Geosciences

Glacial geology, marine environment, and arid climate govern the composition of clay tills. The main purpose of this work is to develop a clear understanding of the engineering behavior of compacted clay till under soil suction and applied stress. The results indicate moderate water adsorption due to the presence of clay minerals (26% corrensite, 10% illite, and 8% kaolinite) with Ca²⁺ as the dominant cation and a flocculated fabric in a slightly basic (pH = 7.5) pore water. The water retention curve comprised four transition points that are associated with capillary water drainage from large pores (air entry value of 2 kPa and residual suction value of 20 kPa) and small pores (air entry value of 700 kPa and residual suction value of 5 × 10⁴ kPa). Beyond the last value, vapor flow is dominant and removes the adsorbed water by evaporation. The ratio of soil volume change to water volume change best described the s-shaped shrinkage path that also comprised four stages, namely: from most large pores with low volume change; from remaining large and most small pores along with almost equal volume change; from some small pores with low volume change; and from the rest of the small pores with no volume change. Likewise, the s-shaped swelling potential curve comprised three stages and correlated well with bimodal hydraulic conductivity curve, that is, slow initial swelling (unsaturated hydraulic conductivity around 10⁻¹⁴ m/s) due to expansion of peripheral clay in lumps; high primary swelling (unsaturated hydraulic conductivity of up to 10⁻¹¹ m/s) due to thickened double layer of most colloids; and slow secondary swelling (albeit unsaturated hydraulic conductivity around 10⁻¹⁰ m/s) due to expansion of remaining particles. Soil compression (compression index of 0.164) was due to a gradual reduction in number of large pores, whereas rebound (swelling index of 0.047) was due to water adsorption on clay with part of the deformations recovered. Finally, the consolidation rate was related to saturated hydraulic conductivity, which varied by three orders of magnitude. Full article

Sabellaria species are among the most important frame-builders in temperate, shallow marine areas. These polychaetes are suspension feeders able to build bioconstructions using sand and shell fragments cemented with a sticky mucous. Such feature makes these invertebrates “unusual bioconstructors”, as they do not produce calcium carbonate. Sabellaridae reefs are widespread in the Mediterranean and along the Atlantic coast of Europe, but their sedimentological aspects are still poorly known. Over short time intervals, these bioconstructions can rapidly alternate between phases of growth, stasis and destruction during different seasons. In this paper, we compare reefs of two Sabellaria species (S. alveolata—Ostia, Roma and Tyrrhenian Sea; S. spinulosa—Torre Mileto, Foggia and Adriatic Sea) found at two different sites along the Italian coast. We describe the morphology of worm tubes at the macro- and microscale. Similarities and differences are discussed based on eco-biological features and physical environmental conditions. This work shows a measurement and observation scheme for this type of bioconstructions that has been verified at both the macro- and microscale and which was shown to be useful for defining evolutionary trends of sabellarian bioconstructions. The monitoring parameters were identified and verified over a long period. Full article

Landslide susceptibility studies are a common type of landslide assessment. Landslides are one of the most frequent hazards in Brazil, resulting in significant economic and social losses (e.g., deaths, injuries, and property destruction). This paper presents a literature review of susceptibility mapping studies in Brazil and analyzes the methods and input data commonly used. The publications used in this analysis were extracted from the Web of Science platform. We considered the following aspects: location of study areas, year and where the study was published, methods, thematic variables, source of the landslide inventory, and validation methods. The susceptibility studies are concentrated in Brazil’s south and southeast region, with the number of publications increasing since 2015. The methods commonly used are slope stability and statistical models. Validation was performed based on receiver operating characteristic (ROC) curves and area under the curve (AUC). Even though landslide inventories constitute the most critical input data for susceptibility mapping, the criteria used for the creation of landslide inventories are not evident in most cases. The included studies apply various validation techniques, but evaluations with potential users and information on the practical applicability of the results are largely missing. Full article

Climate-related geohazards, such as landslides, floods, and coastal erosion due to climate change, are increasingly impacting human settlements and activities. This study, part of the European Project RESPONSe (Interreg Italy−Croatia), investigates the perception of climate change as a catalyst of future geohazards among the citizens of the Veneto region (northeastern Italy). A total of 1233 questionnaires were completed by adult citizens and analyzed by means of inferential statistics. The results highlight a widespread perception of climate change as a general threat for the environment, but not directly transposed to the frequency and intensity of future geohazards. Certainly, changes in temperatures and rainfall are widely expected and acknowledged, yet the comprehension related to the hydrogeological effects seems to vary proportionally to the physical proximity to these hazards. Such outcomes underline that there is still a common lack of understanding of the eventual local impact of the climate crisis. For these reasons, it is suggested that decision makers consider directing their efforts to enhance the citizens’ knowledge base in order to build a climate-resilient society. Full article

Big Harris Creek, North Carolina, possesses a geomorphic history similar to many drainages in the southern Appalachian piedmont, and was used herein as a representative example of the influence of European settlement on contemporary channel form and processes. The integrated use of historical, dendrogeomorphic, stratigraphic, and cartographic data shows that the conversion of land-cover from a mix of natural conditions and small farms to commercial cotton production in the late 1800s and early 1900s led to significant upland soil erosion, gully formation, and the deposition of legacy sediments on the valley floor. Aggradation was followed by catchment-wide channel incision in the mid-1900s in response to reforestation and the implementation of soil conservation measures. Collectively, the responses form an aggradational-degradational episode (ADE) that produced the geomorphic framework for the contemporary processes operating along the drainage network. Defined, characterized, and mapped process zones (stream reaches of similar form and process) show that the type, intensity, and evolutionary sequence of geomorphic responses varied within the catchment as a function of the position along the drainage network, the erosional resistance of the underlying bedrock, and the valley characteristics (particularly width). Understanding the spatially variable influences of the ADE on contemporary, reach-scale geomorphic processes provides valuable insights for restoration as it helps inform practitioners of the sensitivity and ways in which the reach is likely to respond to future disturbances, the potential impacts of processes on proposed manipulations intended to achieve the project’s restoration goals, and the potential risk(s) involved with channel reconstruction. The latter is strongly controlled by geotechnical differences between erosionally resistant precolonial deposits and easily eroded legacy sediments that locally form the channel banks following the ADE. Full article

Rarely, a close correlation between wildfires and the occurrence of channelized debris flows has been observed in the Western Italian Alps. Only two cases in history have been reported, after brief and localized rainfall events of moderate intensity in Italy’s Piemonte region (NW Italy) caused debris flows, on 18 July 2005, in Verbania province (Pallanzeno municipality), and on June 2018 in Turin province (Bussoleno municipality). These phenomena occurred after a large portion of the catchments were affected by wide wildfires in the preceding months. Debris flow deposits showed an unusually large number of fine-grained particles, forming dark-brown mud-rich deposits associated with burnt wood deposits. Rainfall analysis related to the period between the wildfires’ occurrence and the debris flow events, using both raingauge and weather radar data, pointed out that the debris flows triggered in July 2005 and June 2018 were characterized by greater magnitude but associated with less precipitation intensity rates as compared with previous mud flows occurring just after wildfires. These behaviors can be explained by the presence of burned organic material and fine-grained sediment, generated from the soil’s thermal reworking, which formed a thick layer, centimeters deep, covering a large percentage of catchments and slopes. Most of this layer, generated by wildfires’ action were winnowed by rainfall events that had occurred in the months before the debris flow events, of significant magnitude, exhuming a discontinuous hydrophobic soil surface that changed the slopes’ permeability characteristics. In such conditions, runoff increased, corrivation time shortened, and, consequently, discharge along the two catchments’ channels-network increased as well. Consequently, the rainfall effects associated with rainfall events in July 2005 and June 2019 were more effective in mobilizing coarse sediments in channel beds than was typical for those catchments. Full article

Road subsidence and sinkhole failures due to shallow cavities formed by defective water main have increased in recent decades and become one of the important research topics in geotechnical engineering. The present paper numerically studies the stability and its associated failure mechanism of ellipse-shaped cavity above defective water mains using the finite element limit analysis technique. For a wide range of geometrical parameters, the pressure ratio method is used to formulate the stability solutions in both blowout and collapse scenarios. Even though there is no published solution for elliptical cavities under blowout failure conditions, the obtained numerical results are compared with available circular solutions. Several conclusions are drawn based on the failure mechanism study of the various ellipse shape transformations in this study, whilst design charts and equations proposed for practical uses. Full article

Tidal flood risk threatens coastal urban areas and their agriculture and aquaculture, including salt farming. There is, therefore, an urgency to map and portray risk to reduce casualties and loss. In the floodplain of Cirebon, West Java, where salt farming dominates the landscape, this type of flooding has frequently occurred and disrupted the local economy. Based on two recorded events in 2016 and 2018 as benchmarks, this paper formulates an innovative approach to analyze tidal flood risk in salt farming areas. Our study considers the fundamental concepts of hazard and vulnerability, then uses selective parameters for evaluation in an Analytical Hierarchical Process (AHP)-based Geographic Information System. The analytical process includes weighting criteria judged by experts and uses the resulting values to define the spatial characteristics of each salt parcel. Our high-resolution simulations show that the two flood events in 2016 and 2018 affected almost all salt production areas, particularly in the eastern, middle, and western parts of the Cirebon floodplain, although to very different degrees. The study also uses a physical-based approach to validate these results. The damage estimates show a strong positive correlation for economic loss (r = 0.81, r = 0.84). Finally, the study suggests that our multi-methods approach to assessing tidal flood risk should be considered in disaster mitigation planning and integrated coastal zone management in salt farming areas. Full article

Oxygen isotopes are widely used in palaeoenvironmental and palaeoclimatic studies as they record variations in the precipitation temperature of biogenic carbonates and phosphates. Problems associated with the preservation state of fossils, selection of the proper temperature equation, vital effects occurring during biomineralization, habitat effects of organisms as well as salinity, bathymetry and water circulation changes limit, however, the applicability of oxygen isotopes to reconstruction of ancient environmental settings. The progress of oxygen isotope studies, temperature calculations and ambiguities of the isotope record are discussed in this paper. The same applies to the methods of retrieving reliable temperature signals and the record of water chemistry changes based on well-preserved calcareous and phosphatic fossils. Sometimes neglected importance of sedimentological and faunistic data associated with sea-level changes and salinity variations is emphasised as an important tool for refinement of the temperature trends of epeiric sedimentary basins. In addition, published case datasets and new laboratory techniques, including micro-area and clumped isotope analyses, are presented to demonstrate examples and prospective ways of extension of the scope of palaeoenvironmental research. The provided information may be used in discussion and a critical review of published oxygen isotope data and their palaeoenvironmental interpretations. Full article

During the past 25 ka, southern Ethiopia has undergone tremendous climatic changes, from dry and relatively cold during the Last Glacial Maximum (LGM, 25–18 ka) to the African Humid Period (AHP, 15–5 ka), and back to present-day dry conditions. As a contribution to better understand the effects of climate change on vegetation and lakes, we here present a new Predictive Vegetation Model that is linked with a Lake Balance Model and available vegetation-proxy records from southern Ethiopia including a new phytolith record from the Chew Bahir basin. We constructed a detailed paleo-landcover map of southern Ethiopia during the LGM, AHP (with and without influence of the Congo Air Boundary) and the modern-day potential natural landcover. Compared to today, we observe a 15–20% reduction in moisture availability during the LGM with widespread open landscapes and only few remaining forest refugia. We identify 25–40% increased moisture availability during the AHP with prevailing forests in the mid-altitudes and indications that modern anthropogenic landcover change has affected the water balance. In comparison with existing archaeological records, we find that human occupations tend to correspond with open landscapes during the late Pleistocene and Holocene in southern Ethiopia. Full article

As a result of mountain permafrost creep, rock glaciers are common features in high-altitude periglacial areas. From a practical point of view, beyond their localization and inventorying, both the monitoring and prediction of their evolution due to climate changes are crucial. One of the effects of climate change is the thickening of the basal shear zone (the portion of the rock glacier where most deformations are localized), eventually leading to the development of unexpected and unprecedented (in terms of location, magnitude, frequency, and timing) instability phenomena. These phenomena bear consequences for the understanding of landscape evolution, natural hazards, and the safe and sustainable operation of high-mountain infrastructures. Most of the studies about active rock glaciers are focused on the analysis of monitoring data, while just a few studies are focused on modeling their behavior to understand their possible further evolution. The active rock glacier response is characterized by a viscous (rate-dependent) behavior, influenced by seasonal temperature oscillations, and characterized by a seasonal transition from slow to fast. In this work, a new thermo-mechanical model based on the delayed plasticity theory and calibrated on experimental results is proposed. The model is employed to evaluate the influence of geometry and forcing (air temperature) on a real rock glacier (Murtèl-Corvatsch rock glacier) creep behavior. Full article

A first-order seismic characterization of Northern Apulia (Southern Italy) has been provided by considering geological information and outcomes of a low-cost geophysical survey. In particular, 403 single-station ambient vibration measurements (HVSR techniques) distributed within the main settlements of the area have been considered to extract representative patterns deduced by Principal Component Analysis. The joint interpretation of these pieces of information allows the identification of three main domains (Gargano Promontory, Bradanic Through and Southern Apennines Fold and Thrust Belt), each characterized by specific seismic resonance phenomena. In particular, the Bradanic Through is homogeneously characterized by low frequency (<1 Hz) resonance effects associated with relatively deep (>100 m) seismic impedance, which is contrasting corresponding to the buried Apulian carbonate platform and/or sandy horizons located within the Plio-Pleistocene deposits. In the remaining ones, relatively high frequency (>1 Hz) resonance phenomena are ubiquitous due to the presence of shallower impedance contrasts (<100 m), which do not always correspond to the top of the geological bedrock. These general indications may be useful for a preliminary regional characterization of seismic response in the study area, which can be helpful for an effective planning of more detailed studies targeted to engineering purposes. Full article

Geological contexts that lack minimal stratigraphic and piezometric information can be challenging to produce an initial hydrogeological map in remote territories. This study proposes an approach to characterize a regional aquifer using transient electromagnetic (TEM) surveys. Given the presence of randomly dispersed boreholes, the Saint-Narcisse moraine in the Mauricie region of Quebec (Canada) is an appropriate site for collecting the required geophysical data, correlating the stratigraphic and piezometric information, and characterizing regional granular aquifers in terms of stratigraphy, geometry, thickness, and extent. In order to use all TEM results (i.e., 47 stations) acquired in the moraine area, we also correlated 13 TEM stations, 7 boreholes, and 6 stratigraphic cross-sections to derive an empirical and local petrophysical relationship and to establish a calibration chart of the sediments. Our TEM data, combined with piezometric mapping and the sedimentary records from boreholes and stratigraphic cross-sections, revealed the compartmentalization of a multi-kilometer morainic system and indicated the presence of two large unconfined granular aquifers overlying the bedrock. These aquifers extend more than 12 km east to west across the study area and are between 25 and >94 m thick. The TEM method provides critical information on groundwater at a regional scale by acquiring information from multiple stations within a short time span to a degree not possible with other existing methodologies. Full article

The Serre Batholith in Central Calabria (southern Italy) represents the intermediate portion of a continuous cross-section of late Variscan continental crust. The various granitoid units of the batholith were emplaced at depths between 23 and 6 km through an overaccretion mechanism that, at its upper levels, was marked by the emplacement of two-mica granodiorites and granites (MBG) at c. 295 Ma, followed by weakly peraluminous granodiorites (BAG) at c. 292 Ma. These upper crustal granitoid rocks have recorded tectonic stresses, which affected the batholith during cooling of the magmatic bodies, exhibiting a range of deformation microstructures from submagmatic to low-temperature subsolidus conditions, but without developing an evident meso/micro-structural fabric. Anisotropy of magnetic susceptibility (AMS) was employed to identify a possible “internal” fabric of the Serre upper crustal granitoids, revealing a magnetic foliation represented by a mainly oblate AMS ellipsoid. Magnetic foliations and lineations are consistent with a stress field characterized by a shortening axis roughly oriented NW–SE. Further studies are in progress to investigate more in depth the relationships between regional tectonic structures and the emplacement of the late-Variscan Serre Batholith granitoids. Full article

El Sidrón Cave is an archaeological and anthropological reference site of the Neanderthal world. It shows singular activity related to cannibalisation, and all existing processes are relevant to explain the specific behaviour of the concerned individuals. This paper presents geoarchaeological data, primarily based on mineralogical and petrographic techniques, from an investigation of the nature of the encrustations or hard coatings that affect a large part of the Neanderthal bone remains and their relationship with the depositional and post-depositional processes at the archaeological site. Crusts and patina were found to be numerous and diverse, mainly composed of calcite and siliciclastic grains, with different proportions and textures. The analysis indicated different origins and scenarios from their initial post-mortem accumulation to the final deposit recovered during the archaeological work. The presence of micromorphological features, such as clotted-peloidal micrite, needle-fibre calcite (NFC) aggregates, clay coatings, iron–manganese impregnation, and/or adhered aeolian dust may indicate that a significant proportion of the remains were affected by subaerial conditions in a relatively short period of time in a shelter, cave entrance, or shallower level of the karstic system, prior to their accumulation in the Ossuary Gallery. Full article

Surface topography results from complex couplings and feedbacks between tectonics and surface processes. We combine analog and numerical modeling, sharing similar geometry and boundary conditions, to assess the topographic evolution of an alluvial fan crossed by an active thrust fault. This joint approach allows the calibration of critical parameters constraining the river deposition–incision laws, such as the settling velocity of suspended sediments, the bed-rock erodibility, or the slope exponent. Comparing analog and numerical models reveals a slope-dependent threshold process, where a critical slope of ca. 0.081 controls the temporal evolution of the drainage network. We only evidence minor topographic differences between stable and stick-slip fault behavior localized along the fault scarp. Although this topographic signature may increase with the slip rate and the return period of slip events, it remains slight compared to the cumulated displacement along the fault scarp. Our results demonstrate that the study of morphology cannot be used alone to study the slip mode of active faults but can be a valuable tool complementing stratigraphic and geodetic observations. In contrast, we underline the significant signature of the distance between the fault and the sediment source, which controls the degree of channels incision and the density of the drainage network. Full article

Moine metasedimentary rocks of northern Scotland are characterized by arcuate map patterns of mineral lineations that swing progressively clockwise from orogen-perpendicular E-trending lineations in greenschist facies mylonites above the Moine thrust on the foreland edge of the Caledonian Orogen, to S-trending lineations at higher structural levels and metamorphic grades in the hinterland. Quartz c-axis fabrics measured on a west to east coast transect demonstrate that the lineations developed parallel to the maximum principal extension direction and therefore track the local tectonic transport direction. Microstructures and c-axis fabrics document a progressive change from top to the N shearing in the hinterland to top to the W shearing on the foreland edge. Field relationships indicate that the domain of top to the N shearing was at least 55 km wide before later horizontal shortening on km-scale W-vergent folds that detach on the underlying Moine thrust. Previously published data from the Moine thrust mylonites demonstrate that top to the W shearing had largely ceased by 430 Ma, while preliminary isotopic age data suggest top to the N shearing occurred at ~470–450 Ma. In addition, data from the east coast end of our transect indicate normal-sense top down-SE shearing at close to peak temperatures at ~420 Ma that may be related to the closing stages of Scandian deformation, metamorphism and cooling/exhumation. Full article

The objective of this study is to assess the suitability of the analytical infinite moving line source (MLS) model in determining the temperature of vertical grouted borehole heat exchangers (BHEs) for steady-state conditions when horizontal groundwater advection is present. Therefore, a numerical model of a grouted borehole is used as a virtual reality for further analysis. As a result of the first analysis, it has been discovered that established analytical methods to determine the borehole thermal resistance as a mean value over the borehole radius can also be applied to BHEs with groundwater advection. Furthermore, the deviation between a finite MLS and the infinite MLS is found to be only less than 5% for BHEs of a depth of 30 m or more, and Péclet numbers greater than 0.05. Finally, the accuracy of the temperature change calculated with the infinite MLS model at the radius of the borehole wall compared to the temperature change at a numerically simulated grouted borehole is addressed. A discrepancy of the g-functions resulting in a poor dimensioning of BHEs by the infinite MLS model is revealed, which is ascribed to the impermeable grouting material of the numerical model. A correction function has been developed and applied to the infinite MLS model for steady-state conditions to overcome this discrepancy and to avoid poor dimensioning of BHEs. Full article

Since its existence, paleoceanography has relied on fossilized populations of planktonic foraminifera. Except for some extreme environments, this calcareous protist group composes most of the silty-to-sandy fraction of the marine sediments, i.e., the foraminiferal oozes, and its extraction is probably the simplest among the currently existing set of marine fossil proxies. This tool has provided significant insights in the building of knowledge on past climates based on marine archives, especially with the quantification of past hydrographical variables, which have been a turning point for major comprehensive studies and a step towards the essential junction of modelling and paleodata . In this article, using the modern analog technique and a database compiling modern analogs (n = 1007), we test the reliability of this proxy in reconstructing paleohydrographical data other than the classical sea-surface temperatures, taking advantage of an update regarding a set of extractions from the World Ocean Atlas for transfer functions. Our study focuses on the last glacial period and its high climatic variability, using a set of cores distributed along the European margin, from temperate to subpolar sites. We discuss the significance of the reconstructed parameters regarding abrupt and extreme climate events, such as the well-known Heinrich events. We tested the robustness of the newly obtained paleodata by comparing them with older published reconstructions, especially those based on the complementary dinoflagellate cyst proxy. This study shows that the potential of planktonic foraminifera permits going further in reconstructions, with a good degree of confidence; however, this implies considering ecological forcings in a more holistic perspective, with the corollary to integrate the message of this fossil protist group, i.e., the obtained parameters, in light of a cohort of other data. This article constitutes a first step in this direction. Full article