Geomorphological Features Research Articles

Spatiotemporal distribution of pCO2 and CO2 flux and the regulatory factors: From the perspective of a subtropical canyon-shaped reservoir, southwest China

Reservoir carbon cycling is a critical component of the global carbon cycle, particularly in subtropical canyon-shaped reservoirs where unique geomorphological features and hydrological regulation under monsoon climate provide a distinct perspective for carbon cycle research. This study takes the Zipingpu Reservoir (ZPPR) in southwestern China as an example and reveals significant seasonal variations in partial pressure of carbon dioxide (pCO2) and carbon dioxide flux at the water-air interface (FCO2) through annual monitoring. The average pCO2 in ZPPR is 486 μatm, and the average FCO2 is 0.093 g C m-2d-1, with approximately 42.4 % of FCO2 measurements being negative, indicating the reservoir's role can act as a carbon sink. The study also estimated the gas transfer coefficient (K), with an average value of 1.888 md-1. Peak FCO2 during spring and summer is three times higher than in other seasons, consistent with the main influencing factors of inflow dynamics, metabolic processes, and reservoir operation strategies. Inflow and operational activities, particularly during spring and summer, drive CO2 emissions in the downstream reach and upstream tributary, while biological activity facilitates CO2 uptake in the lacustrine area and forebay tributary, with enhanced absorption occurring in the autumn. Concurrently, high-intensity FCO2 emissions from the upstream river section during summer underscore the importance of carbon emission monitoring and management during critical periods. The findings not only enhance the understanding of FCO2 assessment accuracy but also provide a framework for evaluating and optimizing carbon dynamics management strategies in canyon-shaped reservoirs, contributing valuable insights to global carbon cycle research.

Understanding sediment and carbon accumulation in macrotidal minerogenic saltmarshes for climate resilience

Coastal saltmarshes play an essential role in providing services such as sediment and carbon storage, coastal protection and support for biodiversity. Despite their importance, understanding the factors controlling sediment and carbon accumulation in these minerogenic saltmarshes remains challenging due to their diversity and site-specific characteristics. Understanding the respective role of these drivers is essential for effective coastal management, particularly for mitigating the impacts of climate change. This study evaluates the control of forcing factors on the lateral and vertical morphological evolution and carbon burial rates of three minerogenic saltmarshes located on the French Atlantic coast (Pertuis Charentais region). By focusing on these sites, the study isolates specific factors such as wind and wave exposure, inundation frequency, and sediment availability, while minimizing confounding influences like climate and tidal range. Results reveal significant lateral expansion of saltmarsh boundaries towards the sea across all sites, with the highest rates of progradation observed in the protected areas influenced by geomorphological features such as sand spits and sheltered bay heads. Sediment and mass accumulation rates (SAR; MAR), derived from 210Pb and 137Cs profiles of sediment cores (n = 14), range from 0.48 to 2.22 cm yr−1, among the highest reported globally, with notable variability within and between sites. Inundation frequency and accommodation space explain SAR variability within sites, while sediment availability predominantly determines spatial differences in vertical accumulation rates between sites. Organic carbon burial rates range from 75 to 345 gC m−2 yr−1, and show a strong correlation with SAR (r = 0.9, p < 0.001, n = 13) but no dependence on carbon content or density (r = 0.2, p > 0.05, n = 13). This highlights the role of sediment input in the accumulation and sequestration of carbon by minerogenic saltmarshes. Furthermore, isotopic analysis indicates a marine source dominance in organic carbon sediment. This research provides insights into how different environmental conditions affect saltmarsh morphological evolution and carbon sequestration rates, informing targeted coastal management strategies focused on enhancing ecosystem resilience and climate resilience.

Impact of climate change on natural terrain stability and infrastructure integrity: Insights and case studies from Colombia

AbstractClimate change often leads to increased precipitations and thus affects natural terrain stability, leading to landslides and infrastructure damage. Infrastructure failure causes economic losses, societal disruption, and hampers emergency response and recovery efforts. For example, a significant challenge to the stability of natural slopes is the intensification of heavy precipitation events due to climate change. Increased precipitation rates can intensify soil erosion and soil saturation, resulting in increased instability and a higher risk of slope failure. This work consolidates current insights derived from practical engineering based on detailed investigation as well as rigorous research on the interplay between climate change, land‐use changes, geomorphological characteristics, and their collective influence on slope stability, landslides, and infrastructure integrity. Two case studies from South America are presented to analyze such effect of climate change. Collaboration between civil engineering and climate disciplines, foremost meteorology along with predictive risk management, is essential for sustainable infrastructure in evolving climates.

Engineering geomorphology of coastal landslides at Limestone Downs, North Island, New Zealand

Coastal landslides are widespread geomorphological features on New Zealand's North Island, representing a key coastal erosion process. Often, New Zealand's coastal landsliding is rainfall-induced, with young, weak, permeable sediments, failing along a shear surface coincident with an unconformable contact with underlying older, sedimentary rock. An example is the Plio-Pleistocene Awhitu Group sands in the west of the North Island, which in recent years have failed via extremely rapid flows, with little warning, leading to fatalities at built-up coastlines. Understanding the nature of the hazard posed by coastal landslides is often precluded by the heavily vegetated nature of the coast, and site access. We present a case study of two coastal landslides at Limestone Downs, on the Waikato coast, ∼70 km south of Auckland, using field investigation, laboratory testing, remote sensing and modeling. The northern landslide appears to be a relict, low-angle bedding-plane failure in sedimentary rock, possibly between the Miocene Waikawau Sandstone and the underlying Te Kuiti Group. In contrast, the adjacent southern landslide appears active, failing by retrogressive upslope extension, and is limited to Plio-Pleistocene Awhitu Group sediments. While both landslides may have been initiated by marine erosion, triggering from near-field earthquakes and tsunami effects cannot be ruled out.

Integration of seasonal frequency domain electromagnetic surveys and geological data for assessing the integrity of earthen levee systems. The case study of the Panaro River (Northern Italy)

Floods rank among the most widespread and destructive natural hazards worldwide. The progressive degradation, impairment, and breach of earthen riverine levees can occur in both natural and anthropogenic environments, stemming from various scenarios or sequences of events. These may include hydraulic failure due to overtopping because of inadequate height, and structural failure occurring even prior to overtopping, due to insufficient geotechnical and hydraulic characteristics combined with external and internal erosion.Following the catastrophic flood of December 2020, caused by the collapse of a section of the levee system of the Panaro River (a tributary of the Po River, Northern Italy), local Authorities initiated a comprehensive investigation into the causes of the breach. Numerous factors, including geological, geomorphological, and ecological features, were found to have contributed to the progressive decrease of the levee integrity prior to and during the flood. This prompted a broader multidisciplinary study of the Panaro River levee system.The study expanded its focus to include the collapsed section (rebuilt in 2020), as well as an additional 30 km stretch of both the right and left levees north of Modena, totaling 60 km. Detailed geological and geophysical data were integrated into the analysis, with particular emphasis on evaluating the characteristics and integrity features of the levee system.This analysis was carried out using Frequency Domain Electromagnetic Methods (FDEM) on the top of the levees, previously calibrated using Electrical Resistivity Tomography (ERT), geological mapping, core logs, and Cone Penetration Tests (CPTs). The FDEM surveys were repeated in different environmental conditions, specifically in the dry 2021 summer season and in the wet 2023 spring season, during heavy rainfalls that caused disastrous floods in several areas of the Emilia-Romagna Region. Out of the 60 km surveyed in the study area, the comparison of the two datasets highlights an interval of about 4 km where the internal portion of the levees is characterized by relatively coarse-grained materials and higher permeability making it more prone to internal erosion phenomena. This paper describes and integrates the results of these investigations, drawing attention to the strengths and limitations of the FDEM method when applied to extensive surveys on earthen riverine levee systems. The proposed methodology contributes as well to maintenance and retrofitting efforts to reduce flood risk in the context of the present climate change scenarios.

The role of artificial intelligence data in estimating the extent of gully erosion the basin is Wadi Khashm Al-Mujadar

Wadi Khashm Al-Mujadar basin is one of the dry valleys in the southern western plateau of Iraq, it is located astronomically between two latitudes (5314.191◦29) (2437.944◦29) north, and (102.327◦46) (02.79◦46) east. It is characterized by geomorphological, hydrological and natural resource characteristics, contributes to the development of the lands of the southern Western Plateau. The importance of the topic comes from the natural and human characteristics of this basin that contribute to development, with artificial intelligence data, it has become an important tool in the process of analyzing, linking, interpreting and modeling some natural risks, to which the soil and lands are exposed under varying climatic conditions that contribute to the variation in the quality and extent of erosion. The use of artificial intelligence data is an effective tool in achieving valuable and accurate results. The research aims to use artificial intelligence data to estimate the extent of erosion, determine its type, cases, and degree of severity, and model it, depending on the results of the calibrations used, especially the Bergsma criterion for determining groove erosion. Gully erosion in the basin varies from light gully erosion to high gully erosion, due to the variation in the amount of rain, its falling regime, and the characteristics of the soil in the region, in addition to the rock formations, the steepness of the slope, the density of natural vegetation and the role of humans in it. The study showed that there are (4) erosion zones: it is a very light erosion zone(13.03 km2 and a rate of 4.28%), the area of light erosion (218.35 km2, at a rate of 71.81%, the moderate erosion zone (68.71 km2, at a rate of 22.6%, and the high erosion zone (3.99 km2, at a rate of 1.31%. The majority of the area was located within the range of light and moderate erosion, requires finding ways to reduce soil erosion and the deterioration of its structure, composition and natural properties.

Natural and anthropogenic factors that determine the activity of geological processes of the Abakan agglomeration

Relevance. As a result of the construction and operation of buildings and structures within the Abakan agglomeration, there is an activation of existing and the formation of new engineering and geological processes accompanied by accidental destruction of constructions. In order to minimize economic and socio-environmental damage, timely development of scientifically sound urban planning and architectural planning solutions is necessary. It would take into account the results of design studies of engineering protection of the territory from dangerous manifestations of engineering and geological processes. Generalization of the available survey results in order to typify the engineering and geological conditions of the urban area will optimize the construction development of urban areas, develop reliable schemes of engineering protection against the manifestations of dangerous engineering and geological processes. Aim. To establish natural and anthropogenic factors that determine the activity of dangerous geological processes in the territory of the Abakan agglomeration. Methods. Collection, systematization and analysis of available territorial geological, hydrological, hydrogeological, environmental information, results of engineering surveys. Results and conclusions. At a qualitatively new level, a set of maps has been compiled on the factors that determine the development of dangerous geological processes. The authors have carried out a GIS analysis of morphometric indicators of the relief of the agglomeration territory: maps of the steepness and exposure of the slopes were constructed. The analysis of the collected data made it possible to establish the regional characteristics of the components of the geological environment and propose a zoning scheme for the territory for its construction development and engineering protection. The authors identified four taxa during zoning: territories favorable for construction that do not require significant engineering training; territories conditionally favorable for construction, requiring preliminary engineering training; territories conditionally unfavorable for construction, requiring significant costs for engineering training; territories unfavorable for construction. The boundaries of the taxa are based on the analysis of the geomorphological features of the territory. The conducted research was performed for the agglomeration territory for the first time.

Reconstructing palaeogeography and landscapes around the ancient Greek colony of Abdera (Thrace, NE gr.): an integrated remote sensing approach

ABSTRACT We developed a multi-source, integrated remote sensing approach to characterize the geomorphological features of the alluvial and coastal lowlands around the ancient Abdera (coastal Thrace, Gr.). By combining multi-temporal composites of satellite imagery, DEM-derived products, orthophotography, and different cartographic resources, more than 1000 linear km of ancient landforms have been identified and mapped. When crossed with archaeological and historical data, our results allowed to propose a reconstruction of the palaeogeographic evolution and geomorphological dynamics in the eastern lobe of the Nestos Delta, the Kosynthos plain, Lake Vistonida and the Porto Lagos coast since the Antiquity. Our results suggest that the delta developed mainly between Hellenistic times and the Late Antiquity, when it had reached a shape similar to the current. Most of the large palaeochannels visible in the delta seem to be Nestos’ short-lived avulsions occurring in late Byzantine and Ottoman periods. Eastwards progradation of the Kosynthos plain, especially during Byzantine and Ottoman periods and accelerating in the 20th c. due to river channelization, was the main cause of the silting and a significant size reduction of Lake Vistonida since the Antiquity. Lake Lafra was also partially silted in late Byzantine and Ottoman times, likely due to the sedimentary discharge of the Kosynthos after a change in its course. By contrast, other lagoons and wetlands in the coast of Porto Lagos seem relatively stable in the last millennia with only minor silting and coastline progradation. Further geomorphological and geoarchaeological research in the area will allow to draw more precisely long-term interaction of past societies with environmental dynamics and resulting landscape change.

Ophiolites: Geological Heritage with Multifaceted Cultural Values

Cultural geomorphology is a very recent discipline that studies the geomorphological component of a territory which embodies both a cultural feature of the landscape and its interactions with cultural heritage: this cultural approach concerns the dialogue and cultural integration between humanistic and scientific disciplines and can be extended to all the fields of Earth Sciences. Ophiolite rock masses strongly characterize the landscape: their greenish-black, sometimes red-brown colour; the steep profile of the slopes, which results from their greater resistance to erosion than the surrounding softer sedimentary rocks; the scarce or even absent vegetation cover. The value of ophiolites is not only related to scientific and aesthetic interests, but is also due to historical–geographical, cultural and socio-economic issues. In this research, we present the elements of cultural and landscape value related to the ophiolites of the Northern Apennines, and how these geological and geomorphological features have led to specific relationships with humankind and human geography. Indeed, ophiolites represent characteristic elements of popular culture with immediate reference to toponymy, local legends and religion. Ophiolites are also an element of great strategic importance, as they are crucial for human settlement, with specific reference to defence, and for mining and quarrying activities. The landscape of ophiolites is of great geological, geomorphological, hydrogeological and pedological interest, resulting in a high concentration of geosites, hence on the one hand the opportunity for enhancement and potential geotourism, and on the other hand the need for their protection and geoconservation.

Mosaic pattern of sustained rice domestication and its environmental and cultural implications in Neolithic East China

China is one of the main locations in which rice agriculture occurs, with East China now playing a significant role in research on rice domestication and culture interactions. However, the exact timing of sustained rice domestication and the process of prehistoric cultural exchange in East China remain unclear. Here, we present phytolith records of two profiles from Lingjiatan in the Chaohu Lake Basin. Our results show that rice cultivation was practiced throughout the Lingjiatan culture period (5800-5300 cal BP), and that sustained rice domestication began around 5500 cal BP, which was later than on the Taihu Plain (∼6200 cal BP), Ningshao Plain (∼5800 cal BP), and along the middle and lower Huai River (∼5800 cal BP). Combining other archaeological records and geomorphological features in East China, we hypothesize three possible routes for the spread of rice cultivation and cultural exchange between the lower Yangtze River and the middle and lower Huai River. Lingjiatan, situated at the intersection of two of the possible routes, experienced a gradual increase in its settled population as a result of cultural exchange and technological innovations in cultivation, thereby giving rise to its distinctive culture. This study demonstrates the significant role of Lingjiatan in facilitating transportation and fostering cultural exchange in East China during the mid-Holocene.

Assessment of mangrove structures and biomass on islands along the Java Sea: a case study on Bawean Islands and Karimunjawa Islands

Mangroves on the islands along the Java Sea play a crucial role in supporting biodiversity, protecting coastlines, and sequestering carbon. However, there is a lack of information on mangrove structure and biomass in the area. This study aimed to assess the mangrove structures and biomass on Desa Daun, located on the Bawean Islands, and Kemujan Island, located on the Karimunjawa Islands, respectively. The study utilized a combination of line transect and quadrant plot methods with a size plot of 10x10 m. We established 7 line transects and 28 quadrant plots in the mangrove forest of Desa Daun and similarly set up 7 line transects and 21 quadrant plots on Kemujan Island. Within each quadrant, the mangrove species were identified, and their diameters at breast height (DBH) were recorded. To assess the relative significance of each species, the importance value index (IVI) was calculated, and allometric equations were applied to estimate biomass and carbon storage in the trees. PlanetScope imagery was also used to quantify the carbon stock of mangroves on those islands. In Desa Daun, 13 mangrove species were identified, while 12 species were recorded on Kemujan Island. The species Nypa fruticans and Excoecaria agallocha exhibited the highest IVI in Desa Daun and Kemujan Island, respectively. Notably, Rhizophora apiculata demonstrated the greatest biomass in both locations, with measurements of 43.08 Mg B/ha in Desa Daun and 102.22 Mg B/ha in Kemujan Island. Overall, mangrove stands on Desa Daun stored biomass of 113.60 Mg B/ha and carbon of 50.98 Mg C/ha, whereas mangrove stands on Kemujan Island stored biomass of 295.04 Mg B/ha and carbon of 131.95 Mg C/ha. Mangrove stands of the whole Bawean Islands sequestered 22,941 Mg C, while Karimunjawa Islands hold much higher C stocks, 79,451 Mg C. Despite being smaller in size, the Karimunjawa Islands have more extensive mangrove coverage compared to the Bawean Islands due to their geomorphological characteristics, which in turn influence their mangrove structures and carbon stocks. However, the loss of mangroves in the Karimunjawa Islands due to aquaculture expansions could increase carbon loss in the islands.

Natural conditions of Varandey coastal tundra. Anthropogenic transformation of natural landscapes

The author aims to characterize natural conditions in the coastal area of the Barents Sea, from the settlement of Varandey to the Perevoznoye field. The research covered an area of 20 km2, 40 km long. An integrated climatic characteristic of the studied area is given, including the direction and speed of natural processes forming its shape, cryogenic processes, flora and fauna conditions, soil cover formation. The geomorphological, geological, and hydrological features of the area are outlined. The heterogeneity of the water–salt regime of the coastal area, typical of the northern seas of the Arctic, including the Barents Sea, is noted. In the laidas, the prevalence of accumulation of easily soluble salts over their removal is established, which allows the soils to be distinguished in terms of their salinity. Here, halophytic species are identified. The vegetation cover of the studied area is characterized according to the habitat of flora representatives. The research identified 100 species of vascular plants, 51 species of lichens, and 65 species of mosses. A soil survey found 27 soil varieties, which form the structure of the soil cover; their morphological and physicochemical characterization are given. The data obtained during field studies and remote sensing data were used to determine the structure of landscapes to the level of terrain types and units, as well as to propose their description. Their ecological and geochemical typification is carried out. The fauna composition was assessed based on state registration data and open sources; field observations with reference to biotopes were used. The dynamics of fauna population on the Barents Sea coast was assessed retrospectively. Field survey and remote sensing data made it possible to identify areas with anthropogenic disturbance of tundra landscapes. A typification of the identified anthropogenic disturbances of the natural environment and their areas within the survey area is proposed. The data obtained can be used as signs when assessing the state of natural environments in the coastal part of the northern seas of the Arctic, similar in terms of natural and climatic conditions.

Development and evaluation of hydraulic geometry relationships for large Brazilian river basins

ABSTRACT River cross-section characteristics are not available for many regions of the world, and they are generally expressed as hydraulic geometry (HG) relationships. These relationships usually represent average characteristics of a region, which can generate biased estimates in smaller basins. Therefore, to improve the representation of river channel geomorphological characteristics, the objective of this study was to use a large database of river cross-section geometries to refine HG relationships for five river basins in Brazil. HG relationships were developed for the entire basins and for hydraulically homogeneous regions, obtained through a geographical convenience method. The relationship between the coefficients of the geometric relationships and morphoclimatic characteristics was assessed, showing a trend between precipitation and slope and the coefficients of the depth relationships. The estimated bankfull width and depth values were also compared to observed data and global datasets, showing an improvement in estimates with the more refined HG relationships.

Monitoring and Evaluation of Debris Flow Disaster in the Loess Plateau Area of China: A Case Study

The Loess Plateau area, with complex geomorphological features and geological structure, is highly prone to geologic disasters such as landslides and debris flow, which cause great losses. To investigate the initiation mechanism of landslide and debris flow disasters and their spreading patterns, historical satellite images in the Laolang gully were collected and digitized to generate three-dimensional topographic and geomorphological maps. Typical landslides were selected for landslide thickness measurement using a standard penetrometer and high-density electrical method. Numerical models were established to simulate the occurrence and development of landslides under different working conditions and to evaluate the spreading range based on the propagation algorithm and friction law. The results show that the 10 m resolution DEM data are well matched with the potential hazard events observed in the field site. The smaller the critical slope threshold, the greater the extent and distance of landslide spreading. The larger the angle of arrival, the greater the energy loss, and therefore the smaller the landslide movement distance. The results can provide scientific theoretical guidance for the prevention and control of rainfall-induced landslide and debris flow disasters in the Loess Plateau area.

A new paradigm for local infrastructure to enhance the potential of Finiq and its surrounding

The main aim of this report is to promote an innovative approach for Municipalities, engineers and designers showing instruments and methodologies to envision a new paradigm for the future of those areas that area suffering emigration of population and lack of infrastructures. A specific case study has been identify in the village of Finiq, located in the South of Albania - and topic of the 8th International Workshop of Tirana – which, due to the isolation of its population, related to historical and geo-morphological characteristics, is registering a constant shrinking of the inhabitants in search of occupational and educational facilities. Within the development of the investigation Finiq has been first evaluated at local scale – estimating the needs of the inhabitants – and secondly it has been systemised with the sur- rounding villages: Aliko, Mesopotam, Vrion. This approach led to an implementation of the interconnection within the villages as necessary action to overcome the isolation of all the inhabitants. This analysis has been the starting point for the definition of the strategy to adopt as an opportunity to develop an innovative structure for the management of mobility, local resources and energy use, to increase the touristic attractiveness of the site and to provide the inhabit- ant with a strategic and widespread infrastructure. To be truly effective, the mentioned approach includes an active participation of the citizen/ user, who becomes the main actor and prosumer of his own infrastructure and whom, through an adequate information program, becomes able to modify and align his own behaviors to this new one paradigm. The outcome of this report has the characteristics to be implemented and replicated in other context with similar issues, not only by designers but also by public administrations or private stakeholders that have to confront with similar social and demographic issues, putting an end to the systematic abandonment of the areas and to unlock their economic and demographic development.

Outburst flood events since the Last Glacial Maximum in the Hutiao Gorge of Jinsha River: Geomorphological evidence from eddy gravel bars

Breaching of natural dams in the Hutiao Gorge of the Jinsha River across the Yulong-Haba Mountains is one of the major geomorphological events in the largest river of Asia. Catastrophic flood events have an important influence on the geomorphological evolution of the First Bend of the Yangtze River since the Last Glacial Maximum (LGM). However, detailed geomorphological evidence, ages, and depositional phases of outburst flooding remain unclear. In this paper, large-scale gravel bars overlying the river terraces and dammed lakes are analyzed within the Daju Basin. The macroscopic geomorphological characteristics of megaflood landforms with large thickness and uniform gravel bars are similar to those of Missoula and Altai megafloods. Morphological analysis shows that eddy gravel bars (EGBs) with rhythmic structure are characterized by a dome-shaped protrusion in the cross section and a gravel mound in the longitudinal section. Each bar with oblique, parallel and massive bedding was analyzed from the horizontal and vertical directions. Three dome-shaped bars clearly show at least three palaeoflood phases. Quartz grain surface macrotextures are mainly V-shaped pits and conchoidal fractures, which exhibits a high-energy environment during the flood. The stratigraphic sequence model of EGBs is dominated by coarse sand and fine gravel rhythmic bedding in high-energy eddy environments and suspended sand deposits in low-energy backwater environments. Such phenomenon reveals megaflood fluctuates, which is also confirmed by geochemical difference. The episode of natural dam break floods triggered by tectonic activity and glacier fluctuation was dated to 20–17 ka during the LGM. Sedimentary pattern of EGBs offers fresh insights into understanding the megaflood geomorphological characteristics of the upper Yangtze River and better identification similar high-energy palaeoflood landforms in the southeast Tibetan Plateau.

Hydrographic basins dictate the genetic structure of the paradoxical frog Pseudis bolbodactyla (Anura: Hylidae) in the rivers of Central Brazil

Abstract Rivers are prominent landscape features, acting as key promoters of diversification among freshwater organisms. Albeit generally considered potential barriers to species movement, they may also facilitate gene flow and structure populations of semiaquatic species (Riverine Thruway Hypothesis, RTH). We evaluated the role of rivers on the processes responsible for current genetic variation in the semiaquatic frog Pseudis bolbodactyla, testing whether each hydrographic basin harbours distinct genetic lineages. We sequenced three markers on 166 samples from 13 localities along the Paraná (PR), Araguaia–Tocantins (AT), and São Francisco (SF) River basins in Brazil. We recovered three populations geographically matching each hydrographic basin. Our results indicate migration among basins, with the best model selected using approximate Bayesian computation, including migration between AT and SF and ancient gene flow from PR to the AT–SF ancestor. Our findings are likely related to the orogenic events in Central Brazil dating to the Late Miocene (5 Mya), when hydrographic basins and the geomorphological features of the Brazilian Shield were formed. This suggests that P. bolbodactyla probably represents a species complex, with each lineage occurring in a distinct hydrographic basin, matching the predictions of the RTH.

Mussel culture monitoring with semi-supervised machine learning on multibeam echosounder data using label spreading

High diversity seabed habitats, such as shellfish aggregations, play a significant role in marine ecosystem sustainability but are susceptible to bottom disturbance induced by anthropogenic activities. Regular monitoring of these habitats with effective mapping methods is therefore essential. Multibeam echosounder (MBES) has been widely used in recent decades for seabed characterization due to its non-destructive manner and extensive spatial coverage compared to traditional methods like bottom sampling. Nevertheless, bottom sampling remains essential to link ground truth with acoustic seabed classification. Using seabed samples and MBES measurements, machine learning techniques are commonly employed to model their relationships and generate classification maps of an extended seabed. However, limited ground truth data, resulting from constraints in regulations, budget, or time, may impede the development of robust machine learning models. To address this challenge, we applied a semi-supervised machine learning method to classify seabed sediments of a blue mussel (Mytilus edulis) cultivation area in the Oosterschelde, the Netherlands. We utilized nine boxcore samples to generate pseudo-labels on MBES data. These pseudo-labels enlarged the training data size, facilitated the training of three comprehensive machine learning algorithms (Gradient Boosting, Random Forest, and Support Vector Machine), and helped to classify the study site into mussel and non-mussel areas. We found the geomorphological and backscatter-related features to be complementary for mussel culture detection. Our classification results were demonstrated effective through expert knowledge of this cultivation area and brought insights for future research on natural mussel habitats.

Late Quaternary glacial maxima in southern Patagonia: insights from the Lago Argentino glacier lobe

Abstract. Determining the timing and extent of Quaternary glaciations around the globe is critical to understanding the drivers behind climate change and glacier fluctuations. Evidence from the southern mid-latitudes indicates that local glacial maxima preceded the global Last Glacial Maximum (LGM), implying that feedbacks in the climate system or ice dynamics played a role beyond the underlying orbital forcings. To shed light on these processes, we investigated the glacial landforms shaped and deposited by the Lago Argentino glacier (50° S), an outlet lobe of the former Patagonian Ice Sheet, in southern Argentina. We mapped geomorphological features on the landscape and dated moraine boulders and outwash sediments using 10Be cosmogenic nuclides and feldspar infrared stimulated luminescence (IRSL) to constrain the chronology of glacial advance and retreat. We report that the Lago Argentino glacier lobe reached more extensive limits prior to the global LGM, advancing during the middle to late Pleistocene between 243–132 ka and during Marine Isotope Stage 3 (MIS 3), culminating at 44.5 ± 8.0 and at 36.6 ± 1.0 ka. Our results indicate that the most extensive advance of the last glacial cycle occurred during MIS 3, and we hypothesize that this was a result of longer and colder winters, as well as increased precipitation delivered by a latitudinal migration of the Southern Westerly Winds belt, highlighting the role of local and regional climate feedbacks in modulating ice mass changes in the southern mid-latitudes.

Responses of geomorphic indices to the northward migration of the Eastern Himalayan syntaxis

The Eastern Himalayan Syntaxis (EHS), featured by an exceptionally intense compression orogeny and an extremely rapid surface erosion rate, stands out as a prime area for investigating surface processes and landscape evolution. Understanding the formation of the EHS holds significant importance in advancing our comprehension of the evolutionary dynamics within the Tibetan Plateau and the complex interplay between endogenic and exogenic geological processes. Currently, two models, namely the tectonic aneurysm and the syntaxis expansion model, have been proposed to explain the formation and evolution of this syntaxis. In this study, we employ a multi-disciplinary approach, integrating geomorphic indices such as slope, relief, hypsometric integral (HI), normalized channel steepness (Ksn), river slope-basin area integration (χ), Gilbert metric, combined with erosion rates on long-medium-short term timescales obtained from thermochronology, cosmogenic nuclides 10Be and landslide disaster probability data. Our findings suggest a relatively high tectonic activity in the confluence of the Yigong and Parlung Rivers in the northern end of the syntaxis. Moreover, our data reveals that spatial variability of tectonic activity is the primary driver of regional geomorphologic features and the spatial-temporal characteristics of erosion observed in the EHS, with lithology and climatic precipitation playing a lesser role. Furthermore, the northward migration of the EHS appears to elucidate the shift of tectonic activity and rapid erosion from the core of the syntaxis near the Namche-Barwa towards the confluence of the Yigong and Parlung Rivers. This northward migration of the EHS underscores the need for increased attention to the high geological hazard risk in the northern part of the EHS.