Moraine Deposits Research Articles

Terrestrial Dissolved Organic Matter Mobilized From Eroding Permafrost Controls Microbial Community Composition and Growth in Arctic Coastal Zones

Climate warming is accelerating erosion along permafrost-dominated Arctic coasts. This results in the additional supply of organic matter (OM) and nutrients into the coastal zone. In this study we investigate the impact of coastal erosion on the marine microbial community composition and growth rates in the coastal Beaufort Sea. Dissolved organic matter (DOM) derived from three representative glacial deposit types (fluvial, lacustrine, and moraine) along the Yukon coastal plain, Canada, were used as substrate to cultivate marine bacteria using a chemostat setup. Our results show that DOM composition (inferred from UV-Visible spectroscopy) and biodegradability (inferred from DOC concentration, bacterial production and respiration) significantly differ between the three glacial deposit types. DOM derived from fluvial and moraine types show clear terrestrial characteristics with low aromaticity (Sr: 0.63 ± 0.02 and SUVA254: 1.65 ± 0.06 L mg C−1 m−1 & Sr: 0.68 ± 0.01 and SUVA254: 1.17 ± 0.06 L mg C−1 m−1, respectively) compared to the lacustrine soil type (Sr: 0.71 ± 0.02 and SUVA254: 2.15 ± 0.05 L mg C−1 m−1). The difference in composition of DOM leads to the development of three different microbial communities. Whereas Alphaproteobacteria dominate in fluvial and lacustrine deposit types (67 and 87% relative abundance, respectively), Gammaproteobacteria is the most abundant class for moraine deposit type (88% relative abundance). Bacterial growth efficiency (BGE) is 66% for DOM from moraine deposit type, while 13 and 28% for DOM from fluvial and lacustrine deposit types, respectively. The three microbial communities therefore differ strongly in their net effect on DOM utilization depending on the eroded landscape type. The high BGE value for moraine-derived DOM is probably caused by a larger proportion of labile colorless DOM. These results indicate that the substrate controls marine microbial community composition and activities in coastal waters. This suggests that biogeochemical changes in the Arctic coastal zone will depend on the DOM character of adjacent deposit types, which determine the speed and extent of DOM mineralization and thereby carbon channeling into the microbial food web. We conclude that marine microbes strongly respond to the input of terrestrial DOM released by coastal erosion and that the landscape type differently influence marine microbes.

The geology and glacial history of the Walls of Jerusalem, Central Tasmania – a preliminary study

The Walls of Jerusalem, in Tasmania’s Central Plateau, is marked by several dolerite escarpments, or “walls”, enclosing sheltered grassy valleys with Pencil Pine forests. Geologically, the area is a structurally raised block between two faults, with the peaks and plateaus being 100 m or so higher than the surrounding plateau. The valleys and escarpments may be mainly due to intense faulting and shattering of the dolerite by cross-faults, and removal of this material by glaciers. The higher peaks and plateaus have all been abraded by ice, except for an extraordinary patch at Solomons Throne, which retains irregular scree piles coloured red with lichen. Virtually all the valley floors are covered by glacial till, which probably relates to the younger glacial episodes. It consists mostly of dolerite boulders and clay, and shows subdued morainal forms in most places, with a few matrix-free boulder deposits probably representing lag after meltwater washing. Bedded clay deposits formed in lakes and meltwater streams as the ice retreated are extensive within the drift deposits, reflecting the confined nature of the two glacier lobes which entered the valleys from north and south. Dolerite screes along the scarps appear to post-date most of the morainal deposits, but some older screes may also be present. The Temple eminence within the centre of the Walls consists of fragmented dolerite overlying Triassic sandstone, almost completely covered by periglacial and glacial deposits, including superb examples of solifluction flows. There are many unanswered questions concerning the glacial deposits, but the lack of any dates means it is not yet possible to establish a comprehensive glacial chronology.

QUANTITATIVE ASSESSMENT OF GROUNDWATER PROTECTION IN THE ZONE OF INFLUENCED OF THE GOMEL CHEMICAL PLANT

The formation of dumps from the production of phosphorous fertilizers at the JSC "Gomel Chemical Plant" is a significant factor affecting the geological environment, which leads primarily to contamination of soil and ground-water. The insignificant thickness of the aeration zone (0.5 to 5.0 m), the absence of low permeable layers in its section, and the downward aquifer recharge make it possible for sulfate, phosphate, and ammonium migrant components to enter groundwater from the surface. Based on the analysis of actual geological and hydrogeological data, a quantitative assessment of the protection of pressure water within the zone influenced by JSC "Gomel Chemical Plant" was given. It is established that their protection depends on the thickness of low permeable sediments, their material composition, and the ratio of aquifer levels. The time of migration of pollutants between groundwater and pressure water was determined. Categories of groundwater protection were identified and their territorial differentiation was established. The protective properties of low permeable sediments were evaluated, taking into account their potential to reduce groundwater contamination with sulfates, phosphates, and ammonium. It was found that the moraine deposits of the first low permeable layer most effectively reduce phosphate and ammonium contamination, while not interfering with the migration of sulfate ions. The second low permeable layer, represented by siltstones, leads to a significant reduction in the flow of pollutants into the Paleogene aquifer. Analysis of the dynamics of sulfate ion concentrations was given, which generally indicated a downward trend in the studied aquifers.

Investigations on yellowing of chestnut crowns in Trentino (Alps, Northern Italy)

Yellowing of part or the whole canopy of chestnut trees was observed during the summer of 2014 in the areas of Tenno, Pranzo and Drena in Trentino, where chestnut cultivation is traditional on the lateral moraine deposit in a context of a prevalent limestone lithological substrate. Symptoms were observed on chestnut trees of different ages, either grafted or not, scattered or in stripes along the maximum slope. Investigations were carried out in the form of field surveys, chemical and molecular analyses of soil and leaves and greenhouse trials, to assess the damage evolution and its causes. No known pathogens emerged during the field surveys, and laboratory tests excluded the presence of phytoplasma infections. A comparison of yellow and asymptomatic leaves evidenced significant deficiencies of manganese (Mn) and iron (Fe) in the yellow leaves, though the level of the two nutrients was the same in the soil below green and yellowed trees. Experimental run-off trials in the greenhouse reproduced the foliage damage with a continuous basic water regime; open-field fertilizations with Mn and Fe led to a slightly recovery on the part of some treated leaves, thus confirming the hypothesis of a probable, sudden deficiency of the mentioned microelements. A possible explanation of this phenomenon could be, on one side, the high precipitation level of 2014, and, on the other side, the previous outbreaks of the Asian chestnut gall wasp, that had reduced foliage volume and thus the organic substance in the soil. The natural recovery from symptoms was clearly visible in trees after four years in a context of normal rainfall regime and increasing organic acid in the soil, after effective biological control of wasp. Even if related to a particular and rare geological condition, this is the first description of Mn deficiency in Castanea sativa.

Debris flows originating in the mountain cryosphere under a changing climate: A review

Debris flows originating in the mountain cryosphere (DFMC) are one of the most globally important, widely distributed mass flows (and natural geohazards) in mountain areas with a high altitude and/or high latitude. This is particularly the case in high mountain areas that have been undergoing rapid glacier retreat, permafrost degradation, and other melt/thaw related processes. As a consequence, the actual hazards and potential risks of DFMC have drawn increasing attention in the context of global climate change (i.e. a rising temperature and higher occurrence of strong precipitation events). Unlike debris flows at low elevations, where their occurrence is closely related to precipitation (intensity and duration), the breach of a DFMC event depends on precipitation and/or air temperature, which in turn influence melt/thaw processes, rending the formation mechanism much more complicated. Although research has been widely carried out on DFMC in past decades, there is still a long way to go before we have reached a complete understanding of the formation mechanism and triggering conditions. This review summarizes recent progress in the study of DFMC, including typical DFMC events and their causes, the failure mechanisms of rock (or ice-rock joints), the characteristics of moraine deposits, initiation through hydraulic erosion (entrainment), the relationship between DFMC initiation and meteorological conditions, and the slope stability of the mountain cryosphere under a changing climate. Several issues that should be addressed in future research are also discussed.

Landscape evolution, post-LGM surface denudation and soil weathering processes from Dickinson Park mire, Wind River Range, Wyoming (USA)

At mid-latitudes, the transition from the Pleistocene to the Holocene was characterised by distinct and partially abrupt climatic changes. Also during the Holocene, climatic perturbations, with sometimes cold-dry conditions, have occurred. How land surfaces and soil development processes in high-mountains respond to these climatic oscillations is so far only poorly known. We traced the responses of surfaces in the alpine settings of the Wind River Range (Wyoming, US) by using a large mire as natural archive. This enabled us to reconstruct environmental conditions and ecosystem changes during the Holocene in this montane area. Although adjacent moraine deposits display 10Be exposure ages from the Last Glacial Maximum up to MIS16 or even older, the accessible sediment deposits covered only the Holocene (via radiocarbon dating). By applying a geoforensic approach and deriving sedimentation rates, major climatic signals were detected. A higher deposition (and consequently erosion) rate and thus a higher rate of geomorphic activity was measured for the known cold periods 9.4–10.2 ka BP, 4.2 ka BP and 2.5 ka BP. During the LIA, especially rapid aggradation of organic matter organic matter took place here. Rates of chemical weathering and soil formation seem to have been relatively low until about 5–6 ka BP but have since increased during the Late Holocene. This would fit previous observations of increasing moisture conditions after the mid-Holocene aridity period. In contrast to several other studies, no clear signs of major disturbances (erosion, weathering) during the 8.2 ka event could be observed. Together with the low levels of chemical weathering found here, we do not see any evidence that the climate was more humid during this period. Compared to previous findings, more humid conditions seemed to have returned earlier, i.e. about 5 kyr BP. In general, this landscape displayed a patchy pattern of reaction to environmental changes, as all events were not recorded in each mire profile.

Glacial geomorphology and recent glacial recession of the Harmukh Range, NW Himalaya

A comprehensive description of the glaciation and glacial geomorphology of the Harmukh range, northwest Himalaya is reported first time in this study. The geomorphic system of the range is dominated by glaciation and provides an excellent opportunity to assess the glacial fluctuations from the Late Quaternary to the present. Using a time series of the satellite data from 1992 to 2018, the glacier area, snout and equilibrium line altitude (ELA) changes of the existing glaciers in the Harmukh Range were estimated. The glacier cover has receded from 7.47 ± 0.58 km2 in 1992 to 6.24 ± 0.62 km2 in 2018, a deglaciation of 16.46 ± 0.24%. The glaciers showed an upward shift in ELA from 47 m to 80 m during the last two and a half decade. The observations revealed that, other than the climatic factors, the ELA change and glacier recessions are influenced by the glacier size, mean altitude, and the aspect of the glaciers. Further, the high-resolution Google Earth images, supplemented by field observations, were used for mapping various glacial-geomorphic landforms. The nature of glacial grooves, overdeepenings, the height of the lateral moraine deposits and trimlines indicated appreciable thickness of the former glaciers. The pattern of the glaciated valleys revealed that the area has predominantly experienced alpine type of glaciation with most of the glaciers centred on the Harmukh peak. Based on the shape and the number of lateral moraine ridges present, it is suggested that the area has witnessed three major glacial advances. By tracing the outer limits of the glacial valleys, moraine boulders, and ice scoured terrain, it was estimated that the glaciers in the range covered 629 km2 during the glacial maxima. The presence of numerous rock glaciers and debris-free cirque glaciers on the north-eastern slopes of the range indicated a strong climatic and topographical control on the pattern, situation and extent of glaciers. However, there is a need for detailed field-based mapping of the glacial-geomorphology and geochronological study in order to better understand the nature and extent of paleo-glaciation, the observed glacier recession and the past climatic variations in this hitherto understudied glaciated region of the Kashmir Himalaya.

Centennial glacier retreat increases sedimentation and eutrophication in Subantarctic periglacial lakes: A study case of Lake Uruguay

High resolution XRF scanning documented inter-annual paleolimnological changes of a Subantarctic periglacial lake, during a process of centennial glacier retreat in King George Island, Antarctica. Two major paleoenvironmental stages were inferred from the combined analysis of elemental, molecular and isotopic biomarkers, with a boundary or transition set at about 3200 yr BP. The first stage was characterized by a relatively low allochthonous organic content, reduced productivity and nitrogen levels. Such paleoenvironmental conditions are interpreted as a terrestrial system under periglacial influence, where material influx was related to erosion process from the melt water discharge, because of the proximity to the Collins Glacier ice cap. After the major Holocene glacier advance dated at about 3500 yr BP, the ice cap retreat led to the formation of Lake Uruguay, which involved in filling processes leading to moraine deposits, proglacial meltwater channels, and lakes next to the land glacier. During the second stage, with the onset of the Current Warm Period, prior to 1900 CE the stabilization of the Zr/Rb ratio within the laminated sediments documented the origin of the lacustrine sedimentation system, with subsequent increases in the sedimentation rate and biomass content (total nitrogen and organic carbon). Time series analyses revealed that the lake displayed variability cycles related to El Niño Southern Oscillation (ENSO), as reflected by high resolution sedimentological proxies for grain size, weathering, allochthonous inputs from the watershed, increase of biomass and productivity, and changes in redox conditions, all of which displayed similar oscillation cycles from 2 to 6 yr. During this periglacial recession and associated eutrophication process, we detected a striking loss in both bacterial specific richness and diversity as inferred from preliminary selected ancient DNA analyses. Thus, the Antarctic warming scenario leading to glacier depletion appears to exert deterioration consequences on the Subantarctic microbial web.

Equilibrium-line altitude and temperature reconstructions during the Last Glacial Maximum in Chirripó National Park, Costa Rica

Several high areas of Central America show evidence of past glacial activity, including glacial cirques, polished and striated bedrock surfaces and moraine deposits. As glacial remnants, these morphologies can guide the understanding of past climate conditions, such as during the Last Glacial Maximum (LGM). Based on aerial imagery (1:25,000), detailed Digital Elevation Model (DEM) and field geomorphic assessments, we establish paleo-equilibrium line altitudes using four methods: Median Glacier Elevation (MGE), Accumulation Area Ratio (AAR), Area x Altitude (AA), and Area-Altitude Balance Ratio (AABR) during the LGM for the Chirripó National Park in Costa Rica. In addition, we calculate the LGM paleo-temperature decrease multiplying several modern atmospheric lapse rates by the equilibrium line altitude depression. In addition, a Generalized Linear Model (GLM) was applied to describe linkages between obtained paleoglacier areas and multiple land surface parameters such as Basin location, Analytical Hillshading, Aspect, Area Surface Radiation, Diurnal Anisotropic Heating, Slope, Terrain Ruggedness Index, and Wind Exposition. Our results determined thirty-one paleo equilibrium line altitudes (paleo-ELAs) and a mean altitude of ~3490 m a.s.l. Some of the moraines used in this study have been recently dated, confirming the extension of the glaciers during LGM used to calculate the ELAs. We also obtained an annual average temperature decrease of ~10.5 °C applying a lapse rate of 0.65 °C/100. Moreover, Wind Exposition and Terrain Ruggedness Index were the land surface parameters with greater statistical correlation for paleo-glacier areas. Therefore, our results provide new knowledge into the reconstruction of the maximum expansion of the LGM on tropical landscapes.

Cold-based glaciation of Pavonis Mons, Mars: evidence for moraine deposition during glacial advance

The three large volcanoes in the Tharsis region of Mars: Arsia, Pavonis, and Ascraeus Montes all have fan-shaped deposits (FSDs) on their northern or western flanks consisting of a combination of parallel ridges, knobby/hummocky terrain, and a smooth, viscous flow-like unit. The FSDs are hypothesized to have formed in the Amazonian during a period of high spin-axis obliquity which redistributed polar ice to the equatorial Tharsis region resulting in thick (> 2 km), flowing ice deposits. Based on previous ice flow simulations and crater surveys, the ridges are interpreted to be recessional drop moraines formed as debris on the ice sheet surface was transported to the ice margin—forming a long ridge sequence over an extended (∼100 Myr) period of ice sheet retreat. We test this hypothesis using a high-resolution, thermomechanical ice sheet model assuming a lower ice loss rate (~ 0.5 mm/year) than prior work based on new experimental results of ice sublimation below a protective debris layer. Our ice flow simulation results, when combined with topographic observations from a long sequence of ridges located interior of the Pavonis FSD, show that the ridged units were more likely deposited during one or more periods of glacial advance (instead of retreat) when repetitive pulses (approx. 120 kyr periodicity) of ice accumulation during high obliquity produced kinematic waves which advected a large volume of surface debris to the ice margin. If ridge deposition does occur during glacial advance, it could explain the cyclic pattern of ridge spacing and would link the dominant, 120 kyr periodicity in obliquity to the time interval between adjacent ridges. By measuring the spacing between these ridges and applying this timescale, we constrain the velocity of glacial margin to be between 0.2 and 4 cm/Earth year—in close agreement with the numerical simulation. This re-interpretation of the FSD ridged unit suggests that the timescale of FSD formation (and perhaps the duration of the Amazonian high obliquity period) was shorter than previously reported.

The anthropic landscape imprint around one of the largest Roman hydraulic gold mines in Europe: Sierra del Teleno (NW Spain)

This study explores the information gathered from the landscape transformation that occurred during the intense period of Roman hydraulic gold mining activity in northwest Spain. The Sierra del Teleno and its surroundings are characterised by the presence of Quaternary glacial and periglacial deposits and, locally, Neogene alluvial sediments, which were intensely mined by the Romans. However, the mining debris often obscures natural deposits, making their identification and description a challenging task. The aim of this study is to determine the existence of specific geomorphological features that can improve the identification of anthropic elements related to mining activity. River captures and widened drainage systems are among the most outstanding structures remaining, due to the extent and complexity of the work involved. However, other mining elements, such as anthropic modification of alluvial fans, moraine deposits and rock ridges are also evident in the landscape. In many cases, these remains are linked to the hydrologic infrastructure found in the area, which mainly comprises an extensive system of natural and man-made channels and distribution water-tanks. Difficulties arise in areas where no such structures are found. Thus, the use of geomorphic elements and patterns can help to distinguish natural and anthropic landforms. Using this approach, therefore, we have performed the first systematic and detailed analysis of the morphological imprint of Roman hydraulic gold mining activity on the landscape. These data will help piece together the puzzle of how the landscape was transformed by Roman mining activity, and can contribute to discussions surrounding the new epoch: The Anthropocene.

Early glacial maximum and deglaciation at sub-Antarctic Marion Island from cosmogenic 36Cl exposure dating

Southern Hemisphere glacial chronologies can provide valuable insights into interactions between glaciation and past climate changes, but are not well constrained on most sub-Antarctic islands. We present the first cosmogenic 36Cl exposure ages of deglaciated bedrock surfaces and moraine deposits from sub-Antarctic Marion Island in the southern Indian Ocean. Results show that the ice reached a local Last Glacial Maximum before 34 ka and retreated, with no re-advances, but possibly minor stand stills, until ∼17 ka. This early deglaciation left island surfaces below 850 m a.s.l. ice-free after ∼19 ka, and any subsequent advances during the Antarctic Cold Reversal or Holocene cooling periods would have been restricted to the interior. This glacial chronology is similar to that of some other sub-Antarctic Islands (e.g. the Kerguelen archipelago, Auckland and Campbell islands, and possibly South Georgia) and a number of other Southern Hemisphere glaciers (e.g. in Patagonia and New Zealand) and adds to evidence that suggest the Southern Hemisphere was in a glacial maxima earlier than the global LGM. We suggest a combination of declining temperatures, a northward migration of oceanic fronts and the Southern Hemisphere westerly winds (causing precipitation changes), as well as the physiography of Marion Island, created optimal conditions for glacier growth during Marine Isotope Stage (MIS) 3 instead of MIS 2. Our findings redefine the glacial history of Marion Island, and have implications for future investigations on post-glacial landscape development and ecological succession.

Glacier Relics of the Last Glacial and Holocene Periods Discovered in the Middle‐low Mountains of Eastern China: Sedimentary Sequences and Environmental Evolution of Mengshan Mountain in Shandong Province since 80 ka

AbstractThe goal of this research study is to describe academic issues which have been debated in the field of Chinese geosciences for a century. In 1922, Jonquei S. Lee (Li Siguang) discovered Quaternary glacial relics at Taihang Mountainin eastern China. In 1947, he published his research findings in the magazine Mount Lushan in Glacial Age. The research results had established three Ice Ages: Poyang (Gonzi), Dagu (Minde), and Lushan (Lisi). However, at that time, no Wurm glacial relics of the last Ice Age had been found in Lushan Mountain. Since then, the research team represented by Shi Yafeng, who is considered to be “the father of glaciers in China”, questioned Jonquei S. Lee's research results and concluded that “Professor Jonquei S. Lee's Quaternary glacier research in Lushan Mountain having misread the debris flow”. In 2005, the “middle‐low mountains” in eastern China were finally defined as follows: “We clearly and unambiguously believe that there were no glacial activities in the middle‐low mountainous areas of eastern China (east of 102° to 104°E; below 3,000 and 2,500 m) during the Quaternary Period”. Currently, the long‐standing academic debate appears to have come to a conclusion.As of 2015, the author and others began to investigate and study the Quaternary glacial relics in Mengshan Mountain (1,156m above sea level), Shandong Province, one of the “middle‐low mountains” of eastern China. The relics have been observed to posses the systematic features of glacial erosion, trough and valley striations, and moraine deposits. The applied dating method shave confirmed that there were not only glacial relics of the last Ice Age (Wurm), but also Holocene glacial relics in the Mengshan Mountain area. Therefore, in order to further establish the corresponding relationship between the glacier, loess, stream sediment series, and MIS in the Mengshan Mountain area, a large number of chronological studies have been carried out regarding the various types of sediments in the area, and 24 dating datahave been obtained using OSL, CRN, and 14Cmethods. On this basis, the corresponding relationship between the sedimentary sequences and the MIS was established for the first time in eastern China, which in dicates the environmental changes which had occurred in eastern China since 80ka. These discoveries s and chronological study results confirm the existence of the Last Ice Age, as well as Holocene glacial relics at Mengshan Mountain, there by confirming that Quaternary glaciation had occurred in the middle‐low mountain areas of eastern China.

Content of radionuclides (226Ra, 232Th, 40K, 137Cs) in soils of the North-West region of Russia formed on three types of soil forming rocks

The results of a study of the content of natural radionuclides (NR) (226Ra, 232Th, 40K) and technogenic 137Cs in soil samples formed on the most common types of soil-forming rocks of the North-West: lakeglacial (non-boulder and tape clay), glacial and water-glacial deposits are presented. Soil sections laid in the Pskov, Novgorod and Leningrad regions. The granulometric composition in the upper part of the soil profile is lighter than in the parent rock. This is reflected in the NR content in the profile of these soils: with a decrease in the fractions of physical clay and silt, the content of 226Ra, 232Th and 40K decreases. This is due to the fixation of natural radionuclides by secondary clay minerals. According to the increase in the average specific activity of all NRs, the soils form the following sequence: soils on water-glacial deposits soils on moraines - soils on lake-glacial deposits. A comparison of the average specific activity of natural radionuclides and their ranges in the upper part of the soil (0-5, 5-10 and 10-20 cm) and in the parent rock (90-100 cm) revealed a higher content of radionuclides in parent rocks (lake-glacial and moraine deposits). In the soils on water-glacial deposits, no significant difference was found.

Disaster Chain Analysis of Avalanche and Landslide and the River Blocking Dam of the Yarlung Zangbo River in Milin County of Tibet on 17 and 29 October 2018.

As a “starting zone” and “amplifier” of global climate change, the Qinghai–Tibet Plateau is very responsive to climate change. The global temperature rise has led directly to an acceleration of glacial melting in the plateau and various glacier avalanche disasters have frequently occurred. The landslide caused by glacier avalanches will damage the surrounding environment, causing secondary disasters and a disaster chain effect. Take the disaster chain of the Yarlung Zangbo River at Milin County in Tibet on 17 and 29 October 2018 as an example; a formation mechanical model was proposed. The evolution mechanism for the chain of events is as follows: glacial melt → loose moraine deposit → migration along the steep erosion groove resulting in glacier clastic deposition then debris flow → formation of the dam plug to block the river → the dammed lake. This sequence of events is of great significance for understanding the developmental trends for future avalanches, landslides, and river blocking dam disasters, and for disaster prevention planning and mitigation in the Qinghai–Tibet Plateau.

Mapping bedrock topography and moraine deposits by transient electromagnetic sounding: Oslo graben, Norway

ABSTRACTIn this research, we have studied the capabilities and limitations of the transient electromagnetic sounding applied to investigate the structure and composition of the moraine deposits covering a crystalline basement. It has been experimentally demonstrated that using the ungrounded antennas one can not only determine the electrical resistivity of different layers in the alluvium deposits and map the surface topography of the crystalline basement down to a depth of 70–100 m, but can also minimize the costs and the damage done to the environment. Additionally, transient electromagnetics helps to reveal the layers within the moraine strata that often have different resistivities and depths. The use of single antennas of size 12 m × 12 m–25 m × 25 m for field excitation and registration of transient responses allows for maximum localization of the targets and provides a high horizontal resolution in strongly heterogeneous media. The limitations of the method due to the induced polarization effect have also been investigated. Overall, despite some limitations, the transient electromagnetic method appears to be effective in the mapping, assessment and analysis of hazards in landslide‐prone areas, prior to geotechnical soundings in wells.

Quantifying terrain controls on runoff retention and routing in the Northern Prairies

AbstractThe role of hummocky terrain in governing runoff routing and focussing groundwater recharge in the Northern Prairies of North America is widely recognised. However, most hydrological studies in the region have not effectively utilised information on the surficial geology and associated landforms in large‐scale hydrological characterization. The present study uses an automated digital elevation model (DEM) analysis of a 6500‐km2 area in the Northern Prairies to quantify hydrologically relevant terrain parameters for the common types of terrains in the prairies with different surficial deposits widespread in the prairies, namely, moraines and glaciolacustrine deposits. Runoff retention (and storage) capacity within depressions varies greatly between different surficial deposits and is comparable in magnitude with a typical amount of seasonal snowmelt runoff generation. The terrain constraint on potential runoff retention varies from a few millimetres in areas classified as moraine to tens of millimetres in areas classified as stagnant ice moraine deposits. Fluted moraine and glaciolacustrine deposits have intermediate storage capacity values. The study also identified the probability density function describing a number of immediate upstream neighbours for each depression in a fill‐and‐spill network. A relationship between depression parameters and surficial deposits, as well as identified depression network structure, allows parametrisation of hydrologic models outside of the high‐resolution DEM coverage, which can still account for terrain variation in the Prairies.

Geomorfología paraglacial asociada a la inestabilidad de laderas en el Brazo Norte del Lago Argentino, Patagonia, Argentina

El retroceso y adelgazamiento de los glaciares a nivel mundial en las últimas décadas inciden directamente sobre la estabilidad de las laderas. La cuenca del glaciar Upsala y los glaciares del Brazo Norte del lago Argentino, han sufrido un marcado retroceso generando valles con pronunciadas pendientes y cubiertas con depósitos morrénicos inestables. Las laderas se encuentran fuertemente desestabilizadas, favoreciendo la generación de procesos geomorfológicos paraglaciales. El objetivo de este estudio es identificar y analizar la geomorfología paraglacial, asociada a los procesos de inestabilidad. Se realiza un análisis geomorfológico del terreno a través de la combinación de parámetros morfométricos y factores intervinientes que condicionan y desencadenan estos procesos, mediante el uso de imágenes de satélite. Los resultados muestran que la geomorfología paraglacial se encuentra influenciada por la combinación de: (i) parámetros morfométricos del terreno, entre ellos, elevaciones del terreno superiores a 700 m, pendientes promedios con un rango entre 25º-45º, orientación de las laderas este-noroeste con mayor insolación, curvatura cóncava del terreno y rugosidad leve a moderada (0,40-0,65); (ii) factores condicionantes, material morrénico depositado por los glaciares, afloramientos rocosos meteorizados y cobertura vegetal; (iii) factores desencadenantes, aporte de agua subterránea por infiltración de lagunas proglaciales y aporte superficial por precipitaciones, deshielo y escurrimiento, variación de temperaturas del aire y del suelo y variación del nivel del lago. En síntesis, las laderas que presentan mayores procesos geomorfológicos paraglaciales, producto de procesos de remoción en masa, son las que se encuentran en contacto directo con los glaciares Upsala, Bertacchi y Cono, la ladera occidental del canal Upsala y algunas zonas de los valles Moyano y Norte. El área se caracteriza por una combinación de ambientes glacial y paraglacial, siendo cada uno parte integral de la evolución del entorno.

Post‐Last Glacial Maximum glacier fluctuations in the southern Écrins massif (westernmost Alps): insights from 10Be cosmic ray exposure dating

Only a few chronological constraints on Lateglacial and Early Holocene glacier variability in the westernmost Alps have hitherto been obtained. In this paper, moraines of two palaeoglaciers in the southern Écrins massif were mapped. The chronology of the stabilization of selected moraines was established through the use of 10Be cosmic ray exposure (CRE) dating. The equilibrium line altitude (ELA) during moraine deposition was reconstructed assuming an accumulation area ratio (AAR) of 0.67. Ten pre‐Little Ice Age (LIA) ice‐marginal positions of the Rougnoux palaeoglacier were identified and seven of these have been dated. The 10Be CRE age of a boulder on the lowermost sampled moraine indicates that the landform may have been first formed during a period of stable glaciers at around 16.2±1.7 ka (kiloyears before AD 2017) or that the sampled boulder experienced pre‐exposure to secondary cosmic radiation. The moraine was re‐occupied or, alternatively, shaped somewhat before 12.2±0.6 ka when the ELA was lowered by 230 m relative to the LIA ELA. At least six periods of stable ice margins occurred thereafter when the ELA was 220–160 m lower than during the LIA. The innermost dated moraine stabilized at or before 10.9±0.7 ka. Three 10Be CRE ages from a moraine of the Prelles palaeoglacier indicate a period of stationary ice margins at or before 10.9±0.6 ka when the ELA was lowered by 160 m with respect to the end of the LIA. The presented 10Be CRE ages are in good agreement with those of moraines that have been attributed to the Egesen stadial. Assuming unchanged precipitation, summer temperature in the southern Écrins massif at ~12 ka must have been at least 2 °C lower relative to the LIA.

Geomorphologic and Glacial Evolution of the Cachapoal and southern Maipo catchments in the Andean Principal Cordillera, Central Chile (34°-35º S)

We present here a reconstruction of the post late Miocene landscape evolution of the western slope of the Andean Cordillera Principal near 34°20’ S. We base our analysis on the available geological information, a morphological characterization of the landform assemblages in the Cachapoal and southern Maipo catchments, and the first 10Be exposure ages for moraines in this area. The Cachapoal drainage basin is characterized by a variety of morphological features, like an elevated low-relief surface, volcanoes and lava flows on valley slopes, U-shaped valley sections, roches moutonnées, and large glaciated areas. Different kinds of deposits have been included in the study, such as moraines, lacustrine and landslide deposits, and a well-developed system of fluvial terraces in the more distal part of the Cachapoal catchment. Landslides are mostly developed on rocks of the late Eocene-early Miocene Abanico Formation. and are less frequent in outcrops of the overlying, early to middle Miocene Farellones Formation. We estimate that the lowest end moraine in the Cachapoal catchment is located next to the locality Bocatoma Chacayes (~950 m altitude), though covered by a major landslide. No evidence exist for glacial deposits further down stream in this region. Lateral moraine ridges of the Cachapoal Glacier at Los Cerrillos yielded 10Be exposure ages of 20.3±2.9 and 21.9±5.3 ka that indicate they are associated with the Last Glacial Maximum (LGM). Holocene moraines exist next to all glacier tongues. Of particular interest in this region is the 12 km-long debris-covered Cachapoal Glacier, the longest valley glacier in the central Chilean Andes, and its distal and proximal moraine deposits. Two lateral moraines adjacent to the present-day Cachapoal Glacier yielded exposure average ages of 13.5±2.4 ka for the external ridge, indicating the Younger Dryas, and 3.8±0.8 ka for the internal ridge, an age that coincides with the 4.2 ka global climatic event that marks the beginning of the Meghalayan Age, at the end of the Holocene. The large size of this moraine on both sides of the ice tongue indicates the great development of the glacier at that time. Some of these ages coincide with ages obtained further north in the Maipo drainage basin, at the latitude of Santiago, and in the eastern flank of the cordillera, however, no pre-LGM deposits were found here, unlike the other mentioned regions. This difference together with the much lower altitude of the LGM moraine deposits in the study region suggests that the Cachapoal catchment is a transition zone to a more humid region further south, and indicates the great need for further reconnaissance and dating of glacial deposits in this Andean region. Our analysis of the geomorphological evolution is consistent with incision start for the Cachapoal Valley in latest Miocene. In this process, glacier incision was apparently not much effective until mid-Pleistocene time, when volcanism was active in the higher regions of the mountain range covering areas not yet incised, whereas in the western Principal Cordillera lavas flowed in deeply incised valleys. Pleistocene glaciers deepened and shaped the already incised valleys, which are presently mostly occupied by rivers.