We geochemically-fingerprinted a large set of sediments collected from potential source areas (PSAs) in southeastern and southcentral Australia and to compare these data with the record obtained from X-ray Fluorescence (XRF) scanning on a long deep-sea sediment core MD03-2607 obtained offshore Kangaroo Island, South Australia. The entire data set of samples collected on land as well as the downcore measurements were unmixed using the numerical end-member method AnalySize. In this approach, we successfully use the elements Al, Fe, K, Mn, S, Sr and Y to define end members. In addition, the on-land occurrences of the chemical ratios of Zr/Zn, Ti/Rb, Ti/Y and Zr/Rb are used to support the provenance of the chemical end-members. Three main PSA’s are defined: Murray River Basin (MRB), Darling River Basin (DRB) and Kati Thanda – Lake Eyre District (LED), of which the MRB is represented in two different chemical end members. The downcore contributions of these end members in the sediment core are consequently interpreted in terms of fluvial (MRB and DRB) versus aeolian (LED) input. Consequently, the downcore dominance of sediment-transport modes are interpreted in terms of river runoff versus aeolian input over the last 125 kyr. The downcore palaeoclimate proxies show a dominance of MRB during the interglacial intervals versus a dominance of both LED (dust) and DRB input during the glacial ones, suggesting increased seasonal contrasts during glacial austral winter. See: www.nioz.nl/dust
How to cite: Stuut, J.-B., De Deckker, P., and Hennekam, R.: Provenancing dryland sediments recovered from the marine realm to reconstruct Late Quaternary Australian climate variability , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17564, https://doi.org/10.5194/egusphere-egu25-17564, 2025.
Neogene tectonics, geomorphological processes, and Quaternary climate change control landscape evolution in the internally drained basins of the Basin of Great Lakes (BGL), western Mongolia. The interplay of aeolian, fluvial, and lacustrine processes has resulted in a variety of landforms, such as large dune fields, beach bars, and alluvial fans. Their associated sedimentary archives and sediment transport pathways reflect mid-to-late Quaternary landscape evolution. The ongoing project analyzes geomorphological processes and sedimentary records. Different dating methods constrain the timing of landforms and deposits.
(1) Aeolian and fluvial dynamics: Mongolia's three largest dune fields, resulting from a long-term Quaternary sediment cycle, are located in the BGL. Rivers transport sediment into endorheic lakes. During lake-level low stands, winds transport the sand eastwards along the dune fields. The lakes exhibit different paleolake levels, and sandy plains with mobilized sand at their eastern ends exist. Three climatic and paleoclimatic implications are derived from a mapping approach1. (i) The fundamental west-east orientation of the dune fields is a result of the westerly winds that prevailed during the arid periods of the Quaternary. (ii) The highest lake levels occurred during pluvial phases caused by increased moisture supply. (iii) In the modern semi-arid climate, wind systems from north to northwest predominate, while in the southernmost dune field, minor winds from the southeast occur. Preliminary dating results give mid-Pleistocene dates for the core of the dune fields and Holocene dates for the youngest and smaller dunes.
(2) Lake level fluctuations: The first comprehensive late Quaternary chronology of lake level variations for the Khyargas Lake in the BGL is presented. The data is based on a geomorphological approach supported by luminescence dating. The lake is the ultimate sink of a sequential water and sediment cascade from the adjacent Mongolian Altai and Khangai Mountains. Several intercalated lakes repeatedly merged to form a large paleolake, as evidenced by various shoreline features. Twelve paleolake levels between +7m and +188m above the modern lake level (a.m.l.) are identified from well-preserved paleoshoreline sequences. Calculations of paleolake extent and water volumes emphasize times of enhanced inflow and gradual capture and subsequent reduced inflow and abandonment of upstream-located lakes. Three distinct phases of lake level dynamics can be differentiated: (i) A transgression to a maximum level of +129m (a.m.l.) during Marine Isotope Stage 5c primarily controlled by enhanced atmospheric moisture supply. (ii) A post-Last Glacial Maximum lake expansion to a level of +118m (a.m.l.) around 14 ka, ultimately controlled by glacial meltwater pulses. This period was followed by a rapid lake level drop during the Late Glacial–Holocene transition in response to decreasing meltwater supply and a drier climate. (iii) Small-scale lake level fluctuations throughout the Late Holocene reflect a hydro-climatically controlled equilibrium between ~ 2.6 and 0.7 ka.
The final project phase will obtain TCN dating of paleoshorelines and alluvial fan activity.
1 Lehmkuhl, F. et al. Aeolian sediments in western Mongolia: Distribution and (paleo)climatic implications. Geomorphology 465, 109407 (2024).
How to cite: Lehmkuhl, F., Wolf, D., Frechen, M., Rahimzadeh, N., Tskamato, S., Batkhishig, O., Owen, L. A., and Wegmann, K.: Paleoclimate and landscape evolution in an extreme continental interior – Interplay between aeolian, fluvial, and lacustrine systems in the Basin of the Great Lakes, Western Mongolia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3123, https://doi.org/10.5194/egusphere-egu25-3123, 2025.
Loess-Paleosol-Sequences (LPS) are important sedimentary archives that enable to infer climatological parameters during the Quaternary at high temporal resolution. Three isochronous, central European LPS sites (Nussloch, Münzenberg, Hecklingen) were accessed at high temporal resolution by means of heavy mineral, single-grain sedimentary provenance analysis (SPA) using a highly automated, correlative workflow guided by machine learning (Lünsdorf et al., 2023). The goals of this study are (1) to investigate if regional differences exists between the LPS in terms of heavy mineral composition (i.e. Alpine vs. Fennoscandinavian provenance) and (2) if short lived processes that affected the source-to-sink system can be detected.
The studied LPS compose a transect from SW to NE Germany and synchronicity of the archives was controlled by presence of the Eltville tephra (ET; ca. 23.2 – 25.6 ka, Zens et al. 2017) and/or precise OSL age modeling. Thus, the LPS recorded sedimentation during the last glacial maximum. From each LPS 1 m of sediment was continuously sampled in 5 cm intervals, whenever possible centered on the ET. 120 heavy mineral aliquots of the grain size fractions 10 – 30 µm and 30 – 62 µm were analyzed by optical microscopy, Raman spectroscopy and electron probe micro analysis (EPMA) at the single grain level. Resulting in a correlated dataset of optically derived grain parameters (size, shape, roundness, color, etc.), mineralogy and chemical composition for each individual grain analyzed.
First preliminary results suggest that the three LPS are readily differentiated based on heavy mineral composition, supporting a Southern, Alpine and Northern, Fennoscandinavian loess provenance. While heavy mineral ratios and garnet chemical composition reveal abrupt changes in the Southern (Nussloch) and Northern (Hecklingen) LPS. It is assumed that the abrupt changes at the Nussloch site are related to variation in storm intensity with periods of high storm activity reflecting a distal source and periods of low storm activity a more local source. A reasonable explanation for the abrupt change in provenance indicators at the Hecklingen site is the advancement of the Scandinavian Ice Sheet, potentially changing the fluvial drainage pattern and introducing more moraine material to the deflation area.
How to cite: Lünsdorf, N. K., Speck, M.-C., Moine, O., Antoine, P., Fuchs, M., and Lehmkuhl, F.: Isochronous provenance variability during the last glacial maximum revealed by heavy mineral analysis of loess deposits, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12167, https://doi.org/10.5194/egusphere-egu25-12167, 2025.
Reconstruction of hydrological fluctuations in arid regions has proven challenging due to a lack of reliable chronologic constraints on sparse geological archives. The aim of this study was to establish an independent record of hydrologic changes in the hyper-arid Tarim Basin, northwest China, with high spatiotemporal resolution. This paper presents comprehensive radiocarbon and tree-ring data sets of subfossilized medieval forest in the Tarim Basin compiled from geomorphological investigations of the palaeochannels of the Tarim River, the longest endorheic river in China, crossing the world’s second-largest shifting sand desert. This study describes the centennial-scale dynamics in the Tarim River flow over the past millennium, offering a robust long-term context for hydrological assessment in the extensive drylands of the Asian interior. Subsequently, we consider the role of the river-based hydrological fluctuations in connectivity of the ancient continental Silk Road networks.
How to cite: Li, K., Qin, X., Plunkett, G., and Brown, D.: Hydrological fluctuations in the Tarim Basin, northwest China, over the past millennium, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-506, https://doi.org/10.5194/egusphere-egu25-506, 2025.
Identifying reliable indicators of environmental changes is crucial for effective ecosystem management, particularly in drylands which are prone to climate change impacts. Here, we report on how we are integrating time-series remote sensing, advanced data science techniques, and ground-based observations to identify, map, and assess the sensitivity of a diverse suite of wetlands in drylands to environmental perturbations. We are particularly interested in potential ‘sentinel wetlands’: natural features that are highly sensitive to subtle climatic changes. These wetlands may act as early warning systems, reflecting the cumulative effects of various climate stressors on their hydrodynamic state.
We have developed a method to automatically map different surface waterbodies (including a range of low- and high-altitude wetlands) and characterise their wetness dynamics at pixel-scale using time-series multispectral satellite data. We have applied the method to drylands spanning three different continents (western and northern India, southwest Spain, Argentinian Patagonia) and validated the mapped wetness dynamics of key features such as floodplain and valley-bottom wetlands, interdunal depressions, playas and pans through extensive field visits (~10 000 km of road trip).
From our field visits, we conclude that not all wetlands are good candidates for serving as sentinel wetlands. The best candidates are those wetlands which are devoid of direct human interventions, sit within endorheic catchments, and are relatively small in size (<10 km2). Each dryland visited hosts several such candidates. We classify these candidates in two categories: controls and targets. Controls are sentinel wetlands with in-situ hydrometeorological data logging stations (e.g. interdunal wetlands in Doñana National Park, Southwest Spain), while targets are the remaining sentinel wetlands that we plan to use as a distributed sensor array. Our field visits reveal that in some wetlands, there has been an increase in wetness frequency in recent years. In the case of low-altitude wetlands, it is almost exclusively because of human interventions (i.e. these are non-sentinel wetlands) and in the high-altitude wetlands, it is because of increased glacier meltwater supply (i.e. these are sentinel wetlands). By contrast, most sentinel wetlands in low-altitude regions are exhibiting reduced wetness frequency, in some cases dramatically. The next steps are to monitor and evaluate a wider set of hydrodynamic responses to stressors, including by tracking subtle changes at pixel scale and correlating these changes with local to regional climate. The results will help further demonstrate how wetlands in drylands can act as robust indicators of climate change.
Knowing the wetness dynamics of sentinel and non-sentinel wetlands will help us to identify and separate the various climate and direct human stressors that might impact future water availability and hence water security in the world’s diverse drylands. This separation is crucial for developing targeted management strategies. By further characterising the sensitivity of sentinel wetlands, our research will enhance predictive models of waterbody responses to climate change and provide actionable insights for sustaining water resources amidst ongoing climate changes.
How to cite: Singh, M. and Tooth, S.: Time-series remote sensing and multi-continental field work reveals that wetlands in drylands can be robust indicators of climate change, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11577, https://doi.org/10.5194/egusphere-egu25-11577, 2025.
Groundwater serves as an unsung hero in the worldwide freshwater crisis, supporting agriculture, sustaining communities, and mitigating the effects of climate variability. India leads the world in groundwater consumption. It extracts approximately 250 km³ annually, surpassing the combined withdrawals of China and the United States. Groundwater extraction is expected to escalate in the coming future due to agricultural demands, thereby stressing the already over-exploited groundwater reserves. These findings emphasize the critical need for in-depth research on groundwater systems. The present study focuses on the agro-ecological zones (AEZs) of India, as classified by the National Bureau of Soil Survey and Land Use Planning (NBSS&LUP). AEZs are characterized by unique climatic, soil, and hydrological properties, providing an ideal framework for analyzing groundwater trends at a regional scale. The intricate relationship between rainfall and groundwater levels across different agro-ecological zones was analyzed. The Mann-Whitney U test results reveal significant (p < 0.05) differences in groundwater-levels between normal and dry (deficient rainfall) years in Zones 3, 10, 16, and 19, as well as between normal and wet (excess rainfall) years in Zones 3, 10, 11, 15, 16, and 17, highlighting the pronounced impact of rainfall variability on groundwater availability in these regions. A decline in water table over the two decades (1996-2016) is observed in 57.42% of the total geographical area. Furthermore, regression analysis demonstrated strong correlations (r > 0.7) between annual rainfall and post-monsoon groundwater levels in ten out of the eighteen AEZs considered for the analysis. In addition, Zone 11 ‘Central Highlands’ and Zone 16 ‘Deccan Plateau (Karnataka)’ exhibited stronger correlations at a lag of 1 month, highlighting the delayed response of groundwater to rainfall in these regions. It was also observed that the total area where groundwater extraction during monsoon exceeds recharge, expands from 0.68% in 1996, to 1.21% in 2006, and to 3.89% in 2016. The findings of this study emphasize the need for adaptive, zone-specific strategies to ensure sustainable groundwater management under the changing climate and socio-economic conditions.
How to cite: Feroz, Z. and Jha, M. K.: Unraveling the Link between Rainfall and Groundwater: A Regional Approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14669, https://doi.org/10.5194/egusphere-egu25-14669, 2025.
Australia's drylands, covering nearly 70% of the continent exhibit the most variable precipitation and streamflow regimes globally. The endorheic Lake Eyre Basin (LEB) terminates at Kati Thanda-Lake Eyre (KT–LE), Australia’s largest lake and drains 1.14 M km2. This basin experiences remarkable ecological fluctuations with spectacular boom and bust cycles during extreme flooding events. This vast unregulated river basin, despite its ecological significance, has limited stream gauges and no lake monitoring, making the lake's water balance a real challenge due to its vast size, remote location and complex lake geometry. Recent observations reveal significant water loss in endorheic basins worldwide, emphasizing the urgency for improved freshwater monitoring solutions for KT – LE and its basin. Therefore, in this study, we present a space-based monitoring solution to estimate the storage volume of the KT–LE as an alternative to in situ measurements. To do so, we utilized the data from the Surface Water and Ocean Topography (SWOT) satellite, launched in December 2022, to monitor the 2024 KT-LE filling event. The duration of this event was between March and October 2024. The predicted maximum lake storage volume (recorded on 1st May) reached 0.82 Km3 with a predicted average depth of -14.2 metres AHD (Australian Height Datum). We cross-compared the volume estimates from three bathymetry digital elevation models to evaluate the derived estimates in the absence of in situ data. We achieved the accuracy of the derived water surface elevation estimates with a root mean square error (RMSE) of <0.6 meters. This research highlights the potential of SWOT data for addressing critical data gaps in hydrological monitoring and advancing water balance assessments in arid and semi-arid regions and in large wide and shallow playa lakes.
How to cite: Rai, A. K., Cohen, T. J., Armon, M., and Marx, S. K.: Quantifying input volumes in Australia’s largest playa lake using SWOT data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-754, https://doi.org/10.5194/egusphere-egu25-754, 2025.
Effective water resource management in arid and data-scarce regions necessitates innovative approaches that incorporate advanced hydrological modeling and remote sensing technologies. This study focuses on developing nature-based solutions for groundwater recharge, specifically identifying aquifer recharge zones to combat water scarcity in areas characterized by low precipitation and limited streamflow data.
Utilizing the Soil and Water Assessment Tool Plus (SWAT+), this research integrates remote sensing datasets with observed hydrological data for model calibration, aiming to estimate water availability and optimize storage potential. A comprehensive water balance approach is employed to evaluate precipitation, evapotranspiration, runoff, and infiltration dynamics, which enables precise estimation of water availability for recharge efforts.
By coupling SWAT+ with a groundwater module, the study analyzes infiltration capacity at a grid scale, facilitating the identification of high-potential groundwater recharge zones. The integration of remote sensing-derived parameters, including land use, soil type, and topography, enhances the model's ability to simulate water flow dynamics across watersheds.
This methodology is applied to Balochistan, Pakistan’s most vulnerable province to floods and droughts, where groundwater overexploitation and insufficient infrastructure exacerbate water challenges. The study’s findings provide insights into sustainable aquifer recharge strategies, supported by spatial analyses and thematic maps. These results inform the development of targeted interventions for water conservation, flood mitigation, and drought resilience in one of the world’s most water-stressed regions. This approach highlights the transformative potential of combining nature-based solutions with advanced hydrological modeling to secure water resources in arid regions.
How to cite: Naseer, A., Hafeez, M., Arshad, M., and Faizi, F.: Developing Nature-Based Solutions for Sustainable Groundwater Recharge through Advanced Hydrological Modelling and Water Availability Assessment in Arid Regions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1434, https://doi.org/10.5194/egusphere-egu25-1434, 2025.
In semi-arid regions, the growing demand for water, particularly for irrigation, accelerates the overexploitation of water resources, often leading to severe scarcity that constrains sustainable economic development. This issue is particularly acute in the Merguellil watershed in central Tunisia, where the impacts of climate change exacerbate the challenges. This study employs the Water Evaluation and Planning (WEAP) system model to analyze current and future trends in surface and groundwater resources in the Merguellil watershed, assessing the combined effects of climate change and human activities on these resources. The primary objective is to identify critical thresholds, evaluate sustainable solutions and guide adaptive water management strategies. An essential element of the study is estimating the demand for irrigation water in the Kairouan plain using high-resolution Landsat 8 imagery to calculate crop evapotranspiration (ETC). Once the required input data from 2000 to 2020 are introduced in the WEAP model, the impact of different scenarios (Climatic and anthropogenic) for the actual and future water balance were evaluated until 2050. The simulation results under the RCP 4.5 climate scenario indicate a significant decline in aquifer levels across the basin; the Kairouan aquifers being particularly impacted. Additionally, scenarios involving the expansion of irrigated areas show a substantial increase in agricultural water requirements. To address these pressing challenges, this study explores multiple management strategies, including improving the efficiency and satisfaction levels of public irrigation systems, optimizing reservoir management during drought periods, and interconnecting existing water infrastructures. Notably, the findings highlight the importance of gradually increasing water transfers to the El Haouareb Dam to meet irrigation demands effectively. Finally, we conclude by emphasizing the importance of proactive and adaptive measures in order to mitigate the adverse impacts of climate change and human activities on water resources in this area. This study highlights the need for integrated, resilient, and sustainable water management practices to ensure the long-term viability of water resources in this vulnerable region.
How to cite: Ataallah, H., Oueslati, I., Le Page, M., and Lili Chabaane, Z.: Sustainable Water Resource Management in the Merguellil Watershed (Tunisia): Assessing the Impacts of Climate Change and Human Activities Using the WEAP Model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19705, https://doi.org/10.5194/egusphere-egu25-19705, 2025.
Several studies demonstrated that >~100 absolute ages of sand at certain spatial/vertical resolutions are required for constructing a reliable chronological framework for palaeoenvironmental and palaeoclimatic interpretations of dunefield construction (Telfer and Hesse, 2013). As acquiring abundant absolute ages demands significant field and lab resources, several methodological approaches, such as port-OSL-OSL age estimates, have attempted to partly overcome this necessity (Stone et al., 2019).
Arid-zone encroaching dunes in the past and present, often dam drainage systems and generate proximal upstream, dune-dammed waterbodies that when dry, form playas. These waterbodies that are often seasonal, deposit distinct, low-energy, fluvial, fine-grained sediments (LFFDs), often as couplets. This recurring aeolian-dominated aeolian-fluvial (AF) process gradually leads to amplified LFFD accumulation, and partly configures dunefield, and particularly dunefield margin landscape evolution.
The INQUA DuneAtlas of global dunefield chronological data includes some dated samples that are non-dune sediments such as interdune and LFFD samples. However, the complementary contribution of such sediments to interpreting dunefield chronologies has not been fully assessed (Lancaster et al., 2016). Furthermore, and surprisingly, DuneAtlas dune sand samples that date to the LGM are sparse. We demonstrate that OSL ages, partly supported by port-OSL profiling, mainly of sandy units within LFFDs, improves the resolution and reliability of dating dunefield construction events and morphological maintenance of existing dunes, and in some cases even reveals periods of dune mobilization that are absent in dated dune cores.
Spatially dense, OSL-dated dune cores and sections of the ~103 km2 sized northwestern Negev dunefield (Israel) study area, revealed that the dunefield was constructed in two main sand incursion and vegetated linear dune (VLD) buildup/extension periods during the Heinrich 1 (H1) and Younger Dryas (YD) (Roskin et al., 2011; Thomas and Bailey, 2019). In this study, exposed, OSL-dated LFFD sections along the dunefield margins revealed that dune-dammed waterbodies destroyed earlier dunefield-margin dunes, partly erode others, but also preserve remains of eroded dunes between LFFD units. The LFFD sections revealed for the 1st time, significant and initial dune incursion and damming during the LGM, and also LFFD deposition thru the early Holocene (Robins et. al., 2022, 2023). The extent and relative thickness of H1-dated LFFDs suggest that dune encroachment then was greater than during the YD of the climate may have been slightly wetter. Early Holocene sediments may imply partial dune buildup or equilibrium-like dune maintenance in the early Holocene and, or also, a lag between YD dune-damming and later fluvial dune-breaching - when LFFD stratigraphic buildup gradually neared dune crest elevation leading to an outburst flood.
Altogether, studying and dating dune-dammed LFFDs are proposed to not only be a complementary, but rather a primary approach to date dunefield evolution and interpret past forcing drivers of sand mobilization and stabilization, and palaeohydrology.
References
Lancaster, N., et al., 2016. QI
Robins, L., et al., 2022. QSR
Robins, L., et al., 2023. QSR
Roskin, J., et al., 2011. QSR
Stone, A. et al. 2019. QG
Telfer, M.W. and Hesse, P.P., 2013. QSR
Thomas, D.S. and Bailey, R.M., 2019. AR
How to cite: Roskin, J., Robins, L., and Greenbaum, N.: OSL-dated, dune-dammed waterbody sediments along dunefield fringes improves resolution and reliability of dunefield evolution chronologies, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2344, https://doi.org/10.5194/egusphere-egu25-2344, 2025.
Whether the provenance of eolian deposits on the extensive Chinese Loess Plateau (CLP) is spatiotemporally heterogeneous/homogeneous is highly controversial. Here we present detrital zircon U-Pb ages for the eolian dust from the central-eastern Mu Us desert, its underlying Cretaceous sandstones, and the loess from the northeastern CLP. The comparable detrital zircon U-Pb age signatures between the eolian deposits from eastern Mu Us and Cretaceous sandstones suggests that eolian deposits in the eastern Mu Us are largely the product of weathering and recycling of regional bedrock. Typical loess on the northeastern CLP show relatively consistent zircon age spectra with those from the eastern Mu Us, indicating significant contributions of the western North China Craton (NCC) to the loess on the northeastern CLP. Temporal consistencies of U-Pb age spectra for a 13.6 m-thick eolian sand-loess sequence in the eastern Mu Us desert reveals that there is no apparent provenance shift at least since the last interglacial. Comparison of detrital zircon U-Pb age spectra of Late Pleistocene loess developed on the northeastern, eastern, and west-central CLP demonstrates that the contributions from the western NCC increase significantly for the loess on the eastern-northeastern CLP, while the west-central CLP received more eolian dust from the northeastern Tibetan Plateau (NTP) and the Central Asian Orogenic Belt (CAOB). The contribution of detritus from the NTP decreases, and the contribution from the western NCC outweighs that from the NTP on the eastern-northeastern CLP. Our new detrital zircon data provide robust evidence for the spatial heterogeneity of provenance across the CLP, regardless of the general characteristics of multiple recycling and thorough mixing of Chinese loess.
How to cite: Sheng, M., Wang, X., and Zhang, S.: Spatial variations in the provenance of eolian deposits on the Mu Us desert and the Chinese Loess Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7661, https://doi.org/10.5194/egusphere-egu25-7661, 2025.
The high-accumulation-rate eolian deposits in the eastern Hexi Corridor retain invaluable archives of rapid climatic fluctuations in the transitional zone of the northwestern Chinese Loess Plateau, the Tengger Desert, and the northern foothills of the Qilian Mountains. High-resolution mineral magnetic and bulk grain size analyses for the Shagou loess–paleosol sequences since the last interglacial reveal that loess accumulation in northwestern limit of the East Asian summer monsoon is essentially continuous at multi-centennial scales, and variations in magnetic granulometry of the last glacial loess are predominated by the intensity of the East Asian winter monsoon (EAWM). Based on Greenland Ice Core Chronology, the complete recording of all Dansgaard–Oeschger (D–O) cycles and Heinrich events substantiates a rapid response of the EAWM to the northern high-latitude abrupt climatic changes, regulated by the strength of the Atlantic Meridional Overturning Circulation (AMOC) and Arctic sea-ice extent. A synthesis of various high-resolution paleo-proxy records from the Northern Hemisphere further suggests the generally identical phasing of stadial–interstadial oscillations and tight coupling of the atmosphere-ice-ocean system. We propose that the relatively stronger D–O signals in low-latitude tropical marine sequences compared with middle-latitude land-based paleo-records may be accounted for by northward transport of heat and moisture originated from the warmest tropical oceans during interstadials, and the more significant influence of oceanic processes than that of atmospheric processes in propagating the northern high-latitude climatic signals during stadials. This study highlights the pivotal role of AMOC in modulating millennial-scale regional and global climate.
How to cite: Wang, X., Sheng, M., and Yi, S.: Links of abrupt climate events in the eastern Hexi Corridor to Atlantic meridional overturning circulation changes during the last glacial：magnetoclimatological evidence of the Shagou loess record, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7789, https://doi.org/10.5194/egusphere-egu25-7789, 2025.
Evidence of profound climatic changes and wetter conditions during the late Quaternary are mentioned by several authors for the deserts of central Iran (e.g. Khademi and Mermut, 1999; Jalilian et al., 2022). The region today is strongly influenced by aeolian and desertification processes which are mainly attributed to human activities. To examine the role of chemical weathering (under moist conditions) and long-term dust influx (under dry conditions) on soil genesis, we studied the mineralogical composition of soil materials in a relict paleosol of an arid region of eastern Isfahan, central Iran. A high-resolution sampling strategy (10 cm interval) and qualitative and quantitative X-ray diffraction method were applied. The paleosol is located on an upper terrace with a flat surface having a gravelly structure and neither groundwater influence nor input of materials from adjust landforms. The results showed that quartz, calcite, Na-plagioclase and chlorite are dominant minerals in the clast fraction of the paleosol. The comparison of the mineralogical composition of soil materials and gravels revealed that K-feldspar, gypsum, smectite and palygorskite in the soil matrix were not inherited from the gravels but were provided by dust influx and/or pedogenesis processes. K-feldspar was absent in the gravels and was added by dust influx as its neoformation in the soil environment is unlikely. This hypothesis is supported by the exponential increase of its amount towards the soil surface and the maximum accumulation of the mineral in the surface dust-derived (vesicular) horizon. Smectite is also absent in both the clast fraction and the vesicular horizon and showed a maximum abundance in the middle and lower parts of the pedon where pedogenic calcite deposition occurred ~29 ka, suggesting a pedogenic origin of the mineral under the semiarid and seasonal climate. Palygorskite is absent in gravels but occur in the surface vesicular horizon and was relatively uniformly distributed throughout the pedon. It seems that palygorskite has both exogenic (from dust) and endogenic (by pedogenic processes) sources in the paleosol. Scanning electron microscopy (SEM) images support this postulation. SEM images exhibited dense fibers of palygorskite in the soil matrix and broken and small pieces of palygorskite in the dust-derived horizon. The investigated paleosol provided evidence of environmental changes from a semi-arid and seasonal climate during the time of smectite pedogenesis to an arid and dust deposition environment. Consequently, the palaeosol exhibited a mostly natural trend of aridification and desertification in this region during the late Quaternary.
Jalilian, T., Lak, R., Taghian A. and J. Darvishi Khatooni, 2022, Evolution of sedimentary environments and geography of the Gavkhouni Playa during the Late Quaternary, International Journal of Environmental Science and Technology, 19, 1555–1572.
Khademi, H. and A. R. Mermut, 1999, Submicroscopy and stable isotope geochemistry of carbonates and associated palygorskite in Iranian Aridisols, European Journal of Soil Science, 50 (2), 207-216.
How to cite: Bayat, O., Plötze, M., Karimi, A., and Egli, M.: High-resolution mineralogical record of soil genesis and dust influx in a relict palaeosol, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-229, https://doi.org/10.5194/egusphere-egu25-229, 2025.
The hyperarid conditions of the central Atacama, characterized by extremely low precipitation and high evaporation rates, create a unique environment where soil stability is generally thought to be exceptionally high due to the widespread gypsum and salt enrichment. Terrestrial cosmogenic nuclide-based surface exposure ages suggest that many surfaces underwent limited to no changes since the Neogene or early Pleistocene. However, a number of recent studies also underline the younger landscape-scale geomorphodynamic activity, as evidenced by e.g., the incision of the Rio Loa canyon during the late Pleistocene, or by growth of calcium-sulphate wedges and associated patterned grounds in the Central Depression at the onset of the Holocene. Despite this discrepancy, there is a limited understanding of past and present soil dynamics under this extreme hyperaridity, including subsurface turbation processes driven by both biological and salt dynamics (bioturbation, haloturbation). So far, no geochronological framework exists for these important subsurface soil processes, and the factors controlling these processes are still unknown.
Our study aims at providing new insights into the dynamics of subsurface soil processes in the hyperarid Atacama Desert. We use feldspar single grain luminescence dating techniques combined with sedimentological and geochemical analyses to decipher the activity or inactivity of soil material conveyance processes. We present results from investigations of four soil profiles. All profiles are situated in alluvial (fan) deposits along a west-to-east climatic transect stretching from the fog-affected western slopes of the Coastal Cordillera near sea level to the hyperarid core of the Atacama Desert at approximately 2000 m above sea level. Even though all studied profiles are situated in alluvial (fan) deposits, the geomorphic setting and thus the (sub)recent sedimentation dynamics differed considerably between the profiles. Soil dynamics in the form of vertical grain transport as well as material exchange and mixing were only detected in the coastal profiles where sufficient moisture supply supports the presence of vegetation and associated soil fauna. In these lower elevations, alluvial (fan) surfaces appear geomorphologically stable since their deposition, but our profiles exhibit evidence of significant post-depositional soil material reworking. In the hyperarid region above fog occurrence, that is only affected by rare episodic rain, post-depositional turbation processes seem to be absent or restricted to the surface layer. However, in these hyperarid regions, sediment (re)deposition seems to have taken place on relatively recent time scales, thereby adding more data on late Pleistocene to Holocene surface activity in the driest non-polar desert on Earth, that are likely driven by aeolian dust and/or episodic alluvial processes.
How to cite: Maßon, L., May, S. M., Riedesel, S., van der Meij, M., Steiner, J., Opitz, S., and Reimann, T.: Activity and stability of surfaces and soils in the Atacama Desert, Chile, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4036, https://doi.org/10.5194/egusphere-egu25-4036, 2025.
Last major fluvial modification along the hyperarid coast of the Atacama Desert is relatively young. It has been found that the coastal alluvial fans (CAFs) were formed during the Late Pleistocene and Holocene. No remnants older than the last interglacial period could be constrained as yet. However, robust geochronological frameworks by numerical dating using radiocarbon dating, trapped charge dating techniques, and in situ terrestrial cosmogenic nuclides are restricted to few sites. This is related to both the geomorphic and stratigraphic complexity of the multi-stage CAFs as well as the high costs of those numerical dating methods. Consequently, it has remained unclear so far to what extent fan aggradation and progradation is controlled by large-scale allogenic versus individual autogenic forcing.
As a first study, an application of the cost-effective Schmidt hammer exposure-age dating (SHD) technique was explored for constraining the age of terminal aggradation of the CAF generations along the south-central coast of the Atacama Desert (24°15’S–25°15°S) using an 10Be exposure-dated telescopic alluvial fan featuring four control surfaces (after Walk et al., 2023) for age calibration. Apart from the calibration site, SHD was applied on, in total, 19 depositional lobes from 11 CAFs featuring at least one phase of progradation following main channel incision. Morphostratigraphies are primarily based on in-field mapping. Rebound (R) values were systematically assessed using an electronic N-type Schmidt hammer for each abandoned fan generation (Q1–Q3) by randomly sampling 50 surface boulders of comparable lithology. For calibration with recent deposits (Q4), multiple impacts were exerted on a careful selection of few boulders. Linear age calibration and error propagation follows the two-point solution by Matthews and Winkler (2022), adapted to a segmented approach for four control surfaces and complemented by Deming regression.
Calibration results in a negative and significant linear relationship between 10Be exposure ages and R values, presenting a robust regional calibration model for SHD of fan boulders exposed at least since the last interglacial period. SHD of the 19 fan surface generations yield ages of terminal aggradation ranging between the mid MIS 4 (late MIS 3) and early to mid MIS 5. The age range exceeds the usual dating range reported for SHD applied in (sub)humid regions by up to one order of magnitude, which can be explained by the comparatively low weathering rates at the arid-hyperarid transition. The relative age uncertainties amount to 3–20% (10–24%) and allow to deduce a spatial heterogeneity in the Late Quaternary fan morphodynamics. While the CAFs south of 24°53’S show a systematic response probably related to palaeoclimatic changes of the SE Pacific, those to the north are decoupled – indicating a potential control by individual autogenic forcing.
References
Matthews, J.A., Winkler, S. (2022): Schmidt-hammer exposure-age dating: a review of principles and practice. Earth-Science Reviews 230, 104038. DOI:10.1016/j.earscirev.2022.104038
Walk, J., Schulte, P., Bartz, M., Binnie, A., Kehl, M., Mörchen, R., … Lehmkuhl, F. (2023): Pedogenesis at the coastal arid-hyperarid transition deduced from a Late Quaternary chronosequence at Paposo, Atacama Desert. Catena 228, 107171. DOI: 10.1016/j.catena.2023.107171
How to cite: Walk, J.: Expansion of the Late Quaternary morphochronology of Atacama’s coastal alluvial fans (northern Chile) by Schmidt hammer exposure-age dating, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4535, https://doi.org/10.5194/egusphere-egu25-4535, 2025.
Drylands cover approximately 41% of the global land area and support diverse fluvial systems. Identifying the geomorphic diversity of dryland rivers and their maintenance is essential for sustaining ecosystems in arid and semi-arid regions. Furthermore, amidst climate change and the anticipated expansion of dryland areas, gaining insights into this diversity is crucial for developing adaptive and effective management strategies for dryland rivers. However, dryland rivers are often generalized, with studies focusing more on their distinct characteristics than the inherent geomorphic diversity that shapes river character and behaviour. A comprehensive understanding of the occurrence, spatial distribution, and major controls on channel morphological diversity of dryland rivers is still lacking. To address this gap, we have examined the geomorphic diversity within and across two semi-arid dryland river basins in western India: the Mahi River Basin (MRB) and the West Banas River Basin (WBRB). We employed River Styles classification for geomorphic characterization, combined with hydrological analysis, total stream power and specific stream power assessment for a more comprehensive evaluation. Hydrological analysis indicates that MRB and WBRB are monsoon-dominated rivers. MRB is a perennial dryland river with high flow permanence downstream, whereas WBRB is intermittent, with discharge decreasing downstream. Geomorphic characterization shows that MRB predominantly exhibits a confined, terrace margin controlled, meandering, gravel bed River Style. Only a small section of the estuarine zone exhibits a partly confined, terrace margin controlled, fine-grained bed River Style. Terraces impose antecedent confinement on the contemporary river processes in the MRB, limiting floodplain development. On the contrary, WBRB predominantly features laterally unconfined, continuous channel, low sinuosity, gravel-to-sand bed River Style with extensive floodplain development. The midstream section shows a partly confined, terrace margin controlled, gravel bed River Style in the pediment zone. Stream power analysis showed high stream power even in the mid-to-downstream pediment zone of both basins, primarily driven by site-specific structural controls influencing current channel processes. Field investigations indicated that erosion processes, notably plucking, predominantly shape the reaches with higher stream power. The maximum specific stream power in the pediment zone is 98 W/m² and 255 W/m² in the WBRB and MRB, respectively. Geomorphic diversity within the basin is primarily shaped by geological control in the rocky uplands, while the pediment and alluvial zones reflect a combination of geological controls and Holocene climatic imprints. Although both basins are in semi-arid regions, the observed geomorphic diversity across the basin is governed by stream power distribution patterns with underlying geological controls and valley evolution at the millennial time scale. Insights from this study can enhance ground-level river management practices by incorporating the diversity of dryland rivers and contributing to the global inventory, thereby enriching our understanding of dryland river systems.
How to cite: Raj, A. and Jain, V.: Geomorphic diversity of dryland rivers and their controls in the semi-arid region, Western India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4741, https://doi.org/10.5194/egusphere-egu25-4741, 2025.
Conventional interpretations of alluvial fan margins attribute their changes to environmental factors such as tectonic activity or climate variations. Under steady dynamic conditions, fan margin (s) is expected to grow continuously, following the time (t) dependence of s~t(1/3), based on the mass conservation. However, this study aims to propose a new concept that challenges this conventional understanding. A key finding of this research is that the alluvial fan margin can retreat even under constant upstream boundary conditions, a phenomenon significantly influenced by ‘groundwater infiltration’. This study focuses on investigating the role of infiltration process in alluvial fan evolution. Seven tank experiments with varying sediment and water discharge rates were conducted, enabling analysis of fan retreat under constant upstream boundary conditions. Fans typically exhibited continuous progradation, but a critical point was observed where runoff water no longer reached the fan margin, resulting in fan retreat. At this stage, all runoff water infiltrated into the sediment deposit. Applying Darcy’s Law, we found a strong correlation between deposit thickness (dh) and infiltration rate, assuming constant hydraulic conductivity (Ks). Based on these experimental results, a computational model was developed to simulate the alluvial fan trajectories under similar conditions. The findings provide insights into field-scale applications by accounting for infiltration processes on alluvial fans.
How to cite: Shin, H. and Kim, W.: Alluvial Fan Retreat: Tank Experiments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15509, https://doi.org/10.5194/egusphere-egu25-15509, 2025.
In recent decades, the need to quantify and understand water resources in drylands, such as insular volcanic systems, has grown, along with the obligation to assess how climate change might impact them in the future. These resources are constrained not only by climatic, geographic, and geological factors, but also by increasing demand from agronomic, urban, and tourism areas. This, is mostly relevant in the Canary Islands, especially in the coastal region of Maspalomas located in the southern part of Gran Canaria, where an exponential increase in freshwater demand has been observed from 1960 to the present.
Within the framework of the NATALIE project a hydrological model was developed using the Soil and Water Assessment Tool (SWAT) software to estimate the infiltration and recharge rate of Maspalomas aquifers. The water balance results show an average annual precipitation of 272 mm, of which 68% evapotranspires (181 mm/yr). The infiltration rate is estimated at 19% of the precipitation (50.65 mm/yr), equivalent to an annual aquifer recharge of 8.2 hm³.
Gran Canaria faces a unique challenge in water resource management due to strong anthropogenic pressure and the impact of climate change on reserves and available resources. Climate projections towards 2100 suggest a drop of 22.2% in annual precipitation, which would represent a reduction of 34.63 mm/yr in infiltration, i.e., a decrease of 2.59 hm³/yr in groundwater reserves. These results will be key to both prevent scarcity and improve fresh water resource management in volcanic islands.
Keywords: Water resources, Maspalomas, SWAT, recharge rate, climate projection
How to cite: Sariago, R., Marazuela, M. Á., Martínez-León, J., Jimenez, J., Baquedano, C., Gasco, S., Meixueiro Rios, G., Santamarta García-Gil, J. C., and García-Gil, A.: Evaluating Aquifer Recharge in Volcanic Islands: A Case Study of Maspalomas, Gran Canaria, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17392, https://doi.org/10.5194/egusphere-egu25-17392, 2025.
