Cenozoic Tectonics Research Articles

Conjugate extrusion with dextral oblique-slip faulting in SE Tibet: new insights into Oligo-Miocene deformation

SE Tibet experienced significant deformation during the Late Cenozoic, characterized by clockwise rotation of blocks separated by left-lateral strike-slip faults. Through field surveys, structural analyses and microstructural observations, we identified an early phase of ductile shear zones along three major faults: the Anninghe, Jinhe–Jinghe and Jinpingshan faults. New geochronological and thermochronological data collected from these fault zones and from carbonatites associated with a tear fault between two right-lateral oblique faults provide evidence that this slip occurred before c. 30 Ma. These findings lead to a new conceptual model suggesting that these north–south-trending right-lateral oblique-slip faults, together with the NW-trending left-lateral strike-slip faults in SE Tibet, form a network of large conjugate fractures. The conjugate fracture system, as a result of north- to NE-trending contraction, had a crucial role in controlling the overall tectonic framework of SE Tibet during the Oligocene. By integrating previous research and combining this with our latest findings, we propose a two-phases evolution model of Cenozoic tectonics in the region of SE Tibet, in which a drastic change in kinematics took place from an early phase (before ∼30 Ma) oblique dextral shearing to a late phase sinistral strike-slip faulting since the Miocene.

First identification of late Mesozoic intraplate magmatism in the Chinese north Tianshan: implications for the orogenic architecture and crustal evolution

The formation and dynamics of granitoids in an intra-continental setting are crucial for understanding the architecture and evolution of continental crust. Here, we report geochronological, geochemical and Sr–Nd–Hf isotopic data for newly discovered late Mesozoic granitic intrusions in the Tianshan belt, northwestern China. These granitoids are I-type granites derived from an igneous precursor and were emplaced at c . 145–132 Ma. They have positive ε Nd ( t ) values and young Nd model ages, together with relatively low Sr/Y ratios, indicating that they might have originated from partial melting of the juvenile lower crust. There is a prominent decoupling between zircon Hf and bulk-rock Nd isotopes, which may have resulted from the early crystallization of Ti-rich minerals. These granitic intrusions also display subduction-related geochemical characteristics, which are probably inherited from Paleozoic crustal sources that were metasomatized by subduction-related fluids. We conclude that these late Mesozoic granitoids were emplaced in an intra-continental setting, and were probably triggered by thermal relaxation owing to crustal shortening and thickening. These data further imply that the Tianshan changed into crustal reworking during the Mesozoic from its prominent crustal growth in the Paleozoic. Supplementary material: LA-ICP-MS zircon U–Pb dating results, whole-rock major and trace element compositions, whole-rock Sr–Nd isotopic data and zircon Lu–Hf isotopic data are available at https://doi.org/10.6084/m9.figshare.c.7167890 Thematic collection: This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at: https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change

Tracing a remnant of subducted Indian felsic crust: insights from zircon studies

Zircon is a common mineral in nature that survives varied pressure and temperature conditions in the subduction process. It has excellent ability to reveal progressive metamorphic history and, hence, is useful in reconstructing the subduction tectonics in collisional orogenic belts. In the Tso Morari Gneiss of the Indus Suture Zone, Himalaya, eclogite boudins have registered the imprint of subduction-related ultrahigh-pressure (UHP) metamorphism; this imprint is, however, missing in the host gneisses. To search for the missing link, zircons of the gneisses were studied. The zircon overgrowth and the numerous mineral inclusions indicate the metamorphic responses of the gneisses. The Raman spectra of minerals show the cores of the zircon consist of apatite and quartz and the surrounding overgrowth preserves quartz–coesite, c-polymorphs and other metamorphic minerals. The distribution pattern of these minerals in the zircons is consistent with the Th/U ratios ranging from 0.30 to 0.01, recognizing the inner magmatic and outer metamorphic domains. The U–Pb ages from the inner magmatic (at c. 500 Ma) and from the outer metamorphic growth (at c. 45–42 Ma) suggest the former is the protolith age and the latter the metamorphic age of the gneisses. The tectonic interpretation reveals the subduction of Indian felsic crust to UHP depth (>100 km) at c. 45 Ma. Supplementary material : Raman spectra of C-inclusions in the zircon of Tso Morari Gneiss are available at https://doi.org/10.6084/m9.figshare.c.7168228 Thematic collection: This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at: https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change

The impact of faulting-induced uplift and subsidence on terrace formation and abandonment: a case study of the Huangshui River, NE Tibetan Plateau

Fluvial terraces are important archives for inferring changes in river dynamics. In the NE Tibetan Plateau, the Huangshui River flows through broad depressions and narrow gorges. This morphology is the result of strike-slip and reverse faulting. Differential vertical motion has led to the formation of diverse fluvial terraces. We used morphological analyses, sedimentary successions and optically stimulated luminescence dating to map, characterize and date fluvial terraces in two depressions and the connecting gorge. Our results show that an important phase of tectonism occurred shortly after 138 ka because: (1) terraces older than 138 ka in the gorge show clear deformation in their longitudinal profiles; (2) terraces from the last interglacial are composed of a thick fill terrace in the upstream depression, a strath terrace in the gorge and a fill terrace created by an alluvial fan in the downstream depression; and (3) the aggradation of the last interglacial terrace began synchronously in the upstream and downstream depressions, whereas the abandonment age becomes younger in an upstream direction (from c. 131 to c. 91 ka). The transient abandonment reflects an upstream-migrating knickpoint. Thematic collection: This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at: https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change

Exhumation of the Qilian Shan and Miocene activity of the Haiyuan fault: insights from apatite (U–Th)/He thermochronology in the Laolongwan basin, northeastern Tibetan Plateau

The Tibetan Plateau, which is deformed by the collision between the Indian and Eurasian plates, is a natural laboratory in which to study intracontinental deformation related to northeastward growth of the plateau. However, how and when the Tibetan Plateau propagated to its present-day margins remain unclear. The Qilian Shan and Haiyuan fault, which serve as the topographic and geological boundaries of the high plateau, are key to revealing the uplift and expansion of the Tibetan Plateau. Here, we present detrital apatite (U–Th)/He and reverse modelling results from the Laolongwan basin, which is interpreted as a pull-apart basin controlled by activity of the Haiyuan fault in the east portion of the Qilian Shan region. Our results reveal three-stage tectono-thermal evolution of Qilian Shan: (1) Late Jurassic to Cretaceous rapid exhumation; (2) Late Cretaceous to middle Miocene tectonic quiescence period; and (3) exhumation after the middle Miocene. We suggest that the Jurassic to Cretaceous rapid exhumation might be related to the convergence of the Lhasa block with the Eurasian plate or regional extension during the Mesozoic closure of the Meso-Tethys, and the mid-Miocene accelerated exhumation was driven by Haiyuan fault activation related to the growth of the Tibetan Plateau to its northeastern margin. Supplementary material: Time–temperature paths of (U–Th)/He thermal history models (Fig. S1) and AHe age–depth relationship (Fig. S2) are available at https://doi.org/10.6084/m9.figshare.c.7018149 Thematic collection: This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at: https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change

Neogene to modern foreland basin development in the Sub-Andean zone of southern Bolivia and northern Argentina, 21−23°S

The Sub-Andean retroarc region is a unique example of an active continental-scale retroarc foreland basin system. Heavily targeted for hydrocarbon exploration, the region hosts a large volume of subsurface data coupled to surface studies dedicated to refining its evolution in time and space. This paper presents a regional correlation of stratigraphic markers from seismic reflection and well logs across the Sub-Andean foothills at 23−21°S in southern Bolivia and northern Argentina, which reveals the contrasting along-strike history of Mesozoic to Cenozoic tectonics that preceded the foreland basin setting. Supported by published geochronological data and new zircon U-Pb maximum depositional ages, we describe the depositional transition from pre-Andean to Andean stratigraphy and discrete episodes of foreland basin subsidence and shortening. Based on interpreted stratigraphic breaks, we define the extent and stepwise evolution of this foreland basin, which was characterized by the progressive eastward migration of foreland basin depozones. Based on restored thickness profiles, we present flexural models of basin subsidence for the Sub-Andean foothills region. The modeling of discrete episodes of foreland basin subsidence refines the widely accepted bimodal elastic strength in the foreland basin at 21−23°S, which is weaker in the western ranges (∼20 km effective elastic thickness) and stronger eastward (>40 km). Modeling results also reveal minimum values of subsidence rates (up to 1.2 mm/yr) in the sequential foredeep depozones and suggest that the modeled tectonic load migration—as constrained by the record of syntectonic strata—probably increased over time through the incorporation of Sub-Andean rocks into the orogenic wedge.

Interactions between Cenozoic tectonics and landscape dynamics in Londrina, Paraná, Brazil

The Londrina City, located in southern Brazil, is situated on the basalt of the Paraná Igneous Province (PIP), near tectonic structures such as the Guaxupé faults and the São Jerônimo-Curiúva and São Sebastião lineaments, with a history of reactivation in the Cenozoic. Between 2015 and 2018, low-magnitude earthquakes hit the municipality, suggesting a possible connection with these structures. This study investigates the relationship between Cenozoic tectonics and geomorphological dynamics, combining quantitative geomorphological analysis with field analysis of faults. The results reveal signs of tectonic control on the landscape, with two pulses of regional uplift/base level drop affecting the drainage network. Reactivated segments, especially at intersections of NE and NW structures, influence dynamics, with variations in uplift rates between basins and block rotation under a transtensive regime. Recent earthquakes are related to the reactivation of an N50-60E fault scarp, possibly the Guaxupé Fault, indicating recurrent tectonic movement. Paleostress analyses identify three deformation pulses, highlighting the complexity of landscape evolution in intraplate regions. These findings enhance understanding of regional tectonics, emphasizing the need to comprehend landscape evolution in interior plate areas, such as the South American Plate.

Interaction of surface processes and crustal flow in the Eastern Himalayan Syntaxis

The syntaxes at the eastern and western ends of the Himalaya located in the Tsangpo and Indus gorge regions provide examples of the interplay between tectonics and erosion. A previous borehole study along the Yarlung River in the Eastern Himalayan Syntaxis (EHS) revealed an ∼1 km thick sedimentary wedge upstream of the Tsangpo gorge with a >2.5 Ma depositional age. However, the mechanism of formation of this sedimentary wedge remains under debate. Here, we combine low-temperature thermochronology data and thermomechanical modelling to discuss how a sedimentary wedge formed at the highly eroded EHS. Our low-temperature thermochronology results show late Miocene fast cooling episodes focused at the Gyaca and Tsangpo gorges, which are interpreted to be related to coeval rifting at the former and rapid erosion and hot-crust upwelling at the latter. Constrained by the geological and geophysical observations, we apply thermomechanical models to illustrate the mechanism of formation of the sedimentary wedge and present high relief of the EHS. The numerical geodynamic model shows that localized erosion triggers middle ‘crust extrusion’ and regional topographic adjustment at the EHS. Supplementary material : Supplementary figures and tables are available at https://doi.org/10.6084/m9.figshare.c.7008098 Thematic collection: This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at: https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change

Detrital zircons and heavy minerals from the Palu Formation, Sulawesi, Indonesia: constraints on exhumation of the Palu Metamorphic Complex and drainage evolution

The Palu Formation, previously known as the Celebes Molasse in the Palu area, is understudied and was previously considered to be associated with the Pliocene collision between an Australian-derived microcontinent (Banggai Sula) and the eastern margin of Sundaland (West Sulawesi). Here, we present sedimentological, heavy mineral and zircon geochronological data to provide insights into sediment provenance and to elucidate Neogene tectonic activity in Sulawesi. These analyses suggest that the Pleistocene Palu Formation comprises synorogenic alluvial fan to braided river deposits that record the rapid uplift of metamorphic and granitoid rocks in the Neck and west Central Sulawesi. The Palu Formation is characterized by predominant granitoid and metamorphic clasts and heavy mineral assemblages dominated by pyroxene, amphibole and garnet. Detrital zircons record youngest grain ages of c. 2.5 and 3.0 Ma with a significant Pliocene age population and subsidiary Eocene, Cretaceous, Jurassic and Late Triassic age peaks. Rapid uplift and erosion associated with mountain building shaped the topography and influenced the evolution of Palu River networks. Supplementary material : Complete location, heavy mineral and detrital zircon geochronology datasets are available at https://doi.org/10.6084/m9.figshare.c.7033388 Thematic collection: This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at: https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change

Neotectonic landforms of the Neoproterozoic basement of Southeastern Brazil: The case of the north border of the São Paulo Basin

Recent studies have demonstrated that the current tectonics activity plays an important role also in intraplate setting, such as in the Brazilian territory as a whole. The Continental Rift of Southeastern Brazil, which comprises the Neoproterozoic basement and some Paleogene basins (e.g. Taubaté, São Paulo, and Curitiba basins), is one of the most important features affected by Neotectonics, the tectonic regime acting since Neogene. However, information about the effects of the current tectonic regime on the rift surrounding areas is still missing. In this way, the objective of this research is to evaluate the possible effects of Neotectonics on the landform of the Neoproterozoic basement, close to the São Paulo sedimentary basin. In order to achieve this objective, general descriptive characteristics of the drainage system were analyzed, such as: network pattern, drainage and hydrographic densities, junction angles, trophy, and anomalies. These data were compared with the aeromagnetic data and the results of the Stream Length-Gradient (SL), Asymmetry Factor (AF), and Drainage Basin Shape (BS) indexes of the main rivers. In the field, 1330 measurements of tectonic features were surveyed in 122 outcrops. The paleostress orientations were calculated by means of fault and fracture inversions by Daisy3 software. In addition, Geologic-geomorphological Maps (1:25,000) of 3 key areas were prepared. The results suggest that tectonic structures have influenced the general arrangement of hills, ridges, and floodplains, as well as the general characteristics of the drainage system, responsible for the dissection of landforms. Recent deformations indicate Neotectonic activity causing tilting of blocks and channel migration, and formation of escarpments, triangular facets, abandoned meanders, fluvial terraces, knickpoints, and elbows. On the other hand, the field data suggest that the most of faults are related to the Pre Cenozoic tectonics. In this way, Neotectonics is not the principal structural element on the landform evolution of the study area, but it has an important role on the relief formation of some regions.

Extensional exhumation of cratons: insights from the Early Cretaceous Rio Negro–Juruena belt (Amazonian Craton, Colombia)

Abstract. This study presents results from apatite fission track (AFT) thermochronology to investigate the thermal history and exhumation dynamics of the Rio Negro–Juruena basement, situated within the western Guiana Shield of the Amazonian Craton. AFT dating and associated thermal history modeling in South America has largely been restricted to the plate's margins (e.g., Andean active margin, Brazilian passive margin, and others). Our paper reports on low-temperature thermochronological data from the internal part of the western Guiana Shield for the first time. This area is part of a vast cratonic lithosphere that is generally thought to be stable and little influenced by Mesozoic and Cenozoic tectonics. Our data, however, show AFT central ages ranging from 79.1 ± 3.2 to 177.1 ± 14.8 Ma, with mean confined track lengths of ca. 12 µm. Contrary to what might be expected of stable cratonic shields, inverse thermal history modeling indicates a rapid basement cooling event in the early Cretaceous. This cooling is interpreted as a significant exhumation event of the basement that was likely driven by the coeval extensional tectonics associated with back-arc rifts in the Llanos and Putumayo–Oriente–Maranon basins. The extensional tectonics facilitated both basement uplift and subsidence of the adjoining basins, increasing erosional dynamics and consequent exhumation of the basement rocks. The tectonic setting shifted in the late Cretaceous from extensional to contractional, resulting in reduced subsidence of the basins and consequential diminishing cooling rates of the Guiana Shield basement. Throughout the Cenozoic, only gradual, slow subsidence occurred in the study area due to regional flexure linked to the Andean orogeny. Comparative analysis with low-temperature thermochronology data from other west Gondwana cratonic segments highlights that exhumation episodes are highly controlled by tectonic inheritance, lithospheric strength, and proximity to rift zones. This study underscores the complex interplay between tectonic events and the response of cratonic lithosphere over geological timescales and highlights extensional settings as an important geological context for craton exhumation.

Mesozoic evolution of large-scale drainage systems in the Indochina Block: evidence from palaeomagnetic and U–Pb geochronological constraints

The collage of the Indochina Block to the Eurasian continent during the Mesozoic resulted in major changes in source-to-sink systems of East Asia, whilst the sedimentation in the Khorat–Simao Basin of the Indochina Block transited from marine to continental environments. Previous studies uncovered the existence of transcontinental river systems in the East Asia mainland during the Cretaceous to Early Cenozoic, although there have been few studies on pre-Cretaceous drainage systems. To determine the impact on the evolution of palaeo-drainage systems triggered by tectonic movement of the Indochina Block, we performed palaeomagnetic and U–Pb geochronologic analyses on the Late Triassic to Early Cretaceous sedimentary rocks in the Simao Basin. Palaeomagnetic data indicate stable Jurassic tectonic environments between the Indochina and Songpan–Ganzi–South China blocks, following their Late Triassic collision. Based on detrital zircon U–Pb dating, the Late Triassic age spectra consist mainly of Phanerozoic components, while the Jurassic to Cretaceous age spectra display more Precambrian age peaks. The contribution of potential provenance to the Simao Basin changed during the Early Cretaceous, suggesting several sedimentary provenance transitions. Also, we believe that large continental-scale drainage systems flowing through the North Qiangtang, Sichuan, Simao and Khorat Basins were sourced from the Songpan–Ganzi Block since the end of the Late Jurassic. Supplementary material: The findings of a quantitative statistical study (Fig. S1; Table S5), the location of the Late Triassic to Early Cretaceous samples from the Simao Basin (Table S1), palaeomagnetic poles for Eurasia, South China, Indochina, North Qiangtang and Tarim (Table S2), the result of quantitative analysis for the Late Triassic and Middle Jurassic sedimentary rocks from the Simao and Sichuan basins (Table S3), and results of zircon U–Pb dating (Table S4) are available at https://doi.org/10.6084/m9.figshare.c.6862918 Thematic collection: This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at: https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change

Coastal Cliffs of the Rio Grande do Norte State: Geoheritage Characterization and Valorization in Northeast Brazil

The Rio Grande do Norte state, Northeast Brazil, has 410 km of coastal extension, being 107 km approximately composed of cliffs excavated in Cenozoic sedimentary rocks. In the last three decades, these cliffs are passing for transformations due the human occupation, tourism activity and climatic changes. To inventory the geoheritage present in these cliffs is essential to support management plans that include investment to conserving part of this Earth’s natural history. This paper aims to inventory, classify, assess and value the Potiguar cliffs as geological sites. From 46 outcrops that Saraiva Junior (2021) studied to describe the cliffs’ geomorphology, 20 geological sites were selected, these are used in national and international publications and divided in three frameworks: Miocene-Pliocene sedimentation, Pleistocene sedimentation and Cenozoic tectonics. These 20 cliffs were inventoried using the Brilha (2016) methodology in order to qualify and quantify the scientific value, potential educational and touristic uses and degradation risk. The Ponta do Mel, Barra de Tabatinga, Ponta dos Três Irmãos, Barreira do Inferno, Ponta do Reduto and Morro do Chapéu were defined as the most valuable cliffs on the scientific aspect. We proposed monitoring planning based on the cliff’s baselines, protection measures based on the specific threats and three geotouristic routes based on the geographic distribution of the sites and the frameworks.

Cenozoic sedimentary evolution of the Tiereke section on the northern Tarim Basin: implications for the intracontinental mountain building of the Eastern Tian Shan

The Tian Shan is one of the world's largest intracontinental orogens and provides an excellent example for deciphering the intracontinental responses to the tectonics of plate boundaries. Despite its significance, the timing and driving mechanism of the Cenozoic mountain building of the Tian Shan in the context of the India–Eurasia collision remain controversial. In this study, Cenozoic stratigraphy of the Tiereke section along the western Kuqa Depression of the northern Tarim Basin on the south foreland of Eastern Tian Shan (east of 80°E) has been investigated. The results indicate that the Cenozoic deposition of the Tiereke region sequentially experienced a transgression from the Kumugeliemu Group to the Suweiyi Formation and a regression from the Suweiyi to the Kuqa Formations. Based on the contact relationships and conglomerate textures, three stages of high-energy alluvial deposition have been identified in the lower Kumugeliemu Group, upper Jidike and Kangcun–Kuqa Formations, respectively. These sedimentary events were interpreted to represent phases of Eastern Tian Shan mountain building at c. 54 Ma, c. 27 Ma and since c. 9.7 Ma according to previous magnetostratigraphic results, which were possibly related to the initial India–Eurasia collision, the collision between the India and Tarim lithospheric mantles, and the basinward propagation of deformation, respectively. Thematic collection: This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at: https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change

Late Oligocene monsoonal climate in the Lunpola Basin, central Tibetan Plateau: evidence from palaeosol records

The Asian monsoon affects the natural patterns of climate in China and its origin and evolution have been a matter of much debate in palaeoclimatology. Results from recent studies indicate that the Asian monsoon had reached the subtropical zone by at least c. 41 Ma and expanded to the central Tibetan Plateau during the Late Oligocene, although more geological evidence is required to confirm its spatial and temporal evolution. The well-developed Late Oligocene palaeosol in the Lunpola Basin, central Tibetan Plateau is an ideal material for addressing the issue. Observations of various climatic indicators suggest that these palaeosols were forest cinnamon soils, as shown by the compound Bt and Bk horizons, abundant clay coatings and carbonate nodules, and the diagnostic chemical composition of clays in the Bt horizon. A high chemical weather index, the Rb/Sr ratios and high contents of illite/smectite mixed-layer minerals show that these palaeosols experienced intense weathering and leaching during pedogenesis. The mean annual temperature and mean annual precipitation during the developmental period of the palaeosols were 10.4–14.8°C and 615–1128 mm, respectively, as estimated by empirical formulas, which are comparable with those of cinnamon soils in current monsoon climates. This study provides important independent evidence from palaeosols for studies of the evolution of the Asian monsoon. Supplementary material: The data about the clay chemical composition and climatic indicators of palaeosol and modern soils are available at https://doi.org/10.6084/m9.figshare.c.6850703 Thematic collection: This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at: https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change

Khangai Intramantle Plume (Mongolia): 3D Model, Influence on Cenozoic Tectonics, and Comparative Analysis

Khangai Intramantle Plume (Mongolia): 3D Model, Influence on Cenozoic Tectonics, and Comparative Analysis

Inversion of Late Miocene uplift history from the transient Daxia River landscape, NE Tibetan Plateau

The mechanisms of the upward and outward growth of the Tibetan Plateau are crucial for understanding the geodynamic significance of Cenozoic continental collisions. Northeastern Tibet has been suggested as one of the youngest deforming and uplifting margins surrounding the plateau. The existence of fluvial knickpoints and low-relief topographic surfaces along the Yellow River and its tributaries indicate the transience of the landscape in response to active tectonic uplift. Therefore, the uplift history of the North Eastern Tibetan Plateau (NETP) can be potentially inverted from the disequilibrium channel profiles of the Yellow River and its tributaries. The West Qinling Fault (WQF) is part of the geomorphological and topographic boundaries of the NETP. Its uplift history helps to clarify the deformation history of the Tibetan Plateau. In this study, the focus was on the Daxia River (one of the Yellow River tributaries) to identify the distribution of peneplain surfaces and knickpoints, and to present a linear inversion on the fluvial longitudinal profiles for the relative uplift history of the West Qinling. We obtained a relative uplift history with two pulses of change in the uplift rates at ∼5 and ∼2 Ma. Rates of relative uplift maintained low values during the Late Miocene, then slowly increased from 0.1 to 0.2 mm a −1 after ∼5 Ma and suddenly jumped to 0.3 mm a −1 at ∼2 Ma, consistent with recent findings on the deformation records in the NE Tibetan Plateau. We suggest that (1) the Late Miocene–Pliocene landscape evolution was driven by both tectonics and climate change and (2) inversion of the transient longitudinal channel profiles, if applied, may provide broader insights into the upward and outward growth patterns of the NE Tibetan Plateau. Thematic collection: This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at: https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change

Khangai Intramantle Plume (Mongolia): 3D Model, Impact on Cenozoic Tectonics and Comparative Analysis

The Khangai plume is located beneath Central and Eastern Mongolia and corresponds to the mantle volume with significantly reduced longitudinal wave (P) velocities. The plume was identified as a result of the analysis of the MITP08 volumetric model of variations in P wave velocities, expressed as deviations of these velocities from the mean values for the corresponding depths in percent. Above the plume, the lithospheric mantle is thinned to ~50 km. Particularly low velocities (up to –6%) were found in the sublithospheric mantle down to a depth of 400 km. The main body of the plume is located under the Khangai Highland and spreads north to the edge of the Siberian Platform. The Khentei branch of the plume is identified southeast of the Khentei Highlands. It is connected to the main body of the plume at depths of 800–1000 km. Branches of the plume and its Khentei branch spread to Transbaikalia. The size of the plume decreases with depth, and its deepest part (1250–1300 km) is located under the southern part of the Khangai Highland. On the Earth’s surface, the main body of the Khangai plume corresponds to a Cenozoic uplift up to 3500–4000 m high in the south of the Khangai Highland. From the southeast, the territory of the Khangai plume and its Khentei branch is limited by the Late Cenozoic troughs stretching along the southeastern border of Mongolia. On other sides, the Khangai uplift is limited by a C-shaped belt of depressions, consisting of the southeastern part of the Baikal rift zone, the Tunka and Tuva basins in the north, the Ubsunur Basin and the Great Lakes Basin in the west and the Valley of Lakes in the south. The depressions are filled with lacustrine and fluvial sediments from the Late Oligocene to the Pliocene. In the Quaternary, the Southern and Central basins of Baikal, formed no later than the Early Paleogene, became part of the Baikal rift, and other depressions were involved in the general uplift of the region. The structural paragenesis of the Khangai uplift and surrounding basins is due to the impact of the Khangai plume. Above the plume with its Khentei and Transbaikalian branches, the Cenozoic basaltic volcanism of the plume type occurred, in some places inheriting Cretaceous volcanic manifestations. Plume structural paragenesis is combined with structural paragenesis, derived from the interaction of plates and lithosphere blocks, which is expressed by active faults, but developed synchronously with plume paragenesis. The kinematics of active faults shows that the western and central parts of the region develop under conditions of transpression, and the northeastern part ‒ under conditions of extension and transtension. The Khangai plume is connected at depth with the Tibetan plume, located under the central and eastern parts of Tibet north of the Lhasa block. The Tibetan plume rises from depths of 1400–1600 km and is accompanied by thinning of the lithosphere and rise of the earth’s surface. The Khangai and Tibetan plumes represent a special category of plumes that rise from the upper part of the lower mantle and this differs from the upper mantle plumes and the African and Pacific superplumes, rising from the core-mantle boundary. A connection between the Khangai and Tibet plumes with branches of superplumes is possible, but their independent origin is also admitted.

Palaeomagnetism of the mid-Cretaceous red beds from the Tethyan Himalaya: direction discrepancy and tectonic implications

Understanding the northern extension of Greater India is vital for modelling the India–Asia collision process and the formation of the Tibetan Plateau. We present new palaeomagnetic data from the mid-Cretaceous ( c. 106 Ma) Gyabula Formation red beds in the Tethyan Himalaya. Well-defined high laboratory unblocking temperature component magnetizations were isolated from 19 sites and pass the fold tests, indicating that they are pre-folding magnetizations. The tilt-corrected site-mean direction is D s = 222.9°, I s = +39.4° with α 95 = 4.2°. The site-mean inclination increases from 39.4° to 45.8° after anisotropy-based inclination shallowing correction. The declination and inclination differ considerably from those of neighbouring sections. This directional discrepancy of the red beds may be attributed to the fact that the sampled section (sites ZB1–11, 40–52) is overturned and to local vertical-axis rotation. The combination of our new and previously published palaeomagnetic data shows that the Tethyan Himalaya was located at 27.5° ± 2.4°S for the sampled area. Our new results, together with the reliable Cretaceous palaeomagnetic data obtained from the Tethyan Himalaya as well as coeval palaeolatitudes expected from the Indian craton, support a smaller Greater India and that the Tethyan Himalaya did not rift from the Indian craton during the mid-Cretaceous. Supplementary material: Detrital zircon U–Pb ages data, hysteresis parameters data, palaeomagnetic datasets for the Gyabula Formation, anisotropy of isothermal remanent magnetization data, available latest Jurassic–Early Cretaceous palaeomagnetic results from the Tethyan Himalaya and supplementary figures are available at https://doi.org/10.6084/m9.figshare.c.6795683 Thematic collection: This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at: https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change

Multiple stages of continental rifting in Eastern Peninsular Malaysia: new insights from Jurassic–Cretaceous granitoids

Mesozoic granitoids in Peninsular Malaysia provide crucial information on the temporal–spatial relationship between the Tethyan and Palaeo-Pacific domains. This paper presents new ages and geochemical data for newly identified Jurassic–Cretaceous granites and meta-granites from East Malaya. These granitoids can be divided into three groups. Group 1 consists of high-K calc-alkaline granites and granodiorites (171–162 Ma) with variable ε Nd ( t ) values of −7.4–+0.5, zircon ε Hf ( t ) values of −7.4–+8.6, and high initial ratios for 206 Pb/ 204 Pb (20.04–20.65), 207 Pb/ 204 Pb (15.73–15.79) and 208 Pb/ 204 Pb (39.80–40.20). The melting of metasedimentary rocks with a juvenile mafic component formed Group 1 samples. Group 2 granite porphyries ( c. 131 Ma) with A-type affinities and Group 3 granitic gneisses ( c. 130 Ma) with I-type affinities share similar ε Nd ( t ) values (−7.2 to −5.5), zircon ε Hf ( t ) values (−10.1–+6.5), and initial ratios for 206 Pb/ 204 Pb (18.81–19.02), 207 Pb/ 204 Pb (15.71–15.77) and 208 Pb/ 204 Pb (38.95–39.59). Although Group 2 and 3 samples were derived from an ‘ancient’ meta-mafic source region, Group 2 shows evidence for the involvement of a juvenile mafic component. All these granitoids are akin to the Permian–Triassic igneous rocks in East Malaya. The Jurassic–Cretaceous igneous rocks in Eastern Peninsular Malaysia were formed during multiple stages of continental rifting in response to Palaeo-Pacific slab rollback pulses rather than by Tethyan evolutionary processes. Supplementary material : Data for the Middle Jurassic–Early Cretaceous granitoids of East Malaya are available at https://doi.org/10.6084/m9.figshare.c.6689085 Thematic collection: This article is part of the Mesozoic and Cenozoic tectonics, landscape and climate change collection available at: https://www.lyellcollection.org/topic/collections/mesozoic-and-cenozoic-tectonics-landscape-and-climate-change