Search

Coastal sediment stratigraphies, their physical properties and microfossil assemblages are commonly used to reconstruct sea-level change. However, coastal sediments are affected by tidal, wave, aeolian, and overwashing processes at a range of elevations both within and above the tidal frame which means that their sea-level signatures may not always be clearly identified. Saltmarsh is a common coastal sedimentary environment along the Atlantic-facing coastline of northwest Ireland where bedrock headlands and an archipelago of small offshore islands have provided accommodation space for aggradational Holocene sediment sequences. A 2.85 m-long sediment sequence was investigated at Cloughglass, northwest Ireland. This shows weathered granite bedrock overlain by glacigenic cobbles and then in situ Pinus stumps within humified peat that is exposed in the upper foreshore. Above this, organic-rich and laminated saltmarsh sediments are arranged in packages (20–80 cm thick) bounded by undulating erosional surfaces. The saltmarsh sediments are unconformably overlain by a palaeosol (30 cm thick) and 1.5 m of recent dune sand. Sediment samples were removed at 5 cm intervals through the entire logged section and analysed for grain size properties, combustible organic content, CaCO 3 content, and microfossil assemblages. Five samples were dated by the AMS 14C method. Results show organic sediment accumulated around the pine tree stumps at ∼4400 cal yr BP but that later sedimentation was episodic, as evidenced by erosional surfaces throughout the saltmarsh part of the succession that may correspond to episodic storms or flood events. Three microfossil biostratigraphic zones are identified which broadly correspond to the sediment stratigraphy. The lowermost zone has poor preservation. The middle zone contains several halophytic species in low abundance but is dominated by the ubiquitous diatom Achnanthidium minutissimum. The uppermost zone is less diverse, with low but consistent abundance of predominately freshwater species and those that can tolerate brackish conditions. Integrating these results suggests that late Holocene coastal erosion and sea-level rise brought the coastline closer to the site over time, with a concomitant increase in wave and tidal influence as recorded in both sedimentary structures and biofacies. Subsequently, the land surface became stabilized with development of a dune palaeosol and decreased abundance of A. minutissimum. This evolutionary history reflects changing patterns of wave exposure and sediment supply as a result of changes in sand accumulation around the surrounding bedrock islands. Thus, the coastal stratigraphy more strongly reflects local sediment dynamics and accommodation space rather than regional sea-level change in the late Holocene. [ABSTRACT FROM AUTHOR]

In this paper, we present a new model as an alternative to the classical 3D Richards model for the description of water flow in shallow aquifers. The new model is designed to achieve three goals. First, it provides a good approximation to the Richards model over a wide range of time scales. More specifically we show that both models characterize a flow with the same dominant components when the ratio of the horizontal length to the depth of the aquifer is small. Second, the new model accurately describes the velocity field. In particular, it is not based on the Dupuit hypothesis, which is often used in the context of shallow aquifers. This allows the new model to be well accurate even in the presence of wells and in aquifers with variable bedrock. Third, the new model can be viewed as a coupling of numerous 1D vertical Richards problems with a 2D elliptic one. In practice, this coupling is treated numerically using a Picard fixed point scheme, avoiding the need to solve any three-dimensional problem. This results in a significant reduction in computational cost compared to solving the 3D Richards problem directly. [ABSTRACT FROM AUTHOR]

Calcium (Ca) is a highly soluble and mobile element during silicate weathering, and its isotopes could be a promising tracer for continental weathering processes. However, it remains controversial whether Ca isotopes fractionate during granitoids' weathering. Here we investigated Ca isotope fractionation (measured by δ 44/42Ca) behaviours on the weathering profile of the late middle Jurassic Fogang granite (165 ± 2 Ma) under a tropical climate with the help of radiogenic anomaly data (i.e., ε40/44Ca) (both relative to the NIST standard SRM 915a), as well as its implications for the Ca isotopic composition in the hydrosphere. A total of 15 saprolite samples, 2 fresh parent rocks, 3 fresh individual minerals of one granite weathering profile from Fogang county, South China, and 8 stream water samples nearby the profile have been analysed for their Ca isotopic compositions by thermal ionisation mass spectrometry using a double spike method. Results reveal extreme radiogenic and stable Ca isotopic variations among saprolites. The saprolites have ε40/44Ca ranging from 0.8 to 55.6, whereas fresh granite rocks exhibit uniform ε40/44Ca close to 0. The large variation of ε40/44Ca in the saprolites can be attributed to the preferential dissolution of plagioclase and exsolved albite in K-feldspar or the variation of K/Ca molar ratios in K-feldspar. In general, saprolites are enriched in lighter Ca isotopes compared to the parent rocks (0.39 ± 0.04 ‰) and have δ 44/42Ca values ranging from −0.45 ‰ to 0.43 ‰. This suggests that newly formed clay minerals preferentially absorb the lighter Ca isotopes (e.g., 40Ca). However, the δ 44/42Ca of stream waters draining highly weathered granite catchments reflect δ 44/42Ca of bedrock, rather than δ 44/42Ca of the saprolites. One possible reason is that too little Ca was adsorbed by secondary clay minerals in the saprolite to shift the Ca isotope composition of dissolved Ca from the bedrock. Our study shows that a combination of radiogenic and stable Ca isotope data is a promising tracer for the sources, migration, and transformation processes of this key element during continental weathering processes. This research contributes to a broader understanding of Ca isotopes as a tracer for tropical weathering and their implications for global biogeochemical cycles. [ABSTRACT FROM AUTHOR]

To trace Critical Zone processes and to quantify Li fluxes from one Critical Zone compartment into another, we investigated the Li concentration and isotopic composition (δ7Li) of time-series water samples (including subsurface flow, groundwater and creek water), vegetation, bedrock (including separated minerals from bedrock), and regolith (including exchangeable fraction and clay-sized fraction of regolith) in a temperate forested headwater catchment in the Black Forest, Conventwald, Germany. Our estimation of the Li budget shows that atmospheric deposition and biological processes played minor roles in the Li cycle relative to chemical weathering. All water samples (δ 7Li value of 6.5 to 20.4 ‰) were enriched in 7Li compared to bedrock (-1.3 ‰) and regolith (∼-1.7 ‰), but δ7Li differed between water pathways: δ7Li variations in subsurface flow, creek water and groundwater were controlled by conservative mixing, exchangeable pool buffering and Li incorporation/adsorption, respectively. Fractionated heavy Li isotopes in water samples resulted from the formation of secondary solids which preferentially incorporated 6Li, with the separated clay-sized fraction of the regolith exhibiting more negative δ7Li values (-5.4 to −3.5 ‰) than the bulk regolith (∼-1.7 ‰). However, Li in secondary solids only accounted for 8 ± 6 % of the total Li hosted in bulk regolith, and consequently δ7Li in soil did not differ significantly from δ 7Li in bedrock. This is unexpected considering water is continuously removing 7Li in preference over 6Li from regolith. Mass balance calculations applied at the catchment scale point to an irreconcilable imbalance with our data. On one hand, the regolith's δ7Li values are not negative enough to balance the 7Li export by river water, and on the other hand Li in the riverine dissolved load only accounts for ∼ 30 % of the Li solubilized from regolith. Therefore, we suggest that there might be a "hidden export pathway" for Li at our site, possibly subsurface removal of fine particles enriched in 6Li. In light of increasingly frequent observations of such isotopic imbalances in the Critical Zone this phenomenon deserves increased attention. [ABSTRACT FROM AUTHOR]

Hydrothermal circulation around magmatic intrusions affects hazards, critical metal deposition, and heat transfer, however it is often difficult to directly observe. We combine stable isotope and thermochronologic measurements, hydrothermal circulation modeling, and forward thermal history modeling to understand the short-lived hydrothermal circulation system that developed around the Little Devils Postpile, a small-scale mafic intrusion in the eastern Sierra Nevada Mountains of western North America. Bedrock samples collected in transects orthogonal to the intrusion reveal reset and partially reset apatite (U-Th-Sm)/He and zircon (U-Th)/He ages up to ∼13m from the contact. Measurements of hydrogen isotopes in apatite crystals from the same samples show deuterium depletion near the contact; δD values vary between −120‰ and −132‰ within 3m of the contact, −112‰ to −104‰ at 4–6m from the contact, and −85‰ to −95‰ at distances of 12m to 40m from the contact. In contrast, oxygen isotopes do not vary spatially with a δ18O of +6.4 ± 0.4‰. This depletion of δD and consistency of δ18O suggests that short-lived water–rock interaction occurred following the intrusion emplacement, facilitating the exchange of hydrogen isotopes via diffusion rather than dissolution-precipitation processes. Conductive cooling calculations predict an alteration aureole ten times larger than is observed by the low-temperature thermochronometric ages. Numerical models of hydrothermal circulation, for a range of host bedrock permeabilities and magmatic emplacement temperatures, reveal that the geometry of alteration is most consistent with buoyancy-driven hydrothermal circulation and a relatively high crustal permeability. With this case study, we show that combining thermochronology and hydrothermal modeling allows for the opportunity to model hydrogen isotope exchange and predict plausible apatite-water hydrogen fractionation. These new constraints on the geometry of water–rock interactions coupled with hydrothermal circulation modeling provide (1) a rare window into the pressure–temperature evolution of a small magmatic intrusion, (2) constraints on crustal permeability, and (3) a useful tool for interpreting low-temperature thermochronometric data in volcanic settings. [ABSTRACT FROM AUTHOR]

Human activity and climate change are altering natural rates and intensities of wildfire, but the scale and extent of burning prior to the modern era are poorly understood. Paleofire activity may be reconstructed using a variety of records (e.g., charcoal in lake sediments, burn scars on tree rings), but these are not available in all environmental settings. Here we investigate the utility of a novel paleofire proxy: trace pyrogenic organic compounds in stalagmites. Polycyclic aromatic hydrocarbons (PAHs) are linked to burning of biomass and are transported downward through soil and bedrock by infiltrating rainwater and incorporated into stalagmites in underlying caves where they are preserved. In order to test links between the stalagmite PAHs and fire above the cave, we performed a series of experiments using PAH distributions at KNI-51, a shallow cave located in tropical Western Australia, where bushfire is a regular occurrence. First, the possibility of surface contamination was evaluated by measuring PAH abundances and distributions in sequential digestions and by considering other possible additional sources, such as regional oil and gas fields or proximal combustion of fossil fuels. Second, PAHs were measured in soils above the cave and in sediments from the stalagmite chamber floor as possible sources of these organic compounds, and at near annual resolution in three aragonite stalagmites to evaluate the degree of deposition and conservation. Third, possible non-pyrogenic sources of organic compounds were evaluated through alkane distribution and specific m / z ratios. Fourth, signal replication of PAHs was tested in two coeval stalagmites. Fifth, satellite-mapped fire scars were used to examine the relationship between stalagmite PAH abundances and proximity of burning to the cave. The results support the hypothesis that PAHs in KNI-51 stalagmite carbonate reflect paleofire activity within 3 km of the cave, and thus that stalagmites can serve as an important new high resolution proxy for landscape-scale fire activity. Given that karst is present in many fire-prone environments, and that stalagmites can be precisely dated and may grow continuously for millennia, the potential utility of a stalagmite-based paleofire proxy is high. [ABSTRACT FROM AUTHOR]

At the bottom of the geomembrane cut-off walls, pollutants may seep out through the bottom gap between the geosynthetic membrane and the low-permeability bedrock, contaminating the groundwater and the surrounding environment. Therefore, to address the occurrence of bottom gap seepage, this study adopts a mixture of attapulgite and cement in a certain proportion, mixed and stirred to form a sealing material. This sealing material is used to connect the bedrock and the geosynthetic membrane, thereby creating an efficient composite vertical barrier with special containment capacity. A series of laboratory experiments were conducted to investigate engineering properties of cement-attapulgite sealing slurry, including flow value tests, unconfined compressive strength (UCS) tests, improved flexible wall permeability tests, and bedrock and sealing slurry adhesion tests. The results show that the flow value of the slurry decreases with the increase of attapulgite content, and it increases with the increase of water-cement ratio. The UCS strength increases with the increase of attapulgite content, and it decreases with the increase of water-cement ratio, but the range of change is different. The hydraulic conductivity measured with hexavalent chromium solution as the penetrant is less than 50 % higher than that measured with water as the penetrant, and hexavalent chromium solution has little effect on the hydraulic conductivity of sealing slurry. The bonding performance between sealing slurry and bedrock is satisfactory, and the hydraulic conductivity of bedrock-sealing slurry is less than 1 × 10−7 cm/s (28d curing age), it is concluded that use of cement-attapulgite sealing slurry as bonding material between bedrock and geomembrane meets the engineering design requirements. [ABSTRACT FROM AUTHOR]

This study examines dissolved rhenium (Re) concentrations as a function of water runoff using river samples from two contrasting mountainous watersheds, the Eel and Umpqua Rivers in the Pacific Northwest, USA. These watersheds share many key characteristics in terms of size, discharge, climate, and vegetation, but they have a 15-fold difference in sediment yield due to differences in their tectonic setting and uplift and erosion rates. We evaluate concentration-runoff (C-R) relationships and ratios of coefficients of variation (CV C /CV R) for major cations, anions, dissolved inorganic carbon, selected trace elements including Re, and 87Sr/86Sr ratios. Recent research outlines the potential of Re to serve as a tracer for the oxidation of ancient/fossil organic matter because of its close association with petrogenic carbon (OC petro) in rocks. In both the Eel and Umpqua Rivers, our measurements show that Re behaves similarly to major weathering derived-solutes corrected for atmospheric input, such as Ca2+*, Mg2+*, and Na+* with modest dilution across all tributaries with increasing runoff. Rhenium behaves dissimilarly from other trace elements, such as Mo and U, and is also dissimilar to biologically-cycled nutrients, such as NO 3 –, PO 4 3−, and K+*, suggesting differences in sources, solute generation mechanisms, and flowpaths. Rhenium behavior is also distinct from that of colloids, which have increasing concentrations with increasing runoff. We find that Re and sulfate corrected for atmospheric input (SO 4 2−*) have distinct C-R relationships, in which SO 4 2−* undergoes greater dilution with increasing runoff. This implies that Re is not dominantly sourced from sulfide weathering, which leaves primary bedrock minerals and OC petro hosted in bedrock of these watersheds as the likely dominant sources of dissolved Re release. At mean discharge, Re concentration in the Eel river (3.5 pmol L-1) is more than two times greater than Re concentrations in the Umpqua River (1.5 pmol L-1). Furthermore, comparison of two tributary watersheds with similar bedrock but marked differences in erosion rates show higher Re concentrations in Bull Creek (erosion rate of 0.5 mm yr−1) relative to Elder Creek (erosion rate of 0.2 mm yr−1). The results of this study suggest that dissolved Re in the Eel and Umpqua River basins is likely derived from primary mineral dissolution or OC petro oxidation, and Re fluxes are higher in areas with higher erosion rates, suggesting that tectonic setting is one factor that controls Re release and therefore OC petro oxidation. [ABSTRACT FROM AUTHOR]

The global distribution of clay minerals is intricately linked with climatic conditions and bedrock composition, which interact to control the weathering intensity of silicate and other minerals. However, the quantitative relationship between clay minerals and climate is not well understood, partly due to the lack of quantitative assessments of the role of the various factors responsible for clay mineral formation. Here we examine the quantitative relationship between soil clay minerals and climatic factors on the global scale, by extrapolating clay mineral abundances to a large scale. We found that mean annual precipitation (MAP) is the first order control on the global clay mineral distribution, while mean annual temperature (MAT), elevation, slope, lithology, upland hillslope soil thickness (UHST), and upland hillslope regolith thickness (UHRT) have secondary roles or localized impacts on clay mineral distributions. We found that precipitation thresholds exist in weathering intensity and clay mineral formation: (1) Illite decreases monotonically and kaolinite increases monotonically with increasing MAP below the threshold of 1800–2000 mm, whereas gibbsite increases monotonically with increasing MAP below the threshold of 2200–2400 mm. (2) Smectite and Fe oxides increase with increasing MAP below the threshold of 600–800 mm, and then decrease with increasing MAP between 600 and 800 mm and 1800–2000 mm. (3) All clay minerals are insensitive to extremely high MAP, above 1800–2000 mm. We suggest that paleoprecipitation can be semi-quantitatively reconstructed based on variations in the relative contents of clay minerals, which can be used as a proxy indicator of wet and dry variations for paleoclimate studies. [ABSTRACT FROM AUTHOR]

• A DEM-based method was used to link channel-hillslope units and classify hillslopes as outer, inner, or headwater. • Over half of the total landslide volume was triggered on the outer hillslope. • Landslide erosion on outer hillslopes was greater than on inner hillslopes in reaches with a sinuosity > 1.4. • Fluvial lateral erosion effectively triggered landslides only in highly sinuous reaches. River erosion, a geomorphological process undercutting hillslopes, triggering landslides, and shaping the topography, remains challenging to quantify at a watershed scale. This study addresses the gap by investigating landslide erosion triggered by 2009 Typhoon Morakot in a sinuous-meandering, bedrock river watershed in southwestern Taiwan. We propose a DEM-based method to link channel-hillslope units and classify hillslopes (outer, inner, and headwater) to understand the influence of river erosion on landslides. Our results reveal significantly higher average erosion on outer hillslopes (291.80 ± 16.62 mm) compared to inner slopes (246.63 ± 16.39 mm). This disparity amplifies with increasing river sinuosity, reaching nearly 3.8 times greater erosion on outer slopes in sinuous meanders (sinuosity > 1.4). Unit stream power exhibits a significant positive correlation with landslide erosion only in highly sinuous reaches (sinuosity > 1.8) and is insignificant in the relatively straight reaches that comprise the majority of the study area. This non-significance may be attributed to the limitations of the DEM method in capturing complex flow patterns, particularly in areas with relatively straight reaches. Overall, this study supports the notion that lateral erosion by sinuous meanders plays a critical role in hillslope instability. [ABSTRACT FROM AUTHOR]

• River profiles and relict landscapes show two phases of transient erosion across the Liuleng Shan. • The Nihewan Basin initiated in the Late Miocene and the Nihewan Paleolake formed in Pliocene time. • Tectonic activity controlled the evolution of the Nihewan Basin and Paleolake. The Nihewan Basin, renowned for the numerous world-class Paleolithic sites and diverse mammalian fauna preserved in its sedimentary sequence, is a key area for studying early human evolution in East Asia. Despite extensive studies on the fluvial-lacustrine basin sediments, the evolution and formation process and mechanism of the Nihewan Basin and Nihewan Paleolake remain unclear. Here we assess the spatial pattern and recent history of rock uplift of the Liuleng Shan, one of the main bedrock mountain ranges encompassing the Nihewan Basin, using river profile and topographic analysis. The transient topography of the Liuleng Shan is characterized by two generations of elevated non-lithological slope-break knickpoints that delimit the uplifted Dianziliang and Tangxian relict landscape surfaces, suggesting two episodes of accelerated rock uplift during the Cenozoic. We link the first phase of rapid rock uplift to the initiation of the central and northeastern portions of the North Liuleng Shan Fault (NLSF) during the opening of the Shanxi Graben System in the Late Miocene, implying the initiation of the Nihewan Basin at this time. We propose that the dextral transtensional southwestern portion of the NLSF formed and propagated northeastward at around 4.2 Ma, and was responsible for the second phase of surface uplift. This phase of deformation also terminated the Tangxian planation process and led to the further subsidence of the Nihewan Basin. Accordingly, drainage rearrangement and fault activity hydrologically closed the Nihewan Basin, resulting in the development of the Nihewan Paleolake. Our findings outline a timeline for the geomorphic evolution of the Nihewan Basin and Nihewan Paleolake, highlighting the dominant role of tectonics in their formation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rock surface flow inputs promote the generation of surface runoff at the CRSI. • Concave shapes tend to promote surface runoff formation more than straight shapes. • CRSI has lower soil water infiltration and storage capacity than FRSI. • Discriminant conditions for rock surface flow to generate surface runoff were set. Rock surface flow, formed from exposed rock surfaces, is a unique form of runoff in rocky desertified areas with massive bedrock outcrops. The question of whether the rock surface flow promotes surface runoff formation continues to puzzle us. To address this problem, four sites with notable bedrock outcrops and different land use types were selected from a typical desertified area in Guizhou, China. Straight and concave rock-surface shapes that were the most capable of collecting rainwater were selected at each site. Soil infiltration and water storage capacity experiments were conducted to observe the infiltration and water storage properties of the soil closely adhering to the rock–soil interface (CRSI) of the bedrock outcrops by taking the soils far from the outcrops horizontally (FRSI) as the control, and to further explain the conditions for surface runoff formation via rock surface flow. Our results showed that the CRSI is more prone to producing surface runoff than the FRSI, which is attributed to its lower infiltration (stable infiltration rate of 0.2 to 192.6 mm/min) and water storage capacity (total reservoir 441.6 to 613.6 t/hm2) than that of FRSI (4.50 to 272.8 mm/min, 458.8 to 635.4 t/hm2). This phenomenon would be intensified after receiving the rock surface flow input. Concurrently, concave rock surfaces are more likely to promote surface runoff formation than straight rock surfaces, which are affected by the accumulation of rock surface shapes on rainwater. A discriminating condition for whether rock surface flow produces surface runoff at the CRSI is proposed based on the inversely proportional functional relationship between rainfall (rainfall intensity R I and amount R A) and the effective rock surface rainfall catchment area (A RS). When R I or R A exceeds the critical threshold, the surface runoff with mechanisms of excess infiltration or excess saturation is generated around bedrock outcrops. The discriminating equation will help increase surface runoff prediction accuracy in rocky desertified areas with exposed bedrock outcrops. These results help understand the importance and role of rock surface flow hydrologic processes in karst areas. [ABSTRACT FROM AUTHOR]

The 83.5 km Chukyatan-Kumrat Upper Dir road plays a crucial role in transportation and tourism in North Pakistan. Despite its significance, the area faces frequent landslides due to hydrometeorological hazards, posing a threat to its stability. This study conducts the first extensive investigation of landslide susceptibility in the region, considering geological features, geotechnical properties, and rock weathering. The road traverses diverse rock formations, including meta-volcanics, andesites, meta-rhyolites, ignimbrites, volcanic ash, granodiorites, and spotted slates, overlain by residual soils. The presence of the Dir fault has led to significant accumulations of loose, weathered rock debris (>100 m deep). Exposed slopes exhibit polygonal stress fractures, joints, and fissures with steep inclinations (>40°), further enhancing instability. Geotechnical analysis reveals a low internal friction angle (28.5°–31.9°) and cohesion (4.1–5.9 kPa) of slope materials, indicating poor shear resistance compared to stable slopes. The unconfined compressive strength of bedrock (10.7–41.5 MPa) ranges from weak to moderate-strong, emphasizing the contribution of weaker rock formations to instability. Acidic soil pH (3.1–4.2) and clay minerals support the prevalence of weathering conditions promoting landslides. Thin section analysis and X-ray diffraction reveal hydrothermal alteration during low-grade metamorphism, leading to the formation of chlorite, smectite, montmorillonite, and zeolites. Additionally, physical weathering has increased quartz content, potentially impacting slope stability. The combined effect of factors such as steep slope geometry, low shear strength with strain-softening properties, rainfall, snowmelt, freeze-thaw activity, slope base cutting for road development, and massive loading from houses contributes to numerous landslides in the region. The study aids effective mitigation and preparedness in the Chukyatan-Kumrat area and offers insights for landslide susceptibility mapping in similar geological settings. [Display omitted] • Investigates the geological, geotechnical, geochemical aspects of landslides. • Impact of mineralogical parameters in landslides triggering mechanism. • Clay minerals formation due to hydrothermal alteration of meta volcanic rocks. • Geotechnical parameters influence in landslides aggravation. • The Late Paleocene age slope materials in the hilly regions of North Pakistan. [ABSTRACT FROM AUTHOR]

The Fushan Sag, situated on the southeast of the Beibuwan Basin in the northern Hainan Island, represents a semi-graben fault sag, characterized by a near NEE trend. In this study, we conducted LA-ICP-MS U-Pb age dating on detrital zircon from both the Liushagang and Weizhou formations in the Fushan Sag. By integrating our findings with previous research and considering the geological characteristics and bedrock conditions of the surrounding areas, we aimed to ascertain the provenance of the Fushan Sag. The obtained detrital zircon ages (1059 with 80% concordance) can be primarily categorized into three distinct age groups: Mesozoic (90–250 Ma), Paleozoic (250–450 Ma), and Proterozoic (450–2500 Ma). Specifically, detrital zircon grains from the Weizhou Formation reveal three prominent age peaks, approximately falling within the ranges of 100–150 Ma, 250–300 Ma, and 400–450 Ma. Conversely, the detrital zircon grains extracted from the Liushagang Formation predominantly exhibit two age peaks, approximately spanning 100–150 Ma and 200–300 Ma, with a weaker peak observed at 350–450 Ma in the second member, implying a potential change in provenance during this period. A comparative analysis of detrital zircon age characteristics strongly suggests that the primary provenance of the study area is Hainan Island, with the possibility of contributions from the YunKai Massif. Base on the preliminary geochronological data gathered, and in conjunction with extant scholarly research, an inference can be formulated regarding the paleogeographic evolution of the Beibuwan Basin spanning from the Eocene to the Oligocene. This analysis offers insights into the basin's geological history and dynamic changes over this extensive time frame. • The study provides 1059 Zircon U-Pb data with 80% concordance. • The study reveals that the Fushan Sag experienced a provenance shift during the Late Eocene to Early Oligocene. • The study offers valuable insights into the paleogeographic evolution of the Beibuwan Basin from the Eocene to the Oligocene. [ABSTRACT FROM AUTHOR]

During the process of black shale weathering, multiple heavy metal elements are concentrated in the soil, causing pollution. This study selected soil and black shale bedrock samples from high geological background areas to investigate the control of heavy metal element pollution by bedrock using spatial analysis. The research results indicate that the heavy metal content in black shale bedrock is extremely high, ranging from 2.3 to 13.1 times the background values of rock heavy metal elements. The heavy metal content in the soil formed through weathering is positively correlated with the bedrock, ranging from 1.1 to 21.3 times the background values. The coefficient of variation of rock samples ranges from 1.09 to 7.18, indicating significant variability.The analysis reveals that the control ability of pure rock over heavy metal elements is mainly moderate and high, accounting for over 70 %, with d being the most affected metal element. Except for As, the other seven elements exhibit strong spatial autocorrelation, showing distinct regional distribution characteristics. The soil elements demonstrate high homogeneity, with heavy metal elements from black shale bedrock primarily released through weathering serving as the main source of these elements. [Display omitted] • Excessive heavy metal elements in black shale and weathered soil in the Lushao Basin. • A comprehensive study on the soil pollution characteristics of black shale and weathered soil. • The pollution spatial characteristics of pure rock,weathering ecological risk assessment in high geological areas. • Correlation and Main Source Analysis of Heavy Metal Elements in High Geological Background. [ABSTRACT FROM AUTHOR]

The Larsemann Hills, near Prydz Bay is a key region to understand past glacial dynamics in East Antarctica. However, multi-proxy dating constraints for this area indicate an uncertain chronology for deglaciation history during the Last Glacial Period (LGP). In this paper, we report two 26Al exposure ages and eighteen 10Be exposure ages for bedrock samples to better understand past glacial histories. The minimum exposure ages range from 82.84 ± 4.67 ka to 15.1 ± 1.95 ka corresponding to Marine Isotope Stages (MIS) 5–2, and fourteen of these samples date from before the global Last Glacial Maximum (c. 19–26.5 ka). Analysis of 10Be and 26Al concentrations implies a complex deglaciation history, and surface lowering of bedrock may have caused systematic age underestimation. Further comparisons between two adjacent regions in the Mirror Peninsula reveal two major deglaciations involving the Lambert Glacier / Amery Ice Shelf System dated at 61.78 ka to 82.84 ka and 21.98 ka to 49.5 ka during the LGP. • We present new evidence for studying glacial history of Larsemann Hills, Antarctica. • Cosmogenic nuclides 10Be and 26Al dating method is applied for better analysis. • Two major deglaciation events occurred regionally within MIS 2–3 and MIS 4–5. • The exposure age and elevation show a highly significant positive correlation. • Multi-proxy and adjacent evidence are summarized and compared with this study. [ABSTRACT FROM AUTHOR]

Understanding the processes of fluvial geomorphic evolution is based on thorough evaluation of how rivers respond to tectonic activity and climatic change, with river terraces representing a key archive of alternating deposition and incision in response to such forcing, enabling an excellent means for correlation with tectonic and climatic records. An example presented here points to a difference in fluvial response to climate fluctuations along a trunk river and its tributary: the Yellow River and its tributary the Xike River, which has incised the Lajia Gorge to pirate the Zoige Basin, in the eastern Tibetan Plateau. Based on Accelerator Mass Spectrometry 14C dating, the chronological sequence of basin fill top and fluvial terraces below has been established, defining the drainage reorganization of the Yellow River excavation through the Zoige Basin since the Last Glacial Maximum. Spatial and stratigraphic comparison between the two fluvial sequences, combined with correlation with high-resolution climatic records, indicates that the tributary Xike River formed more terraces in response to trunk incision (base-level variation), climatic fluctuations, and underlying weak bedrock than the Yellow River. Thus, our results not only demonstrate a combined archive of climatic fluctuation and tectonic uplift recorded in the fluvial terrace sequences, but also suggest that the generation of fluvial terraces may be influenced by the underlying bedrock within the same tectonic and climatic settings. • The Yellow River excavating through the Zoige Basin is constrained before 19 ka. • Fast uplift drives a sensitive fluvial response to sub-orbital climatic cycles. • Drainage scale affects the sensitivity of fluvial response to climate change. • Fluvial terrace is archive of the coupling between uplift and climate change. [ABSTRACT FROM AUTHOR]

We describe an atypical cave network in the Jura mountains (eastern France), currently the only one known worldwide to be entirely excavated within a subglacial deposits. Extending over 600 m of mapped galleries, this natural cavity developed entirely within a large impermeable drumlin shaped during last glacial stage MIS 2 (Wurm). By using lidar topography, petrophysical, sedimentological and geochemical measurements, as well as U-Th dating, this cave is mainly attributed to mechanical erosion processes (piping cave). The network's morphogenesis seems to be characterized by two main phases. Firstly, thin mini-pipes were probably dug along shear planes previously formed within the drumlin. The first mini-pipes may have appeared under the ice cover during the last glaciation in response to differential hydraulic pressures on either side of the drumlin. They may also have appeared later when the drumlin was free from its glacial cover, forming a natural earth dam across a thalweg and obstructing the flow of surface water. A second phase would correspond to the development of mega-pipes, resulting from sequential capture of flows from mini-pipes. Mega-pipes appeared >2500 years ago, as indicated by U-Th dating of one speleothem. In other regions of the world, intra-till caves have been documented, but are <20 m long. This limitation is mainly attributed to instability of the materials constituting subglacial tills, disfavoring a durable existence of galleries without collapses. In the Jura calcareous mountains the subglacial till contains a high proportion of very fine calcite matrix produced by subglacial abrasion, which was indurated by compaction under several hundred meters of ice. These particular petrographic features appear to be required for the creation and the preservation of this long intra-till cave. Similar caves may likely be found in other regions of the world displaying limestone bedrock and where subglacial till with abundant carbonate matrix was formed. [ABSTRACT FROM AUTHOR]

Estuaries are marine-flooded topographic depressions that receive sediment from both marine and fluvial sources. The morphology of the underlying drainage basin acts as a boundary condition for the spatial distribution of hydrodynamic energy within an estuary, and by extension the resultant depositional environment. In some large estuaries, bedrock structures at the mouth restrict oceanographic forcing, which has impacts on sedimentary infill. Such estuaries are termed here as Large Structural Estuaries (LSEs). For LSEs, the shape of the basin and associated bedrock morphology is fixed on the millennial scale having been formed by geological processes operating over timescales greater than that of the Holocene. However, the distribution and abundance of these LSEs are poorly understood. In this study, a global survey of large estuaries was conducted to identify and characterize LSEs from the worldwide population to understand regional drivers of coastal geomorphology. A total of 271 large (>50 km2) estuaries were identified, and these were clustered into 5 classes using Gaussian Mixture Modelling. These clusters were interpreted as Barrier Estuaries, Rocky Bays, Sandy Bays, Funnelled Estuaries, and LSEs. LSEs comprised 28.04 % of all large estuaries identified and were spatially heterogenous, associated with collision coastlines, and predominantly located at higher latitudes except for the Malay Archipelago. The global distribution of LSEs suggests that regional distribution of tectonic processes strongly influences their formation. LSEs are important global features comprising many of the major ports in the world and this work indicates they are unique landforms and traditional approaches to understanding sedimentation in these settings require adjustment to their unique geomorphology. • Large Structural Estuaries are a globally significant geomorphotype. • LSEs are predominantly found on collision and mid-latitude coasts. • Their rates of Holocene infill are highly variable. [ABSTRACT FROM AUTHOR]

The stable carbon isotopic composition of speleothems is an important but incompletely understood parameter in paleoclimatological and paleoenvironmental reconstruction, recording changes in vegetation and hydrology. This study systematically assesses the influences of karst hydrology, cave environment, and carbon sources on the δ13C values of farmed calcite in Furong Cave, located in Chongqing, southwest China. Six drip sites (MP1-MP5) were monitored between 2009 and 2019, and Δ14C data (Δ14C is the difference in the 14C/12C ratio between a sample and a standard, expressed in permille, ‰) of soil organic matter, drip water and farmed calcite (calcite precipitated on a glass substrate) were obtained. A linear relationship was found between the seasonal variability of p CO 2 in cave air and δ13C Cc of the farmed calcite in "Great Hall" characterised by a relatively stable microenvironment. The growth rate and δ13C Cc values of the farmed calcite was not be affected by the drip rate unless the drip rate decreased to <1 drip/min for a long time, leading to a decrease in growth rate and higher δ13C Cc values because of longer CO 2 degassing. MP2 and MP9 show faster drip rates, higher δ13C DIC and lower Δ14C than MP1 and MP3, which suggests that the "old carbon" in MP9 is derived from the host rock. MP4 and MP5 are characterised by slower drip rates and lower δ13C DIC and δ13C Cc , and the Δ14C values of the farmed calcite are lower than those of MP9. The slow drip rate indicates that less infiltration water reaches MP4 and MP5, and soil CO 2 derived from the decomposition of "old" organic matter enters the fractures that lead to these drip sites. The fast drip rate of MP9 suggests that the fissures feeding this drip site are mostly water-saturated, limiting the exchange between soil CO 2 and CO 3 2− and allowing more "old carbon" from the bedrock to dissolve leading to higher δ13C DIC. This study emphasizes that in addition to changes in the cave environment, the source(s) of the carbon may be a more important factor controlling the δ13C values of drip water (and speleothem) than drip rate. • Carbon isotopic techniques along with 10-year cave monitoring explores multiple carbon sources in drip water and speleothems. • "Old carbon" in drip water feeding by open/close system is from "old" organic matter/bedrock, respectively. • Carbon source is a more important factor to control on δ13C of drip water (and speleothems) than drip rate. [ABSTRACT FROM AUTHOR]

Dissolution of biotite, the main Fe-bearing mineral in granitic bedrock, is of particular importance for the remediation of reducing conditions after the ingress of oxygen, such as after mining activities or the construction of deep repositories for toxic waste. This study investigated the leaching of biotite of size fraction 0.053–0.075 mm under anaerobic conditions at room temperature and pH 4 and 6.5 for a maximum of 160 days. The changes in the concentrations of the major elements in the leaching solutions were monitored. In addition, Fe(II) was analysed separately. pH-independent rate coefficients k H+ were 4.8∙10−10, 6.9∙10−10, 6.3∙10−11, and 1.0∙10−12 mol1-n m−2 s-1, for Fe, Fe(II), Mn, and Si, respectively. The corresponding proton reaction orders n H+ were 0.61, 0.63, 0.33, and 0.09, respectively. The corresponding parameters for Al were not evaluated because of a suspected gibbsite precipitation at pH 6.5. The dissolution of biotite was found to be incongruent (non-stoichiometric) with respect to both the dissolving elements and the pH value. At pH 4, the dissolution was dominated by the octahedral layer element Fe, whereas at pH 6.5, the dissolution of the tetrahedral element Si dominated. There was no evidence of secondary phase formation, and the biotite leaching rates were consistent with those reported in previous studies conducted under aerobic conditions. In addition, the Fe(III)/Fe tot ratio of biotite remained essentially unchanged before and after the experiment. This indicates that the anaerobic conditions alone have little effect on the rate and nature of biotite dissolution, although they may influence vermiculite formation. Therefore, biotite dissolution rates previously obtained under aerobic conditions may also be valid under anaerobic conditions. • The dissolution kinetics for biotite has similar rates under anaerobic as under aerobic conditions in the acidic pH range. • Oxidation of structural Fe may not be a crucial reaction for biotite dissolution. • The dissolution is incongruent and pH dependent. • The octahedral sheets dissolve faster than tetrahedral sheets at pH 4, while at pH 6.5 the behaviour is reversed. • Dissolution of octahedral sheets is more strongly dependent on pH than the tetrahedral sheets. [ABSTRACT FROM AUTHOR]

Luminescence-based thermometry and dating often requires determination of the saturation level for specific signals and the corresponding dose. However, previous studies found non-monotonic dose responses for some monochromatic thermoluminescence (TL) and optically stimulated luminescence (OSL) signals from quartz as well as spectral overlap of emission bands, substantially complicating data interpretation. Therefore, the present study examines (1) the variability in the TL emission spectrum of quartz and feldspar from bedrock and sediment of different provenances and, (2) the saturation characteristics of the blue emission band for both quartz and feldspar in the dose range from 0.25 kGy to 50 kGy. The experimental results confirm differences in the spectra which appear to be characteristic of their geological origin and chemical composition. Spectral analysis shows that in the temperature range 175–220 °C the blue emission band at ∼2.5 eV dominates over other bands for all quartz samples studied. A broad UV-blue TL signal peaking at ∼2.5−3.0 eV and composed of probably three overlapping, individual bands is characteristic for K-feldspar, while one Na-feldspar exhibits an additional band at ∼2.2 eV. In the studied dose range, the emissions at ∼2.5 eV and ∼2.6 eV increase as a function of dose up to 6 kGy for both quartz and feldspar. A difference in dose response was observed for high doses (>6 kGy) where feldspar samples reached a stable saturation level while for quartz the blue emission band intensity decays until 50 kGy after having attained a maximum. Our results suggest the suitability of feldspar TL for palaeothermometry and thermochronometry from the perspective of signal saturation characteristics. However, the spectral overlap of several bands in the UV-blue emission requires careful optical filter selection to isolate the signal of interest. The non-monotonic dose response of the ∼2.5 eV emission of quartz around 200 °C glow curve temperature probably precludes its use for temperature sensing based on relative trap saturation levels. • Feldspar. • Decomposition of emission spectra. • Signal saturation. • Luminescence palaeothermometry. • TL emission spectra. [ABSTRACT FROM AUTHOR]

• Groundwater contributes 26–78 % of streamflow during the low-flow period in a large Himalayan watershed. • The groundwater contribution varies substantially from the upstream to downstream sub-catchments. • Young water fraction ranges from 36 % in the middle catchment to 55 % in the lower catchment. • Hydraulic conductivity of the underlying bedrock is a key control on groundwater discharge to the stream. • Our study emphasizes fractured bedrock's critical role in mountain baseflow. Mountains in general are important sources of water resources and correspondingly, the Upper Indus Basin (UIB) in the Himalayas provides water for hundreds of millions of users. During low-flow periods, streamflow is fed by a combination of groundwater (baseflow), snow/glacier melt and recent precipitation. However, the proportion of stream baseflow generated by different sources and the factors that control these contributions remain poorly understood. In this paper, we focus on the Western Himalayan Liddar watershed (1243 km2) in the UIB and use a multi-method approach to characterize aquifers and baseflow generation in three nested catchments which represent varying geology and topography. Our multi-method approach includes geophysical surveys, slug tests, stable isotope compositions, young water fraction (F yw) estimation and a Bayesian end member mixing model. Specifically, we hypothesize that K sat of the subsurface plays a critical role in the contribution of groundwater to baseflow. The watershed is subdivided into three nested catchments (Limestone, hardrock and alluvium). Our results indicate that the upstream, steep, high-permeability limestone catchment has the relatively largest groundwater contribution to streamflow (63–78 %) and a low F yw (38 %) than the other two sites. The mid-elevation hard rock catchment has a lower permeability on average but is highly variable due to fracture networks and geologic contacts, allowing a substantial groundwater contribution to streamflow (38–66 %) and a similar F yw (36 %) to the limestone catchment. The downstream, low-slope catchment underlain by alluvium has a highly variable hydraulic conductivity and a substantially lower groundwater contribution to streamflow (26–45 %) and a higher F yw (55 %). We find that both hydraulic conductivity and topography exert control on the magnitude of baseflow contribution to the stream. However, K sat acts as a key control in groundwater contribution to baseflow as observed in headwaters and downstream region of the watershed. While unconsolidated deposits are often thought of as important high-porosity mountain aquifers, our results point to the importance of fractured and karstified bedrock in baseflow generation in high mountains. As climate change alters the snow- and ice-melt regimes of UIB rivers, our study underscores the critical importance of improving our understanding of baseflow sources. [ABSTRACT FROM AUTHOR]

[Display omitted] • Karst soils are less conducive to GRSP accumulation compared to non-karst soils. • GRSP accumulation decreases with higher temperature gradients in karst soils. • GRSP accumulation increases with higher temperature gradients in non-karst soils. • Temperature-induced changes in soil pH and fertility shape GRSP accumulation. • Lithological constraints on biotic and abiotic factors determine GRSP accumulation. Glomalin-related soil protein (GRSP) is a crucial contributor to the persistent soil carbon (C) pool. However, its response to temperature gradients is contentious due to variations in soil microorganisms, pH, and fertility. Given that soils inherit many properties from the parent lithological material, we hypothesized that bedrock lithology mediates the divergent patterns of GRSP accumulation along temperature gradients. Here, we assessed GRSP content and its contribution to soil organic C (SOC) in forest soils situated atop carbonate rocks (karst) and clastic rocks (non-karst) across a large climatic gradient (Δtemperature > 10 °C). Despite similar SOC content between karst and non-karst soils, the contents of easily extractable and total extractable GRSP, as well as their contributions to SOC, were significantly lower in both bulk soil and the mineral-associated organic matter fraction in karst soils. This discrepancy was attributed to lower plant diversity, higher soil pH, and increased soil fertility (particularly total and alkali-hydrolyzable nitrogen) in karst ecosystems. Additionally, the contribution of GRSP to SOC decreased with increasing temperature gradients in karst soils, whereas it increased in non-karst soils. As temperature gradients rose, karst soils exhibited higher pH and fertility, whereas non-karst soils showed reduced fertility. These changes resulted in contrasting GRSP accumulation patterns along the temperature gradient. Our findings underscore the necessity of considering bedrock lithology when predicting GRSP responses to temperature change and advocate for lithology-specific conservation strategies to enhance glomalin accumulation. [ABSTRACT FROM AUTHOR]

• We apply in-situ Rb-Sr, Ar-Ar, and Pb-isotope analysis to ice-rafted K-feldspar. • Detrital Rb-Sr ages agree well with known onshore bedrock ages. • Our data support mid-Miocene formation of major Antarctic Ice-sheet embayments. The latest generation of Antarctic paleo-ice sheet models, incorporating bedrock paleo-topography, reconstruct the development of substantial ice-sheet embayments during the Mid-Miocene Climate Optimum, a warm period between ∼17–15 Ma ago. Here, we test these models using ice-rafted debris (IRD) recovered from the central Weddell Sea (Ocean Drilling Program Site 113–694). These IRD are entrained by the ice-sheet expanding into the embayment during the cooling associated with the subsequent Mid-Miocene Climate Transition and ultimately delivered to the deep marine sink by iceberg armadas during higher-frequency instability events. Due to the near-absence of heavy minerals in these volumetrically small samples, we utilise the novel in-situ K-feldspar 87Rb/87Sr provenance technique by laser-ablation inductively coupled mass spectrometer equipped with a mass-filtered reaction cell. We combine these single-grain ages with in-situ Pb-isotope analysis, as well as 40Ar/39Ar dating of a subset of grains. Results identify the Antarctic Peninsula and southern Dronning Maud Land as key sediment sources, including grains sourced from within the Recovery subglacial basin. These findings support ice sheet instability consistent with reconstructions of major ice sheet embayments formed by climatic conditions analogous to those predicted by modern anthropogenic warming trajectories. Additionally, in-situ 87Rb/87Sr and Pb-isotope analysis of detrital K-feldspar provide a high-throughput alternative to conventional single grain U-Pb or 40Ar/39Ar analysis, especially in small samples where the heavy mineral fraction is limited or absent. [ABSTRACT FROM AUTHOR]

The marine isotope stage (MIS) 5a to 4 transition (∼74 ka) was associated with rapid ice sheet expansion, declining moisture availability globally, and significant upheaval of terrestrial ecosystems across the northern hemisphere. Here, we present precisely dated speleothem trace element records spanning ∼90 to 70 ka from Dim Cave (Southern Türkiye) which provide crucial information regarding the climate response to this transition from the Eastern Mediterranean region. Trace element variability recorded in stalagmite DIM-E3 captures shifts in detrital influx, bedrock dissolution, and soil activity that collectively record two climatic signals: (1) high regional moisture availability between MIS 5c and 5b, and (2) increasingly arid conditions across the MIS 5a to MIS 4 transition. Both are contemporaneous with evidence for severe drying recorded across the Eastern Mediterranean and Middle East, as well as Asia, Europe, South America, and the North Atlantic. These results shed new light on the environmental consequences of rapid change in a climatologically sensitive region, and underscore the significance of atmospheric teleconnections in propagation of abrupt climate variability during the last glacial period. • The MIS 5-to-4 transition (∼74 ka) requires closer study in the Eastern Mediterranean. • We present precisely dated speleothem trace element records spanning ∼90 to 70 ka from Dim Cave (S. Türkiye). • Speleothem DIM-E3 records distinct changes in detrital influx, bedrock dissolution, and soil activity. • An abrupt shift to aridity is observed across the MIS 5a to MIS 4 transition. • Results underscore the consequences of rapid climate change in this hydroclimatically-sensitive region. [ABSTRACT FROM AUTHOR]

Mo (isotope) cycling during the chemical weathering of ultramafic bedrock remains poorly quantified, mainly as a result of the analytical challenges caused by low Mo concentration and complex matrix effects in these rock types. Here, we utilize an improved chemical separation protocol that enables the extraction of Mo while reducing Ru and Fe matrix effects. We apply this method to lateritic weathering profiles developed over ultramafic bedrock in a high-intensity tropical weathering regime. The Mo concentrations in the laterite samples are higher (0.022 to 0.58 μg·g−1) than those of the peridotite bedrock (0.006 to 0.021 μg·g−1). The concentration-weighted average δ98Mo of the laterite profiles is −0.05‰ (n = 17), which is slightly higher but very close to the average δ98Mo of the peridotite bedrock (0.17 ± 0.21‰; 2SD; n = 5). Weakly-laterized samples show somewhat low δ98Mo with a minimum of −1.03‰ and Δ98Mo laterite-bedrock up to −0.86‰, possibly as a result of preferential adsorption of liberated light Mo onto Fe (oxyhydr)oxides. In contrast, strongly-laterized samples show an overall Mo concentration gain and a slight isotopic shift towards higher bulk δ98Mo, with a maximum δ98Mo of +0.12‰ and Δ98Mo laterite-bedrock up to +0.42‰. This likely reflects the re-scavenging of Mo released from weakly-laterized horizons to the ubiquitous Fe (oxyhydr)oxides, with potential superimposition of additional heavy Mo from atmospheric and/or groundwater input. Overall, this suggests a small contribution of dissolved Mo derived from ultramafic bedrock weathering in tropical settings to the aquatic environment. • Restricted Mo mobility in lateritic soils during intense tropical weathering. • Restricted dissolved Mo export from lateritic catchments into rivers and oceans. • Mo export from lateritic catchments is mainly by Fe (oxyhydr)oxides particle form. [ABSTRACT FROM AUTHOR]

The growth of the Tibetan Plateau governs Asian tectonics, geomorphology, and climate change in the Cenozoic. The Qilian Shan is a fold-and-thrust belt that defines the northeastern boundary of the Tibetan Plateau. The spatiotemporal evolution of Cenozoic crustal deformation in the Qilian Shan is crucial for revealing the growth process of the Tibetan Plateau and its dynamic mechanisms. Mountain deformation can be revealed through basin sedimentology but is limited by vastly disputed stratigraphic chronologies. Low-temperature thermochronology provides independent dating to reveal deformation-induced exhumation. We provide new and reviewed published low-temperature thermochronologic data from in situ bedrock in the Qilian Shan and from sedimentary detritus in the surrounding basins. The results indicated that the Qilian Shan experienced two phases of enhanced exhumation, one in the Eocene and one in the Miocene. Early Eocene crustal deformation of localized structures in the Qilian Shan was a rapid tectonic response to the Indian–Asian plate collision. Intense and extensive crustal deformation since the early Miocene has been accompanied by shifts in regional tectonic regimes. The Eocene deformation did not follow the present structures, but the Miocene deformation did, indicating that the present structural framework generally formed during the Miocene. This review shows that the Qilian Shan has experienced two phases of temporally and spatially differentiated tectonic deformation since the early Eocene and early Miocene. The Qilian Shan has been the northeastern structural boundary of the Tibetan Plateau since the early Cenozoic. • Thermochronologic data indicated Cenozoic two-phase exhumation of the Qilian Shan. • Early Eocene deformation occurred at localized structures in the Qilian Shan. • Intense and extensive deformation occurred during the early–late Miocene. • Miocene shifted regional tectonic regimes formed the present structural framework. • Qilian Shan was the structural boundary of the TP since the early Cenozoic. [ABSTRACT FROM AUTHOR]

Retrieving detailed subsurface velocity structures down to the seismic bedrock at any given site is a crucial step to delineate the site amplification factors accurately and precisely. The present research work contributes first new estimations for detailed velocity structures down to the seismic bedrock beneath the Egyptian National Seismological Network (ENSN) stations, which are distributed in Egypt nationwide. We used the diffuse field assumption for earthquakes to reproduce the horizontal to vertical spectral ratios (EHVSR) at these stations. We accepted waveform database of 424 earthquakes recorded at 75 ENSN stations. After achieving the inverted subsurface velocity structures, we establish site-specific frequency-depth regression and map the V S30 and seismic bedrock depth beneath Egypt. Because of comparability regarding the seismic site class of B and C, the regression coefficients of the newly established frequency-depth regression exhibit similarity with those achieved from previous regressions in Japan. Furthermore, we observe modest consistency between the seismic bedrock depths and the various geologic features, particularly agreement between basin-shape seismic bedrock depths and the existence of Cretaceous and Jurassic extensional basins. Our findings suggest that the Precambrian basement rocks can be interpreted as the seismic bedrock in Egypt. One of the most significant obstacles in the present work is the low-dense distribution of ENSN stations nationwide. However, the achieved results raise new questions and challenges regarding precise and accurate future estimations for site amplification calculations at different localities in Egypt, particularly for urban planning by engineers. • First new estimates of velocity structures at the Egyptian National Seismological Network down to the seismic bedrock. • Seismic bedrock depths beneath Egypt agree with the Cretaceous and Jurassic extensional basins. • Precambrian basement rocks interpreted as the seismic bedrock. • Mapping V S30 facilitate site response analyses for future urban planning by engineers. • frequency-depth regression is similar to previous regressions arising questions regarding the site-specific dependency. [ABSTRACT FROM AUTHOR]

To explore the development law of tunnel uplift during tunnelling in hard rock and its inherent relationship with the deformation of segmental rings and bolt force, this study carried out field measurements on the deformation and mechanical behaviors of shield tunnel during construction based on the North Extension Project of Changsha Metro Line 1. Five monitoring items were conducted in field measurements, including tunnel uplift, the dislocation between segmental rings, circumferential joint opening, lining circumferential and longitudinal strains, and longitudinal bolt axial force. The measured results indicated distinct stages of tunnel uplift, including the initial rapid uplift stage (Stage I), the relatively gradual uplift stage (Stage II), the second rapid uplift stage (Stage III), and the final stable stage (Stage IV). The uplift was more significant in the location of 4∼8 rings away from the shield tail, and it took approximately 40∼65 hours to be stabilized after detachment from the shield tail. The process of uplift was influenced by factors such as the buoyancy of bedrock fissure water and unsolidified slurry, grouting pressure, and the interaction between the segmental rings. Meanwhile, a notable synchronization between the transverse deformation of the tunnel, dislocation between segmental rings, circumferential joint opening, longitudinal bolt axial force, and the development of tunnel uplift was observed. The flattening effect caused by longitudinal differential deformation of the tunnel resulted in a "horizontal elliptical" shape of the tunnel cross-section. During the process of tunnel uplift, the maximum dislocation between segmental rings was reached, which gradually recovered with the stability of the uplift. Notably, the monitoring conducted over three months after construction confirmed a continuous increase in both the circumferential joint opening and the longitudinal bolt axial force at corresponding locations, providing evidence of longitudinal stress relaxation in the tunnel. Additionally, the curved section of the tunnel showed a trend of recovering toward the inner side of the curve. [ABSTRACT FROM AUTHOR]

Karst springs are one of the most exploited drinking water resources in the world. Isotopic and chemical analyses on these waters reveal essential insights into their hydrodynamics. Valseriana (Northern Italy) is a valley within the Italian Pre-Alps, characterized by high water availability. The main reasons are a bedrock consisting of very permeable carbonate formations and a mean annual precipitation above 1800 mm/y. In this context, the Valseriana spring catchments have become strategically important for the water exploitation and the domestic supply of Bergamo and the neighboring municipalities. This study general aim is to expand the knowledge on the two main karst systems (Nossana and Ponte del Costone), which together include twenty-three major and minor springs, by defining a state-of-the-art that will be useful in future decades to preserve this crucial resource. Specific objectives include i) verifying the applicability of the 3H/3He dating method in karst environments, ii) defining groups of springs according to their chemical and isotopic characteristics for possible safeguard actions, and iii) establishing a conceptual model of the internal dynamics of the two spring systems. A chemical and isotopic sampling campaign was specifically conducted between May 2018 and July 2019. A total of 34 water points were sampled, including natural springs, rivers, wells, karst caves, and nearby mines. Water sampling for 3H/3He isotopic analyses was proved possible through careful selection of the sampling points and the insertion of the pump tubing in the spring fractures. A first classification of springs into uniform hydrochemical groups was obtained by applying the hierarchical cluster analysis technique on major ions contents. These outputs were combined with information from the 3H/3He dating analyses and resulted in three different classes of springs. The three classes showed a clustering for elevations: at high, medium, and valley bottom elevations, respectively. Finally, the elaborations simplified the two karst systems by a hierarchical flow system model, dynamically controlled by different karst network development and infiltration water. [Display omitted] • Valseriana karst springs are strategic for water supply in the Lombardy Pre-Alps. • Three spring groups were defined connecting chemical properties and residence time. • The repetition of 3H–3He analyses proved them robust in a karst environment. • Noble gas air-excess data suggest a tendency towards lower recharge altitudes. • Results will support the sustainable use of water resources in the area. [ABSTRACT FROM AUTHOR]

The seismic amplification of any given area is a combined result of topographic, stratigraphic and valley effects. Nevertheless, quantifying the contribution of each of these three effects in the overall amplification is not straightforward. To this end, this paper proposes a procedure for the approximate decoupling of these effects on the amplification of the peak seismic acceleration at the ground surface. This is performed by setting the pertinent site amplification factor equal to the product of three spatially-variable amplification factors, one for each of these effects. The procedure employs two-dimensional (2D) linear visco-elastic numerical simulations and simplified analytical formulations, the latter aiming at the quantification of the one-dimensional (1D) amplification of soil-bedrock and (solely) bedrock columns. As an example, the decoupling procedure is applied to a slope with irregular topography, characterised by a homogeneous soil layer overlying bedrock. The ground response analyses employ Ricker wavelet excitations, characterised by different predominant periods covering the range of periods related to typical earthquakes, as well as actual seismic recordings. The results depict that the three amplification factors depend on the seismic excitation and vary widely along the study area (taking values that range from 0.6 up to 1.7). The proposed procedure is an approximate, but reliable tool for decoupling the spatially-variable contributions of the aforementioned effects, at least when the visco-elastic conditions are realistic. As such, it may be used as an expeditive tool for identifying regions mostly affected by each of these effects, thus guiding the need for additional site investigation or in-depth analysis. • Approximate procedure to decouple topographic, stratigraphic and valley effects. • Site amplification is the product of the three separately evaluated factors. • Application to slopes with irregular topography and a soil layer overlying bedrock. • Newly proposed expression to estimate the 1D amplification factor. [ABSTRACT FROM AUTHOR]

At regional scale, it is dominantly considered in the European literature that litter decomposition is higher in soils from calcareous than siliceous bedrocks because of higher pH in the former forest ecosystems. We tested the alternative hypothesis that this should rather be due to differences in physical characteristics of the bedrock, with likely higher decomposition on calcareous than siliceous bedrocks in wet climates because of more favourable texture in the former and nutrient leaching in the latter, and the opposite in dry climates because of higher drought stress in calcareous soils. We assessed, four consecutive years with contrasting climates, the litter decomposition of a unified litter of Abies alba needles with the litterbag method in 70 forest sites located on both bedrocks and in wet oceanic and dry continental climates of the European Alps and the Pyrenees. Average and annual climate data were analysed with principal component analyses and the effects of bedrock type, average and annual climate drought stresses on litter decomposition were analysed, separately in the Alps and the Pyrenees, with analyses of variance. We found, in both mountain ranges, a highly significant bedrock type by average climate drought stress interaction on litter decomposition, due to a strong decrease in litter decomposition from wet oceanic to dry continental sites on calcareous bedrocks only. Although litter decomposition did not change over all years in siliceous sites with increasing climate drought stress, it increased during wet years in the dry continental sites only, in particular in the Pyrenees where interannual climate variability was higher. Together our results strongly support the physical hypothesis and not the chemical hypothesis. We argue that the chemical hypothesis was proposed based on studies only conducted in low elevation wet temperate sites comparing mull humus types from deciduous forests on calcareous soils to mor and moder humus types from evergreen forests on highly sandy siliceous bedrocks. Our study conducted on a wider range of climate and bedrock conditions bring strong evidence that litter decomposition is rather dependent on the physical characteristics of the bedrocks. • Litterbag experiment conducted in 70 sites from the Alps and the Pyrenees. • Litter decomposition is higher on siliceous than calcareous soils in dry climates. • Soil pH does not explain differences in litter decomposition. [ABSTRACT FROM AUTHOR]

Spatial machine learning models can be developed from observations with substantial unexplainable variability, sometimes called 'noise'. Traditional point-scale metrics (e.g., R2) alone can be misleading when evaluating these models. We present a multi-scale performance evaluation (MPE) using two additional scales (distributional and geostatistical). We apply the MPE framework to predictions of depth to bedrock (DTB) in the Delaware River Basin. Geostatistical analysis shows that approximately one third of the DTB variance is at spatial scale smaller than 2 km. Hence, we interpret our point-scale R2 of 0.3 (testing data) to be sufficient for regional-scale modelling. Bias-correction methods improve performance at two of the three MPE scales: point-scale change is negligible, while distributional and geostatistical performance improves. In contrast, bias correction applied to a global DTB model does not improve MPE performance. This work encourages scale-appropriate performance evaluations to enable effective model intercomparison. • Reporting model performance relative to data noise improves performance evaluation. • Multiscale performance evaluation supports judgments of data-driven models. • Simple bias correction improves our model performance at two of three scales. • Geostatistical scale metrics provide both noise quantification and fit evaluation. [ABSTRACT FROM AUTHOR]

The optically stimulated luminescence (OSL) sensitivity of the fast component in quartz has been increasingly used in provenance analysis of Quaternary sediments. Quartz OSL natural sensitization is thought to be mainly controlled by the formation conditions of the source bedrock and surface processes occurring mainly in sediment source areas. Thus, quartz OSL sensitivity can be linked to distinct sediment source regions, based on their tectonic setting and erosion conditions. In this way, changes in quartz OSL sensitivity within siliciclastic successions would track variations in sediment provenance. So far, few works evaluated how the OSL sensitivity of quartz sand grains varies in sedimentary successions that experienced long-term cycles of deep burial, exhumation, and erosion. Therefore, this work aims to characterize the sensitivity of the fast OSL component of quartz sand grains retrieved from the Cenozoic sedimentary rocks of the Northern Andes basins and assess its spatiotemporal changes. We found that quartz grains with the lowest OSL sensitivity are sourced by crystalline and volcanic rocks related to the Andean Continental Arc emplaced in the Colombian Central Cordillera, reflecting the onset of denudation in orogenic sources during the Paleocene. Subsequently, increasing trends in OSL sensitivity are related to the sedimentary recycling during the Andean orogeny, reaching maximum values as a result of the progressive unroofing of Cretaceous rocks in the Colombian Eastern Cordillera, originally sourced from the low-relief Amazon Craton. Changes in quartz OSL sensitivity measured in the Cenozoic sedimentary basin-fill sequences of the Northern Andes vary according to the shifts in sediment provenance related to the orogenic construction and sediment recycling of the Andean range. • We characterized the Quartz OSL sensitivity in a thick Cenozoic sedimentary basin-fill sequence of the Northern Andes. • OSL sensitivity is compared with shifts in provenance constrained by mineralogical composition and detrital zircon U-Pb ages. • OSL sensitivity varies according to the main shifts in provenance and episodes of recycling recognized in the Northern Andes. [ABSTRACT FROM AUTHOR]

The late Quaternary history of the bedrock-controlled Brazos River system in central Texas is poorly understood as to the complex interplay between bedrock and climate on episodes of channel incision and aggradation. Through geomorphic assessment, sediment core analysis, and luminescence dating (OSL) we map the alluvial terrace and floodplain deposits in the Steinbeck Bend study area in central Texas. Five stratigraphic (allostratigraphic) units were identified beneath four alluvial terrace-sediment complexes (T3-Unit I, T2a-Unit II, T2b-Unit III, T1a-Unit IV, T1b-Unit V) and the current floodplain (T0-Unit VI) of the Brazos River, with the accompanying OSL geochronology ranging from >60 to 0.3 ka. Channel incision appears to have occurred during the transition to cooler and wetter intervals at the beginning of MIS 4 and MIS 2. Alluvial deposition proceeded mainly during the latter stages of the warmer MIS 5 and during the first half of MIS 3, both characterized by a slight warming trend. The alluvial architecture of all units was formed by single story, mixed load meandering channels migrating laterally across Cretaceous marls. Upstream from the study area, the bedrock valley narrows because of the presence of more resistant limestones forming the bedrock channel floor and valley walls. In the Steinbeck Bend study area, the incised meanders develop into larger radius of curvatures as the Brazos River migrates across less resistant Cretaceous marls. Below the study area in the weakly consolidated Tertiary coastal plain deposits, the Brazos River becomes freely meandering, cutting laterally and vertically through previously deposited alluvium interceded by channel avulsions. [ABSTRACT FROM AUTHOR]

• An analytical solution for a finite thickness soil layer is presented. • The interaction between soil layer and strip footing is considered. • Both rigid footings and deformable footings are reserched. • The complex variable method is applied to the mixed boundary problem. • The mechanical influence of bedrock buried depth on soil layer is studied. Consider an elastic soil layer with a shallow-buried strip footing at the upper boundary and bedrock at the lower boundary, the displacement along the contact surface between the soil layer and the bedrock can be considered as zero when the bedrock is sufficiently rigid relative to the soil layer. The stress and displacement fields in the soil layer are solved on the premise that the displacement on the contact surface between the soil layer and the strip footing is given. The soil layer with the finite thickness on the physical plane is mapped onto the inner domain of the unit circle on the image plane based on the conformal transformation. Then, the complex variable method is applied to give the stress and displacement fields in the soil layer by two analytic functions, the coefficients of which can be determined by the stress and displacement boundary conditions on the upper and lower boundaries of the soil layer. In calculation, the power series method is introduced to establish a set of linear equations containing the analytic function coefficients, and then the coefficients are determined by solving the linear equations. This paper presents the analytical solutions of stress and displacement in the soil layer under two different displacement boundary conditions on the contact surface between the soil layer and the footing. The obtained results are compared with the results of the numerical method based on ANSYS. Finally, the influence of different displacement boundary conditions and soil thickness on the stresses on the surface and internal region of the soil layer is analyzed. [ABSTRACT FROM AUTHOR]

Manganese (Mn) is an essential micro-nutrient that can limit or, along with iron (Fe), co-limit phytoplankton growth in the ocean. Glacier meltwater is thought to be a key source of trace metals to high latitude coastal systems, but little is known about the nature of Mn delivered to glacially-influenced fjords and adjacent coastal waters. In this work, we combine in-situ dissolved Mn (dMn) measurements of surface waters with Mn K-edge X-ray absorption spectroscopy (XAS) data of suspended particles in four fjords of West Greenland. Data were collected from transects of up to 100 km in fjords with different underlying bedrock geology from 64 to 70°N. We found that dMn concentrations generally decreased conservatively with increasing salinity (from 80 to 120 nM at salinity < 8 to < 40 nM at salinities > 25). Dissolved Fe (dFe) trends in these fjords similarly declined with increasing distance from glacier outflows (declining from > 20 nM to < 8 nM). However, the dMn/dFe ratio increased rapidly likely due to the greater stability of dMn at intermediate salinities (i.e. 10–20) compared to rapid precipitation of dFe across the salinity gradient. The XAS data indicated a widespread presence of Mn(II)-rich suspended particles near fjord surfaces, with structures akin to Mn(II)-bearing phyllosilicates. However, a distinct increase in Mn oxidation state with depth and the predominance of birnessite-like Mn(IV) oxides was observed for suspended particles in a fjord with tertiary basalt geology. The similar dMn behaviour in fjords with different suspended particle Mn speciation (i.e., Mn(II)-bearing phyllosilicates and Mn(IV)-rich birnessite) is consistent with the decoupling of dissolved and particulate Mn and suggests that dMn concentrations on the scale of these fjords are controlled primarily by dilution of a freshwater dMn source rather than exchange between dissolved and particle phases. This work provides new insights into the Mn cycle in high latitude coastal waters, where small changes in the relative availabilities of dMn, dFe and macronutrients may affect the identity of the nutrient(s) proximally limiting primary production. [ABSTRACT FROM AUTHOR]

Speleothem records of past environmental change provide an important opportunity to explore fire frequency and intensity in the past, and the antecedent climatic conditions leading to fire events. Here, fire sensitive geochemical signals in a stalagmite from Yonderup Cave, a shallow cave in Western Australia, are compared to well-documented wildfire events that occurred in recent decades. The results are extended to identify wildfires during the growth interval of the speleothem (1760 CE–2005 CE). Principal component analysis of the stalagmite time-series revealed distinct peaks in a combination of phosphorus and metal (aluminium, zinc, copper and lead) concentrations in response to known fire events, which are interpreted to have come from ash. Varying responses in the geochemical signal in the pre- and post-European colonisation period are likely linked to changes in land management, fire frequency and fire intensities. Of note is what we infer to be a particularly intense fire event concluded to have occurred in 1897 ± 5 CE, which climate sensitive proxies (δ18O and bedrock-derived elements) indicate was preceded by a multi-decadal dry period that began in the late 1860s. The intensity of the deduced fire event is supported by a peak in P that is 6.3 times higher than elsewhere in the speleothem, accompanied by a peak in Zn. It was also inferred that changes to the surface-cave hydrology occurred as a result of this event, indicated by increased input of colloidal organic material onto the stalagmite that was interpreted to be caused by shallow karst bedrock fracturing from the heat-induced deformation that is observed after intense fires. These findings show the potential for speleothems to provide dated records of fire intensity and recurrence intervals. Further development could lead to a better understanding of the climate-fire relationship and the effects of land-management practices on wildfire frequency and intensity. [ABSTRACT FROM AUTHOR]

• Long-term erosion rates on Réunion Island range from ∼10−3 to ∼10 mm/yr. • Long-term erosion rates on Mauritius Island range from ∼10−3 to ∼10−2 mm/yr. • Both mean annual precipitation and extreme events control long-term landscape evolution on volcanic islands. Climate's role in governing landscape evolution has been intensely studied for several decades, but few studies clearly document climate-landscape interactions in natural landscapes. This study aims to improve understanding of climate-landscape linkages using hotspot volcanic islands in the tropics as natural laboratories. Relatively uniform lithology, strong precipitation and climate gradients, and known initial topographic conditions on Réunion and Mauritius islands (Réunion hotspot) and Kaua'i (Hawaii hotspot) enable us to explore the impact of climate on erosion rates and geomorphic process. We reconstruct paleo-topography of drainage basins based on preserved remnants of relict topography from past volcanic events that repaved the landscapes that are differenced from the modern-day topography to determine eroded volumes. Existing geochronology of the volcanic flows allows us to constrain the timing of repaving (a proxy for the initiation of erosion) and basin average erosion rates. The initial and final conditions and the duration of erosion are used to calibrate a simple stream power model for bedrock river incision for each basin using a Bayesian inversion. We compare the erosion rate and calibrated stream power parameters to precipitation and climate data for each drainage basin on each island to explore potential relationships. Results show that basin average erosion rates for basins eroding < ∼1 mm/yr show a positive relationship with mean annual precipitation (MAP) and a negative relationship with the duration of erosion. Importantly, MAP and erosion duration are correlated, so we infer that the negative correlation between erosion rate and duration is coincidental. The stream power slope exponent and erodibility coefficient only exhibit significant correlations with climate parameters for Réunion Island, particularly mean annual cyclonic precipitation. Our results demonstrate that both mean annual precipitation and extreme events control long-term landscape evolution on volcanic islands. [ABSTRACT FROM AUTHOR]

The Sutlej River catchment in the tectonically active western Himalayas has several geomorphic signatures of river piracy and drainage reorganization across the Upper Sutlej-Zhada basin upstream. The accelerated growth of the Leo-Pargil Horst across the Kaurik Chango-fault (KC-fault) Zone and affected regional tectonics triggered enormous incisions, causing southward migration of the present Sutlej River, which is highly infested by bedrock landslides and debris flows and evolves as a very steep valley catchment. In order to understand the changing regional landscape and identify the tectonic perturbation over the channels, we evaluate the slope-break knickpoints in the Sutlej River profile. Furthermore, we model the presence of an elevated low-relief relict landscape in the Upper Sutlej-Zhada basin and the rapid incising lower Sutlej valley catchment using the Celerity model. The observation suggests that major knickpoints at ~2000–3000 m elevation comprise the fluvial erosion process, while higher elevation knickpoints recommend the hillslope process. In order to understand how fluvial erosion and surface process imprints have changed the landscape over time, we spatially correlate terrestrial datasets, such as rates of denudation and exhumation ages, with topographic metrics and climate variables. We observe a strong correlation between the pattern of denudation rates and the conditioning factors that modulate the surface processes. Increased channel erosion, high stream power, topographic metrics, and the occurrence of bedrock landslides over a regional structural disruption exhibit a positive spatial relationship, but their role in regional drainage capture, tectonic uplift, and the gradation process remains poorly understood. [ABSTRACT FROM AUTHOR]

When large volumes of meltwater arrive suddenly at the glacier bed, the capacity of subglacial conduits is exceeded, generating transiently high fluid pressures. Yet we currently lack reliable markers for where such conditions developed on the beds of former glaciers. Here, we describe hydraulic damage that developed at close to or above overpressure (P w > P i) at the bed of the last Fennoscandian Ice Sheet in Uppland, east-central Sweden. Hydraulic damage is mostly confined within sharp lateral and vertical limits at the boundaries of former large subglacial conduits. The conduits include large Röthlisberger- and Nye-channels - eskers, esker corridors, and meltwater channels – that operated at full pipeflow. Wider (0.4–1.5 km) meltwater corridors opened under sheetflow with broad, shallow Hooke-channels. Hydraulic damage found in Precambrian gneiss and granite bedrock includes hydrofracturing and hydraulic jacking, with fracture propagation, dilation, and block displacement. Dilated fractures are often plugged by massive sands and diamicts or laminated silts. The fracture fills represent brief, single and multi-phase, injections of viscous, sediment-laden fluids at the ice sheet bed. The most spectacular effects of hydraulic damage are seen in the distension, disruption, and bursting of 1–20 m high rock bumps and hills. We present a detailed taxonomy for hydraulic damage and the consequent glacitectonic damage sustained during glacial ripping. Industrial fracking provides a well understood analogue for hydrofracture in nature. In subglacial settings, pathways for the flow of pressurised fluids are determined by the tensile strengths and hydraulic transmissivity of ice, till, and rock. The easiest flow path is across the glacier bed beneath sliding ice. Abrupt increases in meltwater flow force ice-bed separation. Opening of conduits under high fluid pressures triggers further propagation of hydrofractures into ice, till, and rock. On the floors of subglacial conduits, pressurised fluids entered the hard rock bed via old, mineral coated fractures. Under Poiseuille's law, fracture flow was initially slow due to the narrow apertures, but flow accelerated rapidly as fluid wedging dilated fractures. Fluid pressures in old fractures are constrained by published measurements for near-surface fracture toughness of ≤0.7 MPa at Forsmark, east-central Sweden. Formation of new rock hydrofractures overcame gneiss tensile strengths of 8–18 MPa. Hydraulic jacking required accommodation space that developed during conduit opening. Due to buoyancy and ice bed separation, lower excess pressures of <0.3 MPa were required to lift rock sheets up to 10 m thick. Hydraulic bursting developed in large conduits under very high, but rapidly fluctuating fluid pressures as dilating rock fractures extended to the glacier bed. Distension of rock surfaces was brief due to rapid leak-off and the inherent instability of overpressured conditions in dilatant, fractured rock masses. Hydraulic damage developed in Uppland when accelerating ablation generated large subglacial meltwater fluxes in response to abrupt warming at the Younger Dryas-early Holocene transition (∼10.8 ka). The large volumes of subglacial meltwater, the sudden increases in subglacial water flow and fluid pressures, and the release and transport of 2 m b-axis boulders in esker tunnels suggest that hydraulic damage was triggered at the onset of large subglacial floods. Ice thicknesses at distances of up to 50 km behind the grounding line at the retreating subaqueous ice margin indicate that steady-state hydrostatic pressures were ∼2.9–4.5 MPa. Such pressures are consistent with (i) extensive, but brief ice-bed separation in meltwater corridors under overpressure and (ii) the development of hydraulic damage in conduits close to the ice margin. More extreme fluid pressures developed instantaneously under hydraulic shock, as rapid subglacial pipeflow was suddenly stopped or diverted. The taxonomy of hydraulic damage presented here can be applied to any hard glacier bed to identify where large volumes of subglacial meltwater reached high pressures. Similar markers are widely reported from modern and former glacier beds. • Taxonomy of hydraulic damage proposed for Uppland, Sweden. • Hydraulic damage to rock in subglacial meltwater corridors. • Hydrofracture, hydraulic jacking, and hydraulic bursting. • Fluid pressures exceeded ice overburden pressure. • Similar damage on other hard beds below ice sheets. [ABSTRACT FROM AUTHOR]

The Söğüt Mountains is a fault-bounded carbonate range situated between the active Acıgöl and Akgöl grabens in southwestern Türkiye. The southwestern sector of the Acıgöl Graben floor displays an array of faults that have produced peculiar intra-basin half-grabens with local lakes and drainages. The conspicuous geomorphic expression of the intra-basin faults and depressions in this sector of the basin is attributed to low sedimentation rate (i.e., starved basin) related to very limited runoff and sediment supply from the southwestern carbonate margin of the basin, dominated by subsurface drainage in a carbonate bedrock strongly affected by gravitational deformation and karstification. Detailed mapping reveals the presence of large landslides and extensive DSGSDs in the mountain fronts flanking the Söğüt Mountains, showing ridge-top depression, uphill-facing scarps, high-relief downhill-facing scarps, and toe bulges. Cartographic relationships provide insights into the development and evolution of the deformations in the slopes that experience continuous tectonic rejuvenation and debuttressing. DSGSDs and large landslides take advantage of secondary synthetic tectonic faults, in which gravitational and tectonic displacement are superposed. The transformation of DSGSDs into large to giant short runout landslides (up to ca. 3.5 Gm3) occurs mainly on laterally unconfined slopes associated with bends and stepovers in the basin-bounding faults. Seismicity is likely the main triggering factor controlling the kinematics of the gravitational deformations and landslides. Cartographic evidence indicate downslope propagation of the gravitational deformation (uphill-facing-scarps and associated troughs) in the tectonically growing slopes. Additionally, preferential development of solution sinkholes is observed in gravitationally distorted slopes with impeded surface drainage. • Graben floor compartmentalized into conspicuous half-graben depressions • DSGSDs in an uplifting carbonate range bounded by active normal faults • Fault controlled giant landslide (>1 Gm3) developed from DSGSDs • Downslope propagation of DSGSDs related to tectonic rejuvenation and debutressing • Preparatory role of gravitational deformation for solution sinkhole development [ABSTRACT FROM AUTHOR]

Understanding past sea-level variations is essential to constrain future patterns of sea-level rise in response to warmer climate conditions. Due to good preservation and the possibility to use various geochemical methods to date fossil sea-level index points, the Last Interglacial (Marine Isotope Stage, MIS, 5e, 130–116 ka) is often regarded as one of the best climate analogs for a future warmer climate. MIS 5e coastal stratigraphic sequences, such as fossil coral reefs, are characterized by abrupt shifts in their geological facies, steps within the reef topography or backstepped morphologies, which have been often interpreted as proxies for abrupt sea-level fluctuations within the interglacial. However, the observational evidence and magnitude of such abrupt changes are controversial. Here, we run nearly 50 thousand simulations of a 2D kinematic reef model that can reproduce coral reef growth and demise through time. Our aim is to investigate the parameters of space, the sea-level scenarios, and the processes which multiple-stepped MIS 5e fossil reefs form. As inputs to the model, we use both published and synthetic sea-level histories (17 sea-level curves, with different sea-level oscillation patterns), and a wide range of reef growth and marine erosion rates, and bedrock foundation slopes. Our results show that the only sea-level history that could explain the generation of an emerged MIS 5e backstepped reef is a first sea-level peak followed by an abrupt rise in sea level and a second short-term peak. Any other multiple-stepped stratigraphy can be explained by the interplay between reef growth, marine erosion, and bedrock slope. • Model simulations to study the Last Interglacial sea-level oscillations. • An abrupt sea-level rise followed by a short-term peak create backstepped reefs. • Marine erosion can generate multiple-stepped coral reef stratigraphy. • The steeper the bedrock slope, the more effective marine erosion. • Marine erosion can strip recent reefal limestone units to expose older ones. [ABSTRACT FROM AUTHOR]

The Northeast Greenland Ice Stream (NEGIS) is the main artery for ice discharge from the northeast sector of the Greenland Ice Sheet (GrIS) to the North Atlantic. Understanding the past, present and future stability of the NEGIS with respect to atmospheric and oceanic forcing is of global importance as it drains around 17% of the GrIS and has a sea-level equivalent of 1.6 m. This paper reconstructs the deglacial and Holocene history of Nioghalvfjerdsbræ (or 79N Glacier); a major outlet of the NEGIS. At high elevation (>900 m asl) autochthonous blockfield, a lack of glacially moulded bedrock and pre LGM exposure ages point to a complex exposure/burial history extending back over half a million years. However, post Marine Isotope Stage 12, enhanced glacial erosion led to fjord incision and plateaux abandonment. Between 900 and 600 m asl the terrain is largely unmodified by glacial scour but post LGM erratics indicate the advection of cold-based ice through the fjord. In contrast, below ∼600 m asl Nioghalvfjerdsfjorden exhibits a geomorphological signal indicative of a warm-based ice stream operating during the last glacial cycle. Dated ice marginal landforms and terrain along the fjord walls show initial thinning rates were slow between ∼23 and 10 ka, but post-10 ka it is evident that Nioghalvfjerdsfjorden deglaciated extremely quickly with complete fjord deglaciation below ∼500 m asl between 10.0 and 8.5 ka. Both increasing air and ocean temperatures were pivotal in driving surface lowering and submarine melt during deglaciation, but the final withdrawal of ice through Nioghalvfjerdsfjorden was facilitated by the action of marine ice sheet instability. Our estimates show that thinning and retreat rates reached a maximum of 5.29 ma−1 and 613 ma−1, respectively, as the ice margin withdrew westwards. This would place the Early Holocene disintegration of this outlet of the NEGIS at the upper bounds of contemporary thinning and retreat rates seen both in Greenland and Antarctica. Combined with recent evidence of ice stream shutdown during the Holocene, as well as predictions of changing ice flow dynamics within downstream sections of the NEGIS catchment, this suggests that significant re-organisation of the terminal zone of the ice stream is imminent over the next century. • The Northeast Greenland Ice Stream (NEGIS) thinned slowly between 23–10ka as ice retreated across the continental shelf. • At the opening of the Holocene rising air & ocean temperatures drove surface lowering & basal melt. • Between 10-8.5ka marine ice sheet instability further enhanced grounding line retreat rates into Nioghalvfjerdsfjorden. • During the Early Holocene thinning and retreat rates reached a maximum of 5.29 ma-1 and 613 ma-1 respectively. • Such rates are at the upper bounds of contemporary ice stream thinning and retreat rates in Greenland and Antarctica. [ABSTRACT FROM AUTHOR]

A growing body of evidence supports an association between systemic autoimmune disease and exposure to amphibole asbestos, a form of asbestos typically with straight, stiff, needle-like fibers that are easily inhaled. While the bulk of this evidence comes from the population exposed occupationally and environmentally to Libby Amphibole (LA) due to the mining of contaminated vermiculite in Montana, studies from Italy and Australia are broadening the evidence to other sites of amphibole exposures. What these investigations have done, that most historical studies have not, is to evaluate amphibole asbestos separately from chrysotile, the most common commercial asbestos in the United States. Here we review the current and historical evidence summarizing amphibole asbestos exposure as a risk factor for autoimmune disease. In both mice and humans, amphibole asbestos, but not chrysotile, drives production of both antinuclear autoantibodies (ANA) associated with lupus-like pathologies and pathogenic autoantibodies against mesothelial cells that appear to contribute to a severe and progressive pleural fibrosis. A growing public health concern has emerged with revelations that a) unregulated asbestos minerals can be just as pathogenic as commercial (regulated) asbestos, and b) bedrock and soil occurrences of asbestos are far more widespread than previously thought. While occupational exposures may be decreasing, environmental exposures are on the rise for many reasons, including those due to the creation of windborne asbestos-containing dusts from urban development and climate change, making this topic an urgent challenge for public and heath provider education, health screening and environmental regulations. [Display omitted] • Asbestos exposure presents a current and global public health risk. • Many exposure pathways exist, including urban development, wind, and recreation. • Amphibole asbestos (AA) is associated with ANA and systemic autoimmune diseases. • Recognition of AA as a SAID trigger would advance research and lead to reduced risk. [ABSTRACT FROM AUTHOR]

Gulf of Aqaba in Eastern Egypt is characterized by significant seismic activity and high deformation rate, making it a major source of destructive earthquakes in the region. While previous studies have produced probabilistic seismic hazard analysis (PSHA) maps for the region, they have not adequately accounted for active faults or site response in their calculations. This study introduces a newly developed seismic source model for the Gulf of Aqaba, considering area source, active fault source, and a combination of both models to improve seismic hazard assessment for the region. The study incorporates the previously measured average shear-wave velocity for the upper 30 m (Vs 30), fundamental frequency (F 0), and amplification factor (A 0) at some selected sites in Nuweiba city. Accordingly, site-specific PSHA is carried out for the bedrock condition (Vs 30 = 800 m/s, according to the Egyptian Building Code) and for the surface of soft sediments using F 0 , A 0 , and Vs 30. Uncertainties in slip rate, maximum magnitude, and recurrence model are accounted during PSHA computation. Ground motion parameters such as peak ground acceleration (PGA) and spectral acceleration (SA) for various probabilities of exceedance in 50-year lifetime are calculated for both rock site conditions and soft sediments. The maximum calculated PGA and SA are 0.65 g and 1.25 g, respectively, for a 10% probability of exceedance over 50 years at bedrock conditions. • New seismic source model for Gulf of Aqaba is developed using active faults database. • PSHA is conducted at bedrock site condition and surface of soft sediment using F 0 , A 0 , and Vs 30. • Uncertainty in slip rate, maximum magnitude, and seismicity parameters is considered. • PGA and SA periods for various probabilities of exceedance are computed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A Ni-bearing laterite profile was newly found in the eastern Sulawesi. • The lateritization was resulted from in-situ weathering of ultramafic rocks. • Nickel mainly occurs in serpentine and Fe oxy-hydroxides. • Nickel enrichment was related to secondary adsorption in the saprolitic layer. • Lithology played a critical role in controlling lateritization and Ni enrichment. The Southeast Asia is one of the most important producers of Ni-laterite deposits in the world, attracting more and more attentions in recent years. However, the lateritization processes as well as the enrichment mechanisms of Ni have not been well constrained. Recently, a Ni-rich laterite profile (KPP) was newly found in the Kelurahan Pondidrha area, Sulawesi island, Indonesia. To better understand the lateritization and Ni enrichment mechanisms, in this study, detailed mineralogical and geochemical analyses were conducted on the KPP. The KPP can be divided into bedrock, saprolitic and lateritic layers from bottom to top. The bedrock is serpentinized harzburgite mainly composed of olivine, serpentine and pyroxene, while the saprolitic layer mainly consists of Fe oxides, olivine, serpentine and pyroxene, and the lateritic layer is dominated by quartz and Fe oxy-hydroxides. Nickel is mainly hosted by serpentine in the bedrock and saprolitic layers, but by oxy-hydroxides in the lateritic layer. From the bedrock to the lateritic layer, whole-rock MgO and CaO contents decrease continuously while TFe 2 O 3 contents increase, with TiO 2 /Al 2 O 3 , Zr/Hf and Pd/Pt ratios keeping stable. Combined with whole-rock pH value deceasing from the bedrock to the weathering products, the above results indicate the decomposition of silicate minerals and the formation of Fe oxides/oxy-hydroxides through hydrolysis during in-situ weathering. This led to the release of Ni and its adsorption by secondary minerals (e.g., Fe oxy-hydroxides in the lateritic layer and serpentine in the saprolitic layer). Nickel shows the highest contents in the saprolitic layer rather than the more weathered lateritic layer, indicating the decoupling between the lateritization and the Ni enrichment degrees. This could be due to the enhanced leaching of Ni from the surface under the tropical rainforest climate and the secondary adsorption in the deeper levels. These Ni enrichment features are commonly observed in the Mg-silicate type laterites, which are distinct from the oxide-type showing highest Ni enrichment in the lateritic layer, indicating that lithology played a critical role in controlling the lateritization and Ni enrichment. [ABSTRACT FROM AUTHOR]

Tourmaline is an effective indicator mineral for porphyry Cu-Au-Mo exploration because the compositional and morphological features of tourmaline in such systems are distinct from those found in non-mineralized environments. The texture and chemistry of detrital tourmaline was investigated using local stream sediment samples in the vicinity of the Casino calc-alkalic porphyry Cu-Au-Mo deposit (Yukon, Canada) to identify prospective grains by comparing them to grains in bedrock samples from the deposit. Bulk stream sediment samples were collected up to 18 km downstream of the Casino deposit and as far as 30 km away in a drainage basin that does not contain any known porphyry Cu mineralization. Overall, a method combining the physical and chemical characteristics is effective in discriminating detrital tourmaline, including morphology (i.e., grain clusters), inclusion populations (i.e., lack of inclusions), crystal chemistry (i.e., Na-dominant X -site, Mg/Fe dominant Y -site, and OH−/O2− dominant W -site), and trace-element compositions (i.e., high Sr/Pb values and relatively low Zn/Cu values). Detrital tourmaline was evaluated on the basis of these parameters. Detrital grains are light brown to brown, sub- to euhedral, and range in texture from individual isolated grains to clusters of radiating aggregates. Tourmaline in the Casino deposit compositionally ranges from Fe-rich; 0.03–2.54 apfu , avg. 0.61 to Mg-rich, avg. 2.00 apfu , with a minor povondraite (Fe3+) component. Detrital tourmaline is similar in composition with Fe-rich; 0.03–3.73 apfu, avg. 1.04 to Mg-rich, 0.14–2.93 apfu , avg. 1.83 to tourmaline in bedrock at Casino. In both bedrock and detrital tourmaline, alkali- and alkaline-earth element concentrations are similar with Na > Ca > vacancy. The most relevant distinctions between tourmaline groups comes from grain morphology (i.e., clustered versus individual grains) and trace-element chemistry. A significant abundance of prospective porphyry Cu tourmaline grains (14 % of total recovered tourmaline in one sample) can be observed up to 18 km downstream from the Casino deposit (the current limit of sampling), while in drainages where there are no known porphyry Cu systems, tourmaline fitting these criteria is absent and reflect grains sourced from other geologic environments (e.g., pegmatitic, granitic, and metamorphic). This method provides a new addition to the indicator mineral toolbox for the exploration of porphyry Cu systems. • Detrital tourmaline from porphyry Cu systems can be distinguished from background grains. • Textures, major, and trace-element chemistry are required for effective classification. • Tourmaline morphology and inclusions can be just as effective as trace-elements for determining source. [ABSTRACT FROM AUTHOR]