Glacial Deposits Research Articles

Ethical Responsibility: When the Forensic Engineer is Faced with Notifying Occupants to Vacate

Holding the obligation to protect life, safety and welfare paramount required the forensic engineer in this case to notify the homeowner to vacate her new home constructed in an active landslide. The forensic engineering evaluation of a four-year-old home revealed extensive damages caused by active soil mass flow in glacial lake deposit soils and a natural spring that imposed excessive hydrostatic pressure on the front foundation wall. The homeowner remained in the home for nearly four years during the investigations while insurers and their engineers argued over coverage. The structural analysis revealed significant probability of imminent collapse, threatening the safety and welfare of occupants and creating both a compelling necessity and an ethical obligation to notify the homeowner of grave peril to the occupants and their need to vacate and abandon the premises.

Travertine Mineralogical Characteristics and Spatial Distribution in Huanglong, China, a World Natural Heritage: Derived from Late Pleistocene to Early Holocene Glacial U-Shaped Valley Carbonate Deposits.

In the long and complex process of geological evolution, the rise of the Himalayan movement and the strong Quaternary glacial movement 400,000 years ago have shaped the highly distinctive travertine landform landscape of Huanglong, China. The overflow of karst water in the high travertine layer has formed magnificent waterfalls and wonderful karst caves as well as the world's largest open-air travertine beaches and pools. The unique travertine landscape has entered the public's vision. The travertine landscape composed of rare geological relics such as pools, terraces, beaches, waterfalls, and karst caves is like a gorgeous garland on the eastern edge of the Qinghai-Tibet Plateau, playing a pivotal role in China and even the world. The mineralogical characteristics and development level of Huanglong travertine were studied by means of hydrogeological survey, UAV aerial survey, and rock and mineral analysis. The length of Huanglong Trench is 3.6 km, with an average thickness of 17.8 m, and the thickest part is 31.9 m at the front of Pengjing pool. Due to the strong alteration of superficial plants, the main vertical structure is diversified, with porous travertine, dense travertine, and detritus travertine. Huanglong travertine was born in the late Pleistocene to early Holocene of the Quaternary. The deep carbonate rocks were deposited on the surface through a water cycle. The mineral composition is mainly calcite, and the purity of CaCO3 is generally over 95%. The research results have initially revealed the mineralogy characteristics and landscape spatial distribution of travertine in Huanglong World Natural Heritage.

Microplastics in Lake sediments in Robert Island, Antarctica

Microplastic (MP) pollution was investigated in the sediment of lakes on Robert Island in the South Shetland Islands located in the northwest of the Antarctic Peninsula. Sediment samples were taken from a glacial lake (L1) and three coastal lakes (L2, L3 and L4) in March and April 2018 as part of the Turkish Antarctic Science Expedition-II (TAE-II). MPs were counted, and physically (shape, colour, size) and chemically characterized by stereomicroscope and Fourier-transform infrared spectroscopy (FT-IR). Fiber and fragments were found in the coastal lakes, while only fibers were found in the glacial lake sediment. The meanMP concentration was 28.3 mp. l-1±37.9 mp. l-1 sediment in the glacial lake and 49.6 mp. l-1±97.1 mp. l-1 sediment in coastal lakes. A total of six different colours of MPs were found with transparent and blue were dominant. The size of MPs varied between 0.08-2.12 mm (mean 0.96±0.55 mm). FT-IR analysis confirmed that MPs were composed of Ethylene Vinyl Acetate (EVA), Polyethylene terephthalate (PET), Polypropylene (PP), Polymethyl Methacrylate (PMMA), Polyethylene (PE), Polyurethane (PU), and Polyacrylonitrile (PAN). Presence of MPs in the lake`s sediment highlights the vulnerability of Antarctica's environment to this unbounded and unpredictable pervasive pollutant and raises concerns about the potential effects of MPs on its unique ecosystems, which are critical to global climate regulation. More comprehensive research on distribution, characteristics, sources and transport of MPs in this remote region is recommended to fully understand the level of risk that MPs represents to ecosystem health.

Development of an early warning system to reduce the impact of floods related to glacial lake outburst floods (SAGAZ)

Abstract. The retreat of glaciers has led to increasing in natural hazards due, for example, by emptying of lakes dammed by unconsolidated glacial deposits (moraines) or ice, which are susceptible to catastrophic erosion, generating rapid floods, phenomena known as “Glacial Lake Outburst Floods” (GLOFs). Current systems that warn of the occurrence of a GLOF are activated when the emptying begins, which leaves little time to act, so they should be considered early alarm systems. The challenge is to predict the onset of the flood allowing the generation of an early warning system. To address this problem, SAGAZ ultimately aims to develop a system capable of identifying periods of increased GLOF risk using a predictive model fed by weather forecasts and monitoring station data. This system identifies a period of higher risk, which allows informing authorities several days in advance. This paper presents the results of the first phase of SAGAZ implementation, which aimed to (1) develop and validate a prototype monitoring station and deploy a network of stations on glacial lakes across southern Patagonia, (2) collect the necessary data for the development, training and validation of predictive models and (3) begin the implementation and testing of the predictive model. As a result, a network of 10 monitoring stations was installed in the Aysén and Magallanes regions of Chile and 1 in the Province of Santa Cruz in Argentina, of which 6 are currently operational and transmitting data in real time. The rest went off due to power failures and icebergs damaging sensors. The measures we have taken to avoid station’s failures are described, as well as some characteristics of the implemented prototype, the installed networks and the data obtained so far.

Stages of formation of the plain part of the Bystrytsia-Pidbuzka valley

Based on a thorough morphological and morphometric analysis of the Bystrytsia-Pidbuzka terraces, the structure of their loose accumulations, and the correlation of the Bystrytsia-Pidbuzka terraces with the terraces of the Stryvihor and Dniester, the key features of the structure and stages of development of the river valley within the Precarpathian region have been reconstructed. It has been established that the history of the development of the plain section of the Bystrytsia-Pidbuzka valley comprised five main stages. At the first stage, which occurred during the Kryzhanivka climatolith (MIS 63‒46), the Starosilska denudation surface was formed. However, its formation is not associated with fluvial morpholithogenetic processes, because the Carpathian rivers of that time, like the Bystrytsia-Pidbuzka, did not penetrate the territory of the Precarpathian region. They discharged their waters to the north, into the pre-San, through a system of longitudinal valleys developed in the Carpathians. The second stage is associated with the exit of the Bystrytsia-Pidbuzka from the Carpathians to the Precarpathian region and the deployment of fluvial morpholithogenetic processes that formed the X Torganivtsi terrace. This event occurred during the Shyrokino time (MIS 38‒28). At the third stage, the IX Dubrovytsia terrace was dismembered and an erosional ledge to the VIII Susidivtsi terrace was formed, which led to the formation of the first morphological contours of the Bystrytsia-Pidbuzka valley in the Precarpathian region. The depth of the river valley at that time was 10‒15 meters. This process unfolded at the end of the Azovian Glacial (MIS 27‒22) through the beginning of the Martonian Interglacial period (MIS 21‒17). During the fourth stage, the VI Galician terrace was formed, with alluvial deposits characterized by a well-defined differentiation into “warm” and “cold” horizons. The accumulation of “warm” alluvium occurred in the Lubny climatolith (MIS 15‒13), and “cold” alluvium – in the Tiligulian climatolith (MIS 12). In Tiligulian times, the river valley served as one of the trunk lines for discharging meltwater to the south. The fifth stage is the most pronounced in the upper part of the river valley, developed above the village of Kotovane. Here, a complex of four floodplain terraces can be traced in the wide, flat bottom of the river valley: I terrace above the flood-plain, II Tustan terrace, III Kolodiivka terrace, and IV Yezupil terrace. The formation of this terrace complex began in the Kaydak period (MIS 7), during which the IV Yezupil terrace was formed, and continues to this day, with the first terrace above the flood-plain still being formed. Key words: Bystrytsia-Pidbuzka; Precarpathian area; Pleistocene; terraces; alluvium; glacial deposits; climatolithic; formationstages.

Three-dimensional interpretation of geophysical and geotechnical investigation of landslides

Effective engineering design of structures requires a thorough understanding of the groundwater conditions of the substrate. In some situations, a three-dimensional survey is necessary. Landslides are examples of such cases. They are complex phenomena, and the main factors significantly influencing their behaviour over time are changes in slope geometry, inclination and water conditions. The article discusses the reconnaissance of the substrate structure in an area threatened by mass movements along a modernized section of a railway line. The analysed area is located in the marginal zone of the North Polish glacial moraine. The geological structure of the substrate consists of: glacial tills, glaciofluvial sands, lacustrine clays, and organic soils found in periodically waterlogged areas and depressions in the terrain. Colluvial deposits, mainly consisting of clayey formations, occur on the slope of the escarpment. Surface geomorphology was interpreted using LIDAR data and field observations. Two-dimensional and three-dimensional electrical resistivity tomography (ERT) was used to obtain a detailed subsurface image, which was verified by borehole drilling and laboratory analysis of soil samples for physical properties, including grain size distribution and plasticity, as well as mechanical properties of soils. This research enabled the creation of a three-dimensional substrate model, showing the spatial distribution of colluvium and areas at risk of active landslides. The results indicate that an integrated approach, combining geophysical imaging and geotechnical reconnaissance, allows for a detailed understanding of the structure and lithology of landslide areas.

Chronology of Late Pleistocene glacial advances in a Mount Mercedario catchment, Subtropical Andes of Argentina (32° S)

ABSTRACTGlacial fluctuations leave distinct imprints on the landscapes of mountain environments, such as moraines and outwash terraces, that allow the reconstruction of past environmental changes. Unraveling the environmental history of the valleys of the Subtropical Andes of Argentina poses challenges due to the complex interplay of various surficial processes driven by both climatic and tectonic forces, which affects the preservation of glacial deposits. Consequently, there are few studies on past glaciations in this region compared to the rest of the Andes. This study focused on the lower section of the Blanco River Basin and the piedmont of the Frontal Cordillera in the south of San Juan Province, Argentina. A comprehensive geomorphological map of glacial landforms was created, along with sedimentological studies of outwash terraces. Additionally, numerical ages were obtained for both landforms using terrestrial cosmogenic nuclides for moraine boulders and luminescence dating for sandy layers in the outwash terraces. Our findings reveal at least two glacial advances since the Last Glacial Maximum (LGM), each associated with distinct outwash levels. The Río Blanco Advance occurred during the LGM, and the Laguna Advance is assigned to the late stages of the LGM, both with their corresponding outwash terraces. Additionally, the Amarillo Advance is believed to have occurred during the Holocene period and an older Marine Istope Stage 5 d named Guanaquito Advance. The provided data add valuable numerical information about glacial fluctuations since the LGM and also reveal the impact of glacial downwasting on piedmont landforms.

Chemical succession of naphthenic acid fraction compounds in reclamation landscape mesocosms established on centrifuged and co-mixed fluid fine tailings from the Athabasca oil sands

The Athabasca oil sands region of Alberta, Canada contains one of the world's largest unconventional petroleum deposits. There is concern about residual contaminants where tailings are integrated during reclamation and the related adverse effects this may have. Some of the primary toxic organic contaminants in oilsands tailings are naphthenic acid fraction compounds (NAFCs). To plan for successful reclamation, it is imperative to understand the behaviour and fate of tailings-derived NAFCs over time where these are re-integrated into landforms. In this companion article to Degenhardt et al. (2023), we examine different reclamation integration scenarios using oil sands process-affected materials (OSPMs) at laboratory scale using wetland plants and minimal amounts of caps to explore how cap materials and thickness will affect the of NAFCs in the systems. Specifically, we examine how capping materials and thicknesses affect NAFCs adsorbed to two treated fluid fine tailings, centrifuged (CF) and co-mixed (CM) tailings over three years. Both CF and CM were placed in columns capped with peat mineral mix (PMM) and/or glacial till and planted with graminoid or woody wetland plants. Both CF and CM had considerable NAFC concentrations (CF 3717 mg/kg, CM 321 mg/kg). The O2 NAFC class was >90 % of the total adsorbed to CF and CM throughout. Relatively thin PMM caps reduced NAFC burdens in CF columns, where 10 cm of PMM resulted in the greatest reduction. Expressed water from substrate self-weight consolidation had significantly lower NAFC concentrations when capping material was present. However, NAFC oxidation (i.e., O2 to O3, O3 to O4, etc.) was limited in capped CF and CM. These results indicate that capping CF and CM with a thin (5–10 cm) layer of PMM may help reduce NAFC concentrations and limit their mobility into the cap, potentially lowering plant mortality and improving tailings reclamation success rates.

Volcanically induced glacier collapses in southern Jan Mayen (Sør‐Jan), Norway

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.

New insights into one of the oldest glacial deposits in the northern Alpine foreland (Höchsten, SW Germany)

The present‐day landscape of the northern Alpine foreland is marked by the cumulated impact of weathering during interglacial, and of erosion and deposition during glacial periods of the Quaternary. Direct traces of the earliest phases of ice advance, as well as thorough studies thereof, exist only sporadically. Here, a succession of diamictic deposits, which has been interpreted as the infill of an Early Pleistocene overdeepened basin, is investigated with a combined sedimentological‐geotechnical approach including analysis via μCT scans, and standard tests of the water uptake, consistency, and compaction properties. The diamicts are exposed along a 4.5‐m‐deep profile, and are subdivided into a yellowish‐brown lower unit with a variable, carbonaceous, silty to sandy matrix, and a reddish‐brown upper unit that is free from carbonate and appears largely homogeneous. Although the lower unit is rather loose and surficially bioturbated, it contains microstructures indicative of subglacial deformation, which are lacking in the compact and clay‐rich upper unit. The lower part is interpreted as a secondary glacial deposit (i.e. it has been affected by limited sorting in water) that was overridden and sheared by a glacier briefly after deposition, and recently bioturbated. The upper part is less sorted, more massive and compact, and thus likely of a primary glacial nature. It is further characterized by a strong pedogenetic overprint typical of prolonged warm periods. This suggests that it is separated from the overlying glacifluvial gravel, which has an equivalent petrographic composition, by a full interglacial at least. Thus, the combination of geotechnical testing and CT‐based micromorphology offers a new, practical and cost‐effective approach to the characterization of glacially derived sediments.

Hematite U-Pb dating of Snowball Earth meltwater events

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.

Geomorphology and Sedimentology of a Rapidly Retreating Alpine Glacier: Insights From the Taschachferner, Tirol, Austria

The rapid retreat and fragmentation of Alpine glaciers is widely reported as humanity faces dramatic climate change in mountainous regions. This rapid change leads to changes in sedimentary processes, which are exposed in recently deglaciated regions. These Alpine glacier forefields offer a wide spectrum of settings through which the ancient sedimentary record can be interpreted. Glacial valley orientation, slope inclination and lithology, and plumbing of subglacial and englacial meltwater drainage all influence the immediate preservation potential of glacial sediments upon deposition. In this contribution, we explore the geomorphology and sedimentology of the Taschachferner (a valley glacier), presenting a new geological-geomorphological map. This small glacier drains an icefield in the Ötztal Alps, and its current ice margin lies at approximately 2550 m a.s.l. Thus far, the glacial sedimentology and its bedrock geology have not been subject to investigation. The bedrock geology is dominated by E-W striking units of paragneiss and amphibolite, and the latter exhibit a series of well-preserved striations together with meltwater-sculpted bedforms (p-forms). The lower region of the glacier can be divided into two parts: (i) a clean-ice part, on the northern valley side with a low, subdued profile and (ii) a debris-covered part at the southern valley side, covered with supraglacial debris. The valley margins are dominated by several generations of lateral moraines, the most prominent of which corresponds to the 1852 Little Ice Age Maximum. A well-developed “hanging sandur” is observed immediately in front of the ice margin. This consists of a series of sand and gravel bars cradled in the lee of an interpreted regional fault cross-cutting the bedrock. Sandur deposition is currently influenced and overprinted by dead ice, influencing the trajectory and location of river channels and gravel bars. This paper provides clear lessons regarding the distribution of ice-margin facies associations, which must be incorporated into models of glacier decay in the context of a rapidly warming climate.

Controls on regional sulphate distribution in shallow groundwater in the western Canadian Interior Plains

Sulphate (SO4), predominantly derived from sulphur (S)-bearing glacial sediments distributed widely across the Canadian Interior Plains, contributes to high groundwater salinity and can be detrimental to riparian and dry-land ecosystems, agricultural production, and water use. While previous researchers investigated SO4 distribution and dynamics in shallow groundwater at local scales (<1500 km2), we examine SO4 occurrence in groundwater at larger scales, and to depths of ∼150 m, considering variations in geology, glacial history, climate, and geochemical and hydrogeological settings in the Canadian province of Alberta. Sulphate concentrations in groundwater vary considerably, with 15 % of 139,130 samples above the 500 mg/L Canadian drinking water aesthetic objective. Analysis of δ34SSO4 and δ18OSO4 from 179 wells throughout Alberta shows SO4 is dominantly derived from oxidation of S-bearing material. At this large scale, marine shale bedrock subcrops, glacial ice flow directions, and climate control SO4 distribution. Groundwater contains less SO4 (<200 mg/L) in western Alberta compared to the east due to a lack of S-bearing bedrock, higher groundwater recharge rates, thinner glacial sediments, and increased groundwater circulation. Focusing on a region in south-central Alberta (Red Deer area), hydrogeological characteristics relating to SO4 formation, recharge, permeability, hydraulic gradient, and travel time are included in a principal component analysis to identify six groundwater groups at varying stages of evolution and SO4 concentrations depending on their hydrogeological setting. Low SO4 concentrations are associated with areas of high recharge, where SO4 has been leached from the sediments, or with more evolved bedrock groundwater where SO4 has been reduced or was recharged in pre-glacial times. High SO4 concentrations are found in areas of lower recharge and permeability, where flushing occurs more slowly. Combining the Red Deer area and province-wide analyses, we identify seven regions across Alberta with characteristic distribution and controls on SO4 occurrence in shallow groundwater.

Uranium-series isotopes as tracers of physical and chemical weathering in glacial sediments from Taylor Valley, Antarctica

The McMurdo Dry Valleys of Antarctica formed by extensive glacial erosion, yet currently exhibit hyperarid polar conditions canonically associated with limited chemical and physical weathering. Efficient chemical weathering occurs when moisture is available, and polythermal subglacial conditions may accommodate ongoing mechanical weathering and valley incision. Taylor Valley, one of the MDV, hosts several Pleistocene glacial drift deposits that record prior expansions of Taylor Glacier and sediment redistribution, if not sediment production. We present U-series isotopics of fine-grained sediments from these drifts to assess the timescales of physical weathering and subsequent chemical alteration. The isotopes 238U, 234U, and 230Th are sensitive to both chemical and physical fractionation processes in sedimentary systems, including the physical fractionation of daughter isotopes by energetic recoil following radioactive decay. By comparing U-series isotopic measurements with models of U-series response to chemical weathering and physical fractionation processes, we show that Pleistocene drift sediments record histories of significant chemical alteration. However, fine-grained sediments entrained in the basal ice of Taylor Glacier record only minor chemical alteration and U-series fractionation, indicating comparatively recent sediment comminution and active incision of upper Taylor Valley by Taylor Glacier over the Pleistocene. In addition, the results of this study emphasize the utility of U-series isotopes as tracers of chemical and physical weathering in sedimentary and pedogenic systems, with particular sensitivity to radionuclide implantation by α-recoil from high-U authigenic phases into lower-U detrital phases. This process has occurred extensively in >200 ka drifts but to a lesser degree in younger deposits. U-series α-recoil implantation is an important physicochemical process with chronometric implications in other hyperarid and saline sedimentary systems, including analogous Martian environments.

Proglacial sediments in High Arctic glacier foreland: A case study of Werenskioldbreen, Svalbard

The glacier environment exhibits a high sensitivity to global climate change, leading to progressive deglaciation and the exposure of previously ice-covered land. The newly exposed terrain provides a valuable opportunity to observe rapid ecosystem changes, such as the accumulation of glacial sediments, the development of soil-forming and progressive alterations in water and biogeochemical cycles. While developing hydrological and hydrogeological models for the Werenskioldbreen proglacial expanding zone, we encountered a significant problem due to insufficient data for parameterizing glacial sediments, which constitute the environment for water flow and storage. This study provides detailed insight into the physicochemical parameters of glacial sediments and classifies them in terms of grain size distribution, hydraulic conductivity, pH and the content of carbon (Corg), nitrogen (Nt) and phosphorus (Pt). We found that the marginal outwash plains of Werenskioldbreen are characterised by gravelly sand, sandy gravel and silty sand (28.6%, 23.8% and 19% of the total sample contents, respectively). The lateral moraine contains sandy clayey silt, silty sandy gravel or sandy gravelly silt (7.1%, 4.8% and 2.4 % of the total sample contents, respectively). The chemical parameters of young glaciofluvial sediments have lower values than those of moraines. Corg ranged from 0.07% to 2.70%. Nt was &amp;lt; 1.00 g kg−1 for 95% of the samples and &amp;lt; 0.5 g kg−1 for 81% of them. Pt was between 0.48 and 1.18 g kg−1. In line with the studies on this subject already published, we confirm that there is clear a relationship between the type of geomorphological form, its age, and the physicochemical parameters of glacial sediments.

Deglaciation in the subtropical Andes has led to a peak in sediment delivery

Glaciers are thinning and retreating as climate warms, thus eroding less of the Earth’s surface. However, other hydrological factors in glacierized catchments are likely producing a transient increase in sediment delivery, resulting in ‘peak sediment’. Estimating the trajectory of the peak sediment is ecologically and socially important but scientifically challenging because of the delayed and non-linear response of glacier sediment export to climate forcing. This study used time series of suspended sediment concentration starting in the 1960s from 11 Andean rivers at subtropical latitudes to analyse past changes in sediment export and infer its future behaviour. The recent decade has experienced anomalously high sediment concentration in most glacierized catchments, but the 1970s experienced even higher values. Decadal variations in the relationship between sediment concentration and ice melt suggest that the magnitude of the current decade was lower due to reduced glacial sediment rather than other factors. Combining this result with the fact that glacial runoff is decreasing, it is inferred that, for most of the glacierized catchments, the peak sediment generated by the anthropogenic deglaciation started two centuries ago has already passed its maximum.

Rb-Sr isochron method of sediment source fingerprinting reveals a fundamental shift in erosion in response to anthropogenic land use

Human alterations to landscapes can greatly influence watershed-scale sedimentary processes; therefore, in this study, we test the viability of a novel Rb-Sr isotope and elemental geochemical method for fingerprinting the impacts of human land use on sediment provenance. We analyzed a ∼1200-year sediment core record from Little Kennebago Lake, Maine, USA, that captures negligible anthropogenic activity pre-1900 CE, timber transport downstream during log drives (1900−1952 CE), and increased road construction and timber harvest (1952−2018 CE). 87Sr/86Sr data alone reveal several spikes, likely due to storm events, and variability but no systematic shift at the onset of logging. The pre-logging record Rb-Sr isotope data comprise an isochron corresponding to an age of 354 ± 16 Ma (two standard errors [2SE]; mean square of weighted deviates [MSWD] = 2.1, n = 33). None of the bedrock or glacial till sources that we analyzed fall along the pre-logging isochron, nor did any binary or ternary bulk rock mixtures. However, the linearity of all pre-logging samples and coincidence of the isochron age with Acadian metamorphism in the region suggests that sediment was derived from a single source in the undisturbed watershed, though that exact bedrock or glacial till source remains unclear. The onset of logging coincides with a shift toward generally lower sediment Rb-Sr isotope ratios that are offset from the pre-logging isochron. This logging data forms a scattered pseudo-isochron with an apparent Carboniferous age of 322 ± 32 Ma (2SE; MSWD = 4.5, n = 10). No rocks of this age exist in the region. Therefore, we interpret this age to have no geologic meaning and instead reflect the introduction of new sediment sources due to logging. Logging also coincides with subtle changes in elemental geochemistry. The Big Island Pond Pluton underlies most of the northern part of the watershed and is the only catchment lithology capable of producing each geochemical change; therefore, we conclude that it was the primary new source of sediment introduced by logging. We found little variation in sediment geochemistry between the period of early log drives and later road expansion, suggesting that sediment provenance was constant once altered by the initial onset of logging, which could reflect the same source being tapped by activities in each period. We established a framework for interpreting bulk sediment Rb-Sr isotope ratios and demonstrated their viability for identifying shifts in human impacts on geomorphic processes. Our findings suggest that relative changes in sediment Rb-Sr isotope ratios are a promising tool for investigating changes to sedimentary processes not identifiable by other commonly used fingerprints and that the method should be further tested in a range of other natural and anthropogenic settings globally.

Constraining the origin of the Norwegian strandflat – The influence of isostatic and dynamic surface changes

The Norwegian strandflat is a prominent low-relief bedrock surface found near sea level along most of the west coast of Norway. Its origin has been discussed throughout the last 130 years but is yet to be resolved. Some studies suggest that the strandflat represent a tropical weathering front of Mesozoic age that has since been buried and re-exhumed, while others relate its origin to Pleistocene periglacial and glacial processes and/or wave-induced weathering and erosion. Previous interpretations of the strandflat have considered postglacial isostatic uplift, but the impacts of isostatic changes due to glacial erosion and deposition, as well as dynamic surface changes driven by mantle convection, have been largely overlooked. Here we examine how geomorphological-driven isostatic changes and dynamic surface changes have influenced the land-surface elevation along the Norwegian coast during late Pliocene-Quaternary (the last ca. 3 million years). We employ quantitative estimates of glacial erosion and deposition to assess the flexural isostatic response from the resulting load changes. Our analyses show that patterns of geomorphic isostatic adjustments and dynamic surface changes are generally not reflected in the present elevation of the strandflat. Only the loading effect from the deposition of the North Sea Fan can clearly be correlated with the submerged strandflat found near Stad (∼62 °N). Our results imply that if the strandflat formed synchronously along the Norwegian coast as a flat surface at sea level, the strandflat we observe today must have developed after the majority of late Pliocene-Quaternary glacial erosion took place, but prior to the main deposition of the North Sea Fan. This would place strandflat formation within the last few glacial cycles, but before the Last Glacial Maximum (LGM). This inferred pre-LGM age of the strandflat is generally consistent with cosmogenic nuclide exposure ages and observed striations on the strandflat. Finally, we examine ice cover and land-surface changes relative to sea level during the last 80,000 years and find no extended periods favorable for synchronous strandflat formation across all regions along the Norwegian coast. This implies that either the strandflat is diachronous, or that the processes of formation have either been extremely fast under certain conditions or are independent of sea level, for instance related to glacial erosion.

Quantifying Pleistocene loess provenance in midcontinental North America using a mixing model: Implications for glacial lobe evolution along the southern Laurentide ice sheet

Abstract Quaternary glaciations have significantly impacted the midcontinental North American landscape, leaving behind a proglacial sediment record of glacial lake deposits, glacio-fluvial sand and gravel, and windblown loess. This paper aims to expand upon a previous study using detrital zircon provenance analysis to investigate midcontinental North American loess provenance in relation to the glacial history of the southern Laurentide ice sheet during the middle to late Pleistocene. The study incorporates previously published detrital zircon data from last glacial tills (representing the Huron-Erie Lobe, Lake Michigan Lobe, Green Bay Lobe, Superior Lobe, Des Moines Lobe, and James Lobe), middle to late Pleistocene loess from several sites along the Illinois and Mississippi River valleys, and suspended sediment load inputs from the Missouri River and Arkansas River. A statistical mixing model (DzMix version 2.2) was used to estimate the relative proportions of glacial and nonglacial sources to Wisconsin Episode, Illinois Episode, and pre–Illinois Episode age loess. We show that mixing models that include the modern suspended sediment loads of the Missouri and Arkansas Rivers significantly improve (up to 23% increase in cross-correlation value) the source characterization of Wisconsin Episode (last glacial) and Illinois Episode (penultimate glacial) loess deposits within the Mississippi River drainage basin. These river sources are dominant inputs for certain loess sites (as much as 51%), but their relative contributions are not static across time and space, which has implications for temporal and spatial differences in relative sediment source estimates and glacial and fluvial sediment transport evolution. Specifically, differences in relative sediment proportion estimates among Wisconsin, Illinois, and pre–Illinois Episode loess support previous evidence for the persistence of a Quebec-Labrador ice dome source through multiple glacial cycles, even with the inclusion of river sources in updated mixing models. Illinois and pre–Illinois Episode loess in the southern portion of our study area received ~20% detrital zircon input from sources similar to the present-day Missouri and Arkansas Rivers, suggesting that these river systems were contributing a significant amount of detritus to the lower Mississippi River valley region during the middle Pleistocene.

Geochronology and ice‐flow modelling of the Late Quaternary glaciers on Mt. Soğanlı, Türkiye

ABSTRACTUnderstanding Earth's climate history through the chronology and reconstruction of palaeoglaciers is a central topic of palaeoclimatology. Examining the remnants of past glaciations preserved in isolated alpine environments provides insight into critical palaeoclimatic conditions. Accurate dating techniques, such as terrestrial cosmogenic nuclides, are crucial for understanding the timing of these changes. The Anatolian Peninsula, characterized by diverse topographical and climatic factors, witnessed the presence of glaciers during the Late Pleistocene, shaping its alpine landscape significantly. While mountain ranges such as the Taurus and Pontic favoured glacier development due to their elevation and lower temperatures, isolated mountains such as Mount Soğanlı in the interior hinterland also supported significant palaeoglaciers. Despite previous studies on Anatolia's glaciers, numerical dating of glacial deposits on Mount Soğanlı has remained elusive until now, hindering precise palaeoclimatic interpretations. This study employs cosmogenic 36Cl surface exposure dating and physical‐based ice‐flow modelling using an open‐source framework, Parallel Ice Sheet Model (PISM), to determine the timing of glaciations and to reconstruct past glacier extents on Mount Soğanlı. The results reveal glacier retreat ages of 48.3 ± 13.4 and 18.3 ± 4.4 ka based on two well‐preserved moraines. Additionally, palaeoclimate simulations matched with the field observations indicate considerably colder conditions (6.65–8.15°C colder than today) necessary to sustain glaciers on Mount Soğanlı, when precipitation amounts were the same as today. These findings contribute to a better understanding of Anatolia's palaeoclimatic fluctuations and align with similar studies in neighbouring regions, enhancing our knowledge of past climate dynamics of the Eastern Mediterranean and the Middle East.