Estimating exhumation rates on Pleistocene-Holocene time scales presents a challenge due to the scarcity of suitable low-temperature thermochronometers. Apatite helium (AHe) dating is unable to precisely differentiate cooling ages <1 Ma and whilst optically stimulated luminescence (OSL) thermochronometry resolves younger ages (104-105 years timescale), it is limited in regions with lower exhumation rates (<2-3 mm/yr). These restrictions limit our ability to accurately study exhumation rates on such time scales, thus hindering our understanding of the implications of tectonics, climate, and hydrology. To address this challenge and gain insights into the dynamics of rapid exhumation, we conducted our study in the Sutlej River valley (northwest Indian Himalaya), which features a prominent river anticline with exceptionally high exhumation rates locally reaching up to 12 mm/yr (OSL data from a previous study). For this purpose, we collected 10 samples, including 5 from a 2200 m vertical profile in the Sutlej valley, and 5 from the main tributaries. The new OSL analysis of these samples reveals high exhumation rates at lower altitudes (<2500 m), ranging from 6-8 mm/yr, 350 m above the river, and from 3-5 mm/yr, 720 m above the river. Furthermore, OSL ages of samples from lower elevations along the tributaries were not saturated, also pointing to rapid exhumation in these areas. In contrast, all samples from higher elevations (>2500 m) reach field saturation, indicating lower average exhumation rates that cannot be recorded using OSL thermochronometry. Although the vertical profile data exhibit a significant increase in exhumation rates over the past 200 kyr, this region lacks glaciated landscapes, suggesting a feedback loop within the river anticline. The river incision promotes the development of the anticline, which, in turn, amplifies the river incision, leading to accelerated exhumation over time. By demonstrating the importance of the interplay between river incision and anticline development in driving the progression of exhumation rates in the Sutlej River region, this study offers a new perspective on Late Pleistocene exhumation rates in the Himalayas.
Current climatic warming is causing accelerated melt of the Greenland Ice Sheet. Whilst the changing hydrological response is well known, the sediment export as well as the geomorphic changes in the proglacial area remain uncertain.   Here we present records of sediment transport from melt seasons 2022 and 2023 in the proglacial area of Leverett glacier, a land terminating glacier outlet on the Western part of the Greenland Ice Sheet. The proglacial area here is very well denifed by a waterfall cutting through bedrock functioning as terminal gauge, which allows for the installation of hydrological stations. These hydrological gauging stations, containing turbidity and pressure sensors, allow for estimation of discharge and suspended sediment concentrations over the melt season. Variations in bedload transport can be analysed using the sesimic data obtained from the geophones placed on the river bank close to the hydrological gauging stations. To convert the recorded seismic data into bedload flux, a Fluvial Inversion Model is used, which is calibrated using active seismics surveys and the water stage data from the hydrological gauging stations. The dataset allows us to investigate the relationships between bedload, suspended sediment, and water discharge from the Leverett glacier as well as sediment transport and deposition in the proglacial area. We observe several spring events in the first half of July, where suspended sediment concentration and water discharge increase simultaneously at the start of the melt season. During the first half of August, we observe a clear dilution signal, where increase in water discharge coincides with a decrease in suspended sediment concentration From insights about the relationship between water and sediment discharge from the ice sheet, we can speculate about the sediment export response to increased water discharge from the Ice Sheet.
Two end-member competing models have been proposed to describe the kinematics of the central Nepal Himalayas in the last few Myr. They differ in their interpretations of which surface breaking faults accommodate current shortening and the kinematics responsible for driving rapid exhumation in the topographic transition zone around the Main Central Thrust (MCT). These locally higher uplift and erosion rates in the High Himalaya could reflect (1) thrusting over a midcrustal ramp with the growth of a Lesser Himalaya duplex at midcrustal depth causing underplating along the Main Himalayan Thrust ramp, or (2) out‐of-sequence thrusting along the front of the High Himalaya, possibly driven by climatically controlled localized exhumation.To decipher between the two tectonic models, we compare existing low and medium-temperature thermochronometric data (40Ar/39Ar on muscovite, apatite (U-Th)/He - AHe, zircon (U-Th)/He - ZHe, apatite fission track - AFT, and zircon fission track - ZFT), extracted from the world thermochronometric data file of Herman et al. (2013), to luminescence thermochronometry data from 61 newly collected rock samples along transhimalayan rivers between the Kali Gandaki and the Trisuli. The luminescence thermochronometry data provide a new perspective on Late Pleistocene exhumation rates (timescales of 104 to 105 years) of the Nepalese Himalayas, by offering quantitative high-resolution constraints of rock cooling histories within the upper kilometres of the Earth’s crust.All of the thermochronometric data show younger ages and higher exhumation rates around the topographic transition and the MCT zone through central Nepal. For the higher temperature thermochronometers, there is a continuous trend towards younger ages from the Lesser Himalaya through the topographic transition and the MCT zone. These data suggest that the in-sequence model, with exhumation rates linked to increased erosion and the formation of a duplex below the Higher Himalayas, coincident with the MCT location in some areas, is the model that best describes the thermochronometric ages of this study area on Myr timescales. However, the luminescence thermochronometry data reveal a spatial and temporal variability of the higher exhumation rates at different timescales, suggesting an intermittency of exhumation signal due to geomorphological processes. The luminescence thermochronometry data also highlight a systematic sharp transition at the MCT, pointing to out-of-sequence activity at this tectonic boundary on 100-kyr timescales. Whether this difference in tectonic model between the two timescales is due to low resolution of the higher temperature thermochronometers, shallow isotherms deflected by fluid circulation and hot spring activity near the MCT, or to a change in tectonic regime during the last 200 kyr, out-of-sequence activity of the MCT needs to be considered in seismic hazard models as it could put the local population at risk.
Abstract The Himalayan Main Frontal Thrust (MFT) currently accommodates approximately half, i.e., 12–23 mm/yr, of the convergence between the Indian and Eurasian tectonic plates by uplift and deformation of the Sub-Himalayas. While deformation is well documented at modern and million-year time scales, almost no quantitative data are available that constrain Quaternary time scale deformation rates along and within this key tectonic unit. Filling this knowledge gap is crucial to better understanding tectonics and the seismic cycle in this densely populated Himalayan region. We quantify exhumation rates in the Sub-Himalayas using the recently established luminescence thermochronometry technique over time scales of 105 yr, which documents exhumation over the final few kilometers of Earth’s crust. The ultra-low closure temperature of luminescence thermochronometry enables us to resolve thermal histories from the Siwalik Group (Nepal) rocks, which have experienced maximum burial temperatures of ~120 °C. An extensive set of 33 samples was collected from western Nepal to eastern Bhutan, from which 22 yield exhumation rates of ~3–11 mm/yr over the past ~200 k.y. We converted these values to minimum cumulative thrust slip rates of ~6–22 mm/yr, assuming a thrust dip angle of 30°. Our luminescence thermochronometry results show that the Sub-Himalayan fold-and-thrust belt, particularly the MFT, accommodates at least 62% of Himalayan convergence since at least 200 ka. Our data also show activity of some intra-Siwalik thrusts throughout this period, implying that internal deformation of the orogenic wedge and strain partitioning may have occurred.
<p><em>Girls on Ice Switzerland</em> runs tuition-free wilderness science expeditions for young women from diverse backgrounds. The glacier expeditions interweave science (e.g. glaciology, geomorphology, environmental aspects), art and mountaineering. <em>Girls on Ice Switzerland</em> does not only intend to transfer scientific knowledge, but also aims on a general understanding of the scientific process, on a mediation of nature experiences and on an enhanced self-confidence and self-evaluation. A combination of inquire-based teaching, experiential learning, and the tangibility of climate change science in the alpine environment provide a unique teaching environment. This particular framework allows to communicate science to non- and potential not-yet-peers, to facilitate insights into the scientific work through hands-on experiences, and to enhance the participants&#8217; general interest in science.</p><p>Between 2017 and 2019, <em>Girls on Ice Switzerland</em> organised four glacier expeditions, which were evaluated in detail by pre- and post-inquiry of the participants. Through both quantitative and qualitative methods, the evaluation focused on the (i) perception of science, (ii) scientific knowledge, (iii) critical thinking, (iv) interest in science, (v) self-assessment and self-efficiency and (vi) connection to nature. It showed that the programme overall reached its initially set aims and that it particularly fosters critical thinking, increases physical and intellectual self-confidence and strengthens confidence in women.</p><p>Here, we will present the programme <em>Girls on Ice Switzerland</em>, its link to <em>Inspiring Girls Expeditions</em> and the overall philosophy, but also highlight evaluation results that help to optimize the science communication by demanding a clear set of goals for different characteristics of the programme. The unique women-only environment is ideal to encourage young women to start studies within the field of natural sciences and strengthen young female scientists to pursue their academic career.</p>
Luminescence thermochronometry is sensitive to very low temperatures (below ∼120 °C), and enables the resolution of thermal histories over sub-Quaternary timescales. Here we apply a multi-elevated-temperature post-infrared infrared-stimulated luminescence (MET-pIR-IRSL) measurement protocol to feldspar minerals to extract thermal histories. These thermal histories depend on the thermal stability of the MET signal, and are based on the thermal kinetic parameters extracted from isothermal decay experiments. However, the derived thermal kinetic parameters vary with experimental conditions, specifically with the isothermal holding temperatures (ITL) used. We analyse samples with independently known thermal histories, together with synthetic thermal history samples and samples with unknown thermal histories to test the validity of thermal kinetic parameters obtained from different combinations of isothermal holding data. This approach is tested on feldspars of different mineralogies and lithologies. We find that the temperatures inferred from inverting the data change, depending both on the number and on the highest ITL temperature used for thermal kinetic parameter derivation. Analysed samples validate the MET-pIR-IRSL protocol for extracting thermal histories, and we suggest that four isothermal holding temperatures between 190 and 250 °C are used for appropriate thermal kinetic parameter derivation.
<p>In mountain accretionary wedges, it is generally considered that the preservation of a topography in mechanical equilibrium is modulated by the activation of faults, sometimes internal to the prism, sometimes frontal. The folds of the Himalayan foothills correspond to the most frontal structures of the Himalayan prism. Understanding the timing of the initiation and the activity of these frontal folds can provide valuable information on the deformation sequences within the range (reactivation of the MCT, prograde sequences and transfer to frontal folds, ...) in response to tectonic and climatic forcing. Late Cenozoic climatic changes, including glaciations, might have impacted the denudation of the Himalayan range. The study of recent deformation rates is thus key for understanding lateral variations in deformation along the entire Himalayan arc, which will bring new constraints on the interactions between tectonics and surface processes at different scales time, as well as deepen our understanding of the seismic behaviour of the range.</p><p>&#160;</p><p>Here we quantify exhumation rates in the Himalayan foothills using luminescence thermochronometry, which is a recently developed very-low temperature thermochronometer applicable between tens of years and a few hundred kyr. In contrast to classical methods, it can resolve thermal histories from the upper few km of the Earth&#8217;s crust, allowing spatial variations in exhumation rates across the Himalayas to be deciphered on sub-Quaternary timescales. An extensive data set of more than 40 Siwalik rock samples, from Western Nepal to Eastern Bhutan, was measured to complement other thermochronometric data and understand the sub-Quaternary deformation on the Himalayan foreland.</p><p>&#160;</p><p>The results show along-strike variations in exhumation rates in the Himalayan foothills during the late Quaternary, with exhumation rates across the sub-Himalaya varying locally independently of precipitation trends and changes in the modern convergence rates. These along-strike variations may suggest that over the last 300 kyr, Himalayan shortening has not only been accommodated by the most frontal faults along the Himalayan range.</p>
<p>A semi-3D stratigraphic architecture of the Lower Ktawa Group, deposited during the early Late Ordovician on the northern Gondwana platform in a shallow marine environment, was investigated in the Anti-Atlas. The logging of 42 sections reveals that the Lower Ktawa is dominated by shales, punctuated by fine to coarse sandstones forming successive cuestas. Here, focus is put on three main sand cuestas recording major sea-level drops.</p><p>The lowermost cuesta (Foum-Zguid Member) outcrops along >85 km, and dips southward. Three facies associations albeit with complex lateral relationships were distinguished: 1. In the West, coarse-grained cross-bedded sandstones. 2. In the central part, sandstones dominated by Hummocky-Cross-Stratifications (HCS), in amalgamated beds towards the West but isolated within shales towards the East. 3. In the East, dominance of highly bioturbated sandstones. A second cuesta (&#8220;Tissint Member&#8221;) outcrops exclusively on the western part of the transect, approximately 25-50 m above the Foum-Zguid cuesta, and also dips South-southwestward. This 40 m-thick sandstone complex has a sharp base and is composed of fine to coarse cross-bedded sandstones. At its northeastern limit, the 40 m-thick succession disappears within 3.5 km. The upper cuesta (Bou-Hajaj Member, 5-40 m thick) is found ca.160 m above the base of the Ktawa Group and outcrops in the eastern zone of the study area. Its southern part is characterized by the thickest stack of sandstones, organized in a shallowing upward trend, and comprises HCS-beds and channelized structures a few meters in width. The eastern part is dominated by coarse, bioturbated, cross-bedded sandstones lacking shallowing upward stacking patterns. Its dip is northward, in the opposite direction to the underlying two members. Moreover, from satellite images, a clinothem dipping towards the Northeast is identified, together with the dissociation of the cuesta in two sets pinching out northwestward.</p><p>On a regional scale, the directly underlying First Bani Group was reconstructed as a shallow shelf having a northward oriented proximal-to-distal trend (Marante, 2008). A study of the Ktawa Group ca. 200 km Northeast of our study zone evidenced a southwestward proximal-to-distal trend (Meddour, 2016). Furthermore, a regional depocenter of the Ktawa Group is generally thought to occur eastward from our study.</p><p>Three interpretation lines are considered to reconcile these apparently contradictory observations: 1. A locally eastward oriented proximal-to-distal trend within a complex sequence stratigraphic framework including superimposed high-frequency cycles. 2. A range of source feeders that may be successively active along an irregular coastline, thereby forming lobes with opposite dispersal patterns. 3. An interplay of reactivation of Panafrican faults (Anti-Atlas/Ougarta) cannot be excluded and may have locally changed the place(s) of maximum accommodation space during deposition. It may also have induced the formation of shoals that would have been partially eroded and recycled. Thus, these apparently contradictory proximal-to-distal trends may actually depict a turning point in the re-organization of the basin predating the end-Ordovician glacial advance.</p>
