Tectonics

Journal: Tectonics

Publisher

American Geophysical Union

ISSN

1944-9194

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Publications 1 - 10 of 65

Raising the Roof of the World: Intra-Crustal Asian Mantle Supports the Himalayan-Tibetan Orogen
Sternai, Pietro; Pilia, Pierre; Ghelichkhan, Armel; et al. (2025)
Tectonics
The Himalayan-Tibetan orogen formed via the ongoing collision of India and Asia. Its colossal elevations stem from buoyant crustal roots that doubled in thickness during continental collision, widely believed to result from Indian crust under-thrusting its Asian counterpart and Asian crustal thickening. However, a single crustal layer of up to ∼70–80 km thickness conflicts with experimental-rheological and observational constraints, especially if related to the vertical juxtaposition of Indian and Asian crusts. For instance, crustal thickness above ∼40 km implies reduced strength of the continental lithosphere, which may become unable to sustain a plateau the size of Tibet throughout much of the Cenozoic. In addition, the geochemistry and association of ultramafic xenoliths and K-rich magmas from Southern Tibet indicates the presence of mantle material between ∼50 and 80 km depths. The mechanisms controlling the rise and persistence of Earth's highest orogen, therefore, remain enigmatic. Here, new fully-coupled numerical petrological-thermomechanical geodynamic models reconcile the wealth of available structural and petrological constraints through viscous underplating of Indian crust beneath Asian lithosphere, which together supply buoyancy and strength to raise and support the Himalayas and Tibet. We further convert our geodynamic models into receiver functions and shear waves velocity maps that match, to a first order, the available geophysical data from the Himalayas and southern Tibet. We propose that viscous underplating of Indian crust beneath Asian lithosphere, not crust, forms the overall architecture of the Himalayan-Tibetan orogen.
Coupling of Tectonics, Climate, and Lithology in Orogenic Systems: Insights From Cosmogenic ¹⁰Be Erosion Rates and River Profile Inversion Modeling in the Talesh Mountains, NW Iranian Plateau
Moumeni, Mohammad; Delchiaro, Michele; Ballato, Paolo; et al. (2025)
Tectonics
The landscape of the Talesh Mountains, located in the NW sector of the Iranian Plateau (within the Arabia-Eurasia collision zone), results from the interplay of multiple forces. To explore the interaction between tectonics, climate, and lithology we present 11 new erosion rates derived from meteoric ¹⁰Be on the eastern (wetter) and western (drier) flanks of the range. The erosion rates range from approximately 100 to 400 m/Myr, with lower values in the more arid plateau interior and higher values in the more humid plateau exterior (western and eastern Talesh flanks, respectively). These rates exhibit a positive correlation with topographic metrics and a moderate correlation with mean annual precipitation, suggesting a tectonic control possibly enhanced by the across-strike precipitation gradient. Conversely, erosion rates do not correlate with rock strength. However, along- and across-strike changes in rock erodibility suggest that lithology may have influenced the landscape response time to evolving boundary conditions. Furthermore, relative rock-uplift histories from river profile inversion analysis indicate that mountain-building processes accelerated around 12–10 Ma, possibly due to a combination of short-wavelength (i.e., shallower) processes, such as thrusting, and long-wavelength (i.e., deeper) processes, such as lower mantle inflow. This led to a progressive precipitation concentration along the windward side of the orogen, leading to efficient mass removal via erosion and further enhancing tectonic activity. Additionally, an increase in erosion rates occurred during the 0.6–1.5 km lowering of the Caspian Sea base-level between ∼6 and 3.2 Ma. Overall, the efficient erosion on the wetter side likely concentrated tectonic deformation, ultimately contributing to the development of a stationary wedge.
The growth of northeastern Tibet and its relevance to large-scale continental geodynamics: A review of recent studies
Yuan, Dao-Yang; Ge, Wei-Peng; Chen , Zhen-Wei; et al. (2013)
Tectonics
Recent studies of the northeastern part of the Tibetan Plateau have called attention to two emerging views of how the Tibetan Plateau has grown. First, deformation in northern Tibet began essentially at the time of collision with India, not 10–20 Myr later as might be expected if the locus of activity migrated northward as India penetrated the rest of Eurasia. Thus, the north-south dimensions of the Tibetan Plateau were set mainly by differences in lithospheric strength, with strong lithosphere beneath India and the Tarim and Qaidam basins steadily encroaching on one another as the region between them, the present-day Tibetan Plateau, deformed, and its north-south dimension became narrower. Second, abundant evidence calls for acceleration of deformation, including the formation of new faults, in northeastern Tibet since ~15 Ma and a less precisely dated change in orientation of crustal shortening since ~20 Ma. This reorientation of crustal shortening and roughly concurrent outward growth of high terrain, which swings from NNE-SSW in northern Tibet to more NE-SW and even ENE-WSW in the easternmost part of northeastern Tibet, are likely to be, in part, a consequence of crustal thickening within the high Tibetan Plateau reaching a limit, and the locus of continued shortening then migrating to the northeastern and eastern flanks. These changes in rates and orientation also could result from removal of some or all mantle lithosphere and increased gravitational potential energy per unit area and from a weakening of crustal material so that it could flow in response to pressure gradients set by evolving differences in elevation.
Surface Uplift and Topographic Rejuvenation of a Tectonically Inactive Range: Insights From the Anti‐Atlas and the Siroua Massif (Morocco)
Clementucci, Romano; Ballato, Paolo; Siame, Lionel; et al. (2023)
Tectonics
The Atlas-Meseta intracontinental orographic system of Morocco experienced recent, large-scale surface uplift as documented by elevated late Miocene, shallow-water marine deposits exposed in the Middle Atlas Mountains. The Anti-Atlas Mountains do not present any stratigraphic records that document regional vertical movements, however, the presence of a high-standing, erosional surface, and the transient state of the river network, provides insights into the uplift history of the belt and the mechanisms that drove it. Here, we combine geomorphic and stream profiles analyses, celerity of knickpoints and linear inverse landscape modeling with available geological evidence, to decipher the spatial and temporal variations of surface uplift in the Anti-Atlas and the Siroua Massif. Our results highlight the presence of a transient landscape and document a long wave-length topographic swell (∼100 × 600 km) with a maximum surface uplift of ∼1,500 m in the Siroua Massif and ∼1,100 m in the central Anti-Atlas most likely starting from ∼14 to 10 Ma. Surface uplift occurred in association with the onset of late Miocene magmatism in the Siroua and Saghro Massif and contractional deformation in the High Atlas. Regional surface uplift was most likely due to deep-seated mechanism, such as asthenospheric upwelling. Additional processes such as magma injection and faulting contributed to the surface uplift of the Siroua Massif. Overall, our approach allows to quantitatively constrain the transient state of the landscape and the contribution of regional surface uplift on mountain building processes.
Potentially active faults in the rapidly eroding landscape adjacent to the Alpine Fault, central Southern Alps, New Zealand
Cox, Simon C.; Stirling, Mark W.; Herman, Frédéric; et al. (2012)
Tectonics
Potentially active faults are exposed in the steep glaciated topography of the central Southern Alps, New Zealand, immediately adjacent to the Alpine Fault plate boundary. Four major faults exposed along the flanks of three of the highest mountain ranges strike 10–23 km (potentially 40 km) NNE oblique to the Alpine Fault, dipping 57° ± 12° NW in the opposite direction. Youngest discernable motions were reverse dip-slip, accommodating both margin-perpendicular shortening and dextral margin-parallel components of plate motion. Kinematic analysis yields a compression axis (295/10° ± 9° trend or plunge) equivalent to the contemporary shortening determined from seismological and geodetic studies, suggesting the faults may be active, although definitive evidence for recent movement or single event displacements is lacking. There are 106 other potentially active faults mapped in central Southern Alps with strike lengths 4–73 km. Earthquake parameters were assigned from fault trace lengths and historical earthquake statistics, indicating potential for MW 5.5–7.4 earthquakes at recurrence intervals of 1000–10,000 years. Such long recurrence intervals are consistent with the faults having little surface expression, with rapid erosion of these seismically agitated mountains erasing any evidence of surface rupture during periods between earthquakes. The central Southern Alps faults exemplify the difficulty in fully deciphering long-term (e.g., Holocene or Quaternary) records of seismicity in tectonically active regions with rapidly evolving landscapes. Although there may be little evidence of surface ruptures remaining in the landscape, the faults are still an important potential source of earthquakes and seismic hazard.
Accelerated Tectonic Activity, Rather Than Paleolake Regression, Drives Increased Pleistocene River Incision Along the Jinshan Gorge in the Middle Yellow River
Zhong, Yuezhi; Picotti, Vincenzo (2025)
Tectonics
The Jinshan Gorge in the middle Yellow River, northern China, currently connecting the upstream Hetao Graben to the downstream Weihe Graben, is hypothesized to have recently developed, which implies changing incision rates along the gorge. However, different integration processes have been proposed, such as paleolake regression in the Weihe Graben or integration with a paleolake in the Hetao Graben. These different mechanisms imply different timings, from the Late Miocene to the Late Pleistocene. In this study, we model variations in channel profiles and incision in response to different integration processes using the stream power law. We show that variations due to paleolake regression in the Weihe Graben or integration with paleolake in the Hetao Graben are inconsistent with the incision history preserved by river terraces and reconstructed by inverse analysis of tributary profiles. Instead, a recent increase in the slip rate of the Weihe Graben's boundary faults can explain the main features. Inverse analysis of channel profiles along the Jinshan Gorge suggests that relative uplift rates were a steady ∼0.04 mm/yr before the Early Pliocene, and increased to ∼0.16 mm/yr at present, especially since the Middle-Late Pleistocene. Our analysis is supported by further data from paleoseismic, drilling and paleostress studies.
Multiproxy Isotopic and Geochemical Analysis of the Siwalik Sediments in NW India: Implication for the Late Cenozoic Tectonic Evolution of the Himalaya
Mandal, Sanjay K.; Scherler, Dirk; Romer, Rolf L.; et al. (2019)
Tectonics
Tectonics, Base-Level Fluctuations, and Climate Impact on the Eocene to Present-Day Erosional Pattern of the Arabia-Eurasia Collision Zone (NNW Iranian Plateau and West Alborz Mountains)
Kaveh-Firouz, Amaneh; Burg, Jean-Pierre; Haghipour, Negar; et al. (2023)
Tectonics
The NNW Iranian Plateau and west Alborz within the Arabia-Eurasia collision zone are characterized by three main tectono-stratigraphic zones, crosscut by the Qezel-Owzan River (QOR) Basin. The interplay between present-day deformation and climate, which control the landscape evolution of the region, is still poorly constrained. We addressed this gap by measuring millennial-scale erosion rates from 10Be-concentration in the QOR sands along with topographic/climatic metrics analyses. Results reveal low erosion rates in the Plateau and relatively high in the west Alborz. The regional consistency of topographic parameters with geomorphology suggests that they control sediment fluxes in the Plateau, while the surface uplift, active thrust-faulting, and shallow crustal seismicity in the west Alborz are the main controlling factors. Climate has a secondary role on erosion rates. Furthermore, we calculated exhumation rates from published thermochronometric AFT/AHe ages to determine their relationship with 10Be short-term data. Results imply that the exhumation rates increased slightly in the Plateau and west Alborz from ∼26 to ∼10 Ma, simultaneous with hard collision processes between the Arabia-Eurasia. This trend accelerated from ∼10 to ∼2.8 Ma due to the isolation of the Caspian Sea and extreme base-level fall. From ∼2.8 to ∼2 Ma, base-level rise occurred under climate influence, and erosion rates decreased. Millennial-scale data show the erosion rate decreased from ∼2 Ma to the Present-day, which is attributed to the change in deformation style and fault kinematics from fold/thrusting to mainly strike-slip faulting. The significantly lower erosion rates in the Plateau compared to west Alborz suggest a relatively stable plateau surface.
Structural Evolution of Orogenic Wedges: Interplay Between Erosion and Weak Décollements
Dal Zilio, Luca; Ruh, Jonas; Avouac, Jean-Philippe (2020)
Tectonics
Orogenic wedges commonly display an inner wedge, where crystalline units have been exhumed, and an outer wedge formed by imbricated sedimentary units detached from the basement. Analog experiments have shown that similar structures can emerge naturally in the presence of weak décollements due to the interplay between erosion and deformation. In this study, we further investigate this hypothesis using two-dimensional, visco-elasto-plastic numerical models. Our experiments assume a basal and an intermediate décollement within the wedge. Experiments with a frictional strength of the basal décollement lower or equal to that of the intermediate décollement show a structural evolution of fold-and-thrust belts dominated by out-of-sequence thrusting. Conversely, when the intermediate décollement is weaker than the basal décollement, distinct outer and inner wedges are formed. This process leads to episodic migration of midcrustal ramps, tectonic underplating, and antiformal stacking facilitated by erosion. Comparison between our models and the Himalayan wedge suggests a low effective friction (∼0.10), which is probably due to dynamic weakening during large (M8+) Himalayan earthquakes. The deeper décollement, along which the lower plate thrusts beneath the High Himalaya, must be a thermally activated ductile shear zone with an apparent friction of ∼0.18. Fold-and-thrust belts worldwide exhibit various architectures in which different décollement levels might be activated. Thus, our study provides a framework to help assess under which conditions a variety of structures observed in orogenic systems can arise. © 2020. American Geophysical Union. All Rights Reserved.
Structure and Deformation History of the Rapidly Growing Tainan Anticline at the Deformation Front of the Taiwan Mountain Belt
Le Béon, Maryline; Marc, Odin; Suppe, John; et al. (2019)
Tectonics

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