Marie-Luce Chevalier

The timing and mechanisms of Cenozoic deformation and landscape evolution in the eastern Tibetan Plateau remain contentious, particularly the roles of crustal shortening, strike‐slip faulting, and fluvial erosion. Here we integrate low‐temperature thermochronological data, including apatite fission‐track, apatite (U–Th)/He, and zircon (U–Th)/He ages, from the northern Jinsha region of eastern Tibet, between the low‐relief plateau interior and the deeply incised eastern margin. Our results reveal two broad phases of rapid cooling/exhumation: an early phase at ca. 68–45 Ma, with cooling rates of 4–10°C/Myr, broadly compatible with early Cenozoic crustal shortening and thickening; and a later phase at ca. 20–0 Ma, with cooling rates of ≥5°C/Myr. The three profiles record similar late Cenozoic cooling histories; therefore, the post–20 Ma signal cannot be uniquely attributed to local activity on the Jinsha Fault or to simple local river incision. Combined with published thermochronological data from the Jinsha River corridor, the results suggest a segmented regional cooling/exhumation pattern more compatible with fault‐influenced drainage organization and focused incision than with a single upstream‐propagating river‐incision wave. Between the two cooling/exhumation phases, the study area experienced prolonged thermal stability, or near‐isothermal holding, from 45 to 20 Ma, with cooling rates of <1°C/Myr. This interval is consistent with development and/or preservation of a high‐elevation, low‐relief landscape by the late Eocene to Oligocene. Overall, our results provide new constraints on the multi‐stage Cenozoic cooling/exhumation history of the northern Jinsha region and offer insight into the coupled tectonic and surface‐process evolution of eastern Tibet.

The extent to which surface processes drive continental deformation remains a pivotal question in geodynamics. Here, we demonstrate that Late Quaternary lake‐water unloading is a primary driver of fault slip and rift asymmetry in southern Tibet. Since the last interglacial (∼116 ka), significant water‐level drops of large lakes have induced crustal rebound and Coulomb stress changes. At Nam Co Lake, a ∼130 m drop produced ∼0.1 MPa of stress change, preferentially reactivating the adjacent fault and contributing ∼15 m of vertical displacement ∼23% of the total near Damxung. Likewise, the southern lakes (Yamzho Yumco and Puma Yumco) caused ∼70 m of vertical displacement on the adjacent fault. We establish that climatically‐controlled lake unloading can directly shape continental rifting by selectively enhancing fault slip on the lake‐bounding side of the rift, thereby amplifying its structural asymmetry. This highlights a significant, quantifiable role of surface processes in actively shaping tectonic deformation.

The Xianshuihe fault, located in the southeastern Tibetan Plateau, stands as one of the most active faults in China. As assessing earthquake hazard relies on access to long‐term paleoseismological archives, this paper seeks to optimize the interpretation of paleoseismological records. We retrieved nine sediment cores from three lakes over a 30 km fault segment. Earthquake‐related deposits were identified through grain‐size analysis, XRF core scanning, and SEM observations of thin sections. Age models based on short‐lived radionuclides correlate these events with historical earthquakes, which are recorded with varying sensitivities to seismic intensity across the three lakes. We developed a code that evaluates the plausibility of rupture scenarios against sedimentary evidence: Each site is used as a binary paleoseismometer, indicating whether or not an earthquake reached a local intensity threshold. The combined evidence from the three sites allows to evaluate rupture scenarios on the Xianshuihe fault, according to rupture length‐magnitude scaling laws and intensity prediction equations. The most probable scenarios allow to discriminate the rupture area and magnitude range providing a good agreement with historical reconstructions. Our work demonstrates the potential of combining earthquake records to infer the magnitude and rupture zone of paleo‐earthquakes, even with a limited data set. Our approach, applicable across diverse geological settings and timescales, offers enhanced precision in understanding long‐term paleoseismology covering multiple earthquake cycles. However, establishing the synchronicity of events in such an active area—where earthquake return times are typically <100 years—demands highly accurate age models, which remains challenging.

The tectonic and topographic evolution of the southeastern Tibetan Plateau based on low‐temperature thermochronology data is controversial, especially whether it is tectonically‐ or climatically‐controlled, especially along the Lancang fault (LCF) that links the flat central plateau to the west with the high relief southeastern Tibetan Plateau to the east. To explore the tectonic evolution of the LCF and its role in the tectonic and topographic evolution of the southeastern Tibetan Plateau, we carried out detailed field investigation and low‐temperature thermochronology (AHe, AFT, and ZHe) analyses. Field evidence indicate that the northern LCF splits into two branches, the Yangda‐Yaxu and Baqing‐Leiwuqi faults, the latter striking N50°W and dipping to the SW at ∼55°, exposing >100 m‐wide fault rocks composed of a fault damage zone, breccia, and gouge. New thermochronology data and thermo‐kinematic modeling results suggest rapid exhumation of the region located between these two fault branches during ∼22–10 Ma at an exhumation rate of ∼1.57 km/Ma, compared to slow cooling prior to 22 Ma and since 10 Ma. We propose that internal anti‐clockwise block rotation triggered rapid local exhumation, and that the final merging of different parts of the LCF during the Early‐Middle Miocene assisted the southeastward escape of Sundaland, which profoundly affected the evolution of the regional geomorphology.

The Xianshuihe fault, located in the southeastern Tibetan Plateau, stands as one of the most active faults in China. As assessing earthquake hazard relies on access to long-term paleoseismological archives, this paper seeks to optimize the interpretation of paleoseismological records. We developed a code that evaluates the plausibility of rupture scenarios against sedimentary evidence from nine cores in three lakes over a 30 km fault segment. Earthquake-related deposits were identified through grain-size analysis, XRF core scanning, and SEM observations of thin sections. Age models based on short-lived radionuclides correlate these events with historical earthquakes, which are recorded with varying sensitivities to seismic intensity across the three lakes. Each site is then used as a binary paleoseismometer, indicating whether or not an earthquake reached a local intensity threshold. The combined evidence allows to evaluate rupture scenarios on the Xianshuihe fault, according to rupture length-magnitude scaling laws and intensity prediction equations. The most probable scenarios allow to discriminate the rupture area and magnitude range providing a good agreement with historical reconstructions. Our work demonstrates the potential of combining earthquake records to infer the magnitude and rupture zone of paleo-earthquakes, even with a limited dataset. Our approach, applicable across diverse geological settings and timescales, offers enhanced precision in understanding long-term paleoseismology covering multiple earthquake cycles. However, establishing the synchronicity of events in such an active area—where earthquake return times are typically < 100 years—demands highly accurate age models, which remains challenging.

While the Xianshuihe fault displays continuous creeping behavior, it is also the most seismically active fault in the eastern Tibetan Plateau, and its earthquake mechanisms remain unclear. Here, we aim at the stick‐slip portion of the creeping Qianning segment of the Xianshuihe fault to determine the characteristics of fault rocks and how fluids at depth influence fault behavior. Field survey, optical and scanning electron microscope observations, X‐ray diffraction and fluorescence analyses, as well as carbon and oxygen isotope analyses were performed on the collected samples. The fault core consists of 3–5 cm‐thick black fault gouge and ∼2.5 m‐thick breccia, surrounded by ∼12 m damage zone. In contrast to fault breccia (1–8 cm in diameter), the black fault gouge, which represents the principal slip zone of repeated seismic events, contains angular quartz particles (∼10 μm on average) and clays dominated by illite. The fluid‐rock interactions altering silica minerals into illite, and the thermal decomposition of carbonate minerals, passively increase the relative content of quartz and feldspar (total 63%–73%) in the fault gouge. The deeply sourced CO₂ (from mantle and metamorphic degassing) within the hydrothermal fluids causes carbonate precipitation in breccias (21%–53%), composed of calcite, dolomite, and aragonite. These fluid‐assisted reactions lead to more abundant strong mineral phases (quartz, feldspar, and carbonates, 64%–87%) than weak clays (12%–36%) within the fault core, and locally strengthen the fault, which inhibits slow release of stress at shallow depth and promotes seismic rupture of the fault.

Large earthquakes are among the most dangerous natural disasters with potentially devastating effects on society and infrastructure across the globe. In order to better understand earthquakes, research in active tectonics aims at quantifying crustal deformation throughout the active fault’s earthquake cycles by studying geomorphic and stratigraphic evidence of recent and past earthquakes. The underlying assumption in this approach is that a fault’s current and previous seismic behavior is representative of its future behavior. Constraining a fault’s seismic behavior in such a manner requires high-resolution geomorphic and stratigraphic records that enable us to resolve the spatial and temporal characteristics of co-, post-, and interseismic phases, ideally over multiple earthquake cycles. Recent technological developments have dramatically increased not only the amount and resolution of topographic and geophysical survey data sets but also our ability to date stratigraphic units and geomorphic surfaces. These technological advances have enabled us to better understand the interplay between crustal deformation, earthquake ruptures, and their signature in geomorphic and stratigraphic records. In particular, the availability of high-resolution data sets from LiDAR, SfM, or geophysical surveys and the use of accurate dating methods such as cosmogenic or OSL dating allow us to quantitatively study surface deformation at high spatial resolution over large areas and at multiple time scales—from a few years to millions of years. In this special issue, we focus on the tectonic activity of active faults and the geomorphic processes in various tectonic regimes worldwide. It covers active tectonics, earthquake geology, remote sensing, tectonic geomorphology, Quaternary geochronology, geohazard, and seismology.