Massive Limestone Research Articles

Chromatic evolution, chemical changes, and biological colonisation in the quarry fronts of the Santullán limestone massif (Cantabria, Spain): implication for the mitigation of visual impact in mountain quarrying

The visual impact of the chromatic contrast between quarry faces and rocky outcrops represents one of the prominent disturbances to natural environments. This study, therefore, aims to quantify color changes over time in quarries by analyzing three faces of an active limestone quarry in Santullán, Cantabria, that were exposed to atmospheric conditions in 1978, 2003 and 2021. To achieve this, the contribution of biological colonisation to natural darkening, along with the physicochemical changes occurring on the quarry faces, have been evaluated using scanning electron microscopy in secondary and backscattered electron mode, UV–Vis spectrophotometric techniques, Raman spectroscopy and XRD and XRF analysis. The analysis revealed that the color change was primarily due to microbial colonisation rather than oxidative chemical reactions. Although color change does not follow a direct and progressive relationship with exposure time, biological colonisation, identified primarily as microbial communities dominated by phototrophic microorganisms, shows a clear increase in microbial presence, bioalteration, and penetration into the rock substrate in older samples. The most significant visual changes appear to occur during the first years of exposure of the massif to atmospheric conditions.

Shear wave velocity profiling of Riyadh City, Saudi Arabia, utilizing the multi-channel analysis of surface waves method

Abstract Geotechnical site characterization is very important for construction purposes. This study has been conducted in Diriyah area northwest of Riyadh City, Saudi Arabia, using the Multichannel Analysis of Surface Waves (MASW) method for site characterization through shear wave velocity profiling to 30 m depth. Nineteen MASW lines were carried out in various directions and lengths through the area. The entire process was meticulously parameterized to extract shear wave velocity for subsurface characteristics. MASW results revealed four distinct velocity zones based on National Earthquake Hazard Reduction Program. Fill material was approximately half a meter thick and was classified as very dense soil. The second layer exhibited velocities ranging from 800 to 1,500 m/s, indicating weathered and highly fractured limestone. The third layer showed velocities varying from 1,500 to 1,800 m/s, representing slightly weathered limestone. The fourth layer displayed high velocities ranging from 1,800 to 3,600 m/s, indicating hard and compact limestone rocks. Geotechnical boreholes were drilled down to depths of 10–35 m. These boreholes exposed the geological model that consisted of fill material (silty sand with gravel), followed by highly to moderately weathered limestone with vugs and cracks, and finally, massive limestone rock. Analysis of shear wave velocities identified weak zones, particularly fractured and weathered limestone rocks extending to 12 m in depth. Sinkholes of circular, elongated, and/or conical shapes were observed within this depth range. Moreover, some sinkholes were detected at depths greater than 12 m in specific locations (sites 1, 6, 9, 11, and 17). These sinkholes agreed with the previous study. These results highlight the need for targeted ground improvement methods, such as grouting or underpinning, particularly for construction over weaker zones. Accurate site classification and effective risk management are crucial for addressing these geotechnical and seismic challenges.

An Upper Devonian Kadzielnia-type carbonate buildup in Skrzelczyce Quarry, southern Holy Cross Mountains (Poland)

In Skrzelczyce Quarry, located in the southern part of the Holy Cross Mountains in central Poland, a large Upper Devonian carbonate mound is exposed. The Skrzelczyce mound, developed as massive and faintly bedded limestones, measures nearly 100 m in lateral extent and over 20 m in thickness, and laterally passes into coral-rich biostromal limestones belonging to the Sitkówka Beds. Four facies have been identified within the massive limestone unit: stromatactis-bearing limestones with scarce macrofossils (M1), macrofossil-rich limestones (M2), stromatoporoid-microbial limestones (M3), and limestones with fenestral structures (M4). These facies indicate varying depositional conditions and microbial activity, reflecting a complex interplay of environmental factors. The mound’s lithological features and spatial facies distribution resemble the late development stage of Devonian atolls in the Ardennes. This analogy suggests that the initial mound setting at Skrzelczyce might have been at depths of 30–60 m, in a moderate energy zone. The mound, composed predominantly of polygenetic biomicrite with a significant presence of laminar stromatoporoids and corals, features various forms of stromatactis, some typical and others related to sediment winnowing or to shelter cavities. The foraminiferal assemblages, along with lithostratigraphic correlation, suggest that the Skrzelczyce mound may belong to the lower to middle Frasnian, although the precise age remains uncertain due to the lack of conodont dating. The Skrzelczyce mound aligns with the definition of the Kadzielnia Member, and particular facies from Skrzelczyce can be matched with those described from the Kadzielnia Quarry. The structure outcropping in Skrzelczyce is the second largest Upper Devonian carbonate buildup after Kadzielnia in the Holy Cross Mountains, and the largest on the southern edge of the Kielce carbonate platform.

Caves and Fractured Zones Investigation Using 2D Electrical Resistivity Imaging in an Engineering Site, Haqlaniyah, Western Iraq

Engineering risks in karstic areas are represented by cavities and voids near the surface, which are considered potential geotechnical hazards (land subsidence and building cracks). These hazards are caused by dissolution processes that occur when carbonate rocks interact with water, forming weak zones. This study used 2D electrical resistivity imaging with a dipole-dipole array. The spacing of 5 m and an n-factor of 6 were applied to investigate four parallel traverses covering an area of 95x45 m. Electrical resistivity imaging data was inverted using RES2DINV software by robust method inversion. The results show relatively high resistivity values interpreted as massive limestone with cavities and relatively low resistivity values interpreted as fractured limestone with clay or moisture content. Because of the consequence of these caves' haphazard existence in the area, the region was characterized by significant heterogeneity levels of resistivity rise until a depth of 15 m. At that point, they begin to decline.

An overlooked contribution to Devonian studiesin the Holy Cross Mts: rediscovering Alexei Doronin’s 1893 article on the Kadzielnia Limestone

The unused Kadzielnia quarry in Kielce is the most publicly known geological site in the Holy Cross Mts and its geotouristic landmark (now the Kadzielnia Park and Reserve). The ‘rocky’ (coral) Kadzielnia Limestone, corresponding to a stromatoporoid-microbial mud mound, now treated as the Kadzielnia Massive Limestone Member of the Kowala Formation, has been studied for almost 200 years. This large bioherm is famous for its exceptionally diverse fossil inventory. The history of its geological exploration is insufficiently known, as exemplified by the overlooked contribution of Alexei Doronin, a master’s student at the Imperial University of Warsaw (IUW). In 1893, under the guidance of Professor Vladimir Amalitsky, he published a note on the age of the Kadzielnia Limestone. The paleontological basis for this discussion was the IUW student’s fossil collection, in which Doronin identified 28 taxa, mainly brachiopods (19 species). He was the first to recognize the occurrence of gastropods (e.g., Loxonema) and crinoids, and at least four species of brachiopods (e.g., Dielasma sacculus). In a comprehensive brachiopod-based stratigraphic discussion, Doronin emphasized the great similarity of the Kadzielnia assemblage to the Middle Devonian fauna of Western Europe, but also including the typical Upper Devonian species Rhynchonella cuboides. Ultimately, he advocated assigning a terminal Middle Devonian age to the Kadzielnia Limestone. Despite this erroneous dating, Doronin’s noteworthy but unnoticed contribution holds significant implications not only for further study of Kadzielnia but also for understanding the development of geosciences in the late 19th century in the Congress Poland (then part of partitioned Poland within the Russian Empire), including the academic role of the IUW. Unfortunately, for reasons unknown, the scientific career of Amalitsky’s talented pupil never truly began.

A new species of treefrog (Litoria: Pelodryadidae) from the karstic South-fold Mountains of New Guinea.

The frog fauna of New Guinea is exceptionally diverse but very poorly known. Here we describe a new species of pelodryadid treefrog that is currently known only from two specimens from a single site in Hela Province in the highlands of Papua New Guinea. Genetic data show that the new species is closely related to the torrent-breeding species Litoria angiana (Boulenger, 1915) from which it can be readily distinguished by its more slender body and limbs, relatively long forelimbs, and aspects of body colouration and tuberculation. The type locality is on Gigira Ridge, a massive limestone spur extending off New Guinea's Central Cordillera and we hypothesise that the distinctive slender limbs and relatively long forelimbs of the species may be adaptations for clambering, either in complex montane forest habitats or potentially within karst. The ongoing discovery of rare and seemingly localised frog species in Melanesia emphasises that recent estimates of a regional anuran fauna in excess of 700 species that were derived from known candidate species are likely conservative.

Palaeoenvironmental analysis of the Langshan Formation in the Xiongba area

The mid-Cretaceous Langshan Formation is a massive limestone unit, outcropping typically in the northern Lhasa block. A Xiongba section, measured near the type section of the Langshan Formation, is here described. The succession consists of orbitolinids limestone, where eight microfacies have been recognized. The lower part of the Langshan Formation consists of discoidal orbitolinids with other heterotrophic associations, including echinoderms, sponge spicules, and bivalves. In contrast, the upper part of the Langshan Formation features conical orbitolinids with an abundance of green algae and small benthic foraminifers. We interpret the morphological changes in orbitolinids as being influenced by bathymetry. Consequently, the microfacies variations in the Langshan Formation in the Xiongba section represent a shallowing upward sequence.

Eocene larger benthic Foraminifera from the Jahrum Formation (Kalbibak Section, Boldaji Region) in High Zagros, Iran: an approach on paleontology and biostratigraphy

The Jahrum Formation is a major Eocene carbonate deposit of High Zagros in the west of Iran. It consists of thin bedded to thick massive limestone, accumulated on a shallow marine platform within the Neo-Tethys Ocean realm. Fifty-five surface samples were collected throughout a 215 m section in the Kalbibak area (Boldaji region, Chahar Mahal Bakhtiari province). The stratigraphic distribution of benthic foraminifers allows characterizing five foraminiferal biozones, which are in the following order: Alveolina aff. schwageri Taxon Range Zone, A. decastroi Taxon Range Zone, A. aff. frumentiformis–A. cf. stercusmuris Interval Zone, A. aff. stercusmuris–A. aff. fusiformis Interval Zone and Nummulites–Alveolina Assemblage Zone. The benthic foraminiferal associations in the studied area are similar to those recorded in Tethys realms and enable us to correlate the Jahrum Formation with the early to middle Eocene. Keywords: benthic foraminifers, biostratigraphy, Jahrum Formation, Kalbibak section, West Iran.

Cave monitoring in the Peruvian Andes reveals monsoon climate preserved in speleothem calcite

Speleothem paleoclimate records from the Peruvian Andes have been interpreted to reflect the strength of the South American monsoon. While these interpretations have been verified through comparison with other regional and global climate records, the mechanics of the cave environment that facilitate the preservation of this signal with such consistency remain unstudied. Here, we present four years of environmental data from Huagapo and Pacupahuain cave, and one year from Antipayarguna cave. The data reveal that the cave environment is very stable with little to no change in temperature and 100% relative humidity year-round. This stability in cave air is juxtaposed with the monsoonal drip water pulse that increases drip rates over 40 times on average across all seven monitored drip sites. Compared to the amount-weighted precipitation average δ18Oprecip value, the cave drip water δ18ODW values are evaporatively 18O enriched during infiltration through the soil/epikarst. As the monsoonal precipitation pulse fades and drip rates decrease, changes in the drip water chemistry (trace elements Mg/Ca and Sr/Ca, dissolved inorganic carbon δ13CDW, and δ18ODW values) indicate that prior calcite precipitation (PCP) drives the trace element and δ13CDW variability. The δ13Cc and δ18Oc values of farmed slide calcite are highly variable. However, high drip rate and lower cave air pCO2 during the monsoon combine to increase calcite precipitation rates. This causes speleothem records from these caves to be weighted toward annual monsoon conditions. Calcite isotope values from actively growing stalagmite tops support this finding. These results suggest that speleothems from these caves are sensitive to changes in monsoon precipitation amount, because it determines the duration of the monsoon drip water pulse, and therein, the extent of dry season PCP. Further, these data indicate that heterogeneity in the dolomitic limestone massif causes offsets between the carbon isotopes and trace metal concentrations between the caves, highlighting the need to normalize these datasets when chronology-stacking these proxies.

Rock Mass Quality Type Analysis On The New Kretek Girijati Road Construction Site Based On Reconnaissance Survey

Abstract The research activity was carried out at the location of the national road construction plan for The Kretek-Girijati Road Section. The National Kretek-Girijati Section is in the Nglanggran Formation, which consists of volcanic breccias, agglomerates, tuffs, andesitic-basalt and andesitic lava flows, and the Wonosari Formation, which is dominated by carbonate rocks consisting of layered limestone and massive limestone. This investigation aims to obtain a typical analogy of excavation slopes at road construction sites, making recommendations for additional drilling locations and geophysical surveys for appropriate data by making an engineering geological map. Based on the geological engineering description, the location plan for the construction of The Kretek-Girijati Road Section is dominated by limestone and andesite. The types of limestone rock mass quality consist of Massive limestone (very hard) with good to very good rock mass quality with a GSI value of >80 and Clastic limestone with poor to medium rock quality with a GSI value of 30 – 60. The types of andesite rock mass quality consist of massive andesite (weakly jointed) with good – excellent rock mass quality with an RMR value of 70-80 and moderately fractured andesite with moderate rock mass quality (good 50 – 70).

The Space of the Stylite

For scholars and students of Late Antiquity, the stylite’s column exerts a special appeal. Scholars have examined literary representations of stylites and sought out visual parallels for the phenomenon of column-standing. This article shows that topographical contexts were central to establishing the potency of the column as a holy object and the trajectory of stylitism in history. I employ the term topography broadly to encompass the physical characteristics of an area, the ways in which humans augmented physical characteristics through the built environment, and specific architectural organizations. I examine three topographical contexts and make three interconnected arguments. By selecting the hill adjacent to Telanissos as the location for his columns, the premier stylite Symeon (d. 459) participated in a long-standing regional tradition of activating the numinous power of high places and stone through cultic activity. The monumental pilgrimage complex built after Symeon’s death made the column a relic and integrated veneration of Symeon into liturgical ritual. The incorporation of stylites into northern Syria’s cenobitic communities circumscribed stylitism as a distinctly monastic vocation. These three contexts illustrate that the significance of the column was located in processes of production and reception. At the same time, stylite columns were not passive objects. They faced the gods of old; they enriched ecclesiastical rituals; they molded the bodies of those who activated them; they proclaimed the ascendancy of monastic institutions. As both products of their topography and agents within it, stylite columns constructed a distinctive Christian landscape in Syria’s limestone massif.

Hyperconcentrated flows shape bedrock channels

AbstractGeomorphological evidence of incised bedrock channels is widespread in all mountain landscapes worldwide. However, the processes controlling incision and gorge formation in bedrock have not directly been observed in an actualistic way. Here, we show a LiDAR change detection deciphering the erosive power of a 60,000 m3 hyperconcentrated flow (transition between flood and debris flow) in a deeply incised rock gorge in June, 2020. The flow laterally eroded up to 1 m of massive limestone and widened a 4 m narrow section of the gorge by up to 15%. Sinuosity, convergence, and gradient of the channel were proven to not influence erosivity indicating the hyperconcentrated nature of erosion. Furthermore, other than in prior studies no abrasion of thin rock veneer dominates erosion but mechanically excited breakout of rock fragments. Magnitude-frequency relations of eroded volumes mimic subaerial rock wall retreat. We show how single hyperconcentrated flows can erode bedrock channels far more efficient than decades of turbulent flows and hypothesise that repeated hyperconcentrated flows in phases of enhanced precipitation or by elevated material supply could control erosion boosts in gorge formation, e.g. in the Lateglacial or during climatic fluctuations.

Depositional Model of Early-Middle Turonian Deep Water Gulneri Formation, in Selected Outcrop and Subsurface Sections in Northern Iraq

The Gulneri Formation (Early-Middle Turonian) Deep-water depositional model was constructed using detailed microfacies analysis from the northern Iraqi wells of Kirkuk (K-116) and Bai Hassan (BH-81) as well as the Dokan outcropped area. In the outcropped section, the formation consists of 2 m of thin friable marly limestone with high organic matter and thin-bedded black shale in addition to boulder and gravel-like limestone masses in the lower part. In the K-116 and BH-81 wells, the formation is 4.3 m and 9 m thick, respectively. It is composed mainly of black bituminous, pyritic calcareous shale, and shaley limestone with scattered glauconites. Petrographic studies of seventeen thin sections of the Gulneri rocks reveal that the pelagic/deep marine faunas are the dominant skeletal grain in the micritic groundmass. Three main microfacies were recognized in the studied rocks of the Gulneri Formation, namely lime mudstone, lime wackestone, and lime packstone. However, the latter is absent in the Dokan section. According to their environmental interpretation, these microfacies were grouped into two facies associations (basinal deep water and deep shelf). Based on the results of petrographic and microfacies analyses, it is concluded that the Gulneri Formation was deposited in a basinal deep marine environment with quiet and reducing conditions in the Dokan section and a basinal deep marine environment in the K-116 and BH-81 wells which changed at intervals to a shallower deep shelf setting toward the upper part with semi reducing conditions. The euxinic deep basin that formed at the beginning of the Kurdistan foreland basin's formation was quite anoxic and deeper from the northeast to the relatively shallower basin with semi-reduced conditions towards the southwest. This is how the depositional model of the Gulneri Formation in northern Iraq changed.

ОЦЕНКА СВЕРХНОРМАТИВНЫХ ПОТЕРЬ ПОЛЕЗНОГО ИСКОПАЕМОГО НА ПРИМЕРЕ РАЗРАБОТКИ ИЗВЕСТНЯКОВОГО МЕСТОРОЖДЕНИЯ

The article presents methodological provisions for the assessment of increased mineral losses during open-pit mining of deposits with difficult mining and geological conditions. As an example, the indicators of mineral losses during the development of the Kostanok site of the Chanvin deposit of limestones used for the production of caustic soda are given. The actual level of losses exce-eding 30 % of the volume of extraction of raw materials has been established. The main reasons for the increased limestone losses compared to the level justified by the project are outlined. It was found that during the detailed exploration of the limestone massif, karst zones and areas with a high clay content, lying in the form of «veins» in areas of increased fracturing, were not identified. As a result, as a result of blasting, the exploding quarried, clogged areas with pure limestone are mixed, its contamination to values exceeding those allowed by the project, which leads to the loss of balance reserves of minerals during excavation. Recommendations are given for calculating the level of losses during the development of complex faces, which are characterized by the intermittency of rocks with productive limestone strata and karst zones.

Beheaded, Burnt, and Buried: A Deposit of Royal Statue Fragments in the Temple of Heliopolis

In 2022, two successive excavation campaigns by the Egyptian-German mission focused on the area surrounding the museum of Matariya, which collects the monumental pieces discovered on the archaeological site of Heliopolis around the obelisk of Senusret I. These excavations unearthed the massive limestone block foundations of a Late Period temple, as well as a limestone pavement that once covered the temple forecourt. A preserved part of this pavement to the south of the obelisk of Senusret I revealed a deposit of fragments of statues and cult objects from the Middle and New Kingdoms, buried in the Late Period. The fragments belong almost exclusively to the heads of sphinxes, which seem to have been ritually broken and burnt before being buried, perhaps reflecting a practice of deactivating the statues accompanying their decapitation before the reuse of their bodies.

Mineralogical and geochemical features of the Sirna Mn‐Fe deposit in the Kurdistan region, northeastern Iraq: Unveiling the formation of a Mn‐Fe silica gel plume via serpentinization hydrothermal mechanisms

AbstractThe study probes the mineralogical and geochemical features of manganese‐iron deposits located in the Sirna area, which is a part of the late Cretaceous Walash Group in the Zagros suture zone, situated in the Kurdistan region of northeastern Iraq. Our investigation comprised field surveys, examination of ore petrography, besides using x‐ray diffraction, SEM‐EDS analysis, x‐ray fluorescence analyses, and inductively coupled plasma mass spectrometry techniques conducted on a set of representative samples. A significant Mn‐Fe ovoidal ore body, extending across 25 meters in diameter, protrudes between the lower strata of soft gray shale and the upper strata of massive limestone within the Walash group. The deposit exhibits a distinct separation into three layers: a lower horizon characterized by abundance of oxide of silicon, an upper horizon enriched in manganese oxide, and a transition layer dominated by hematite (Fe2O3). From a geochemical perspective, there is a gradual decrease in Fe2O3 and SiO2 from the lower to the upper part of the deposit, while MnO, BaO, and SO3 demonstrate a gradual increase. The co‐association of Mn‐Fe‐mineralization in a small restricted tabular ore body suggests that they are genetically related. Within the Sirna manganese‐iron deposit, the prevalent manganese and iron mineral phases are braunite, hollandite, and hematite. Concurrently, the gangue minerals in this deposit encompass cryptocrystalline spheroidal quartz, barite, calcite, and apatite. The Sirna Mn‐Fe deposit exhibits geochemical characteristics such as elevated levels of MnO (reaching up to 68 wt.%) and significant Fe2O3 content (up to 45 wt.%) in the upper manganese and transitional iron horizons, respectively. The Co/Zn ratio (0.28), Ce/La ratio (1.78), low levels of transitional elements (Co + Ni + Cu <0.01 wt.%), and varying concentrations of Ba (up to 6.9 wt.%) suggest that the Siran Mn‐Fe deposit is likely originated from a manganese‐iron silica gel plume that separated from hydrothermal fluids linked to serpentinization. This process is thought to have occurred in the mantle wedge along subduction zone, typically within an arc tectonic environment. Moreover, the presence of remnants of micro‐organisms such as EPS layers, different types of filaments, which are densely covered by biominerals, are important evidence of microbial effect in the mineralization of Mn‐Fe in the study area.

Geological History of Caves and Conservation Values of the World Nature Heritage Phong Nha-Ke Bang National Park

The long development history and geological diversity of the Phong Nha-Ke Bang area is shown by the rich and diverse lithological composition of the stratigraphic units ranging in age from Devonian to Present day: granite, terrigenous rock, thin-bedded limestone, and massive limestone. The geomorphology of the national park includes limestone mountain terrain alternating with terrigenous rock mountain terrain surrounding the karst valley system. The formation of the cave is an endogenous-exogenous geological process that occurs according to the cycle of global sea level change. The tectonic activity is the mother that gives birth to the caves of different heights and ages. The higher the cave, the older it is, and the oldest cave is 32 million year old-Khe Ry cave. The four fault systems of Northeast - Southwest (NE-SW), Northwest - Southeast (NW-SE), West - East (WE), and North - South (NS) create four cave systems that are deep faults with strong destructive intensity. Exogenous geological activities in the cave have created a uniquely beautiful landscape including three simultaneous processes: i) Chemical washing of driftwood, mechanical abrasion, polishing of the cave walls, and ceiling caused by travertine floods pouring into it from outside the cave; ii) Precipitation forming stalactites from the ceiling of the cave and precipitation forming stalagmites from the floor of the cave slowly over millions of years; and iii) Travertine sedimentation on the cave floor resulting in many unique sedimentary bodies, specifically filling the rough terrain of limestone blocks, covering the ancient stalactites falling from the cave ceiling, forming spiral mushroom island in the Son Doong cave, and creating gem pebbles located in fan-shaped sunken cells of the cave.

Microfacies and Depositional Model of the Shuaiba Formation (Lower Cretaceous), in Selected Wells, Southern Iraq

The Shuaiba Formation (Aptian age) is an important formation due to its wide extent in Iraq and Arabian Gulf. In northern Iraq, it is called Qamchuqa Formation and has an important role in contracting the Arabian plate. The study focused on several wells, which are: ZB-290, WQ1-353, RU-358, R-624, and R-5 from several selected fields, such as Zubair, Rumaila, and West Qurna in southern Iraq. The purpose of the study is to determine the sedimentary and paleontological components of the Shuaiba Formation. The lithology of the Shuaiba Formation consists of very fine crystalline massive limestone that gradually converts to chalky limestone with a large percentage of dolomites, especially in the middle part of the formation. The thickness of the studied formation is about 50 – 110 meters and its main microfacies are two types, which are carbonate and dolomite. The carbonate is subdivided into five secondary types, which are burrowed bioclastic lime mudstone, planktonic foraminiferal lime mudstone, larger foraminifera wackestone, algal wackestone and mixed planktonic, and benthonic Foraminifera wackestone, in addition, to dolostone microfacies. The effect of the diagenesis in the formation is distinguished and most of these processes are destructive, such as dissolution and stylolite. The first depositional stage of the investigated area began with sea level rise following the deposition of the Zubair Formation from still stand. Shuaiba Formation deposited within the ramp setting as the water level rose. During the late Aptian, tectonic and sea levels were the active factors that controlled the deposition of the formation. According to data collected from microfacies and diagenesis processes, the Shuaiba Formation has several depositional environments, which are from the shallowest: restricted, open marine (inner ramp), mid ramp, and finally outer ramp. Generally, toward the upper sequence, the formation reflects deep deposits and then starts to be less deep until it is a shallow basin (Nahr Umr).

Multi-property digital soil mapping at 30-m spatial resolution down to 1 m using extreme gradient boosting tree model and environmental covariates

Information on the variability of soil properties including clay, calcium carbonate equivalent (CCE) and acidity (pH) in space and depth play major role in sustainable agricultural development but scarce in many regions in the world, specifically in developing countries. Digital soil mapping technique has shown strong success in the prediction of soil properties both in space and depth from their relationship with environmental covariates. The aim of the study was to digitally map soil properties including clay, CCE and pH at multiple depths and identify the dominant factors controlling their variability using Minadoab region of Iran as a case study area due to its significance for agricultural production and economic development in the country. A total of 104 soil profiles were randomly selected and described in field during 15–30 July 2017, and 386 samples were collected from each genetic horizon with variable depths. A continuous spline function was fitted to the horizon data and properties were estimated at five standardized depths following GlobalSoilMap project. The soil layers were then grouped into three classes: i) H1: top (0–5 cm); ii) H2–H4: middle (5–15, 15–30 and 30–60 cm); and iii) H5: bottom (60–100 cm) for easy interpretation. A total of 17 static environmental covariates were derived from terrain-related attributes. Additionally, matching with the soil sampling date, a total of eight band ratios in addition to six individual bands were derived from Landsat-8 OLI (Product ID: LC08_L1TP_168034_20170721_20170728_01_T1) for the study area. Finally, all covariates were categorized in nine groups representing various factors controlling soil variations. The digital maps associated with uncertainties were prepared using extreme gradient boosting (XGBoost) Tree model and bootstrapping method, respectively. Overall, the highest accuracy using XGBoost Tree model was found for CCE (R2 = 0.73, on average), followed by pH (R2 = 0.72, on average) and clay (R2 = 0.70, on average). The highest amount of clay was observed for the bottom layer, followed by middle and top layers across the study area. H1 to H3 layers were subjected to tillage operations over the time and may have contributed to the redistribution of clays. A similar trend was also observed for CCE and pH as the location of the study area is underlain by massive limestone. The uncertainties helped quantify over- and under-estimation of the predictions and the factors with the highest variable importance was identified as the dominant factor. The information generated for the study area provides soil variability information that is critical for developing management strategies for sustainable production in the area.

Assessing Endokarst Potential in the Northern Sector of Santo António Plateau (Estremadura Limestone Massif, Central Portugal)

Karst is a peculiar natural landscape arising from high rock solubility and well-developed underground solutional channel porosity. It is unique for its surface relief (exokarst) and subsurface drainage, including cave systems (endokarst). In Portugal, karst areas mainly consist of marginal or low-density territories with great fragility and vulnerability and great geo-environmental richness that merits better policies and practices regarding their geo-conservation. Endokarst potential assessments can provide decision-makers and local authorities insight into present and future territorial management and planning. In this context, the main objective of this study was to produce a cartographic model to identify areas with a greater probability of containing karstic caves—i.e., a greater endokarst potential—in the northern sector of the Santo António Plateau (Estremadura Limestone Massif, Central Portugal). Geological, topographic, hydrogeological, and land cover data were collected, processed, and integrated into a spatial database using a Geographic Information System. The locations of known cave entrances in the study area were also identified from local public institutions and speleological team records. Subsequently, four conditioning factors were extracted from the data: lithostratigraphic units, fracture density, relief energy, and land cover. Using a multi-criteria decision-making analysis, each previously chosen conditioning factor and its respective classes were weighted using an analytic hierarchy process. The locations of known cave entrances served to evaluate the cartographic model built, with results showing an agreement of 81.9%. This prototype of the endokarst potential map for the study area may be used for strategic and operational environmental planning (at least on a local scale) to assist decision-makers, competent authorities, and local speleological teams. Its application may promote a more accurate and thoughtful definition of areas to be investigated, substantially reducing the time and costs associated with field prospecting.