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The active deformation field between northern Tibet and central Mongolia is dominated by diffuse sinistral transpressional reactivation of the southern Altaids Phanerozoic terrane collage. The angular relationship between NE-directed SHmax and pre-existing basement trends is the dominant control on Quaternary fault kinematics. Along Tibet’s northern margin, the Altyn Tagh system is widening northwards by transpressional duplexing. The Nanjieshan and Sanweishan comprise sinistral oblique-slip thrust ridges within a regional asymmetric flower structure centered on the Altyn Tagh Fault. In the southern Beishan, interconnected lensoidal domains of transpressional and transtensional faulting are subtly indicated by Quaternary fault scarps, low-relief rejuvenated landscapes and alluvial sedimentation. The SE Beishan and western Hexi Corridor region contain numerous Late Quaternary fault systems including the Heishan-Jinta'Nanshan sinistral strike-slip corridor and the Helishan-Longshoushan fault array that connects eastwards with the transtensional grabens of the Yabrai and Langshan in the eastern Alxa Block. Further north, the Paleozoic terrane collage of the Gobi Corridor was repeatedly reactivated during the Permo-Triassic, Jurassic, Cretaceous and Neogene. Late Cenozoic reactivation was likely facilitated by thermal weakening of the crust due to Jurassic-Miocene volcanism, and diffuse Cretaceous rifting and crustal thinning. Although terrane boundaries and other faults are reactivated in many areas, thrust and oblique-slip reactivation of WNW striking shallowly dipping sedimentary bedding and metamorphic fabrics is equally important. Conversely, modern E-W trending strike-slip faults in the Gobi Altai typically crosscut older basement trends. In the Altai and Gobi Altai, the Late Cenozoic fault array has created a transpressional basin and range physiographic province. Coalescence of separate ranges into topographically continuous mountain belts in the Altai, Gobi Altai and easternmost Tien Shan is an important mechanism of transpressional mountain building not predicted by classical plate tectonic models. Throughout the vast deforming region north of Tibet, tectonic loading is shared amongst a diffuse fault network challenging assumptions about earthquake recurrence intervals and seismic hazard forecasting.

The 2008 Mw 7.9 Wenchuan, China, earthquake produced many damaging landslides in the Longmenshan region along the eastern margin of the Tibetan Plateau, China. Among the thousands of reported landslides, some are geologically notable because of their close spatial relationship to local fault rupture complexities. The Leigu landslide is particularly interesting because it formed at a restraining bend along the Beichuan-Yingxiu fault system in a structural position that favored hill-slope collapse because of a variety of preexisting structural and geomorphological conditions. The 2008 landslide reactivated an older landslide that is indicated by a preserved paleo-scarp upslope from the main 2008 event scarp. Our field and analytical results coupled with a review of existing geological information on the region indicate that the landslide site is located between two regional folds with opposing plunge directions and that the restraining bend is the displacement transfer zone between two parallel, but offset segments of the Beichuan-Yingxui Fault system. In addition, NE-oriented steep joints were reactivated as slip surfaces in the upper slopes of the landslide area within an anticline hinge zone that focuses vertical uplift. Steep valley walls due to incision of the antecedent Laochangkou River and abundant rainfall during the earthquake period, combined with intense seismic acceleration were contributing factors to the landslide event. During the earthquake, approximately equal components of strike-slip and SE-directed thrusting occurred on surface ruptures within the bend, offsetting older landslide deposits and man-made structures. Field results indicate that sliding was facilitated by loose unconsolidated materials from the previous landslide that were remobilized above a soft, low-friction basal slip surface. The Leigu landslide provides an important case study for evaluating potential landslide hazards close to active fault systems where complex 3-D structural geometries and high-relief, steep terrain combine to generate significant ground instability during large magnitude earthquakes.

We present results from a multidisciplinary investigation of the Jiujing fault (JJF) system and adjacent Jiujing Basin in the southern Beishan block, western China. Structural and geomorphological fieldwork involving fault and landform investigations, remote sensing analysis of satellite and drone imagery, analysis of drill-core data, paleoseismological trench studies, and Quaternary dating of alluvial sediments suggest the JJF is a late Pleistocene to Holocene oblique sinistral-slip normal fault. Satellite image analysis indicates that the JJF is a connecting structure between two regional E-W-trending Quaternary left-lateral fault systems. The Jiujing Basin is the largest and best developed of three parallel NE-striking transtensional basins within an evolving sinistral transtensional duplex. Sinistral transtension is compatible with the orientation of inherited basement strike belts, NE-directed SHmax, and the modern E-NE-directed geodetic velocity field. Cosmogenic 26Al/10Be burial dating of the deepest sediments in the Jiujing Basin indicates that the basin began to form at ~5.5 Ma. Our study reveals a previously unreported actively deforming domain of transtensional deformation 100 km north of Tibet in a sector of the Beishan previously considered tectonically quiescent. Recognition of latest Miocene-Recent crustal reactivation in the Jiujing region has important implications for earthquake hazards in the Beishan and western Hexi Corridor/North Tibetan foreland sectors of the Silk Road Economic Belt. Additionally, we compare the timing of latest Miocene-Recent crustal reactivation in the southern Beishan with the documented onset of reactivation in other deforming regions north of Tibet.

The 2015 Mw 7.8 Gorkha earthquake and its aftershocks caused nearly 9000 deaths and more than 23,000 injuries and triggered thousands of landslides and other mass-wasting effects in the steep, rugged topography of Nepal. In this paper, new slope failures and tension cracks induced by the 2015 Nepal earthquake are documented in steep terrain west of the Tatopani Border Station, which lies along the deeply incised Bhote Koshi River valley, a critical trans-Himalayan transport route between south Asia and Tibet/China. The affected area west of the Tatopani station is the site of a large reactivated paleo-landslide that has experienced repeated failures. The Tatopani station is downslope from the amphitheater-like landslide scar and is constructed on distal landslide debris in a position vulnerable to future landslide and fluvial erosion hazards. We carried out detailed field investigations to document different types of geohazards around the station and present an evolutionary model for past and present landslide development. In addition, a simple numerical model was constructed to evaluate the stability of the large paleo-landslide body under different earthquake conditions. Simulated results suggest that the paleo-landslide body is stable without seismic loading. However, the large paleo-landslide will be remobilized again by large slope failures if the PGA of future earthquake exceeds 0.35 g. We suggest that the results presented in this paper should be taken into consideration during earthquake-resistant design of the border station and other infrastructural development along the Bhote Koshi Valley.

We report remote sensing evidence and reconnaissance field observations for an actively evolving transpressional duplex 150 km north of Tibet, in the southern Beishan region of western China. We analyze Landsat-8, Google Earth and SRTM-30 data to reveal active fault traces, kinematics, offset contacts and landforms, and the overall duplex geometry in an area of limited recorded seismicity compared to surrounding regions. Eight NE-striking faults transfer sinistral displacement between E-W bounding faults and accommodate N-S shortening by sinistral-reverse displacements that have tilted the internal duplex blocks. The potential moment magnitude of a surface-rupturing event on one fault, that displays a twenty km-long, 1–3 m-high surface scarp, is estimated to be 6.6. Our study adds to the growing body of evidence that suggests the Beishan is a region of subtly expressed, but widespread, continental interior, strike-slip reactivation at low strain rates - challenging the long-held view that the Beishan has anomalous crustal stability within the huge Indo-Eurasia deformation field.

In this study, new structural field data and geological observations are coupled with remote sensing analysis and compilation of previous published work to establish a new kinematic framework for the neotectonic reactivation of the Alxa block, China. The Alxa block occupies a key position in Central Asia north and east of the contractional and sinistrally transpressive deforming zones of the Qilianshan-Hexi Corridor-easternmost Altyn Tagh Fault and Beishan deforming belts, south of the sinistrally transpressive southernmost Gobi Altai, and west of – or overlapping with - Ordos block extensional and transtensional graben systems. In addition, the Alxa block is internally transected by important fault systems (Bayan Nuru, Bayanwula, Chahanbulage) that record previously unrecognized Late Cenozoic activity. Active mountain building processes in the Alxa block show remarkable variation from large extensional horst blocks (Helanshan, SW Langshan, SW Yabrai) to localized uplifts along sinistral wrench-belts (Bigesitai) to dominantly contractional (Longshoushan) and sinistral transpressional ranges (Helishan). The triangular wedge-shape of the Alxa block likely pre-disposed it to eastward extrusion in response to NE-directed India-Eurasia collision-derived compressional stresses from the south, and E-W tensional forces driven by Pacific margin rollback to the east. A combination of inherited regional lithospheric structure and the modern east-directed geodetically derived crustal velocity field led to: 1) crustal thinning and subsidence of the Ejina basin to the west in the wake of the eastward extruding Alxa block, and 2) distributed sinistral transtension and crustal extension within the Alxa block interior, and in the Hetao and Yinchuan grabens to the east.

Predicting approximate earthquake-induced landslide displacements is helpful for assessing earthquake hazards and designing slopes to withstand future earthquake shaking. In this work, the basic methodology outlined by Jibson (1993) is applied to derive the Newmark displacement of landslides based on strong ground-motion recordings during the 2013 Lushan Ms 7.0 earthquake. By analyzing the relationships between Arias intensity, Newmark displacement, and critical acceleration of the Lushan earthquake, formulas of the Jibson93 and its modified models are shown to be applicable to the Lushan earthquake dataset. Different empirical equations with new fitting coefficients for estimating Newmark displacement are then developed for comparative analysis. The results indicate that a modified model has a better goodness of fit and a smaller estimation error for the Jibson93 formula. It indicates that the modified model may be more reasonable for the dataset of the Lushan earthquake. The analysis of results also suggests that a global equation is not ideally suited to directly estimate the Newmark displacements of landslides induced by one specific earthquake. Rather it is empirically better to perform a new multivariate regression analysis to derive new coefficients for the global equation using the dataset of the specific earthquake. The results presented in this paper can be applied to a future co-seismic landslide hazard assessment to inform reconstruction efforts in the area affected by the 2013 Lushan Ms 7.0 earthquake, and for future disaster prevention and mitigation.

A regolith map for the Lawra Belt has been developed by categorising the regolith-landform units by processing and interpreting remote sensing data. Regolith landform units were extracted from Landsat band ratios 3/1 and 5/4 to map ferruginous saprolite and lags; band ratio 5/7 was used to identify residual regolith and band ratio 4/2 was employed to separate ferruginous units from non-ferruginous regolith. Additional regolith landform units' discrimination was provided by compiling and interpolating radiometric data particularly for Landsat TM poorly defined areas. SRTM images were used to mark out the extent of the alluvial plains. High topographical terrains were marked from DEM image to represent the residual areas. Regolith landform unit (RLU) map that showed residual (relict and erosional), ferruginous, and depositional domains of the Lawra Belt was developed by superimposing the extractions made from the remote sensed data. Interpretive map generated from the remote sensed image analysis was validated by first creating a non-genetic regolith map through ground truth survey. The non-genetic map based on spatial distributions of the different regolith mapping units were classified on genetic classes or regimes based on regolith-landform similarities to develop a genetic map. The interpretive and the genetic map were superimposed to develop the regolith map for the Lawra Belt. The inliers and outliers presenting compositional overlaps within broad regolith classes were rectified from the field mapping information. The combined approach of image analysis and the ground truth mapping grouped the regolith of Lawra Belt into ferruginous (F), relict (R), erosional (E) and depositional (D) regimes.

The distribution of landslides induced by the 2008 M w 7.9 Wenchuan earthquake was investigated following the method of Meunier et al. (2007) to examine the relationships to peak ground acceleration (PGA). Results suggest that landslide densities are quantifiably related to PGA. Thresholds of PGAcr for landslide failure are ![Graphic][1] for average horizontal PGA and ![Graphic][2] for average vertical PGA. As with other earthquakes, the distribution of the Wenchuan earthquake‐triggered landslides can be described by two equations, based on area and source densities, respectively. The similar damping factors of ∼20 in these two equations suggest that both density distribution patterns of landslides reflect the dissipation of seismic energy. Landslide‐derived PGA equations were then produced for the hanging‐wall region of the earthquake‐affected area. The results indicate that it should be possible to produce an earthquake shake map from the distribution of earthquake‐triggered landslides in an area where there are few or no seismic instruments but many landslides. [1]: /embed/inline-graphic-1.gif [2]: /embed/inline-graphic-2.gif

The Xiaoxia anticline is a basement-cored fold in the northeastern Qinghai–Tibetan Plateau. It formed during the Middle–Late Cenozoic in a NNE-orientation oblique to prevailing WNW-striking thrusts in the surrounding region. The fold lies within the fault-bounded Xining Basin, which has behaved as a clockwise rotating and internally deforming block during the mid–late Tertiary. Proterozoic crystalline basement rocks and Jurassic–Cretaceous–Cenozoic terrestrial sediments exposed within the fold record three separate oblique-slip deformation events as determined by cross-cutting generations of faults and folds. The modern Xiaoxia anticline developed by: (1) outward-directed thrusting on the two fold limbs and, (2) oblique-slip thrusting on closely spaced minor NNE-striking faults that caused distributed uplift and passive shear folding of the sedimentary cover within the fold core. Tilted and thrusted river terraces on the flanks of the Xiaoxia anticline dated by optically stimulated luminescence and electron spin resonance indicate that folding has continued into the Late Quaternary (post-45.5 ± 5.5 ka) and therefore may still be active today. The development of the Xiaoxia anticline appears to be best explained in the context of the kinematic evolution of the Xining Basin's bounding strike-slip faults. Formation of the Xiaoxia anticline demonstrates that partitioned transpression in an evolving transpressional setting can invert intra-montane basins and produce basement-cored folds, thereby contributing to regional plateau uplift.

This paper presents a review of the Quaternary–Recent deformation field and mountain building processes within the Gobi Corridor region of Central Asia, which includes the North Tibetan foreland, Beishan, Gobi Altai and easternmost Tien Shan. The region can be considered the ‘soft core’ of Central Asia which has been reactivated due to the continuing Indo-Eurasia collision to the south. Favourable preconditions for reactivation of Gobi Corridor basement include a mechanically weak Palaeozoic terrane collage sandwiched between rigid Precambrian basement blocks to the north and south, thermally weakened crust due to Jurassic–Miocene volcanism and widespread Palaeozoic–Mesozoic granitic magmatism with associated high radiogenic heat production, and crustal thinning due to widespread Cretaceous rift basin development. The network of Quaternary–Recent faults within the entire region defines a diffuse sinistral transpressional deformation field that has generated a transpressional basin and range physiographic province. Typically, thrust and oblique-slip thrust faults are WNW-striking and reactivate basement faults and fabrics, whereas left-lateral strike-slip faults are ENE-striking and cut across basement trends. The angular relationship between SHmax and pre-existing basement structural trends is the fundamental control on the kinematics of Late Cenozoic deformation. Along-strike and across-strike growth and coalescence of restraining bends, other transpressional ranges and thrust ridges is an important mountain building process. Thrust faults throughout the region are both NNE and SSW directed and thus there is no common structural vergence, nor orogenic foreland or hinterland. Root structures appear to be vertical faults, not low-angle decollements and flower structure fault geometries within individual ranges are common. Published earthquake and geodetic data are consistent with a diffusely deforming continental interior region with tectonic loading shared amongst a complex network of faults. Therefore, earthquake prediction is likely to be more complex than in plate boundary settings and extrapolation of derived Late Quaternary fault slip rates is not straightforward. Modern mountain building within the Gobi Corridor demonstrates that reactivation of ancient accretionary and collisional orogens within continental interiors can play an important role in continental evolution and the life cycle of orogenic belts.

In mining areas, vertical ventilating shafts are often threatened by ground movements induced by underground mining. In this paper, damage characteristics related to collapse of the vertical ventilating shaft at the No. 14 exploratory line in Jinchuan Nickel Mine, China are documented. The damage mechanism is then analyzed based on comprehensive consideration of geological conditions and distribution of underground excavations. The results indicate that the high dip angle of the ore body and fault/fissures were responsible for the damage of the shaft when ground movements occurred. Although the damaged shaft was repaired in a short time, its stability and safe usage are still threatened by potential future ground movements, because the shaft is located within a subsiding depression induced by underground mining. This case study indicates that when designing an underground mining operation, it is very important to locate a shaft outside of any area where future mining-induced subsidence may occur.

Structural maps are traditionally produced by mapping features such as faults, folds, fabrics, fractures and joints in the field. However, large map areas and the spatially limited ground perspective of the field geologist can potentially increase the likelihood that not all structural features will be identified within a given area. The ability to recognise and map both local and regional structural features using high-resolution remote sensing data provides an opportunity to complement field-based mapping to help generate more comprehensive structural maps. Nonetheless, vegetation cover can adversely affect the extraction of structural information from remotely sensed data as it can mask the appearance of subtle spectral and geomorphological features that correspond to geological structures. This study investigates the utility of airborne Light Detection And Ranging (LiDAR) data and airborne multispectral imagery for detailed structural mapping in vegetated ophiolitic rocks and sedimentary cover of a section of the northern Troodos ophiolite, Cyprus. Visual enhancement techniques were applied to a 4-m airborne LiDAR digital terrain model and 4-m airborne multispectral imagery to assist the generation of structural lineament maps. Despite widespread vegetation cover, dykes and faults were recognisable as lineaments in both data sets, and the predominant strike trends of lineaments in all resulting maps were found to be in agreement with field-based structural data. Interestingly, prior to fieldwork, most lineaments were assumed to be faults, but were ground-verified as dykes instead, emphasising the importance of ground-truthing. Dyke and fault trends documented in this study define a pervasive structural fabric in the upper Troodos ophiolite that reflects the original sea-floor spreading history in the Larnaca graben. This structural fabric has not previously been observed in such detail and is likely to be continuous in adjacent regions under sedimentary cover. This information may be useful to future exploration efforts in the region focused on identification of structurally controlled mineral and groundwater resources. Overall, our case study highlights the efficacy of airborne LiDAR data and airborne multispectral imagery for extracting detailed and accurate structural information in hard-rock terrain to help complement field-based mapping.

Practical and financial constraints associated with traditional field-based lithological mapping are often responsible for the generation of maps with insufficient detail and inaccurately located contacts. In arid areas with well exposed rocks and soils, high-resolution multi- and hyperspectral imagery is a valuable mapping aid as lithological units can be readily discriminated and mapped by automatically matching image pixel spectra to a set of reference spectra. However, the use of spectral imagery in all but the most barren terrain is problematic because just small amounts of vegetation cover can obscure or mask the spectra of underlying geological substrates. The use of ancillary information may help to improve lithological discrimination, especially where geobotanical relationships are absent or where distinct lithologies exhibit inherent spectral similarity. This study assesses the efficacy of airborne multispectral imagery for detailed lithological mapping in a vegetated section of the Troodos ophiolite (Cyprus), and investigates whether the mapping performance can be enhanced through the integration of LiDAR-derived topographic data. In each case, a number of algorithms involving different combinations of input variables and classification routine were employed to maximise the mapping performance. Despite the potential problems posed by vegetation cover, geobotanical associations aided the generation of a lithological map – with a satisfactory overall accuracy of 65.5% and Kappa of 0.54 – using only spectral information. Moreover, owing to the correlation between topography and lithology in the study area, the integration of LiDAR-derived topographic variables led to significant improvements of up to 22.5% in the overall mapping accuracy compared to spectral-only approaches. The improvements were found to be considerably greater for algorithms involving classification with an artificial neural network (the Kohonen Self-Organizing Map) than the parametric Maximum Likelihood Classifier. The results of this study demonstrate the enhanced capability of data integration for detailed lithological mapping in areas where spectral discrimination is complicated by the presence of vegetation or inherent spectral similarities.

Cenozoic sedimentary deposits in central-southern Ningxia province, NW China are an important record of Tertiary tectonic events along the evolving Qinghai–Tibetan Plateau’s northeast margin. Shortly after the onset of the Indo-Eurasia collision to the south, a thrust belt and adjoining foreland basin began to form during 40–30 Ma. The Eocene Sikouzi Formation developed in a distal setting to this basin, in normal fault-bound basins that may have formed in a forebulge setting. Subsequent deposition of the Oligocene Qingshuiying Formation occurred during a phase of apparently less intense tectonism and the previous underfilled foreland basin became overfilled. During the Early Miocene, contractional deformation was mainly distributed to the west of the Liupan Shan. This resulted in deformation of the Qingshuiying Formation as indicated by an unconformity with the overlying Miocene Hongliugou Formation. The unconformity occurs proximal to the Haiyuan Fault suggesting that the Haiyuan Fault may have begun movement in the Early Miocene. In the Late Miocene, thrusting occurred west of the southern Helan Shan and an unconformity developed between the Hongliugou and Qingshuiying Formations proximal to the the Cha-Gu Fault. Relationships between the Miocene stratigraphy and major faults in the region imply that during the Late Miocene the deformation front of the Qinghai–Tibetan Plateau had migrated to the Cha-Gu Fault along the western Ordos Margin, and the Xiang Shan was uplifted. Central-southern Ningxia was then incorporated into the northeast propagating thrust wedge. The driving force for NE propagation of the thrust wedge was most likely pronounced uplift of the northeastern plateau at the same time. Analysis of the sedimentary record coupled with consideration of the topographic evolution of the region suggests that the evolving fold-and-thrust belt experienced both forward-breaking fold-and-thrust belt development, and out-of-sequence fault displacements as the thrust wedge evolved and the foreland basin became compartmentalised. The documented sedimentary facies and structural relationship also place constraints on the Miocene-Recent evolution of the Yellow River and its tributaries.

Controversy exists regarding the sources of the eolian dust for the immense Loess Plateau of north-central China, the largest accumulation of windblown loess in the world. Because the loess accumulation rate, unit thickness and particle size all decrease from northwest to southeast, it has long been thought that the northern deserts, especially the Mongolian Gobi, are the major loess source, a view supported by newly applied mineralogical (electron spin resonance, ESR) provenance techniques. Here, we examine surface samples from the Gobi Desert, and compare their magnetic and geochemical properties with those of last glacial loess samples from across the Loess Plateau region. The mineralogy, geochemistry and magnetic properties of Gobi Desert samples are variable (most likely reflecting local lithological complexity), distinctive and, critically, non-overlapping with the notably homogenous characteristics of the last glacial loesses spanning the Loess Plateau. It is likely that the source areas for the Plateau encompass a much larger area than any one proximal desert region, in order to account for a) the extreme degree of mixing, b) the volume of loess generated and transported, and c) the mineralogical and magnetic mismatch evident here between the Mongolian Gobi samples and the last glacial loess.

The Gobi Altai region of southern Mongolia contains intramontane basins dominated by Jurassic–Cretaceous clastic and volcanic deposits. The origin of the basins is poorly documented because Late Cenozoic transpressional mountain building and associated alluvial sedimentation have overprinted and obscured the older Mesozoic history. In this study, we report the discovery of Cretaceous high-angle normal faults and a major low-angle extensional detachment fault bordering the Altan Uul range in southern Mongolia, which indicates that NW–SE crustal stretching was responsible for creating the accommodation space for thick Jurassic–Cretaceous sedimentary accumulations in southern Mongolia. The detachment fault separates chlorite-grade metasedimentary rocks in the footwall from intensely sheared and flattened unmetamorphosed conglomerates and breccias in the hanging wall. The significant metamorphic break across the detachment fault, associated extensional structures in the hanging wall, and domal form of the footwall block indicate that NW Altan Uul has some structural and topographic characteristics typically associated with metamorphic core complexes. However, NW Altan Uul lacks ductile extensional fabrics along the detachment fault and in the adjacent footwall, and limited stretching in the upper plate suggests less total extensional slip than is reported from typical metamorphic core complexes. Unconformable relations in hanging-wall strata and palynological data indicate that extensional detachment faulting at NW Altan Uul occurred in the Aptian (120–112 Ma) similar in time to metamorphic core complex development previously reported in Mongolia–China border areas and the Daqing Shan of northern China. Post-detachment fault Cretaceous sedimentation buried NW Altan Uul, which is now exposed only as a result of erosional denudation associated with uplift of the recent Nemegt–Altan Uul restraining bend. The discovery of significant Aptian crustal extension in the southern Gobi Altai suggests that Early Cretaceous diffuse rifting encompassed an even wider region than was previously recognized, including areas of the eastern Altai, central, southern and eastern Mongolia, and adjacent areas of northern and northeastern China and Transbaikalia, constituting one of Earth9s largest continental interior extensional provinces. Workers investigating the neotectonic development of the Gobi Altai should consider the extent to which the pre-existing rift basin architecture may have influenced the recent range development and network of seismically active faults in the region.

In this study, we demonstrate the utility of SRTM topographic data as a tool for mapping alluvial fans and documenting the distribution of tectonically reactivated crust in the Gobi Altai region of southern Mongolia. The topographic data clearly reveal three diagnostic indicators of crustal reactivation: visible fault scarps, sharply defined faulted mountain fronts, and alluvial fan complexes adjacent to steep mountain fronts. These three variables are combined to produce a new surface tectonic activity map of the region. By selecting terrain with slope thresholds between 1 and 8° and then applying a topographic roughness filter, alluvial fan complexes are automatically discriminated and mapped throughout the region for the first time. This allows clear identification of Quaternary uplifted regions (and associated thrust faults) and the distribution of clastic basins which have experienced a two-stage history: Mesozoic rifting and Late Cenozoic alluvial sedimentation. By analysing mountain front sinuosity and alluvial fan topographic roughness, the tectonic activity of individual mountain fronts is quantitatively compared and ranked. Most ranges are upthrust fault blocks with outward directed thrusts and bajadas bounding their N-NE and S-SW fronts. The spatial distribution of youthful mountain ranges, flanking fan complexes, and Quaternary thrust and strike-slip faults is consistent with ongoing sinistral transpressional crustal reactivation throughout the region.

The Ravne Fault is an actively propagating NW–SE trending dextral strike-slip fault in the Julian Alps of NW Slovenia, which has been responsible for two moderate sized earthquakes in the last decade. Strike-slip displacements on moderate-steep fault planes are responsible for the recent seismic activity that is confined to shallow crustal levels. The fault is growing by interaction of individual right stepping fault segments and breaching of local transtensional step-over zones. The fault geometry is controlled by the original geometry of the NW–SE trending thrust zone, modified by successive faulting within the fault zone. In the modern N directed maximum horizontal stress regime, the segmented fault is lengthening by active growth at the fault's NW end. The spatial distribution of earthquake clusters shows that activity on strike-slip segments and thrust faults is contemporaneous. Detailed analysis of the spatial pattern of earthquake events and surface fault geometries suggests that for earthquakes of similar magnitudes and similar fault kinematics, the deciding factor for whether an earthquake rupture will breach a step-over zone is the relationship between the lengths of individual neighbouring fault segments and fault separation distances in the step-over-zones. The Ravne Fault represents an example of a tectonic structure that lies in an area subjected to multiple tectonic events under different regional stress conditions. At epicentral depths, the fault system is accommodating recent strain along newly formed fault planes, whereas in upper parts of the crust the activity is distributed over a wider deformation zone that includes reactivated brittle thrust faults.

The Saykhandulaan Inlier in South East Mongolia lies within the Central Asian Orogenic Belt (CAOB), and records a complex history of Palaeozoic tectonism and magmatism associated with terrane accretion on the northern margin of the Palaeo-Asian ocean. The inlier spans the boundary between the Gobi Altai back-arc basin terrane in the north and the Mandalovoo and Gurvansayhan island-arc terranes in the south which are notable for their many mineralised intrusions, including the Oyu Tolgoi gold-rich copper porphyry deposit. Results from cross-strike transects within the Saykhandulaan Inlier reveal that it can be subdivided into five parallel east–west striking litho-tectonic domains; (1) the Northern Slate Belt, comprising Devonian greenschist grade pelites and psammites with deep-marine to coastal siliciclastic protoliths; (2) the Saykhandulaan Valley Lineament Zone (SVLZ), a tectonised zone of faulted and lithologically altered volcanic rocks; (3) the High Strain Belt, consisting of tightly folded and flattened metamorphosed clastic sedimentary rocks; (4) the Molasse Succession, consisting of relatively undeformed coarse conglomerates and sandstones and, (5) the Oyut Ulaan Volcanic Group, a nearly 5 km-thick folded Carboniferous volcanic succession that hosts the mid-Carboniferous Oyut Ulaan mineralised granite. The Northern Slate Belt metasedimentary rocks record a northerly cratonic provenance, whereas all rocks to the south of the SVLZ have arc affinities. The SVLZ is thus interpreted to be the boundary between the Gobi Altai and Mandalovoo terranes. Two major deformation events are documented; (1) back-arc basin closure and inversion involving regional scale folding and greenschist grade metamorphism in the Northern Slate and High Strain Belts; (2) contraction associated with Mandalovoo terrane accretion and final closure of the Palaeo-Asian Ocean to the south. Following terrane accretion and cessation of subduction, crustal extension and strike-slip faulting further modified the crustal architecture of the inlier. The results presented here provide a useful framework for understanding the crustal evolution of adjacent regions within the southeast Gobi mineral belt.

An unusual late Neoproterozoic ( c . 572 Ma) ophiolite is exposed in the Dariv Range (western Mongolia), which contains intermediate to acidic lavas and sheeted dykes, and an igneous layered complex consisting of gabbro–norites, websterites, orthopyroxenites and dunites underlain by serpentinized mantle harzburgites. Based on the compositions of the crustal units and the crystallization sequences in the mafic and ultramafic cumulates we conclude that the entire oceanic crust, including the cumulates, was made from arc magmas with boninitic characteristics. The Dariv rocks bear a strong resemblance to rocks recovered from the modern Izu–Bonin–Mariana fore-arc, a fragment of proto-arc oceanic basement, and we propose that the Dariv Ophiolite originated in a similar tectonic setting. A metamorphic complex consisting of amphibolite- to granulite-facies metasedimentary and meta-igneous rocks was thrust over the ophiolite. This metamorphic complex probably represents a Cambrian arc. Thrusting started before 514.7 ± 7.6 Ma as constrained by new sensitive high-resolution ion microprobe U–Pb zircon analyses from a syn- to post-tectonic diorite. The Dariv Ophiolite is a type-example of a proto-arc ophiolite, a special class of supra-subduction zone ophiolites.

Mountain ranges that are actively forming around the western and northern perimeter of the Indo-Eurasia collisional deformational field, such as the Mongolian Altai, comprise a unique class of intracontinental intraplate transpressional orogen with structural and basinal elements that are distinct from contractional and extensional orogens. Late Cenozoic uplift and mountain building in the Mongolian Altai is dominated by regional-scale dextral strike–slip faults that link with thrust and oblique–slip faults within a 300-km-wide deforming belt sandwiched between the more rigid Junggar Basin block and Hangay Precambrian craton. Dominant orogenic elements in the Mongolian Altai include double restraining bends, terminal restraining bends, partial restraining bends, single thrust ridges, thrust ridges linked by strike–slip faults, and triangular block uplifts in areas of conjugate strike–slip faults. The overall pattern is similar to a regional strike–slip duplex array; however, the significant amount of contractional and oblique–slip displacement within the range and large number of historical oblique–slip seismic events renders the term “transpressional duplex” more accurate. Intramontane and range flanking basins can be classified as ramp basins, half-ramp basins, open-sided thrust basins, pull-apart basins, and strike–slip basins. Neither a classic fold-and-thrust orogenic wedge geometry nor a bounding foredeep exists. The manner in which upper crustal transpressional deformation is balanced in the lower crust is unknown; however, crustal thickening by lower crustal inflation and northward outflow of lower crustal material are consistent with existing geological and geodetic data and could account for late Cenozoic regional epeirogenic uplift in the Russian Altai and Sayan regions.

The Sutai Range is a structural and topographic culmination at the southeastern end of the Mongolian Altai and a world-class example of an actively forming restraining bend. The range occurs at a major stepover zone along the Tonhil dextral strike-slip fault within a wider region dominated by late Cenozoic transpressional deformation. Analysis of satellite imagery and the results of field investigations reveal that the range is structurally asymmetric with an overall NE tilt due to several major SE-directed thrusts within the core of the range and along its SW margin. The distribution of alluvial sediments shed from the range and stream length asymmetries also indicate a regional NE tilt for the range. Faults that splay off of the main Tonhil Fault bound discrete uplifted blocks that define an oblique-slip duplex at the surface and asymmetric flower structure in cross-section. Outward growth of the range is partly accommodated by growth of foreberg thrust ridges within the adjacent Dariv Basin. Thrust blocks within the centre of the range expose basement schists and mylonitic granite suggesting that the greatest uplift and crustal exhumation has occurred within the core of the restraining bend, although much of the exhumation is likely to be due to older Palaeozoic structural events. The southeast and northwest ends of the range are characterized by smooth unbroken surface ramps (“gangplanks”) that are upwarped towards the centre of the range where maximum Cenozoic uplift has occurred. The geometry and evolution of Sutai Uul and other intracontinental and intraplate restraining bends is fundamentally influenced by the initial width of the stepover zone, the attitude of regional basement structures and extent of brittle reactivation, the direction of SHmax relative to basement structures, and progressive fault and block rotation which may change the kinematics along faults or lead to their abandonment.

The Barkol Tagh and Karlik Tagh ranges of the easternmost Tien Shan are a natural laboratory for studying the fault architecture of an active termination zone of a major intracontinental mountain range. Barkol and Karlik Tagh and lesser ranges to the north are bounded by active thrust faults that locally deform Quaternary sediments. Major thrusts in Karlik Tagh connect along strike to the east with the left-lateral Gobi–Tien Shan Fault System in SW Mongolia. From a Mongolian perspective, Karlik Tagh represents a large restraining bend for this regional strike-slip fault system, and the entire system of thrusts and strike-slip faults in the Karlik Tagh region defines a horsetail splay fault geometry. Regionally, there appears to be a kinematic transition from thrust-dominated deformation in the central Tien Shan to left-lateral transpressional deformation in the easternmost Tien Shan. This transition correlates with a general eastward decrease in mountain belt width and average elevation and a change in the angular relationship between the NNE-directed maximum horizontal stress in the region and the pre-existing basement structural grain, which is northwesterly in the central Tien Shan (orthogonal to SH max ) but more east–west in the eastern Tien Shan (acute angular relationship with SH max ). Ar–Ar ages indicate that major range-bounding thrusts in Barkol and Karlik Tagh are latest Permian–Triassic ductile thrust zones that underwent brittle reactivation in the Late Cenozoic. It is estimated that the modern mountain ranges of the extreme easternmost Tien Shan could have been constructed by only 10–15 km of Late Cenozoic horizontal shortening.

We present a new terrane synthesis for Mongolia that incorporates geological, geochemical and geochronological data from more than 60 years of Mongolian, Russian and joint international studies. Forty-four terranes are distinguished and classified into cratonal, metamorphic, passive margin, island arc, forearc/backarc, accretionary complex, or ophiolitic types. New detailed stratigraphic columns for all terranes are presented which summarize the geological evolution of each terrane. Our analysis reveals that small Precambrian cratonic blocks in the Hangay region acted as a central nucleus around which Paleozoic arcs, backarc/forearc basin assemblages, associated subduction complexes and continental slivers were accreted. The temporal and spatial order of accretion and amalgamation was complex and probably not simply from north to south with time. The timing of terrane accretion is partly constrained by sedimentary overlap assemblages and post-amalgamation intrusive complexes. The main stages of amalgamation occurred during the Neoproterozoic, Cambrian–Ordovician, Devonian, Pennsylvanian–Permian and Triassic. The arcuate trends of terranes around the central Hangay region provide the first-order structural grain for Mongolia. This crustal anisotropy has played a major role in controlling the geometry and kinematics of all subsequent Phanerozoic deformation and reactivation of structures in the region, including the Cenozoic development of the Altai and Gobi Altai. Our results provide the most detailed synthesis to date of the basement geology of Mongolia which should provide an important crustal framework for interpreting the Phanerozoic tectonic evolution of a large part of Central Asia. In addition, our synthesis allows the economic resources of Mongolia to be placed in a modern tectonic context.

This book will disappoint most geologists and is not to be recommended. The authors are geomorphologists who believe that the importance of geomorphology in understanding mountain building has been under-appreciated by the geological community. This may be true, but this book will not help their cause. The stated theme of the book is the narrow assertion that all mountain ranges form by vertical uplift of plateaus followed by erosion with or without gravity sliding. This book is basically anti-plate tectonics and, instead of enlightening the reader, we are treated to one-sided views, unsupported assertions, obsolete information and generally sloppy scholarship. The book is uncomfortably organized between chapters covering mountains on four of seven major continents and topical subjects such as mountains with gravity structures and mountains on passive margins. The overall writing is not concise, nor well organized, and there is widespread redundancy of the authors’ opinions. The figures are generally very poor. Many are obsolete cartoons such as a 1965 cross-section of the …

The original version of this article unfortunately contained a mistake. The presentation of Fig. 1 was incorrect.

Vegetation cover can affect the lithological mapping capability of space- and airborne instruments because it obscures the spectral signatures of the underlying geological substrate. Despite being widely accepted as a hindrance, few studies have explicitly demonstrated the impact vegetation can have on remote lithological mapping. Accordingly, this study comprehensively elucidates the impact of vegetation on the lithological mapping capability of airborne multispectral data in the Troodos region, Cyprus. Synthetic spectral mixtures were first used to quantify the potential impact vegetation cover might have on spectral recognition and remote mapping of different rock types. The modeled effects of green grass were apparent in the spectra of low albedo lithologies for 30%–40% fractional cover, compared to just 20% for dry grass cover. Lichen was found to obscure the spectra for 30%–50% cover, depending on the spectral contrast between bare rock and lichen cover. The subsequent impact of vegetation on the remote mapping capability is elucidated by considering the outcomes of three airborne multispectral lithological classifications alongside the spectral mixing analysis and field observations. Vegetation abundance was found to be the primary control on the inability to classify large proportions of pixels in the imagery. Matched Filtering outperformed direct spectral matching algorithms owing to its ability to partially unmix pixel spectra with vegetation abundance above the modeled limits. This study highlights that despite the limited spectral sampling and resolution of the sensor and dense, ubiquitous vegetation cover, useful lithological information can be extracted using an appropriate algorithm. Furthermore, the findings of this case study provide a useful insight to the potential capabilities and challenges faced when utilizing comparable sensors (e.g., Landsat 8, Sentinel-2, WorldView-3) to map similar types of terrain.

The mechanism of continental growth of Central Asia is currently debated between models invoking continuous subduction–accretion, or punctuated accretion due to closure of multiple ocean basins. Ophiolites in Central Asia may represent offscraped fragments in an accretionary complex or true collisional sutures. The Bayankhongor ophiolite, a NW–SE-striking sublinear belt 300 km long and 20 km wide, is the largest ophiolite in Mongolia and possibly Central Asia. We present results of the first detailed structural and lithological study of the ophiolite. The study area is divided into four zones: Baidrag complex, Burd Gol, Bayankhongor, and Dzag zones. The Archaean Baidrag complex comprises tonalitic granulites and metasediments. The Burd Gol zone is a metamorphosed sedimentary and igneous mélange. The Bayankhongor zone contains the dismembered ophiolite forming a serpentinite mélange. The Dzag zone consists of asymmetrically folded chlorite–mica schists resembling meta-turbidites. The structure is dominated by steeply dipping, NE directed thrusts and NE-vergent folds. We suggest the Bayankhongor ophiolite marks the closure of an ocean separating two microcontinents: the Baidrag complex with the Burd Gol accretionary complex to the south, and a northern continent that forms the basement for the Hangai region. Subduction was towards the SW with NE-directed ophiolite obduction onto a passive margin represented by the Dzag zone.

The Archean and Paleoproterozoic Sao Francisco craton of eastern Brazil is surrounded on all sides by Brasiliano (=Pan African) orogens. The N–NE trending orogen that separates the eastern edge of the southern Sao Francisco craton from the Atlantic coast can be divided into the largely greenschist and amphibolite facies Aracuai belt on the west and the largely granulite facies Ribeira belt on the east. A pronounced linear gravity and magnetic anomaly, the Abre Campo discontinuity, defines the boundary between these two belts. We obtained Sm–Nd mineral ages and whole-rock Sm–Nd model ages for garnet-bearing metamorphic rocks along an E–W transect across the southern Sao Francisco craton, the southern Aracuai belt, and the Ribeira belt at about latitude 20°S. A recrystallization age of 2.1 Ga from metasediments recrystallized during the development of the classic dome-and-keel province of the southern Sao Francisco craton (the ‘Quadrilatero Ferrifero’) indicates that dome emplacement occurred during the waning stages (extensional collapse) of the Transamazonian collisional orogeny. Seven mineral ages from the southern Aracuai and Ribeira belts date the thermal peak of metamorphism at between 538 and 589 Ma, confirming that these belts were pervasively remobilized during the Brasiliano event. Samples from the Aracuai belt yield either Archean (>2.6 Ga) or Transamazonian (2.1–2.3 Ga) TDM model ages, indicating that the protoliths were either fragments of the Sao Francisco craton crust or were sediments derived from that craton, which presumably had been stretched to form a thinned continental margin during Meso- and Neo-Proterozoic rifting events. Notably, a mixed meta-pelite and metabasite sequence in the southern Aracuai belt, the Dom Silverio Group, has Transamazonian ancestry and thus may represent oceanic sediments deposited on or east of this stretched margin and then thrust back onto the continent to mark a collisional suture between the Sao Francisco block and an Archean (?) crustal sliver to the east. The rocks of the Ribeira belt (i.e. the region east of the Abre Campo discontinuity) have younger model ages (TDM=1.6–2.0 Ga), indicating that this belt was not originally part of the Sao Francisco craton — it may represent an accreted Transamazonian terrane. Therefore, the Abre Campo discontinuity marks an important crustal boundary, possibly a suture. Brasiliano shear zones appear to steepen and root into the Abre Campo discontinuity, suggesting that it formed in Brasiliano time.

Bedrock and Quaternary alluvial fans in the forelands of the northern Gobi Altai have been faulted and warped by foreland-propagating thrust faults to form elongate hills known as forebergs. Forebergs near Bogd town, north of Arsta Bogd, and at Ih Hetsuu, north of Baga Bogd were mapped and their formation constrained using luminescence dating of lacustrine and fanglomerates sediments to give localized uplift rates of c. 0.05 m ka − 1 , and between c. 1.6 and 4.1 m ka − 1 , respectively. Comparisons between vertical surface rupture during the 1957 Gobi Altai earthquake with the age and amount of uplift of lacustrine sediments provide a tentative estimate of between 1288 ± 382 to 497 ± 120 years for the average recurrence interval of great earthquakes in the Baga Bogd region. These localized uplifts rates support the view that the Gobi Altai Mountains probably took between 50 and 25 million years to form and were, therefore, coeval with the uplift of the Himalayas and the Tibetan Plateau.