Abstract New regional mapping and two focused geological maps with two crustal‐scale balanced cross‐sections along the Dudh Kosi and Tama Kosi Rivers in the Okhaldhunga region reveal the structural architecture of the eastern Nepal Himalaya. Our detrital zircon U‐Pb ages for 14 samples and igneous zircon U‐Pb ages for four samples show that the Okhaldhunga window primarily exposes the Ramgarh thrust sheet, which is composed of Paleoproterozoic Lesser Himalayan metasedimentary and igneous rocks. Structurally, the Ramgarh thrust sheet lies in the footwall of the Main Central thrust and is underlain by the Lesser Himalayan duplex (LHD), a hinterland dipping bumpy‐roofed duplex, comprising Paleo‐Mesoproterozoic Lesser Himalayan rocks and upper Paleozoic Gondwana Sequence rocks. The frontal part of the LHD is exposed in the southern sector of the Okhaldhunga window, above a major footwall ramp on the Main Himalayan thrust. Neoproterozoic‐Cambrian Greater Himalayan rocks in the hanging‐wall of the Main Central thrust are exposed toward the south in the synformal Mahabharat Range and in the north in the Sagarmatha‐Rolwaling region. Kinematic restorations for our two transects, combined with published chronometric data, indicate that most of the deformation has been accommodated by Lesser Himalayan rocks since Middle‐Late Miocene. The two balanced cross‐sections indicate minimum shortening of ∼561 and 544 km. Comparison of these estimates with published data for rocks structurally below the South Tibetan detachment system in the Himalaya indicates that heterogeneous post‐collisional crustal shortening has determined the current tectonic configuration of the region.

No abstract is available for this article.

Abstract Contemporary kinematic characteristics of the Pamir plateau are characterized by (a) significant NS‐shortening across the northern front, (b) EW‐extension within the Pamir and (c) gravitationally driven westward mass‐outflux of the western Pamir into the Tajik basin. The 2015 Mw 7.2 Sarez and 2023 Mw 6.8 Murghab strike‐slip earthquakes highlight the crucial role of shear deformation in the Pamir's interior, but the detailed secular kinematics of the remote Plateau are still elusive. Here, we employ elastic block models to fit GNSS velocities compiled from our own reprocessed velocity solution and from previous studies to determine slip rates along major active faults within and bounding the Pamir plateau. Our favored model separates the Pamir's interior into three micro‐blocks along the NNE‐trending sinistral Sarez‐Karakul fault system and the SSE‐trending Kongur Shan extensional system. The model confirms significant crustal shortening along the Pamir's northern boundary and strike‐slip motion along its western boundary, namely the Pamir thrust system and the Darvaz fault, respectively. In contrast, strike‐slip motion on the eastern boundary is minor. In the interior of the Plateau, we find an upper limit of sinistral shear of 8.8 ± 0.3–9.5 ± 0.2 mm/yr along the Sarez‐Karakul fault system and dextral shear of 6.3 ± 0.3 mm/yr along the WNW‐trending Muji fault. Our model also confirms recent observations of an active, SW‐continuation of the Sarez‐Karakul fault system. In the eastern Pamir, crustal extension mainly occurs across the northern segment of the Kongur Shan extensional system. The recent large strike‐slip earthquakes on the Pamir plateau suggest that shear motion on the plateau is accommodated on a much wider range than only by the Sarez‐Karakul fault system.

Abstract Major influences on the architecture of orogens include the overall thermal conditions of orogeny (hot vs. cold) and the angle of collision (orthogonal vs. oblique). In the French Massif Central of the Variscan orogen, a cold‐orogen style crustal nappe architecture was interpreted in the Haut‐Allier, located in the core of the orogen. Based on this model, the Variscan orogenic crust is described as the superposition of three main allochthonous tectonic units juxtaposed along major thrust faults. However, based on a detailed structural analysis, we have found instead that the region is dominated by a network of anastomosing conjugate and coeval dextral and sinistral shear zones striking WNW‐ESE and ENE‐WSW, respectively. The dextral WNW‐trending shear zones are predominant, whereas the sinistral NE shear zones are mainly located in the eastern part of the massif. Between these sub‐vertical shear zones, a sub‐horizontal foliation is observed. Our results indicate that all planar fabrics were partially synchronous during suprasolidus low‐pressure‐high‐temperature conditions. Strain partitioning occurred from high‐temperature suprasolidus conditions to subsolidus retrogression and may represent orogen‐parallel flow, suggesting hot‐orogen style. These results call into question the validity of the crustal nappe model in the Haut‐Allier. Based on new structural data and related observations, we propose a new model in which metamorphic gaps between tectonic units are explained by the juxtaposition of different structural domains by displacement along strike‐slip shear zones.

Abstract The Erqis tectonic belt, situated at the junction of the Chinese Altai‐East Junggar, originated through the subduction of the Ob‐Zaisan Ocean, playing a pivotal role in unraveling the tectonic evolution of the southern Altaids. Tectonic and provenance analyses discern three distinct arcs: the Chinese Altai in the north exhibits a protracted history from the late Cambrian to early Permian with a slender accretionary complex (AC) termed the Supute AC; the Kuerti intra‐oceanic arc in the middle emerged during the Silurian to Devonian coevally with a minor AC known as the Tesibahan AC; and the Dulate arc in the south predominantly evolved from the Middle Devonian to Permian, giving rise to the Fuyun AC that independently developed on its northern margin at least until ∼273 Ma. Our findings indicate the existence of multiple arcs within the Ob‐Zaisan Ocean, forming an archipelago paleogeography in the Paleo‐Asian Ocean. Provenance studies lead us to propose that cryptic sutures demarcating the Chinese Altai, Kuerti, and Dulate lie approximately along the Kuerti and Tesibahan faults, respectively, and that the oceanic branches between these arcs subducted northward beneath the Chinese Altai and Kuerti arcs and southward beneath the Dulate arc. Additionally, our work demonstrates the closure of the Ob‐Zaisan Ocean most probably postdates ∼273 Ma. Combining our data with previous research, we present a novel tectonic evolution model, elucidating several arc amalgamations with multiple subduction polarities between Chinese Altai and East Junggar throughout the late Cambrian to Permian.

Abstract The Late Eocene–Oligocene post‐breakup magmatism of the North Atlantic Igneous Province (NAIP) in East Greenland, is represented by sub‐volcanic intrusions associated with a NE‐SW oriented magmatic lineament, the Werner Bjerge Rift. This onshore magmatism extends for more than 100 km from eastern Traill Ø to Werner Bjerge. In the same region, strike‐slip post‐breakup faulting is documented along N‐S trending faults extending more than 300 km from Traill Ø up to the north, along the Loch Fyne Fault Zone. Offshore East Greenland, the NW‐SE trending East Jan Mayen Fracture Zone, has represented the northern boundary of the Jan Mayen Micro Continent in the Eocene–Oligocene, and extended westward, toward Traill Ø. The Werner Bjerge Rift, the Loch Fyne Fault Zone and the East Jan Mayen Fracture Zone were active during the Late Eocene–Oligocene and intersected in eastern Traill Ø with a 120° angle, resembling a triple junction. This study presents the onshore deformation and magmatism associated with a failed triple junction that was active between 40 and 25 Ma, highlighting the importance of inherited structures in response to stress variations and plate tectonics modifications. The tectonic trends of the Fault‐Fault‐Ridge Traill Ø triple junction are inherited structures from the Caledonian Orogeny and from multi‐stage rifting episodes that characterized the East Greenland basin system since the Late Carboniferous. New age and geochemistry of the magmatism in the Werner Bjerge Rift, combined with structural analyses of fault systems suggest that the Traill Ø triple junction was generated by plate tectonics configuration and not by a mantle plume.

No abstract is available for this article.

Abstract The present tectonic regime of the Qilian Shan is dominated by large northeast and northwest striking strike‐slip faults and northwest striking thrust faults. Deformation distribution between the subparallel Haiyuan Strike‐slip Fault and the Minle‐Damaying Thrust Fault (MDF) is crucial for understanding the orogenic mechanism of the northeastern Tibetan Plateau. However, the uncertain kinematics of the MDF and the stress variation along the strike‐varying Haiyuan Fault inhibit further discussion of their relationship. Five key sites along the MDF were selected for analysis of terrace abandonment ages and vertical offsets to determine the slip rates. Two finite element models were constructed to calculate the stress‐strain relationship between the Haiyuan Fault and MDF. We find that the activity of the MDF can be divided into two segments by a stepover with less activity and lower terrain at the Xida River site. Shortening rates of the MDF vary between 0.2 and 2.4 mm/a since the late Pleistocene with trapezoidal trends on both fault segments. The two finite element models and GPS data reveal that the strain rates are lower at the Xida River site but higher at the Menyuan Bend on the Haiyuan Fault. We infer that long‐term strain accumulation at the Menyuan Bend may have mitigated the tectonic activity northeast to the bend under the northeastward stress field, including the activity of the MDF at the Xida River site, and resulted in the segmentation of the MDF.

Abstract This contribution explores the formation and evolution of hyper‐extended basins, associated with the early stage of core complex formation, controlled by low‐angle normal faults active at <30°. Based on a high‐resolution industrial 3D seismic reflection survey along the southern margin of the South China Sea (SCS) (Dangerous Grounds), we mapped and analyzed the 3D geometry of low‐angle normal fault systems and the related stratigraphy. Two main hyper‐extended basins were documented, filled by up to 6 km of sediments including pre‐ to post‐rift sequences. The observed normal faults on depth migrated seismic sections show an average dip angle of <30° and appear planar, characterized by continuous reflections with no clear steepening at depth and sole‐out on distinct decollement levels. Detailed fault surface mapping reveals the occurrence of km‐scale corrugations together with large wavelength undulation. The formation of these hyper‐extended basins is associated with polyphased syn‐rift infill during the development of the low‐angle normal faults. The first syn‐rift sequence appears as chaotic and discontinuous packages that has been dismembered and fragmented during the activity of low‐angle normal faults. The second syn‐rift package shows unexpected sedimentary wedges developing successively toward the footwall and the hangingwall. This geometry results from the interplay between the main low‐angle normal fault and antithetic faults defining a so‐called extensional fishtail. The deep structure of these basins shows nascent domes with limited evidence of magmatism. Eventually, these basins likely capture the earliest stage of core complex development in the proximal margin of the southern SCS.