and-paste (CAP) method with a broadband waveform to determine the focal mechanism of the mainshock in 2003: the strike is 311°; the dip is 34°; and the rake is 90°. The fault plane parameters obtained in these two ways are roughly consistent. We also used a digital elevation model (DEM) derived from the SPOT 6 stereo image pair and high-precision differential Global Positioning System (GPS) to measure the displacement of terraces. Topographic profiles along the terraces across the Minle-Yongchang fault show that high alluvial terrain exhibits fold deformation. The vertical offsets of the T2 and T3 terraces along the Tongziba River are approximately 2.3 and 22 m, respectively. Optically stimulated luminescence (OSL) dating indicates that the ages of T2 and T3 are 11.3 and 106 ka, respectively. We calculated an average uplift rate of 0.21 ± 0.05 mm/a by dividing the vertical offset by age. According to the spatial distribution of the relocated earthquake sequence and terrace deformation in the study area, the Ms6.1 Minle earthquake in 2003 was caused by the latest activity of a blind reverse fault-related fold in the Hexi Corridor Basin.

The Altyn Tagh fault is the northern boundary of Tibetan Plateau. As one of the most well-known strike-slip fault in the world, great achievements on tectonic deformation and Late Quaternary slip rate have been made. However, there is a long-lasting debate on whether the Altyn Tagh fault extends into the Jinta Basin or even eastward. In this paper, we use satellite image interpretation, field investigation, trench excavation, and optical stimulated luminescence dating to study newly found NS striking scarps in the eastern end of Jinta Nan Shan. The results are as follows: firstly, a group of normal faults develop on terrace T2 of Heihe River, the total length amounts to ∼40 km, total scarp height is 30±5 m; secondly, four paleoseismic events have been interpreted from three trenches, approximate ages of events are 79.97±19.14 ka BP, 62.55±13.10∼55.41±10.77 ka BP, before 16.89±2.08 ka BP, 8.52±1.49 ka BP, respectively; thirdly, just like NS normal faults in the western end of Altyn Tagh fault, the newly found NS extensional faults are likely the terminating tectonics of the eastern end of Altyn Tagh fault, the large Altyn Tagh fault may end in the eastern end of Jinta Nan Shan.

Cenozoic basins and ranges constitute the high topography of the northeastern Tibetan Plateau which is derived from the Indo-Asian collision. The geomorphological characteristics of the ranges provide direct insight into the uplift processes which are responsible for the patterns of the ranges and the growth of the northeastern Tibetan Plateau. This study analyzed the geomorphological features of Qinghai Nanshan (one of the youngest ranges within the northeastern Tibetan Plateau), including elevation, slope distribution and the channel steepness index. Topographic analysis revealed that elevations and slopes in western and central portions of Qinghai Nanshan were higher than those in the eastern portion, whereas the channel steepness index revealed a step-growth mode from west to east. Considering the topographic features, the lateral gradient of precipitation (increasing from west to east) and the lithology distribution, it is concluded that the geomorphological features of Qinghai Nanshan are influenced mainly by tectonic activities and reflect the growth pattern and/or the tectonic setting of the range. Comparing with previous studies, it is shown that the formation mechanism of Qinghai Nanshan follows a middle-to-sides growth pattern. Furthermore, the degree of inclination of the erosion surface distributed on the northern flank of the range suggests that Qinghai Nanshan is controlled jointly by the listric Qinghai Nanshan thrust fault and the influences from the Elashan and Riyueshan dextral strike slip faults. In addition, the northeastern Tibetan Plateau exhibits an outside-in growth process, which might reflect the northeastward growth of the entire northeastern Tibetan Plateau.

The appearance of detritus shed from mountain ranges along the northern margin of the Tibetan Plateau heralds the Cenozoic development of high topography. Current estimates of the age of the basal conglomerate in the Qaidam basin place this event in Paleocene-Eocene. Here we present new magnetostratigraphy and mammalian biostratigraphy that refine the onset of basin fill to ∼25.5 Myr and reveal that sediment accumulated continuously until ∼4.8 Myr. Sediment provenance implies a sustained source in the East Kunlun Shan throughout this time period. However, the appearance of detritus from the Qilian Shan at ∼12 Myr suggests emergence of topography north of the Qaidam occurred during the late Miocene. Our results imply that deformation and mountain building significantly post-date Indo-Asian collision and challenge the suggestion that the extent of the plateau has remained constant through time. Rather, our results require expansion of high topography during the past 25 Myr., The timing of mountain building along the Tibetan Plateau remains unclear. Here, the authors present new magnetostratigraphic and mammalian biostratigraphic data from sediments to show that mountain building at the edge of the Tibetan Plateau commenced at 25.5 Ma with a separate emergence in the north at 12 Ma.

We derive a slip rate for a frontal thrust in the western Hexi Corridor along the northern Qilian Shan by combining topographic profiling and 10Be exposure dating. The active Yumen-Beidahe thrust fault offsets late Pleistocene alluvial-fan deposits, and a prominent north-facing scarp is well preserved. To quantify the slip rate, we surveyed the uplifted terraces and sampled quartz-rich pebbles on terrace surfaces and river channels to determine surface exposure ages and pre-depositional inheritance. The minimum vertical slip rate of the fault is 0.73 ± 0.09 mm a−1. This represents a horizontal shortening rate of 1.26±0.31 mm a−1 for a fault dip of 30±5°. This estimated slip rate supports the inference made from previous geological and GPS constraints that NNE-directed shortening across the western Qilian Shan and the Hexi Corridor is distributed on several active faults with a total shortening rate of 4~10 mm a−1. This article is protected by copyright. All rights reserved.

Historical archives of earthquake occurrence provide a millennial view of fault system behavior with precision beyond the capability of radiometric dating techniques. Understanding the long historical record of earthquake activity in China presents a great opportunity to develop such an archive. However, the complex distributed nature of faulting here leads to uncertainty and requires matching historic events to the paleoseismic record from fault excavations. We present paleoseismic evidence for the most recent rupture of the north Danghe Nanshan thrust (NDNT) and correlate the age of this event to nearby historical archives. We use high‐resolution topography generated from airborne drone photography to measure an average coseismic fault throw of 0.8±0.2 m. Three trenches excavated across these small scarps show shortening of ∼1.3 m, consistent with event magnitude of M w 7.0±0.5 that probably ruptured the entire ∼45‐km‐long northern strand of the eastern NDNT system. Geochronology data and the historical record from Dunhuang and Anxi together indicate that this event likely occurred at A.D. 1289, during the Yuan Dynasty. Electronic Supplement: Description of the test procedure of optically stimulated luminescence (OSL) samples, and figure showing natural OSL decay curve, growth curves, and equivalent dose (De) distributions.

The uplift processes of the Qilian Shan (northern Tibetan Plateau) play a central role in our understanding of the dynamics of outward and upward growth of Tibet due to sustained convergence of the Indian and Asian plates. We employ apatite fission track chronology and geological mapping to reveal the time and pattern of the deformation along the Qilian Shan. Our results indicate that the emergence of the Tuolai Shan in the central Qilian Shan occurred at 17–14 Ma, that northern Qilian Shan thrusting began at 10–8 Ma, and that the Laojunmiao anticline formed ca. 3.6 Ma. Together with previous results that show that uplift of the southern Qilian Shan began in the Oligocene, we suggest that the Qilian Shan has undergone progressively northward expansion in the Cenozoic due to significant crustal shortening driven by Qilian Shan thrust fault systems.

Flood control initiates Chinese civilization Around four millennia ago, Emperor Yu the Great succeeded in controlling a huge flood in the Yellow River basin. This is considered to have led to the establishment of the Xia dynasty and the start of Chinese civilization. However, the dates of the events and the links between them have remained uncertain and controversial. Using stratigraphic data and radiocarbon dating, Wu et al. verify that the flood occurred and place the start of the Xia dynasty at about 1900 BC, thus reconciling the historical and archaeological chronologies (see the Perspective by Montgomery). Science , this issue p. 579 ; see also p. 538

The Qinghai Nanshan is located interior of northeastern Tibetan Plateau, extending W-E trending for 200 km between the Ela Shan and Riyue Shan, constituting the northern boundary of the Gonghe Basin. Qinghai Nanshan is very important to understand the Qinghai lake Basin-Gonghe Basin landscape evolution process, and it also provides a clue to understand the deformation of northeastern Tibetan Plateau. Our study focuses on identifying the unrecognized segment of the Qinghai Nanshan fault along the Gonghe Basin by applying river longitudinal profiles, and geomorphic indices such as stream length (SL) gradient index and mountain front sinuosity (Smf), as well as combining the field investigation. The results show that the anomalies of river longitudinal profiles in their upper reach may result from lithological contact, whereas the pronounced convex and deflection that occurred especially in the mid-reach are most likely related to recent tectonic activities caused by the Qinghai Nanshan thrust fault. Moreover, SL values are in agreement with the anomalies shown by the longitudinal profiles. Combining the results of geomorphic indices and topography analysis, as well as the field investigation, we project the distribution of the Qinghai Nanshan fault and discussed the tectonic implications. The listric Qinghai Nanshan thrust fault and the influences from the Elashan and Riyueshan dextral strike-slip faults are controlling factors for landscape of the Qinghai Nanshan.

In the western front of the Qilian Shan, NE Tibetan Plateau, a series of 5 fluvial (T1 – T5) terraces developed along the Baiyang River are deformed across the Shiyougou anticline, which is related to the Yumen–Beidahe (YB) blind thrust. In this study, we measure the deformed terraces across the anticline using differential GPS, which provides data for us to reconstruct the thrust fault geometry. The ages of terrace abandonment are constrained by 10Be exposure dating for T2, T4, and T5 to be 8.6 ± 1.7 ka, 21.6 ± 1.4 ka, and 48.4 ± 2.1 ka, respectively. A four-segment fault model is inferred with changing dips at depths of 0.3 ± 0.1 km, 2.2 ± 0.1 km, and 5.9 ± 0.9 km. Combining terrace ages with the fault geometry model, we derive a vertical slip rate of 0.9 ± 0.1 mm/yr and a shortening rate of 1.9 ± 0.5 mm/yr for the YB blind thrust. This result suggests that the northern frontal thrust system accommodates only ∼30% of the total shortening rates across the western Qilian Shan. The river incision rate has increased from ~1.5 mm/yr to ~5.2 mm/yr from the late Pleistocene to the Holocene. The mismatch between river incision and rock uplift is likely related to climate change since the Last Glacial Maximum.

The northeastern Tibetan Plateau constitutes a transitional region between the low-relief physiographic plateau to the south and the high-relief ranges of the Qilian Shan to the north. Cenozoic deformation across this margin of the plateau is associated with localized growth of fault-cored mountain ranges and associated basins. Herein, we combine detailed structural analysis of the geometry of range-bounding faults and deformation of foreland basin strata with geomorphic and exhumational records of erosion in hanging-wall ranges in order to investigate the magnitude, timing, and style of deformation along the two primary fault systems, the Qinghai Nan Shan and the Gonghe Nan Shan. Structural mapping shows that both ranges have developed above imbricate fans of listric thrust faults, which sole into decollements in the middle crust. Restoration of shortening along balanced cross sections suggests a minimum of 0.8–2.2 km and 5.1–6.9 km of shortening, respectively. Growth strata in the associated foreland basin record the onset of deformation on the two fault systems at ca. 6–10 Ma and ca. 7–10 Ma, respectively, and thus our analysis suggests late Cenozoic shortening rates of 0.2 +0.2/–0.1 km/m.y. and 0.7 +0.3/–0.2 km/m.y. along the north and south sides of Gonghe Basin. Along the Qinghai Nan Shan, these rates are similar to late Pleistocene slip rates of ∼0.10 ± 0.04 mm/yr, derived from restoration and dating of a deformed alluvial-fan surface. Collectively, our results imply that deformation along both flanks of the doubly vergent Qilian Shan–Nan Shan initiated by ca. 10 Ma and that subsequent shortening has been relatively steady since that time.

The Tibetan Plateau is a prime example of a collisional orogen with widespread strike-slip faults whose age and tectonic significance remain controversial. We present new low-temperature thermochronometry to date periods of exhumation associated with Kunlun and Haiyuan faulting, two major strike-slip faults within the northeastern margin of Tibet. Apatite and zircon (U-Th)/He and apatite fission-track ages, which record exhumation from ~2 to 6 km crustal depths, provide minimum bounds on fault timing. Results from Kunlun samples show increased exhumation rates along the western fault segment at circa 12–8 Ma with a possible earlier phase of motion from ~30–20 Ma, along the central fault segment at circa 20–15 Ma, and along the eastern fault segment at circa 8–5 Ma. Combined with previous studies, our results suggest that motion along the Haiyuan fault may have occurred as early as ~15 Ma along the western/central fault segment before initiating at least by 10–8 Ma along the eastern fault tip. We relate an ~250 km wide zone of transpressional shear to synchronous Kunlun and Haiyuan fault motion and suggest that the present-day configuration of active faults along the northeastern margin of Tibet was likely established since middle Miocene time. We interpret the onset of transpression to relate to the progressive confinement of Tibet against rigid crustal blocks to the north and expansion of crustal thickening to the east during the later stages of orogen development.

[1] Based on field investigations, aerial-photo morphological analysis, topographic profiling, and optically stimulated luminescence (OSL) dating of alluvial surfaces, we estimate vertical components of the slip rate along the South Heli Shan thrust fault, which lies on the northern margin of the Hexi Corridor and the northeastern edge of the Tibetan Plateau. The fault consists of three segments with scarp heights ranging from less than 1 m to more than 16 m. OSL dating indicates that most of the alluvial fans cut by fault scarps formed during the transition from the last glacial stage to the present interglacial stage from ~19 to ~9 ka along southern Heli Shan and from ~27 ka to ~22 ka along its northern margin. In addition, remnants of older alluvial fan have been abandoned after ~67 ka. Scarp heights increase from west to east and reach a maximum of more than 16 m near the eastern end. Using three approaches, we calculate late Quaternary slip rates for each of the three fault segments along the southern margin and the fault on the northern flank. These approaches yield maximum vertical slip rates from 0.18 to 0.2 mm/a for the western segment, 0.3 to 0.43 mm/a for the central segment, 0.36 to 0.53 mm/a for the eastern segment, and 0.21 mm/a for the Wutongjing Fault, which lies on the north side of the Heli Shan. For a range of likely fault dips, these correspond to 0.1–0.2 mm/a of average horizontal shortening for the western segment, and increase to 0.4–0.5 mm/a across the eastern segment of the southern Heli Shan Fault. Combining the height of the eastern parts of the Heli Shan (Daqing Peak) above the Hei He (a major river that incised the western end of the range) and the vertical component of the slip rate of the eastern segment, we suggest that the Heli Shan was uplifted by motion on the South Heli Shan Fault beginning sometime between 1 and 4 Ma, most likely since ~2 Ma. This age suggests that the Tibetan Plateau continues to grow northeastward across the Hexi Corridor.

Studies of Late Quaternary geological slip-rates and the GPS decadal slip-rates along the major strike-slip faults in the northern margin of the Tibetan Plateau show that slip-rates remain relatively constant along the middle sections of each fault and decrease rapidly toward the ends. Our recent studies suggest that the slip rates are low (

Based on field mapping, section measurement and magnetostratigraphy, ∼1700 m of sedimentary rocks have accumulated in the Wushan basin between ∼16 Ma and ∼6 Ma. Basin geometry, sedimentation characteristics and the early syn-depositional deformation along the northern margin of the basin indicate that formation of the Wushan basin was related to tectonic deformation along the West Qinling fault zone during the middle Miocene. A series of basins of similar age to the Wushan basin were generated along and to the south of the West Qinling fault zone while basalts also erupted in this region at this time. We suggest that the middle Miocene (∼16 Ma) may represent a change in kinematics and deformation style in the region along and to the south of the West Qinling fault zone. At this time, there was a transition from NNE–SSW compressional deformation, that dominated the region since the late Paleogene, to the development of WNW–ESE and/or E–W trending strike-slip movement and associated transpressional and transtensional activity that continues today. The Miocene Wushan basin may have developed in association with transpression along the West Qinling fault zone. Whether this transition was related to the onset of strike-slip along the east Kunlun fault and related deformation transfer, lower crustal flow, or removal of mantle lithosphere, the middle Miocene provides direct evidence for a change in the kinematic style along the plateau margin.

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.

Magnetostratigraphy of sedimentary rock deposited in the Chaka basin (north‐eastern Tibetan Plateau) indicates a late Miocene onset of basin formation and subsequent development of the adjacent Qinghai Nan Shan. Sedimentation in the basin initiated at ∼11 Ma. In the lower part of the basin fill, a coarsening‐upward sequence starting at ∼9 Ma, as well as rapid sedimentation rates, and northward paleocurrents, are consistent with continued growth of the Ela Shan to the south. In the upper section, several lines of evidence suggest that thrust faulting and topographic development of the Qinghai Nan Shan began at ∼6.1 Ma. Paleocurrent indicators, preserved in the basin in the proximal footwall of the Qinghai Nan Shan, show a change from northward to southward flow between 6.5 and 3.8 Ma. At the same location, sediment derived from the Qinghai Nan Shan appears at 6.1 Ma. Finally, the initiation of progressively shallowing dips observed in deformed basin strata and a change to pebbly, fluvial deposits at 6.1 Ma provide a minimum age for the onset of slip on the thrust fault that dips north‐east beneath the Qinghai Nan Shan. We interpret a decrease in sediment accumulation rates since ∼6 Ma to indicate a reduction in Chaka basin accommodation space due to active faulting and folding along the Qinghai Nan Shan and incorporation of the basin into the wedge‐top depozone. Declination anomalies indicate the beginning of counter‐clockwise rotation since 6.1 Ma, which we associate with local deformation, not regional block rotation. The emergence of the Qinghai Nan Shan near the end of the Miocene Epoch partitioned the once contiguous Chaka‐Gonghe and Qinghai basin complex. In a regional framework, our study adds to a growing body of evidence that points to widespread initiation and/or reactivation of fault networks during the late Miocene across the north‐eastern Tibetan Plateau.

Lithologic, magnetostratigraphic, and stable isotope records from the Neogene Xunhua and Linxia basins along the Tibetan Plateau9s northeastern margin suggest that topography in the intervening Jishi Shan mountain range began to develop between 16 and 11 Ma. Perturbations to local climate patterns resulting from the evolution of local topography are tracked through comparison of stable isotope compositions of calcareous basin-fill materials across the Jishi Shan. Similarity of isotopic compositions is interpreted to reflect the presence of integrated basins, whereas distinct isotopic compositions reflect unique basin hydrologies. Divergent isotope trends develop between ca. 16 and 11 Ma and are indicative of hydrologic separation in the adjacent Xunhua and Linxia basins and increased aridity in the leeward Xunhua basin. The development of aridity in the lee of the growing topography along the plateau9s northeast margin highlights the importance of evaporative enrichment in this extremely continental setting and explains the presence of anomalously positive δ 18 O values in modern rainfall. Our findings add to a growing body of evidence for deformation along the plateau9s north and northeastern margins in the middle to late Miocene.

The stratigraphic chronology of Yellow River terraces was investigated and studied in Lanzhou Basin, western Chinese Loess Plateau. The optically stimulated luminescence (OSL) dating results show that terraces T 1 , T 2 and T 3 formed at 8 ka, 20 ka and 70 ka, respectively. Lateral accretion of the riverbed facies gravel sediments occurred during interglacial periods while vertical aggradations of the terrace sediments deposited predominantly under cold and dry glacial period. A thick layer of aeolian loess with a basal age about 35 ka indicates a remarkable drop of air temperature and a dry, cold climate. The temporal correlation between terrace formation and tectonic movement has not yet been established in this research, but the stratigraphic chronology of the terrace sections provides the timing of the terrace formation, the incision rate of the Yellow River, and the slip rate of the fault horizon.

Terra Nova, 22, 180–187, 2010 Abstract We constrain the slip rate for the frontal thrust of the Qilian Shan (north-eastern Tibet) by combining structural investigations, satellite imagery, topographic profiling, and 10Be exposure dating. We surveyed two terrace levels, and from each, we took 6–7 samples in profiles dug to depths of 2 m. These constrain inheritance and determine the precise ages of abandonment of the terraces: 29.9 ± 7.8 ka for the upper terrace and 16.3 ± 4.4 ka for the lower one. Topographic profiles with a determination of burial of the footwall by sediment yield offsets of the surfaces of 96.4 ± 4.4 and 40.1 ± 2.8 m. The average vertical rate is 2.8 ± 1.3 mm a−1 with a horizontal slip rate of ∼2.5 mm a−1. This rate is higher than those determined farther north on similar structures, but is consistent with the GPS velocity field, and accounts for roughly half of the geodetic shortening across the Qilian Shan.

On the basis of textual research on the historical earthquake data and the field investigation of 1219 A.D. Guyuan earthquake, we suggest that there is only one strong earthquake occurred in Guyuan area in 1219 A.D., instead of two or three strong earthquakes. We further suggest that the earthquake parameters recorded in the present earthquake catalogs are not definite and should be modified. The occurrence time of this earthquake should be about 11 am, August 7, 1219 A.D. and the heavily-damaged area of this earthquake, the VIII intensity area, should be located among the regions of Guyuan, Pingliang and Longde county cities. The epicenter area should be near Guyuan city. The magnitude of this earthquake is about 7 and it has intensity about larger than or equal to IX within the epicenter area. The major axis direction of the heavily-damaged area strikes in north-northwest that is approximately consistent with the strike of the Liupan Shan thrust fault zone. The new tectonic activity of the Liupan Shan thrust fault zone resulted in the M7 Guyuan earthquake in 1219 A.D.

On the basis of the textual research on the historical earthquake data and the field investigation of Wudu earthquake occurred in 186 B.C., we suggest that the earthquake parameters drawn from the present earthquake catalogs are not definite and amendments should be made. The heavily-damaged area of this earthquake should be located between Jugan township of Wudu County and Pingding township of Zhouqu County. Its epicenter should be in the vicinity of Lianghekou in Wudu County with a magnitude of about 7∼7¼ and an intensity of about IX∼X. The major axis direction of the heavily-damaged area should be in the WNW direction that is approximately consistent with the strike of the middle-east segment of Diebu-Bailongjiang active fault zone, and the origin time should match up to that of the latest paleoearthquake event [before (83±46) B.C.] obtained by the trench investigation. Certain seismic rupture evidences are still preserved on this fault segment. Therefore, we propose on the basis of comprehensive analysis that the causative structure of the M 7∼7¼ Wudu earthquake in 186 B.C. should be in the middle-east segment of Diebu-Bailongjiang active fault zone.

The Liupan Shan Mountain is one of the outermost ranges in northeastern Tibetan Plateau. The onset of its uplift provides insight on whether the plateau grew sequentially outward or broad areas of the plateau deformed simultaneously. The apatite fission-track method can be used to date rapid cooling as the result of unroofing of rocks in response to tectonically induced vertical motion. Fission-track data from apatite in Early Cretaceous sedimentary strata exposed on the hanging-wall of Liupan Shan thrust fault in northeastern Tibet suggest that a late Cenozoic rapid cooling events occurred at 7.3–8.2 Ma or ~ 8 Ma. This age apparently dates fault activity of the Liupan Shan thrust in response to northeastward growth of the Tibetan Plateau uplift and lateral growth, which continues today. Numerous studies of the Tibetan Plateau suggest that the onset of deformation in eastern and northern margin of Tibetan Plateau occurred in the latest Miocene.

Lanzhou Institute of Seismology, China Seismological Bureau, Lanzhou 730000, China 2) Institute of Geology, China Seismological Bureau, Beijing 100029, China

Wu et al ., Han, and Huang et al . question our reconstruction of a large outburst flood and its possible relationship to China’s Great Flood and the Xia dynasty. Here, we clarify misconceptions concerning geologic evidence of the flood, its timing and magnitude, and the complex social-cultural response. We also further discuss how this flood may be related to ancient accounts of the Great Flood and origins of the Xia dynasty.

Recent studies of the northeastern part of the Tibetan Plateau have called attention to two emerging views of how the Tibetan Plateau has grown. First, deformation in northern Tibet began essentially at the time of collision with India, not 10-20 Myr later as might be expected if the locus of activity migrated northward as India penetrated the rest of Eurasia. Thus, the north-south dimensions of the Tibetan Plateau were set mainly by differences in lithospheric strength, with strong lithosphere beneath India and the Tarim and Qaidam basins steadily encroaching on one another as the region between them, the present-day Tibetan Plateau, deformed, and its north-south dimension became narrower. Second, abundant evidence calls for acceleration of deformation, including the formation of new faults, in northeastern Tibet since ~15 Ma and a less precisely dated change in orientation of crustal shortening since ~20 Ma. This reorientation of crustal shortening and roughly concurrent outward growth of high terrain, which swings from NNE-SSW in northern Tibet to more NE-SW and even ENE-WSW in the easternmost part of northeastern Tibet, are likely to be, in part, a consequence of crustal thickening within the high Tibetan Plateau reaching a limit, and the locus of continued shortening then migrating to the northeastern and eastern flanks. These changes in rates and orientation also could result from removal of some or all mantle lithosphere and increased gravitational potential energy per unit area and from a weakening of crustal material so that it could flow in response to pressure gradients set by evolving differences in elevation. Key Points The north-south limits of Tibet were set by lateral variations in strength Roughly 15 million years ago, deformation of NE Tibet accelerated Since 20-15 million years ago, the orientation of shortening rotated eastward ©2013. American Geophysical Union. All Rights Reserved.

Author(s): Lease, RO; Burbank, DW; Hough, B; Wang, Z; Yuan, D | Abstract: Sedimentary rocks in Tibetan Plateau basins archive the spatiotemporal patterns of deformation, erosion, and associated climate change that resulted from Cenozoic continental collision. Despite growing understanding of basin development in northeastern Tibet during initial India-Asia collision, as well as in the late Miocene-Holocene, surprisingly little is known about the intervening period: a time when the plateau may have undergone fundamental tectonic changes. To fill this gap, we present new magnetostratigraphy from a g2300-m-thick fluviolacustrine succession that spans ca. 30-9.3 Ma. An integrated analysis of sedimentology, subsidence, and provenance from this section reveals the sequential, pulsed erosion of multiple ranges bordering the Xunhua Basin. Emergence of the WNW-trending Laji Shan is highlighted by a doubling of sediment accumulation rates between 24 and 21 Ma and a transition to coarse allu vial facies at 20.3 Ma. Detrital zircon U/Pb age spectra show that these coarse sediments came from basement terranes within the Laji Shan. Together these observations suggest accelerated growth of the Laji Shan and its coupled foreland basin at ca. 22 Ma. The most rapid accumulation rates in Xunhua Basin occur within the finest-grained strata and suggest an underfilled basin during the fastest interval of Laji Shan deformation. Growth of the Laji Shan occurred northward of the contemporaneous plateau margin, which had been defined since ca. 45-50 Ma by the West Qinling, lying ~60 km farther south. Hence, following ~20-25 m.y. of apparent stability, the deformation front in this region jumped ~60 km to the north at ca. 22 Ma. Subsequently, growth of the north-trending Jishi Shan occurred at ca. 13 Ma and is highlighted by an acceleration in Xunhua Basin accumulation rates between 12 and 9 Ma, as well as by a significant change in detrital zircon provenance of nearby Linxia Basin deposits by 11.5 Ma. Initial growth of the WNW-trending Laji Shan in the early Miocene and subsequent growth of the north-trending Jishi Shan ~10 m.y. later support interpretations of a middle Mio cene kinematic reorganization in northeastern Tibet. © 2012 Geological Society of America.

International audience; High-resolution (HR) air photographs and a 1-m horizontal and 2-m vertical resolution digital elevation model derived from them by stereophotogrammetry provide new constraints on the behavior of the western stretch of the active Haiyuan fault, in Gansu province, China. The photographs cover three swaths along the fault, each about 2-km-long and at least 500-m-wide, near the village of Songshan, at 103.5øE. This high-resolution data set is used to map and measure cumulative horizontal offsets of alluvial terraces and risers that range between 115 and la 135 m, and 70 and 90 m, at two sites. Dating these terraces with 14C yields minimum and maximum ages of 8400 and 7600, and 14,200 years B.P., respectively. This leads to a postglacial slip rate of 12±4 mm/yr, with a most likely minimum value of 11.6±1.1 mm/yr. The smallest stream offsets observed on the HR photographs range between 8 and 16 m and are interpreted as coseismic displacements of the last few earthquakes with M ≥ 8 that ruptured the 220-km-long Tianzhu gap of the fault, west of the Yellow River. Earthquakes of that size within this gap, which has been quiescent for at least 800 years, would recur at intervals of 1050±450 years.

Although detrital zircon has proven to be a powerful tool for determining provenance, past work has focused primarily on delimiting regional source terranes. Here we explore the limits of spatial resolution and stratigraphic sensitivity of detrital zircon in ascertaining provenance, and we demonstrate its ability to detect source changes for terranes separated by only a few tens of kilometers. For such an analysis to succeed for a given mountain, discrete intrarange source terranes must have unique U/Pb zircon age signatures and sediments eroded from the range must have well-defi ned depositional ages. Here we use ~1400 single-grain U/Pb zircon ages from northeastern Tibet to identify and analyze an area that satisfi es these conditions. This analysis shows that the edges of intermontane basins are stratigraphically sensitive to discrete, punctuated changes in local source terranes. By tracking eroding rock units chronologically through the stratigraphic record, this sensitivity permits the detection of the differential rock uplift and progressive erosion that began ca. 8 Ma in the Laji Shan, a 10‐25-km-wide range in northeastern Tibet with a unique U/Pb age signature.