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Despite early hydrological studies of 234U/238U in groundwaters, their utilization as a paleoclimatic proxy in stalagmites has remained sporadic. This study explores uranium isotope ratios in 235 datings (230Th) from six stalagmites in Ejulve cave, northeastern Iberia, covering the last 260 ka. The observed 234U enrichment is attributed to selective leaching of 234U from damaged lattice sites, linked to the number of microfractures in the drip route and wetness frequency, which under certain conditions, may result in the accumulation of 234U recoils. This selective leaching process diminishes with enhanced bedrock dissolution, leading to low δ234U. Temperature variations significantly influence bedrock dissolution intensity. During stadial periods and glacial maxima, lower temperatures likely reduced vegetation and respiration rates, thereby decreasing soil CO 2 and overall rock dissolution rates. This reduction could enhance the preferential leaching of 234U from bedrock surfaces due to lower bulk rock dissolution. Additionally, the temperature regime during cold periods may have facilitated more frequent freeze–thaw cycles, resulting in microfracturing and exposure of fresh surfaces. Conversely, warmer temperatures increased soil respiration rates and soil CO 2 , accelerating rock dissolution rates during interstadials and interglacials, when low δ234U is consistent with high bedrock dissolution rates. The contribution of a number of variables sensitive to bedrock dissolution and wetness frequency processes successfully explains 57% and 74% of the variability observed in the δ234U in Andromeda stalagmite during MIS 3–4 and MIS 5b-5e, respectively. Among these variables, the growth rate has emerged as crucial to explain δ234U variability, highlighting the fundamental role of soil respiration and soil CO 2 in δ234U through bedrock dissolution. I-STAL simulations provides the potential for a combination of Prior Calcite Precipitation (PCP) indicators like Mg/Ca with PCP-insensitive indicators of bedrock dissolution such as δ234U, along with growth rate data, may be useful to diagnose when PCP variations reflect predominantly changes in drip intervals and when changes in bedrock dissolution intensity contribute. The relationship between stalagmite δ234U, bedrock dissolution, and initial dripwater oversaturation suggests two significant advancements in paleoclimate proxies. First, δ234U could serve as a valuable complement to δ13C since it is significantly influenced by soil respiration and soil CO 2 , thereby reflecting soil and vegetation productivity sensitive to both humidity and temperature. Secondly, since PCP does not fractionate uranium isotopes, δ234U could be used in combination with Mg/Ca or δ44Ca to deconvolve PCP variations due to changing drip rates from those due to changes in initial saturation state. This study emphasizes the overriding climatic control on δ234U, regardless of the absolute 234U/238U activity ratios among samples and their proximity or distance from secular equilibrium, and advocates for its application in other cave sites. [ABSTRACT FROM AUTHOR]

Continental glaciations during the Pleistocene Epoch created complex systems of aquifers and aquitards across many northern regions of the Earth. The low hydraulic conductivities of glacial till aquitards suggest that limited recharge will reach the underlying aquifers, potentially preserving old groundwaters. Here, we characterize the recharge history in intertill and buried valley aquifers in Saskatchewan, Canada using 14C, 3H, 4He δ2H, δ18O, and major ions. Intertill aquifers with depths of <30 m had corrected 14C ages ranging from 0 to 15.5 ka. These aquifers also contained 3H and/or elevated NO3 in some locations, indicating that a component of modern recharge had mixed with older water. A single sample from the Judith River bedrock aquifer in the region had a corrected 14C age of 10.2 ka and elevated NO3. Samples from buried valley aquifers with depths of 89 to 123 m contained older waters with ages >38 ka in some locations, indicating that recharge occurred before the last glacial advance over the region. While measuring tracers that cover a wide range of ages is necessary to understand these flow systems, δ2H and δ18O were less diagnostic because values of modern winter precipitation overlapped with groundwaters with a wide range of ages. The range of ages present in the intertill aquifers of the region indicates that these systems are currently being recharged, which indicates some development of groundwater resources is possible but also points to a need for groundwater protection measures. [ABSTRACT FROM AUTHOR]

Ion-adsorption-type rare earth element (REE) deposits are the source of more than 90% of global heavy REEs (HREEs). Thus, understanding the ore genesis of REEs, particularly the distribution characteristics and enrichment mechanisms of HREEs, is vital for efficient exploration and mining of ion-adsorption-type REE deposits worldwide. The characteristics and petrogenesis of bedrock and the aqueous mobility of REEs are known to be important factors controlling REE accumulation and fractionation in the weathering crust of REE deposits. However, the effect of REE adsorption on secondary minerals, a crucial step in deposit formation, remains poorly understood. This problem was addressed by the study described herein, which involved a systematic analysis of the complete weathering profile (78 m) of the Renju ion-adsorption-type REE deposit in South China and a simulated adsorption experiment. Clay minerals and iron (Fe) (hydr)oxides are the dominant REE adsorbents in the weathering crust and most are micro-to-nanosizedparticles. Thus, the fine-particle fraction (<2 μm) was separated from field samples to disclose better their effects on the concentration and redistribution of REEs. Phase compositions and morphologies were characterized by X-ray diffraction, Mössbauer spectrometry, and scanning/transmission electron microscopy (SEM/TEM), which revealed that various clay minerals and Fe (hydr)oxides form composites along the profile of the deposit. Composites of ferrihydrite-kaolinite, goethite-kaolinite/halloysite, and hematite-kaolinite/halloysite were found to be distributed in the semi-weathered, completely weathered, and topsoil layers, respectively, with different sizes and shapes. The concentrations and partition patterns of REEs in different occurrence states were distinguished after sequential extraction. Ion-exchangeable-REEs were the major state and enriched in the upper completely weathered layer. These species were found to be adsorbed onto kaolinite and halloysite via electrostatic attraction without obvious fractionation. Fe (hydr) oxides were determined to comprise ca. 20% of REEs at most depths and over 50% of REEs in the topsoil and semi-weathered layer. It was found that Fe (hydr)oxides scavenge REEs through complexation and oxidation, resulting in HREE enrichment and a positive cerium (Ce) anomaly, respectively. In addition, compared with crystalline Fe (hydr)oxides, amorphous Fe (hydr)oxides immobilize more REEs but exhibit weaker preferential adsorption of HREEs. The above-described findings are consistent with the results of simulated experiments for REE adsorption onto a clay mineral-Fe (hydr)oxide composite (Bt-60d), which was obtained from hydrothermal processing of biotite. Furthermore, the distributions and stabilities of LREEs and HREEs were distinguished by TEM-energy-dispersive spectroscopy (EDS) of Bt-60d before and after REE extraction by ammonium sulfate. The phase transformation pathways of clay minerals and Fe (hydr)oxides and their different enrichment and fractionation characteristics in REEs were also discussed in terms of the structure and surface properties of minerals, adsorption mechanisms, and variations in chemical properties across the REE group. The results shed new light on how clay minerals and Fe (hydr)oxides affect the enrichment and fractionation of REEs in ion-adsorption-type deposits. [ABSTRACT FROM AUTHOR]

Present day submarine canyons are active conduits for the transfer of large volumes of sediment, carbon and pollutants from continents to oceans. However, the evolution of submarine canyons over geological timescales remains poorly understood due to their erosional nature and low preservation potential. The Late Cretaceous Punta Baja Formation represents a well‐preserved submarine canyon‐fill that evolved on a tectonically‐active ocean‐facing margin. Exposures provide kilometre‐scale continuous strike and dip sections of the 120 m thick and 1.2 km wide feature. An inherited tectonic fabric influenced the location and orientation of canyon incision into fluvial bedrock. The stratigraphic evolution of the Punta Baja submarine canyon is reconstructed from incision to fill, which shows that it remained an active sediment conduit throughout the time represented by the preserved fill. The depositional architecture of the north–south oriented erosionally confined canyon‐fill is asymmetrical, with sub‐vertically stacked channel‐fills to the west, and an overbank confined by the canyon margin to the east. Sedimentary process interactions led to depositional patterns that are considered distinct to submarine canyon fills. Dynamic topography generated by mass‐wasting processes captured sediment and drove knickpoint development, an autogenic mechanism that modifies sediment delivery to the ocean floor. Widespread upstream dipping surfaces in channel‐fills are interpreted as the stratigraphic expression of upstream migrating supercritical‐flow bedforms, which played an important role in sediment storage and transport in the canyon. The steep relief and internal topography of canyons leads to complicated and characteristic confined overbank flow behaviour and depositional patterns. This study provides insight into how processes that are observed in modern canyons are selectively preserved through the lifetime of the canyon and construct or destroy stratigraphy on geological timescales. [ABSTRACT FROM AUTHOR]

The driving forces of transpiration are not only atmospheric evaporation but also root zone water supply and stomatal regulation among species. However, the biophysiological drivers of transpiration remain incompletely understood in heterogeneous karst habitats. This study investigated the commonly coexisting tree species Mallotus philippensis and Celtis biondii in two typical karst habitats: rock‐dominated (RD) habitat and control soil‐dominated (SD) habitat. Over 2 years, soil moisture, transpiration, root distribution, and leaf water potential were measured. The results showed that soil moisture in the RD habitat was significantly lower than in the SD habitat. Transpiration patterns also differed between habitats, with species‐specific distinctions driven by biophysiological traits. M. philippensis showed small hydroscape areas and its root system mainly distributed in the soil zone in both habitats. The isohydric behaviour and lower root density in the RD habitat drove M. philippensis to reduce transpiration in response to soil water deficiency. Conversely, C. biondii had large hydroscape areas and roots capable of penetrating bedrock. It transpired higher relying on ample accessible water through anisohydric behaviour and having a more robust root system both in soil and bedrock zones in the RD habitat. Our study highlights the critical role of root water accessibility and leaf iso/anisohydric tendencies in driving transpiration. Summary statement: Isohydric behaviour and low root density drive Mallotus philippensis to reduce transpiration under soil water deficiency. Conversely, Celtis biondii can maintain high transpiration by accessing bedrock water through anisohydric behaviour and a robust root system extending into both soil and bedrock zones. [ABSTRACT FROM AUTHOR]

The ancient city of Elaiussa Sebaste, currently Ayaş, is located on the southeastern coast of Turkey. It was one of the main trading Mediterranean harbours from the Augustan period until the early Byzantine era. The Arab invasion in the 7th century ce marked its definitive abandonment. A significant historical topic concerns the palaeoenvironmental evolution of the northern and southern harbours of Elaiussa Sebaste, including their decline and burial. An interdisciplinary study analysed six cores drilled in the current plains corresponding to the former harbour basins. A geoelectrical study, integrated with borehole stratigraphy, reconstructed the geometry of the carbonate bedrock that forms the accumulation base of the marine sediments. Sediments deposited from the 8th century bce to the 6th century ce include the development phases of the ancient city from the 3rd century bce onwards. Sedimentology, micropalaeontology (foraminifers, ostracods), palaeobotany (pollen, non‐pollen palynomorphs, microcharcoals, plant macroremains) and Pb isotopes provided a model of the environmental evolution in both harbour basins. The main harbour expansion phase, marked by a change in Pb concentration, is hypothesized to have occurred between 140 and 220 ce, which is consistent with the historical sources indicating the development of the city during the mid‐Roman Imperial period. [ABSTRACT FROM AUTHOR]

Radon (222Rn) and thoron (220Rn) were reported as the highest contributors to natural radiation received by humans. Furthermore, radon has been stated as the second-highest cause of lung cancer. The concentrations of 238U and 232Th (the parent nuclide of radon and thoron, respectively) in nature vary with geological conditions and can be enhanced by human activities. Bangka Island in Indonesia is one such case with tin mining, where the environment contains a high amount of 232Th due to the island's granite bedrock. This study assesses the public's exposure to radon and thoron inhalation on Bangka Island by conducting measurements using a continuous radon-thoron monitor and a time-integrated monitor for radon, thoron, and thoron progeny concentrations. From those measurements, their diurnal and seasonal variation in the dwellings on Bangka Island were analyzed. From 135 dwellings on Bangka Island, the estimated annual effective dose derived from the inhalation of radon, thoron, and their progenies reaches 4.3 mSv at the highest and a mean of 1.7 ± 0.8 mSv in which thoron contributes more than two times higher than radon. Note that the public exposure to radon and thoron inhalation in Bangka was within the reference level for the existing exposure situation. [ABSTRACT FROM AUTHOR]

Large rock avalanches play a key role in shaping alpine landscapes. However, the complex interplay between mass movement and other surface processes poses challenges in identifying these deposits and understanding the underlying process controls. Here, we focus on the rock avalanche deposit of the Lurnigalp valley in the Bernese Alps (Switzerland), originally mapped as till. The Lurnigalp valley is a U-shaped tributary valley located in the southwest of Adelboden, Canton Bern. To explore the timing and dynamics of the rock avalanche event, we employed detailed remote and field mapping, sedimentary petrology, surface exposure dating with cosmogenic 36Cl, and runout modelling with DAN3D®. For the reconstruction of the chronology, we analyzed cosmogenic 36Cl in surface samples from 15 boulders of the rock avalanche deposit. We developed three distinct scenarios to investigate the dynamics and contextual conditions of the rock avalanche event. In the first scenario, we consider a rock avalanche depositing 1 Mm3 of sediment in a valley devoid of ice. The second scenario uses the same deposit volume but introduces a hypothetical glacier occupying the uppermost part of the valley. Finally, the third scenario, similar to the first scenario with a glacier-free valley, assumes a substantially larger volume of collapsed rock mass. We consider the third scenario the most plausible, in which approximately 6 Mm3 of rock mass, composed of limestone and sandstone, was released from a limestone cliff around 12 ± 2 ka during the Younger Dryas. The collapsed rock mass fell into the ice-free valley floor, ran up the opposite valley side and was deflected towards the northeast following the valley orientation. The rock mass stopped after 2.2 km leaving approximately 6.4 Mm3 deposits spread across the entire valley floor. Subsequently, most of the rock avalanche deposit have been reworked by periglacial activity. We suggest that structural features, lithology and glacial erosion and debuttressing were involved in the weakening of the in-situ bedrock that finally led to the collapse. Our study not only enhances the understanding of rock avalanche mechanisms and their profound impact on Alpine landscape evolution but also elucidates the complex interplay of geological processes that led to the collapse and altered the rock avalanche deposit afterwards. [ABSTRACT FROM AUTHOR]

To effectively predict the water richness of weathered bedrock aquifers, the West First Plate area of the Hongliulin coal mine was taken as the study area, and 42 sets of pumping test borehole data from the weathered bedrock in the study area were used as training and testing samples. A total of five indicators related to the water richness of weathered bedrock, namely, the aquifer thickness, sand–base ratio, core take rate, degree of weathering, and lithological structure index, were selected. A prediction model for the water richness of weathered bedrock aquifers (WOA-RF) was subsequently proposed by combining the whale optimisation algorithm (WOA) and random forest (RF). This model can predict the water-richness level of weathered bedrock in an area with no pumping test data. The geological information from 98 sets of exploration boreholes in the study area was comprehensively used to achieve water-richness zoning of the weathered bedrock. The results indicated that the WOA is effective in optimising parameters and improving model performance. The accuracies of the optimal WOA-RF model in the training set and the test set were 93.1% and 92.3%, respectively. Compared with those of the single RF model, the accuracy, recall, and F1 value of the optimal WOA-RF model were increased by 11.3%, 18.2%, and 11%, respectively, and the differences before and after optimisation were obvious. A comparison and analysis of the predictive performance of each model revealed that the overall performance of the WOA-RF model was better than that of the other models. The weathered bedrock in the study area as a whole is weakly to moderately rich in water, and the predicted results are in good agreement with reality, which can provide a reference for future safe production in the West First Plate area. [ABSTRACT FROM AUTHOR]

Climate and geological diversity have been proven to make an important contribution to biodiversity. Volcanic ecosystems often have a long geological history and diverse bedrock, thus shaping a variety of habitats. Understanding the relative importance and role of the contemporary climate and geological bedrock environment in volcanic biodiversity still needs further exploration. To address this knowledge gap, we investigated the patterns of plant diversity and phylogenetic structure at the community level in Qiniangshan Mountain, while also exploring the relationship between biodiversity and regional environmental factors (e.g., climate and bedrock types). In the Qiniangshan Mountain plant communities, species richness is higher at mid-to-high elevations. Montane communities exhibit higher species richness compared to coastal communities. There are significant differences in species richness among plant communities on different bedrock, with the highest species richness found on pyroclastic lava. Bedrock, along with climate factors related to energy and precipitation, collectively influence the patterns of species richness in plant communities. The Net Relatedness Index (NRI) of plant communities is influenced by climate factors and aspects, while the Nearest Taxon Index (NTI) is affected by both bedrock and climate factors. The Phylogenetic Diversity Index (PDI) is primarily related to climate factors. Climate and bedrock collectively influence the patterns of species richness and phylogenetic structure within Qiniangshan Mountain's plant communities. These findings highlight the profound impact of both climate and bedrock on montane vegetation and community biodiversity. [ABSTRACT FROM AUTHOR]

Ultra‐deep excavations in karst areas pose a substantial risk due to the presence of unknown karst caves. However, the literatures on deep excavations in karst regions remain limited and lack comprehensive discussion. This study investigates the effects of karst caves on the stability of the diaphragm walls (D‐walls) during an ultra‐deep excavation. A statistical analysis was conducted to examine the distribution of various parameters related to karst caves, including height, embedded depth, and roof thickness. It is revealed that these parameters follow a log‐normal distribution. There is a strong probability (99.8%) that the embedded depth will exceed 10 m, a high likelihood (82.6%) of the height being under 6 m, and similarly, an 82.2% chance that the roof thickness will be less than 5 m. A three‐dimensional finite element analysis was conducted to investigate the effects of the karst cave height, roof thickness, and location on the horizontal displacement of the D‐walls. The results show that the karst cave have significant effects on the horizontal displacement of the D‐wall, particularly at the bottom of the D‐wall. Specifically, when the karst cave has a height of 6 m, a roof thickness of 1 m, and is located at a distance of 1 m from the wall, the horizontal displacement at the bottom of the D‐wall can increase by 59 times compared with the condition without the presence of the karst cave. This severe increase in displacement results in a pronounced kick‐in failure of the D‐wall. The reason lies in the presence of the karst cave greatly reduces the bearing capacity of the bedrock within the foundation pit, thereby, rending it incapable of resisting the active earth pressure. The findings in this study can provide valuable references for formulating principles and treatment planes of the karst caves. [ABSTRACT FROM AUTHOR]

Kars province, located on the Erzurum-Kars Plateau of the Eastern Anatolia Region, has been inhabited since ancient times with the contribution of the favourable environment created by rich river resources, fertile pastures and agricultural areas. Located at the intersection of important road routes, the region has also played an important role in the spread of cultures. The Urartians, who pursued an expansion policy towards the north since the first millennium BC, organized many expeditions to the region in order to dominate the Dia(u)ehi Kingdom, an important kingdom in the region, and to reach further north. For this purpose, the Urar-tians, who wanted to control the region, built fortresses on important road routes in order to strengthen themselves militarily and logistically. Castles were also built for this purpose in and around Kars, which is within the northern expansion of the Urartian Kingdom. Taşdere/Sosgert Fortress located in Taşdere village of Arpaçay district of Kars province is thought to be an Urartian settlement. This is because Arpaçay is a region rich in water resources on the route from Anatolia to the Caucasus. In this respect, the fact that the fortress is located on this road route and in a strategic location suggests that the Urartians used the fortress effectively during their northern campaigns. Taşdere/Sosgert Fortress was built just south of the valley formed by the Karahan Stream, on a rocky area about 30-40 m above the valley. In the castle, there are architectural structures carved into the bedrock such as a warehouse, a cistern, a water tunnel with rock steps, and fortification walls built in cyclopean technique. [ABSTRACT FROM AUTHOR]

This paper is an inventory of cold-climate landforms present in the andesitic Jersak Hills on King George Island in maritime Antarctica. These landforms developed under distinctive rock control imposed by columnar jointing in andesite. Multiple distinct types of slopes – ranging from low-angle rock surfaces to steep cliffs – have formed according to the spacing and inclination of joints. Numerous joints in the rock mass facilitate efficient mechanical weathering, which has produced in situ regolith on summits, sorted scree slopes and less regular talus slopes. Debris is then transported downslope by solifluction, which acts concurrently with frost sorting, responsible for the origin of patterned ground, particularly stone stripes. Slope-channel coupling, however, is limited. The diversity of periglacial landforms associated with frost-induced degradation of bedrock outcrops has developed in a relatively short time interval following deglaciation approximately 7,000 years, as suggested by dating from localities nearby. [ABSTRACT FROM AUTHOR]

In the Campania region (Southern Italy), in the Matese Mts. (Albian to Turonian/Coniacian) and Caserta district (Albian to Cenomanian), two karst bauxite deposits outcrop, consisting of flat lenses over shallow karst carbonate. Although the mineralogy and geochemistry of Campania bauxite deposits have been widely studied in recent years, new major and trace elements relationships were provided to highlight paleoclimatic and paleoenvironmental conditions that occurred during their formation. The purpose of this research is to provide for the first time information on the paleoclimatic and paleoenvironmental conditions that affected the bauxites of Campania. These deposits formed during different periods since the Matese deposit formed during intense weathering processes with more abundant precipitation while the Caserta district deposit experienced a more long-lasting exposure event. During the formation of the studied bauxites, the drier conditions favored the replacement of kaolinite by boehmite. R-mode factor analysis showed geochemical affinity among Al2O3, TiO2, and Nb. REEs minerals are mainly associated with the bauxite matrix while Zr, Hf, and V were mainly concentrated in detrital minerals during the later stages of bauxitization. Parental affinity indices (Eu/Eu* vs. Sm/Nd; Eu/Eu* vs. TiO2/Al2O3) assessed the origin of the protolith of the Campania bauxites by rejecting the hypothesis of the dissolution of the bedrock carbonate. The results confirmed the eolian transport of parental material with an Upper Continental Crust and an intermediate to mafic magmatic composition. [ABSTRACT FROM AUTHOR]

Situated throughout the southeastern United States within the Laurentian craton are occurrences of various aged deposits (Late Proterozoic to Early Paleogene) that contain volcanics spanning from lamprophyres to carbonatites and basalts to rhyolites. Several are intrusive, while others have been reworked detritally, deposited as river gravels out onto the Gulf Coastal Plain. The earliest occurrence of igneous gravel clasts in the coastal plain of the lower Mississippi Valley lie along the Mississippi River's eastern valley wall in the ancestral Mississippi River's pre-loess terrace deposits (PLTDs). The coarse clastics of the PLTDs are dominantly chert gravels derived from Paleozoic carbonate bedrock, but also include clasts of Precambrian Sioux Quartzite, glacially faceted and striated stones, and ice-rafted boulders, which indicate a direct relationship between the PLTDs and glacial outwash during the cyclic glaciation of the Pleistocene Epoch. The PLTDs also contain the oldest known examples of igneous gravels exposed at the surface in Mississippi. An understanding of their igneous bedrock provenance and the timing of their contribution to the sedimentary record of the lower Mississippi River Valley sheds a valuable light onto the geologic history and evolution of the ancestral Mississippi River during the Pleistocene Epoch. The use of fusion inductively coupled plasma mass-spectroscopy (ICP-MS) in the identification of the igneous suites of one of the pre-loess terraces, well-delineated by geologic mapping, adds important geochemical source data from the gravel constituents for the further interpretation and correlation of the individual PLTD allounits. Gravel constituent geochemistry also offers a better understanding of the evolution of the ancestral Mississippi River watershed and the contributions of bedrock sources during Pleistocene glaciation. This petrological study suggests that the igneous gravels sampled from within the Rawhide PLTD allounit originated from the St. Francois Mountains (SFMs) in southwestern Missouri, with the implications that the SFM igneous terrain was in the direct path of the Independence "Kansan" glaciation. This could indicate a glacial extent further southwest than previously documented. [ABSTRACT FROM AUTHOR]

Understanding paleo-ice flow chronology is essential for reconstructing past ice mass dynamics, interpreting the current landscape, and identifying the sources of Quaternary sediments in deglaciated regions. A recent systematic mapping of striated bedrock and streamlined landforms south of Lake Mistassini in Canada reveals a complex sequence of five ice flows. The earliest flow was directed to the southeast (SE) and originated from a NE-SW ice divide located northwest of Lake Mistassini at the Last Glacial Maximum. A progressive clockwise rotation of this ice divide, likely triggered during the early deglaciation, appears to have generated ice flows toward the south–southeast (SSE) and then toward the south (S). During the later stages of deglaciation, the flow originated from the Québec–Labrador Dome, initially toward the south–southwest (SSW) and then toward the southwest (SW). This study presents new data on ice flows south of Lake Mistassini and shows that the southward and south–southeastward ice events occurred before the late stage of deglaciation. This interpretation contradicts some previous studies and will contribute to the discussion on the dynamics of the Laurentide Ice Sheet in the Mistassini area and support mineral exploration efforts in the region. [ABSTRACT FROM AUTHOR]

In this study, we focused on the bedrock-dependent effects of climate change on terricolous lichen communities along elevational gradients in the Alps. In particular, we contrasted between carbonatic and siliceous bedrock, hypothesizing more favourable conditions on siliceous than on carbonatic bedrock, where dryer conditions may exacerbate the effects of climate change. To test this hypothesis, we compared terricolous lichen diversity patterns between the two bedrock types in terms of (1) species richness, (2) beta-diversity, (3) proportion of cryophilous species, and (4) functional diversity, also testing the effect of the elevational gradient as a proxy for expected climate warming. Our results indicate that the most cold-adapted part of the terricolus lichen biota of the Alps could be especially threatened in the near future, mainly on carbonatic bedrock. Actually, contrasting diversity patterns were found between carbonatic and siliceous bedrock, clearly revealing a bedrock-dependent effect of climate change on terricolous lichens of the Alps. As hypothesized, siliceous bedrock hosts a richer lichen biota than carbonatic bedrock, reflecting a general richness pattern at the national level. In general, siliceous bedrock seems to be less prone to rapid pauperization of its lichen biota, providing more suitable climatic refugia that can mitigate the effects of climate warming on terricolous lichens. [ABSTRACT FROM AUTHOR]

Fault reactivation of bedrock structures in active fault zones influences stress state and earthquake rupture phenomena through the introduction of weak slip surfaces that impact fault zone geometry and width. Yet, geometric relationships between modern faults and older reactivated faults are difficult to quantify in rocks that have experienced multiple deformation episodes. We used new geologic mapping, geomorphic tools, and structural modeling to quantify rock uplift and subsurface fault geometry of the central part of the Maacama Fault Zone near Ukiah, California, USA, and the surrounding area. Results suggest that the northern Mayacamas Mountains are in a tectonically driven disequilibrium, with differential rock uplift focused on the western side of the range. Steeply east-dipping fault surfaces and splays characterize the geometry of the Maacama Fault Zone. We mapped two newly identified faults to the east of the main Maacama Fault, the Cow Mountain-Mill Creek Fault, and Willow Creek Fault, which align with a moderately east-dipping cluster of microseismicity between 4-10 km depth beneath the Mayacamas Mountains. Static stress modeling on the Maacama Fault Zone and newly identified faults to the east quantify slip tendency values of 0.5-0.4, which suggests that the faults are moderately to poorly suited for slip in the modern stress field and may be weak. We infer that modern uplift is driven by oblique reverse, upto-the-east, dip-slip motion on the reactivated Cenozoic Cow Mountain-Mill Creek and Willow Creek Faults as material is advected through a restraining bend on the Maacama Fault. This study shows that reactivated bedrock faults increase the fault zone width and introduce fault surfaces that contribute a component of vertical deformation and uplift in major strike-slip fault zones. Deformation is accommodated on an interconnected network of new and reactivated faults that delineate a complex seismic hazard. [ABSTRACT FROM AUTHOR]

Tree growth is a multifaceted process influenced by various factors at different spatial and temporal scales, including intrinsic tree traits and environmental conditions. Climate factors have a significant impact on tree growth dynamics, while geological controls can also play a crucial role. However, our understanding of the interplay between these factors concerning tree growth is currently limited. This study focuses on Norway spruce (Picea abies [L.] Karst.), one of the economically most important coniferous tree species in Europe, to investigate the interplay of growth, climate, and environment at the forest and corresponding treeline sites in the High Tatra Mountains of Slovakia. Specifically, we developed chronologies of tree-ring width (TRW) and late-wood density (MXD) for different tree size classes across two limestone and granitic sites. Growth rates of Norway spruce trees have been increasing in forests since the 1930s and from the 1950s at treelines. Growth rates were consistently higher on limestone bedrock compared to granitic bedrock conditions. Variability of radial growth is primarily driven by climate at both geological settings with trees on granitic bedrock displaying more pronounced responses to climatic variables. We observed weakening (non-stationarity) in climate signals over time and across all size classes in both geological settings. The magnitude of these effects is small, but varies across size classes, with larger trees generally displaying stronger climate sensitivities compared to smaller ones. Therefore, our findings accentuate the potential implications of geological settings, climate, and environmental factors on the absolute growth and growth dynamics of Norway spruce, highlighting the need for further research to fully understand and manage forest ecosystems in mountainous regions. [ABSTRACT FROM AUTHOR]

This study examined hydrogeological factors, including specific capacity, transmissivity and hydraulic conductivity, in the Geumgang River region of South Korea. A total of 4,329 well data (3,337 from bedrock aquifers and 992 from alluvial and weathered soil/rock aquifers) were collected from the basic groundwater survey reports and validated. To analyze geology-related ground-water productivity in this study, specific capacity and transmissivity data of nine geological units were considered. Alluvial and weathered soil/rock aquifer wells exhibited average specific capacity and transmissivity values of 147 m3/day/m and 84.1 m2/day, respectively. Meanwhile, bedrock aquifer wells showed average specific capacity and transmissivity values of 13.4 m3/day/m and 13.0 m2/day, respectively. Notably, in terms of specific capacity and transmissivity, alluvial and weathered soil/rock aquifer wells were more productive than bedrock aquifer wells. In case of bedrock aquifers, non-porous volcanic rocks and Cretaceous igneous intrusive rocks showed relatively low productive features and meta-sedimentary rocks showed higher productivity than other geological units. Box plot analysis for logarithmic specific capacity values was used to decide the criteria for groundwater productivity of wells. For bedrock aquifer wells, this study suggested that the lower whisker (−0.413), 1/4 quartile (0.457), 3/4 quartile (1.05), and upper whisker (1.94) can be used as the criteria for very low, low, moderate, high, and very high productivity. Spatial statistical analyses using kernel density and optimized hot spot methods identified several potential sites for large-capacity groundwater development with high probability. These hot spots are located in crystalline gneisses at Gongju-Sejong area, in Triassic-Jurassic intrusive igneous rocks at Gimje-Jeongeup and Boeun areas, and in meta-sedimentary rocks at Nonsan-Geumsan, Yeongdong, Boeun and Hongseong areas. Specifically, the Okcheon meta-sedimentary rocks aquifer, which is a significant bedrock aquifer in the Geumgang River region and widely distributed throughout the Okcheon Belt, was suggested as a prime candidate for groundwater development. Major aquifers in Okcheon meta-sedimentary rocks are closely associated with intercalated thin beds of brittle quartzite or carbonate rocks with dissolved cavities. The Jurassic granites aquifer can also be served as another important bedrock and/or alluvial and weathered soil/rock aquifers in the Geumgang River region, owing to its widespread distribution and moderate groundwater-yielding productivity. This aquifer type is related to the development of a stratiform fissured layer and an upper saprolite part due to weathering processes. [ABSTRACT FROM AUTHOR]

Mathura city, located in Uttar Pradesh, India, faces a high earthquake risk due to its proximity to earthquake-prone regions, population growth, and nearby seismic sources. This study aims to assess seismic hazard by estimating Peak Ground Acceleration (PGA) values for a 2% probability of exceedance in 50 years, with a return period of 2475 years. Using Deterministic Seismic Hazard Analysis (DSHA), we created seismic hazard maps and spectral acceleration response curves. Since we lacked region-specific Ground Motion Prediction Equations (GMPEs), a logic tree approach consisting of four different models to estimate PGA values was used, each assigned a weight based on likelihood. Our analysis predicts future PGAs from 0.14 to 0.35 g. The study identifies the northern parts of Mathura, including Bajna, Nauhjhil, Surir, Shahpur, and Kosi, as more vulnerable to seismic hazards. The seismic hazard maps were divided into three regions, and the site-specific spectral acceleration responses were produced with IS-1893, Part 1 (2016) for 5% damping, assuming bedrock conditions. [ABSTRACT FROM AUTHOR]

Erzurum province is located close to two important faults, namely the North Anatolian Fault Zone and the East Anatolian Fault Zone. Additionally, numerous local faults such as the Aşkale, Başköy-Kandilli, Erzurum-Dumlu, Palandöken, and Horasan-Narman Fault Zones could potentially trigger devastating earthquakes for Erzurum province. All these seismic hazard sources require a well-understanding of the soil dynamic properties in Erzurum province. The single-station microtremor method were carried out at 45 points to determine the Atatürk University Central Campus-Erzurum soil dynamic parameters with this motivation. Seismic vulnerability index and seismic bedrock depth values were calculated with the help of empirical relations using the soil dominant frequency and soil amplification factor values calculated from the horizontal/vertical spectral ratio method. The south-eastern region of the study area exhibits characteristics such as low soil dominant frequency values, high soil amplification factor values, elevated Kg values, and considerable engineering bedrock depth. This area is particularly vulnerable to potential earthquake damage due to its high sediment thickness and susceptibility to site effects. Notably, points three and four also demonstrate low soil dominant frequency values, coinciding with the locations of hospitals and administrative units. Therefore, it is imperative to intensify site effect investigations, especially using active sources of geophysical methods in these specific areas. [ABSTRACT FROM AUTHOR]

Copyright of Remote Sensing for Natural Resources is the property of Remote Sensing for Natural Resources Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Summit flats are low-relief, gently sloping landforms common in periglacial mountain environments. Apart from at their edges where summit flats are truncated by glacial headwalls and at their crests where isolated tors are occasionally present, bedrock is typically mantled on a summit flat by a continuous layer of regolith. This study applied ground-penetrating radar (GPR) to survey the thickness of regolith on a summit flat in the Uinta Mountains (Utah, USA). More than 500 m of GPR data were collected along transects extending from the edge of the summit flat to the crest, as well as adjacent to a deep soil pit. Results indicate that the regolith thickness is quite variable, with a mean of 91 ± 38 cm when calculated with an appropriate radar velocity. Because the ground surface of the summit flat is notably smooth, the variability in thickness is a consequence of irregularities in the bedrock surface at depth, which is significantly rougher. Recognition that regolith thickness can vary considerably beneath an alpine summit flat has implications for soil formation, carbon storage, and the transmission and storage of shallow groundwater, as well as evolutionary models for periglacial mountain landscapes. [ABSTRACT FROM AUTHOR]

The current research on rocky desertification primarily prioritizes large-scale surveillance, with minimal attention given to internal agricultural areas. This study offers a comprehensive framework for bedrock extraction in agricultural areas, employing spatial constraints and spatio-temporal fusion methodologies. Utilizing the high resolution and capabilities of Gaofen-2 imagery, we first delineate agricultural land, use these boundaries as spatial constraints to compute the agricultural land bedrock response Index (ABRI), and apply the spatial and temporal adaptive reflectance fusion model (STARFM) to achieve spatio-temporal fusion of Gaofen-2 imagery and Sentinel-2 imagery from multiple time periods, resulting in a high-spatio-temporal-resolution bedrock discrimination index (ABRI*) for analysis. This work demonstrates the pronounced rocky desertification phenomenon in the agricultural land in the study area. The ABRI* effectively captures this phenomenon, with the classification accuracy for the bedrock, based on the ABRI* derived from Gaofen-2 imagery, reaching 0.86. The bedrock exposure area in the farmland showed a decreasing trend from 2019 to 2021, a significant increase from 2021 to 2022, and a gradual decline from 2022 to 2024. Cultivation activities have a significant impact on rocky desertification within agricultural land. The ABRI significantly enhances the capabilities for the dynamic monitoring of rocky desertification in agricultural areas, providing data support for the management of specialized farmland. For vulnerable areas, timely adjustments to planting schemes and the prioritization of intervention measures such as soil conservation, vegetation restoration, and water resource management could help to improve the resilience and stability of agriculture, particularly in karst regions. [ABSTRACT FROM AUTHOR]

A scour hole in the pre-excavated plunge pool bed downstream of a dam can develop if the energy dissipation of the plunging jet from a spillway is underestimated. The objective of the research was to predict the equilibrium geometry of the scour hole downstream of a high-head dam to safeguard the stability of the dam foundation. A study incorporating both physical and numerical modeling was undertaken to examine the hydrodynamic and geo-mechanical aspects involved in rock scour. Experimental tests were performed to determine equilibrium scour hole profiles in an open-ended, jointed, movable rock bed under various conditions, including different flow rates, dam heights, plunge pool depths, rock sizes, and joint structure orientations. Based on the experimental findings, non-dimensional equations that describe the scour hole geometry were developed. The proposed innovative three-dimensional fluid–solid coupled numerical model is capable of realistically reproducing the equilibrium scour hole profile observed in the experimental tests. The numerical model allows detailed scour computations of fully developed rectangular jets plunging into shallow plunge pools. [ABSTRACT FROM AUTHOR]

Areas around western Vestfold Hills, East Antarctica, feature two sedimentary units in outcrops and excavations. Uppermost Dingle Sand is a gravelly, silty sand with boulders, which drapes bedrock ridges and more thickly covers valley floors and continues below modern sea level. Underlying Vestfold Beds are gravelly, muddy sands that are found in deeper valley fills. High-resolution aerial photography, topographic and bathymetric surveys, sediment grain size and field observations indicate that Dingle Sand formed as ablation till during the last deglaciation. Post-depositional modifications of Dingle Sand by decay of ground ice, mass movement, water, wind and marine transgression and regression have altered the texture, structure and fossil content in this region. Vestfold Beds are older, finer-grained tills. Indirect age estimation of Dingle Sand suggests deglaciation-age deposition with younger (Holocene) reworking in places, whereas Vestfold Beds may be as old as the Pliocene. These sediments post-date the early Pliocene Sørsdal Formation found on Marine Plain in southern Vestfold Hills. Identification of Dingle Sand as a separate, primarily glacial deposit helps clarify the glacial history of the Vestfold Hills. Evidence for marine modification of the deposits after deglaciation suggests that other regions might also have glacial deposits interpreted as marine because of post-depositional processes. [ABSTRACT FROM AUTHOR]

The erodibility of bedrock and rock masses is an important parameter for understanding landform development, landscape evolution modelling and engineering applications. Yet, complex geotechnical properties and the difficulty of directly quantifying erodibility limit the theoretical understanding and prediction of erosion processes. Several proxy methods have been suggested to assess bedrock erodibility by fluvial impact erosion. Yet, none of these proxy methods have been rigorously benchmarked with direct laboratory or field measurements. Here, we assess the usefulness of proxy methods described in the literature in the quantitative prediction of fluvial impact erosion. We compare four proxy methods – Mohs' hardness, the Schmidt hammer rebound value, Annandale's erodibility index and the Selby score – to erodibility laboratory data measured using erosion mills. We assess these methods using three statistical parameters: Kendall's tau and Spearman's rho rank correlation coefficients, and the adjusted R2 from an exponential fit. We distinguish between three applications, which require increasing correlation strength. These are (i) trend detection (sorting groups of data by their relative erodibility), (ii) quantitative ranking (relative erodibility of groups of data can be quantitatively assessed), and quantitative prediction (erodibility for individual sites can be quantitatively assessed). Mohs' hardness, Schmidt hammer measurements and Annandale's method are suitable for trend detection, while Selby's method is not. None of the methods is suitable for quantitative prediction. As such, none of the methods is a suitable proxy for estimating erodibility in fluvial bedrock erosion at a particular location. For quantitative ranking, we suggest to use either Mohs' hardness or Schmidt hammer measurements, because of (i) the correlation with mill‐measured erodibility, (ii) their ease and quickness of application in the field and (iii) the minimum of required training. When applying these methods, investigators should obtain data both from the same and from different lithological units at many sites. Then, the results can then be used for bulk assessment, but not for individual sites. [ABSTRACT FROM AUTHOR]

Controls on the physical and chemical architecture of the subsurface critical zone are somewhat controversial, with multiple hypotheses proposed to account for variations in the depth of weathering between sites, and with landscape position at a site. In the Piedmont region of the Mid‐Atlantic US weathering of crystalline bedrock has been observed to extend tens of meters below the surface and groundwater in a'bow‐tie' shape – i.e. weathering extends to lower elevations below ridges than below channels. The chemical and physical structure of a hillslope transect in the Maryland Piedmont was explored with a 45 m borehole in the ridge, as well as shallow bedrock boreholes at the toe of the slope and valley. Chemical weathering fronts were characterized using elemental abundances and mineralogical analysis. The ridge borehole did not extend deeper than the chemically and physically weathered rock. Surface and borehole geophysics and density measurements were used to characterize the weathered rock and saprolite. Na and Ca results suggest that plagioclase feldspar weathering is similar between samples collected from 45 m under the ridge and 2.2 m under the valley bottom. A narrow Fe oxidation garnet weathering front co‐insides with the transition from weathered bedrock to saprolite, suggesting that this reaction may generate initial saprolite porosity. Muscovite weathering co‐occurs with complete depletion of plagioclase a few meters above the Fe oxidation front. These nested weathering fronts in the saprolite appear to follow a subdued version of the surface topography. The location and shape of the nested saprolite weathering fronts may be controlled by the feedback between the transport of reactants and solutes and reaction‐generated porosity, consistent with the conceptual "valve" hypothesis. Differing dominant control mechanisms on deep bedrock weathering and saprolite initiating reactions may explain the thickness and structure of the critical zone at our site. [ABSTRACT FROM AUTHOR]

Observing the subsurface architecture of the deep Critical Zone (CZ), which lies beyond the uppermost layer of accessible soil, is a complex but crucial task. Near‐surface geophysics offers an alternative to accessing the deep CZ at scales relevant to fluid, nutrient and gas transport. As geophysical instruments are sensitive to different subsurface physical properties, their combination can enhance insight into CZ architecture. However, the agreement between and complementarity of multiple geophysical techniques has not been widely assessed for CZ‐related questions. This study employed geophysics to image a highly weathered lateritic hill rich in iron oxides developed from Archean granite within the Avon River Critical Zone Observatory, Western Australia. Data gathered from an electrical resistivity tomography (ERT) and horizontal‐to‐vertical‐spectral‐ratio (HVSR) passive seismic transect were used to visualise CZ architecture through specific resistivity values and ambient noise contrasts. Both techniques revealed a notable degree of lateral variability consistent with the formation of the ~3–4 m thick duricrust‐capped hilltop, the creation of gullies in the sodic material of the pallid zone exposed along the slope and the deposition of ~11 m thick colluvial sediment at the foot slope. Calculated bedrock depth was consistent between the HVSR and ERT instruments along the hilltop plateau but varied from ~23 m to 31 m on the slope and 32 m to 39 m at the foot slope, respectively. Overall, the vertical variation depicted by the ERT, including the differentiation of two layers within the lateritic weathering profile ‐ the pallid zone and saprolite – made up for the inaccuracy of the HVSR technique in depicting layers of similar composition. Moreover, the HVSR method clearly depicted bedrock depth, overcoming the partial masking of the bedrock by saline groundwater in the ERT model. The complementarity of these two methods allowed the development of a detailed conceptual model of subsurface CZ architecture within a saline lateritic weathering profile. [ABSTRACT FROM AUTHOR]

Physical wear during bedload transport influences downstream changes in the size distributions and shapes of riverbed sediment, which in turn affect myriad fluvial processes ranging from incision into bedrock to provision of aquatic habitat. Here we use laboratory tumbling experiments to address several remaining knowledge gaps, including the roles of lithologic susceptibility to fragmentation, particle size distributions and particle angularity in controlling wear rates and the size distribution of wear products. To focus on the dynamics of particle wear in headwater channels, we used initially angular sediment and ran the experiments until 10% of the initial bedload particle mass had been lost to fine‐grained wear products. We measured individual particle mass and diameter by hand and used photo analysis to quantify particle shape and angularity. We find strikingly different wear patterns between limestone and welded tuff. Although wear rates in the tuff were an order of magnitude slower than the limestone, tuff wear was primarily by fragmentation while limestone wear was dominantly by attrition. Fragmentation of the tuff resulted in a widening of the bedload size distribution, a lack of consistent particle rounding and a fine‐wear product dominated by sand. In contrast, limestone particles rounded substantially and produced silt‐sized wear products. Differences in wear product size and susceptibility to fragmentation may reflect contrasts in the size distribution of mineral crystals in each lithology. Wear rates in both rock types declined substantially with increasing cumulative mass loss, due to rounding in the limestone and reduced fragmentation in the tuff. These results suggest that applications of the conventional exponential model to predict mass loss with travel distance need to account for lithologic influence on susceptibility to fragmentation and the influence of rounding on particle wear rates. [ABSTRACT FROM AUTHOR]

The aim of this research is to present the abiotic geological environment, morphology and the need to protect geoenvironment and the possibilities of using the geoheritage of mining districts of the region located between Zawichost and Puławy city, within the Geopark. The Geopark is the best example of scientific and educational presentation of Mesozoic and Cenozoic outcrops along the Vistula gorge. The Cretaceous sediments (Middle Albian to Maastrichtian) are especially significant, they are unique on the European scale, showing a record of the evolution of the sea basin - from the Middle Cretaceous transgression and its disappearance at the end of the Cretaceous. The landscape and geomorphological values ​​constituting the heritage of the region are extremely important. An additional circumstance conducive to the creation of the Geopark is the fact that in the area covered by the project, areas of geological heritage protection have been operating for many years and tourist traditions date back to the 18th century. [ABSTRACT FROM AUTHOR]

Copyright of Urban Geology is the property of Urban Geology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The AD 1209 M6.5 Fushan earthquake caused significant casualties and damage. The Fushan Fault, forming the boundary between the Linfen Faulted Basin and uplifted Taihang Mountains, may have been the seismogenic fault, but research is lacking. Based on UAV and field surveys, we found that the Fushan Fault has a surface exposure length of 24 km and displaces Holocene strata. Samples from offset layers within a trench showed that the most recent event occurred within the last 7 ka (i.e., Holocene activity) and that the fault has the potential to generate earthquakes exceeding magnitude 7. Since 17 ka (late Quaternary), two significant paleoearthquakes have been identified: (1) between 17 and 7 ka (displacement: 2.04 m, average slip: 0.2 mm/yr) and (2) within the last 7 ka (displacement: 3.93 m, average slip: 0.56 mm/yr). Since the Late Pleistocene, the displacement rate has increased, indicating an increasing potential seismic hazard. These results were confirmed by terrestrial LiDAR; the bedrock fault surface fractal dimensions are consistent with two paleoearthquake events since the late Quaternary (coseismic displacements of 2.51 and 3.18 m). This article uses an empirical formula to evaluate the potential maximum magnitude of the Fushan Fault based on the relationship between the distribution range of the fault surface and the magnitude. Therefore, the maximum assessed earthquake magnitudes of the Fushan Fault are Ms = 7.07, 6.94, and 7.31. This assessment result basically matches the strength of the 6.5 magnitude Fushan earthquake in 1209 AD. By comparing with historical records, our results confirm that the Fushan Fault was the seismogenic structure responsible for the AD 1209 M6.5 Fushan earthquake. [ABSTRACT FROM AUTHOR]

Waterfalls are often interpreted as transient, upstream‐propagating features that mark changes in external conditions. Thus, waterfalls are commonly used to infer past tectonic and climatic forcing, making understanding the controls on waterfall erosion central to predicting how external perturbations move through landscapes. Surprisingly, there exist few direct field measurements of waterfall erosion, and existing waterfall retreat measurements are rarely paired with measurements of waterfall morphology and frequency, which, theory suggests, modulate retreat rates. This lack of data limits our ability to test existing theory and explore how waterfalls alter reach‐scale bedrock erosion rates. Here, we use cosmogenic 10Be accumulated in bedrock riverbeds to measure erosion rates in fluvial reaches with varying waterfall frequency and morphology. We find that waterfall‐rich reaches erode one to five times faster than the landscape average, and that reach‐averaged erosion rates increase with increasing waterfall frequency. We develop a new, process‐based model combining waterfall and planar‐channel erosion to explore mechanistic controls on the relative erosion rate between waterfall‐rich and waterfall‐free reaches. This model predicts that reach‐averaged erosion rates increase with waterfall frequency at low sediment supply, consistent with our field measurements, but that waterfalls can also slow reach‐averaged erosion rates for high sediment supply, large grain sizes, low water discharge, or large plunge pools. Our work is consistent with previous suggestions that waterfall erosion rates may decrease in low drainage areas and can influence long‐profile morphology. Plain Language Summary: Waterfalls are often created by geologic or climatic events (e.g., changes in fault motion or sea level), allowing scientists to learn about geologic history from waterfall erosion and retreat. While previous studies show how fast waterfalls or sections of rivers (reaches) with waterfalls move upstream, few studies have examined how waterfall retreat rate is affected by waterfall geometry and frequency. Here, we studied ten waterfall‐rich reaches in the Kings and Kaweah Rivers in the southern Sierra Nevada, CA. We used geochemical measurements of river bedrock and sand to assess the long‐term erosion rate of the reaches and surrounding landscapes. We found that all 10 reaches eroded at or above the average landscape erosion rate and that waterfall frequency was the best indicator of reach erosion rate. We then created a model of how rivers erode through mixed waterfall and non‐waterfall processes. We used the model to examine how fast waterfall‐rich reaches erode under a range of conditions and found that sometimes, especially under large and abundant sediment loads, waterfalls can slow erosion. These findings increase our understanding of how river erosion and river form can differ from place to place. Key Points: Cosmogenic analysis indicates that the waterfall‐rich study reaches erode at or above the basin averaged erosion rateWaterfall frequency is the strongest indicator of reach‐averaged erosion rate in waterfall‐rich study reachesModel results suggest that waterfall‐rich reaches may erode slower than waterfall‐free reaches under high sediment loads [ABSTRACT FROM AUTHOR]

The topographies of soil erosion and deposition are critical factors that significantly influence soil quality, subsequently impacting the erodibility of soils in karst regions. However, the investigation into the effects of erosion and deposition topographies on soil erodibility across different stages of vegetation succession in karst trough valleys is still at a preliminary stage. Therefore, three distinct topographic features (dip slopes, anti-dip slopes, and valley depressions) were selected at erosion (dip/anti-dip slope) and deposition sites (valley) to investigate the spatial heterogeneity of soil physicochemical properties, infiltration capacity, aggregate stability, and erodibility in karst trough valleys. Additionally, five different stages of vegetation succession in karst forests were considered: Abandoned land stage (ALS), Herb stage (HS), Herb-Shrub stage (HES), Shrub stage (SHS), and Forest stage (FS). Additionally, the relationships among these factors were analyzed to identify the key driving factors influencing soil erodibility. The results revealed that soil physicochemical properties and soil aggregate stability at the deposition site were significantly superior to those at the erosion site. The FS resulted in the best soil physicochemical properties, whereas the HS resulted in the highest soil aggregate stability within the deposition site. However, the soil infiltration capacity at the erosion site was significantly greater than that at the deposition sites. The ALS had the strongest soil infiltration capacity at both the erosion and deposition sites. The soil erodibility at erosion sites (0.064) was significantly greater than that at deposition sites (0.051), with the highest soil erodibility observed on anti-dip slopes during the HES at erosion sites (0.142). The structural equation model reveals that erosion and deposition topographies, vegetation succession, soil physicochemical properties, soil aggregates, and soil infiltration characteristics collectively account for 88% of the variation in soil erodibility under different conditions. Specifically, both direct and indirect influences on soil erodibility are most significantly exerted by soil aggregate stability and vegetation succession. This study provides scientific evidence to support the management of soil erosion and ecological restoration in karst trough valleys while offering technical assistance for regional ecological improvement and poverty alleviation. [ABSTRACT FROM AUTHOR]

Uganda has suffered from many damaging landslides like the 1966 Rwenzori, 1994 Kisomoro and 2010 Bududa events. Despite escalating landslide risks exacerbated by rapid deforestation, urbanization and population growth coupled with a substandard building stock, comprehensive national co-seismic and rainfall-induced landslide hazard and risk maps for Uganda do not exist. This study therefore aims to conduct landslide hazard assessment and zonation for Uganda using a geospatial-based fuzzy logic methodology. In this methodology, landslide frequency ratios obtained for the 1966 Toro and 1994 Kisomoro earthquakes are assigned to the stochastic event-based probabilistic seismic hazard map derived using OpenQuake-engine. The available co-seismic and rainfall-induced landslide inventory datasets are used to derive the distribution of landslide frequency ratios based on geology, topographic slope position index, slope aspect, slope angle, distance from streams, and proximity to major active faults. The spatial distribution of fuzzy membership functions obtained from frequency ratios are overlaid and aggregated to produce landslide susceptibility maps showing relative probabilities of landslide occurrences across Uganda. Results indicate that the highest overall landslide hazard susceptibility is expected in areas comprising highly weathered outcropping rocks of precambrian granites, dominantly metasedimentary, and granulites and gneisses geologies within 40 km from major active faults; where the bedrock peak ground acceleration ≥ 0.1 g, topographic position index ≥ 3.8, slope gradient ≥ 10°, and the distance from streams ≤ 1.25 km. These findings can inform Uganda's directorate of disaster preparedness and management towards pioneering the development of co-seismic landslide risk mitigation measures for the country. [ABSTRACT FROM AUTHOR]

Analysis of PRISM and SNOTEL station data paired with USGS streamflow gage data in the western United States shows that, in snow‐dominated mountainous watersheds, streamflow regimes differ between watersheds with karst geology and their non‐karst neighbours. These carbonate aquifers exhibit a spectrum of flow paths encompassing karst conduits, including large fractures or voids that transmit water readily to springs and other surface waters, and matrix flow paths through soils, highly fractured bedrock, or porous media bedrock grains. A well‐connected karst aquifer will discharge a large portion of its accumulated precipitation to surface water via springs and other groundwater flow paths on an annual scale, exhibiting a lagged response to precipitation presenting as a "memory effect" in hydrograph time series. These patterns were observed in the hydrologic records of gaged watersheds with exposed or near‐surface carbonate layers accounting for > 30% of their drainage area. In western snow‐dominated watersheds, where paired streamflow and SNOTEL data are available, analysis of the precipitation and flow time series shows low‐flow volume is strongly related to karst aquifer conditions and winter precipitation when compared to low‐flow volumes present in non‐karst watersheds, which have a complex relationship to multiple driving metrics. Analysis of normalised streamflow and cumulative precipitation in karst watersheds show that low‐flow conditions are highly dependent on the preceding winter precipitation and streamflow in both wet and dry periods. In non‐karst watersheds, increased precipitation primarily impacts high‐flow, spring runoff volumes with no clear relationship to low‐flow periods. When comparing cumulative streamflow and precipitation volumes within each water year and over longer timescales, karst watersheds show the potential filling and draining of large amounts of karst storage, whereas non‐karst watersheds demonstrate a more stable storage regime. Communities in many western US watersheds are dependent on snow‐dominated karst watersheds for their water supply. This analysis, using widely available hydrologic data, can provide insight into the recharge and storage processes within these watersheds, improve our ability to assess current flow regimes, anticipate the impacts of climate change on water availability, and help manage water supplies. [ABSTRACT FROM AUTHOR]

Waterfall retreat transmits base‐level perturbations upstream, thereby providing markers of changing climate and tectonics. In homogeneous rock, waterfalls often retreat either by direct waterfall‐face erosion or incision from repeating ('cyclic') steps formed above waterfalls. We lack knowledge on the conditions driving these different erosion styles, limiting our ability to predict waterfall retreat. We address this knowledge gap through flume experiments assessing how changing flow hydraulics modulates bedrock erosion. We show that, under large discharges, changes in flow hydraulics cause spatial variability in particle impact velocity, leading to cyclic step formation. As discharge decreases, both the magnitude and spatial variability of particle impact velocity decreases, causing more uniform erosion, limiting cyclic step development and potentially allowing direct erosion of the waterfall face to become the dominant retreat mechanism. These results suggest climate change and water‐resource management can alter the rate and style of waterfall retreat. Plain Language Summary: Waterfalls retreat upstream as they erode and, due to their rapid erosion, waterfalls can set erosion rates within landscapes. Waterfall retreat rates depend, in part, on the physical processes driving waterfall erosion. Waterfalls typically retreat either via direct waterfall‐face erosion or via forming smaller steps (called 'cyclic steps') which form immediately upstream of waterfalls and erode vertically. However, the conditions that cause one of these erosion mechanisms to dominate over the other are not well known. We performed laboratory experiments simulating waterfall erosion under variable water discharge while measuring changes in flow velocity and the velocity of sediment impacting the bedrock river bed. We pay particular attention to particle impacts because, like sandblasting, it is the impacts from sediment that drive bedrock erosion. Our experiments show that sediment impact velocity is sensitive to water discharge, and that this should lead to waterfalls retreating via cyclic step formation for rivers for relatively large floods, whereas for relatively small floods, waterfalls are more likely to retreat via direct erosion of the waterfall face. Key Points: The spatial distribution of particle impact velocity above waterfalls is sensitive to flow hydraulicsAt large discharges, increased spatial variability in particle impact velocity drives cyclic step formation above waterfallsAt low discharges, reduced variability in impact velocity limits cyclic step formation and promotes retreat via waterfall‐face erosion [ABSTRACT FROM AUTHOR]

Karst subterranean estuaries within globally ubiquitous carbonate aquifers are coastal groundwater ecosystems that provide an essential water resource for human populations. To understand the drivers of salinization within a coastal aquifer in the Yucatan Peninsula (Mexico), we employed hydroacoustics in flooded caves to observe how oceanic and atmospheric events facilitate mixing between the meteoric lens (fresh‐brackish groundwater) and the saline groundwater on tidal and episodic timescales. Precipitation during Tropical Storm Carlotta increased the flow and salinity of the meteoric lens without evidence for vertical mixing across the halocline. We postulate that vertical migration of haloclines in the conduit relative to those within the rock matrix during precipitation creates lateral density gradients that drive mixing, and ultimately creates a brackish layer within the meteoric lens. These results provide a mechanistic explanation for vertical and lateral exchange in a coastal carbonate aquifer, which has implications for groundwater response to future climatic change. Plain Language Summary: Karst subterranean estuaries are regions of coastal aquifers where fresh and marine water mix within porous limestone bedrock that often contains extensive cave networks. These coastal aquifers are globally distributed and are a critical water resource increasingly stressed by sea‐level rise, climate change, and human activity. We installed acoustic devices and other sensors in the most extensively mapped underwater coastal cave on Earth to image and understand how rainfall‐derived fresh water and saltwater mix underground. We found that salinization of the low‐salinity portion of the aquifer following intense rainfall‐led mixing can temporarily render the water unsafe for drinking and useless for irrigation. We developed a conceptual model that describes how tides and rainfall‐driven changes cause saline water to drain laterally from the porous limestone bedrock and mix with fresher waters in open cave passages rather than by vertical mixing between water layers, as previous studies have suggested. Key Points: We present novel hydroacoustic observations of halocline dynamics within a karst subterranean estuary during Tropical Storm CarlottaIncreased precipitation resulted in increased salinity of the brackish layer of the aquifer despite stability of haloclinesDifferential vertical halocline movement in caves and the adjacent rock matrix drives lateral mixing between brackish and saline groundwater [ABSTRACT FROM AUTHOR]

Jan Mayen is a small volcanic island situated in the Norwegian–Greenland Sea. The entire island was covered by a contiguous ice cap during the Last Glacial Maximum. The deglaciation of the ice cap was interrupted by a glacier advance in the southern part of the island in the Early Holocene. Today, there are no glaciers in this area, and until now it has been unknown whether any glaciers survived there into the Middle–Late Holocene. We show here that glaciers existed at several sites in the mountain areas of southern Jan Mayen. The investigations were triggered by the discovery of a relict glacier completely covered by tephra and impacted by a lava flow. Samples of ice from the glacier have 18O values that are isotopically indistinguishable from modern precipitation values and fall along the local meteoric water line trend. The lava flow in the glacier catchment and sculpted forms along the base of dry meltwater channels in bedrock show that glacier melting was abrupt and marked by sudden meltwater outbursts (jökulhlaups). Three more sites in southern Jan Mayen have meltwater channels with sculpted beds, gorges and/or sediments associated with lava flows and can be attributed to jökulhlaups caused by rapidly melting glaciers. Radiocarbon dates associated with glacial outwash sediments, cosmogenic dates of meltwater channel incisions, and cosmogenic and K‐Ar dates of lava flows associated with former periods of rapid glacier melting show that the four glaciers collapsed at different times in the Holocene. None of the glaciers reformed after their collapses despite subsequent cooling event(s). Likely, the glaciers were on the brink of existence before their sudden demise. [ABSTRACT FROM AUTHOR]

AbstractGeological action is one of the main forces in the formation of topography, especially in the southeastern part of the Qinghai-Tibet Plateau. Collapse, landslide, mud-rock flow and other geological actions are the main factors affecting the evolution of river valley landforms. However, existing inference methods primarily rely on theoretical calculations and multi-temporal remote sensing image interpretation, lacking direct analysis and validation through geological exploration techniques. In response, this study employed geological engineering and geotechnical exploration techniques to investigate the impact of debris flows, landslides, and collapses on the evolution of topography and geomorphology in a 5.0 km section of the Yigong Zangbo Basin. Through drilling and geophysical exploration, 6 geological profiles were constructed, identifying the distribution range and development characteristics of the geological phenomena within this section of the river valley, revealing the distribution positions of both the new and old river channels, and inferring the evolution of the river bedrock based on the original topography. The study found that when geological phenomena occur, substantial material is transported into the river channel, altering its original shape and influencing the river’s erosion process. Additionally, the occurrence of geological phenomena is closely correlated with the evolution of river valley morphology. When the river valley is wide, material accumulation on one side causes the river to flow along a lower position on the opposite side, primarily resulting in the river’s bending on the plane. In contrast, in narrow river valleys, material accumulation on the sides can fill the entire river channel, leading to a rise in the riverbed. These research findings provide a critical theoretical basis for understanding river valley morphological evolution and informing basin engineering construction. [ABSTRACT FROM AUTHOR]

The Snowball Earth hypothesis predicts global ice cover; however, previous descriptions of Cryogenian (720-635 Ma) glacial deposits are limited to continental margins and shallow marine basins. The Tavakaiv (Tava) sandstone injectites and ridges in Colorado, USA, preserve a rare terrestrial record of Cryogenian low-latitude glaciation. Injectites, ridges, and chemically weathered crystalline rock display features characteristic of fluidization and pervasive deformation in a subglacial environment due to glacial loading, fluid overpressure, and repeated sand injection during meltwater events. In situ hematite U-Pb geochronology on hematite-quartz veins, which crosscut and are cut by Tava dikes, constrain sand injection at ~690-660 Ma. We attribute early Tava sand injection episodes to basal melting associated with rifting and geothermal heating, and later injections to meltwater generation during ~661 Ma Sturtian deglaciation. A modern analog is provided by the Ross Embayment of Antarctica, where rift-related faults border sediment-filled basins, overpressurized fluids circulate in confined aquifers below ice, and extensive preglacial topography is preserved. Field evidence and geochronology in Colorado further highlight that deep chemical weathering of Proterozoic bedrock and denudation associated with the Great Unconformity predate Cryogenian injection of fluidized sand, consistent with limited glacial erosion. [ABSTRACT FROM AUTHOR]

The Himalaya orogen evolved since the Eocene as the Tethyan‐, Greater‐, Lesser‐ and Sub‐Himalaya thrust sheets were uplifted and exhumed in sequence. Reconstructing the provenance of sediment in Himalayan River systems can inform on stages in the tectonic history of the orogen. Here, we analyze the oxygen, carbon and "clumped" isotope compositions of carbonate minerals from Himalayan bedrock, Ganga River sediments and Bengal Fan turbidite deposits. We demonstrate that river sediments consist of a mixture of Himalayan‐derived and authigenic calcite precipitated in the river system. The relative abundance and clumped isotope apparent temperatures of detrital calcite in turbidite deposits decreased between the Late Miocene and Pliocene, while chemical weathering intensity did not increase during this interval. Considered together, these results reflect the establishment of the Lesser Himalaya as an important carbonate sediment source for Himalayan rivers, driven by the uplift and exhumation of this thrust sheet. Plain Language Summary: The Himalaya Range consists of a series of tectonic units that accreted during the last 50 million years as the Indian and Asian continents collided. Sediment provenance analyses are commonly used to reconstruct stages in tectonic evolution of mountain‐belts, but often capture local conditions and/or are altered by various sediment‐transport processes. We overcome these complexities by measuring oxygen, carbon and "clumped" isotope compositions of carbonate minerals in turbidite deposits cored from the Bengal Fan, to constrain sediment provenance at a Himalaya‐wide scale since the Early Miocene. Considered together with records describing weathering intensity, our data suggests that the Lesser Himalaya became the dominant source for detrital carbonate as this tectonic‐unit was uplifted and exhumed between the Late Miocene and Pliocene. Key Points: Detrital calcite in Himalayan river systems derives from Himalayan‐bedrock and authigenic sourcesTΔ47 values of detrital calcite in the Bengal Fan drop between the Late Miocene and Pliocene while weathering intensity remains invariantOn a Himalayan‐wide scale, the Lesser Himalaya became an important source of detrital carbonate between the Late Miocene and Pliocene [ABSTRACT FROM AUTHOR]

Difference in vegetation composition between communities from calcareous and siliceous soils might be due to high competition on siliceous soils for species from calcareous origin, and high rock‐induced drought stress on calcareous soils for species from siliceous origin. We tested the hypothesis that, with increasing climate stress, competition should decrease on siliceous rock for species of calcareous origin and drought stress increase on calcareous rock for species of siliceous origin because of decreasing community biomass with increasing cold or drought stress. This question is of high interest for predicting changes in species distribution with climate change since bedrock type and climate change are both complex factors that are likely to interact with climate. We set up a transplant removal experiment in contrasting climate conditions of the south of France, warm and wet temperate, warm and dry Mediterranean, and cold temperate in the Alps and the Pyrenees. In each climate condition, three targets (two species and one population from a third species) from each origin were transplanted with and without neighbours on the two rock types and during two years with different levels of drought stress. Variation in the effects of neighbours and rock‐induced drought stress on transplant survival with and without neighbours were analysed with linear modelling at each site, separately, and with ANCOVA in the whole design. Competition was the highest on siliceous rock in the more favourable climate conditions but for species of siliceous origin. The lower competition found for species of calcareous origin was likely due to the occurrence of allelopathic effects that decreased the negative effect of neighbours as measured with the removal method. The rock‐induced drought stress was the highest on calcareous rock, in particular for species of siliceous origin. Thus, the decrease in competition intensity on siliceous rocks with increasing climate stress was more important for species from siliceous than calcareous origin. Additionally, the importance of the rock‐induced drought stress was relatively low in the most stressful climate conditions as compared to the overwhelming importance of climate drought stress over the two years of our experiment, which likely induced a collapse of the positive effect of growing on a siliceous rock. [ABSTRACT FROM AUTHOR]

The extraction of thin bedrock coal seams with thick alluvium poses a challenging issue in the realm of coal safety production in China. Especially for mining under aquifers, knowing the development height of water-conducting fracture zones above the goaf is crucial for coal mine safety and production. Taking the 11092 working face of lower slice mining in Zhaogu No. 1 Mine as an example, the failure transfer process of the overlying strata is analyzed first. On this basis, the development height of the water-conducting fracture zone is predicted using empirical formulas and the BP neural network. According to the empirical formula, the height of the roof caving zone ranges from 6.93 m to 27.72 m, while the height of the water-conducting fracture zone ranges from 22.17 m to 71.73 m. The BP neural network predicts that the development height of the water-conducting fracture zone in the working face after mining is 56.83 m. CDEM numerical simulation is employed to analyze the development height of two zones of overburden rock. The findings indicate that with a mining height of 2.5 m and a cumulative mining height of 6 m, the maximum caving ratio is 2.61. It is observed that for a cumulative mining thickness of less than 6 m, a bedrock thickness of not less than 30 m, and a clay layer thickness exceeding 5 m, the clay layer effectively obstructs the upward development of the water-conducting fracture zone. Finally, the prediction results of the development height of the two zones of overlying strata in the working face are verified by using the height observation method on the underground water-conducting fracture zone and the borehole peeping method. In conclusion, the height of the overlying strata after mining the lower slice working face in the first panel of the east can be used as a basis for determining the thickness of coal (rock) pillars for waterproofing and sand control safety during the mining of lower slice working faces in mines. [ABSTRACT FROM AUTHOR]

Rapid changes in river geomorphology can occur after being disturbed by external factors like earthquakes or large dam obstructions. Studies documenting the evolution of river morphology under such conditions have advanced our understanding of fluvial geomorphology. The Dajia River in Taiwan presents a unique example of the combined effects of a coseismic fault (the 1999 Mw 7.6 Chi-Chi earthquake) and a dam. As a result of the steep terrain and abundant precipitation, rivers in Taiwan have exhibited characteristic post-disturbance evolution over 20 years. This study also considers two other comparative rivers with similar congenital conditions: the Daan River was affected by a thrust fault Chi-Chi earthquake as well, and the Zhuoshui River was influenced by dam construction finished in 2001. The survey data and knickpoint migration model were used to analyze the evolution of the three rivers and propose hypothesis models. Results showed that the mobile knickpoint migrated upstream under the influence of flow, while the dam acted as a fixed point, leading to an increased elevation gap and downstream channel incision. Thereby, the narrowing and incision of the Dajia River began at both ends and progressively spread to the whole reach under the combined effects. [ABSTRACT FROM AUTHOR]

The regolith-hosted rare earth element (REE) deposits in South China are important sources of the world's REE production. The alteration processes of primary REE-bearing minerals in granitic bedrock remain unclear so that the pathways of REE mobilization from primary minerals to regolith-hosted REE deposits have not yet been well established. Allanite is the principal REE repository in granitic bedrock and may have undergone alteration during deuteric fluid metasomatism and supergene weathering. Here, we document the allanite in the bedrock of the Zuokeng regolith-hosted REE deposit in South China to decode the REE mobilization during interaction of allanite with two different types of fluids. Most allanite grains have four distinct domains in the backscattered electron (BSE) images. Domain 1 is of magmatic origin and enriched in light REE (LREE), whereas Domains 2, 3 and 4 are of hydrothermal origin with different degrees of enrichment in middle to heavy REE (M-HREE). In particular, Domain 4 appears as overgrowth rims with the highest M-HREE concentrations among hydrothermal domains and likely crystallized from Cl-rich deuteric fluids exsolved from granitic magmas, evidenced by consistent U–Pb ages (ca. 159 Ma) and εNd(t) values (-9.4 to -7.3) of Domains 4 and 1. The preferential removal of LREE and uptake of M-HREE from Domains 2 and 3 to Domain 4 is thus attributed to metasomatism by Cl-rich deuteric fluids. On the other hand, some allanite grains in weathered bedrock also interacted with F- and carbonate-rich groundwater and were gradually replaced by synchysite-(Ce) and calcite. Consequently, LREE were concentrated in synchysite-(Ce), whereas M-HREE may have been lost to groundwater. This study unravels that the enrichment of LREE and M-HREE in altered bedrock was initially facilitated by F-, carbonate-rich fluids and Cl-rich deuteric fluids, respectively, which are likely crucial for developing regolith-hosted LREE and M-HREE deposits in South China. [ABSTRACT FROM AUTHOR]