ICG2022-14

The Inception Horizon Hypothesis (IHH) was developed to explain the spatial distribution of subsurface karst features. In large cave systems, passages are commonly developed within quite narrow elevation ‘levels’ that correlate with stratigraphic horizons (bedding planes) between lithologically distinct limestone beds. These horizons guide the first phases of speleogenesis and, combined with structural surfaces such as faults and joints, provide a framework for speleogenesis in a karst area. Despite the established link between speleogenesis and surface karst landforms, the IHH has not been extended thus far to explain the development of surface karst geomorphology. Using the example of the world-renowned limestone karst area of the Burren in Co. Clare, Western Ireland, we here show that an ‘inception framework’ concept can be used to explain the evolution of both subsurface and surface karst features.

Over 60 km of cave passages have been previously mapped in the Burren. Speleogenesis is guided by both stratigraphic and structural surfaces. Some limestone units contain numerous paleokarstic surfaces, as well as thin non-carbonate horizons (‘clay wayboards’), along which cave passages are preferentially developed. Additionally, a suite of sub-vertical, north-north-east orientated veins, associated with the Variscan orogenic stress field, are vertically persistent through the entire limestone sequence. These calcite or silica-rich veins guide cave passage formation for several kilometres over a vertical range of > 100 m in some cases.

We conducted a new mapping of the surface karst in the Burren, with a focus on the distribution and morphology of enclosed depressions (dolines and uvalas). High-resolution remote sensing datasets, consisting of optical aerial imagery and associated digital surface models, were acquired for the Burren’s entire 250 km² area in 2017. We have used these data, complimented by fieldwork, to record over 2500 karst depressions, representing a 25-fold increase on the existing database (109 dolines were recorded previously). We also performed a morphometric analysis to elucidate the primary controls on depression distribution and form. Our new data demonstrate that evolution of the surface karst geomorphology in the Burren, like the subsurface karst, is also primarily controlled by an inception framework comprising key stratigraphic horizons and structural surfaces (vein-associated lineaments).

How to cite: Watson, R. A., Fiaschi, S., and Holohan, E. P.: The Inception Horizon Hypothesis applied to karst development in the Burren: linking subsurface to surface, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-213, https://doi.org/10.5194/icg2022-213, 2022.

In karst landscape, caves are loci prone to trap and accumulate clastic, chemical, and organic sediments, covering a time span from several million years up to the present. Different types of cave sediments can be distinguished: (a) autochthonous (breakdown and insoluble bedrock remains) and para-autochthonous (overlaid fluvial and hydro-aeolian deposits); (b) allochthonous, with water and/or gravity-driven transport (filtrates, fluvial, lacustrine, aeolian, marine, organic); (c) chemical sediments—secondary cave minerals. The (a) and (b) are clastic cave sediments (CCS), while the most widespread and best-known chemical sediments are calcite speleothems in the form of stalactites, stalagmites, or flowstones.

Based in the knowledge of Central Portugal’s karst (Sicó and Estremadura massifs), previously obtained through studies focusing geomorphology/hydrology and palaeokarst stratigraphy/evolution, an innovative and ambitious investigation is “now” necessary to overcome the current shortcomings, whose main challenge is to link surface dynamics (reasonably well studied) to the cave sedimentary record (relatively unknown), providing new insights about Quaternary landscape evolution at local/regional scale.

New data were produced through fieldwork and laboratory analyses of the sedimentary record (CCS and speleothems) preserved in the largest endokarst system of the Sicó massif, which includes a set of exsurgences, and ponors linked by few caves with mainly horizontal passages that take advantage from laterally extended bedding planes to which other conducts are added that developed vertically along faults/joints. Among these caves, the Soprador do Carvalho cave stands out with an active underground river runs along its lower level, which is prone to seasonal flooding; here two main orders of ancient alluvial terraces show the evidence of fluvial dynamics during Middle Pleistocene—as confirmed by the obtained ²⁶Al/ ¹⁰Be data (burial ages ranging from ~0.43 to 0.18 Ma). The geometry and composition of the oldest endokarst terrace—a clast-supported and well-cemented conglomerate with imbricated shist pebbles—with a ²⁶Al/¹⁰Be burial age of 0.4 ± 0.03 Ma, indicate a palaeodrainage direction opposite to the present-day hydrologic flow, as well as a catchment area that extended to the Hercynian massif to the east. Instead, the sedimentary and geomorphological characteristics of younger endokarst alluvial terrace—a clayey deposit with sandy intercalated lenses—with a burial age of 0.2 ± 0.02 Ma, indicate a palaeodrainage direction compatible with the current one. These underground finding agree with some surface geomorphological observations that point out, for the Middle Pleistocene, to a general reorganization of the hydrographic network, with fracture adaptations, inversions, and captures, due to local tectonic deformations. Furthermore, a regional geochronological correlation between cave palaeoflood events and the oldest lower Mondego River terraces can be established, representing a sedimentary record of the period between MIS11 and 7 for the central Portugal.

In addition, detrital interlayered material (clayey layers) trapped between laminae of a stalagmite formed between ~5760 BCE and ~1920 CE (dated using U/Th and ¹⁴C methods), suggests that the studied cave was periodically affected by palaeoflood events also during Holocene. Further geochemical analysis, including speleothem’s stable isotopes and trace-element determinations, coupled by petrographic observations (microstratigraphy), could provide more valuable paleoclimate information.

How to cite: Dimuccio, L., Cunha, L., Iurilli, V., Braucher, R., and Bourlés, D. L.: Linking regional Quaternary surface evolution to the palaeoflood events recorded by cave sediments in central Portugal, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-701, https://doi.org/10.5194/icg2022-701, 2022.

Geoscience has been devoting increased attention to understanding the complex pathways and flows of material, energy, and the multidimensional coupling between various geological systems. This understanding includes the “concept of connectivity”, which provides an overall framework better to investigate hydrological systems. So far, the concept has largely been used for fluvial geomorphic systems, whereas we intend to use it within the karst system. In relation to the concept of connectivity between the karst surface and subsurface, hydrological, sediment, and geochemical connectivities are the most relevant from the perspective of geoscience and to measuring human impacts through a long time span.

Our main interest is to study the direct flow between enclosed karst depressions (solution dolines) and near-surface caves (50 m below the surface) that are prone to human influence. The doline-cave coupling zone represents the upper part of a karst aquifer for which specific connectivity characteristics between dolines and near-surface caves can be identified. Polina peč Cave (NW Dinaric Karst) was selected as a case study cave. We used geoinformatic methods (three-dimensional (3D) laser scanning) and available data (Registry of maps, Lidar DEM 1x1m, optical remote sensing data), geomorphometric analyse, geological mapping and surveying. With precise georeferencing (using the GNSS system), we placed the 3D point cloud of the cave in a geographical coordinate system, compared 3D cave map with the surface map (using existing national aero-laser scanning data – Lidar DEM 1x1m), and selected dolines that are most directly connected to cave. The results were controlled and further improved by geophysical methods (electrical resistivity tomography/ERT).

How to cite: Breg Valjavec, M., Ciglič, R., Tičar, J., Čonč, Š., and Šebela, S.: 3D characterisation of doline-cave coupling zone by using 3D laser scanning and electrical resistivity tomography, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-671, https://doi.org/10.5194/icg2022-671, 2022.

Denuded caves are surface expressions of cave passages due to lowering of the surface by denudation and/or breakdown propagation of caves towards the surface. They appear as fragments of channels on the surface, often filled with clastic cave sediments and occasional speleothems. Elongated shallow depressions were recently observed on the surface of the southeastern part of the Nullarbor Plain, and close association with associated collapse dolines suggests that they are denuded caves.

The Nullarbor Plain in southern Australia is among the largest karst outcrops in the world and covers a surface area of approximately 200.000 km². The bedrock comprises the middle to late Eocene Wilson Bluff Limestone, the Oligocene to early Miocene Abrakurrie Limestone, and the middle Miocene Nullarbor Limestone. The plain has been since the deposition of the Nullabror Limestone uplifted and exposed to subaerial denudation. It is renowned for outstanding flatness with collapse dolines and vertical cave openings (blowholes) being the most common surface karst features. Most of the discovered caves are “shallow caves” in Nullarbor Limestone, generally less than 30 m deep with low collapse chambers. On the other hand, “deep caves” generally extend 50-120 m below the surface in the Wilson Bluff Limestone and may reach exceptional dimensions. Deep and shallow caves are thought to be genetically unrelated, but the speleogenesis of deep caves is still not understood completely, and the recognition of denuded caves might help understand their timing of initial formation.

One hypothesis suggests the phreatic origin of deep caves after the deposition of the Wilson Bluff Limestone and its exposure on the surface during the warm wet climate around 35 to 25 million years ago. Later, around 25 to 10 million years ago, the tectonic basin underwent subsidence and sea transgression in the west-central part, which is on the present surface obscured by even lateral deposition of younger limestones. Therefore, the relatively greater number of denuded caves in the east expressed as simple uniform lines of shallow elongated depressions, the combination of a line of collapses and shallow depressions in the central part of the plain, and greater discovered number of deep caves towards the west could confirm this hypothesis. Namely, the subsidence of the Wilson Bluff in its western part (with caves already formed) could have caused thinner deposition of younger limestones towards the east and the position of cave passages relatively higher. Progressive cave collapses therefore reached the surface on the eastern side sooner (expressed as denuded caves), whilst in the west the breakdown propagation of deep caves has not yet reached the surface.

How to cite: Ferk, M. and Lipar, M.: Denuded caves on the Nullarbor Plain, Australia, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-162, https://doi.org/10.5194/icg2022-162, 2022.

Underground karst systems have an unique geomorphological relevance for the reconstruction of long-term landscape evolution as it is widely acknowledged that “(…) cave features tend to be preserved far longer than correlative surface features [(e.g., alluvium-mantled terraces in fluvial environments)], which are more susceptible to weathering and erosion” (Audra and Palmer, 2013, p. 187). In this contribution, we thus consider (i) endokarstic fluvial sediments deposited in multi-levels cave systems or networks, which have formed in response to regional base-level changes over long periods of time (typically 10⁵-10⁶ years), and (ii) how to date them. More specifically, we aim at fostering the use of cosmogenic burial dating of cave-deposited clastic sediments to unravel the long-term evolution of fluvial landscapes. The formation of epigenic cave systems and their geomorphological relevance as a marker of long-term river incision is firstly discussed. After a brief presentation of cosmogenic burial dating works and how it can be applied to cave-deposited alluvium, this contribution focuses on how/where to sample within multi-level cave systems and on selecting the sampling material. It afterwards highlights the main drawbacks (analytical and geomorphological uncertainties) associated to this method and presents some strategies to avoid them (if possible). The combination of cosmogenic burial dating with other geochronological tools in the underground realm is also tackled in that respect. Whilst the multi-purpose use of this approach to unravel evolution of fluvial landscapes is briefly reviewed, we focus on the reconstruction of long-term incision rates, including their variation through time, and the drivers of incision. We conclude by a number of useful recommendations to fully benefit from this approach.

Reference

Audra, P., Palmer, A.N., 2013. The vertical dimension of karst: controls of vertical cave pattern. In: Shroder, J. (Editor in chief), Frumkin, A. (Ed.), Treatise on Geomorphology. Academic Press, San Diego, CA, vol. 6, Karst Geomorphology, pp. 186–206.

How to cite: Rixhon, G.: Going deeper underground: multi-level cave systems dated by 26Al/10Be cosmogenic burial as valuable geomorphological markers of long-term landscape evolution, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-612, https://doi.org/10.5194/icg2022-612, 2022.

The studied region located in the Rio Vermelho watershed, situated at the foot of the Serra Geral de Goiás in the Brazilian Cerrado, hosts a covered fluviokarst system containing ~150 mapped caves that capture the rivers (sediment loads) upstream. The present study aims at developing a better understanding of the geomorphological controls, considering the impacts of climatic conditions and land use types on the production and transport of the sediments to the caves using an integrated approach (GIS mapping, hydrosedimentological monitoring, and geochronological analysis).

The preliminary results indicate the influence of two sites on sediment production: a) downstream, constituted by the karstic system developed in the Neoproterozoic carbonates (Bambuí group), where the soils are occupied by natural vegetation or pastures (family farming), and, b) upstream, on a plateau, which supplies water to the karstic system, with soils developed on Cretaceous sandstones (Urucuia group), the areas of growing mechanized agriculture. Models of the upper and lower fluviokarst systems are developed using the soil types and recharge zonation information. The chronology of the preserved sedimentary deposits, formed by the alternation of clayey and sandy facies, has been established, between 60ky and 200ky in the upper cavities and up to 20 ky in the fluviokarst blind valleys. Hydrosedimentological monitoring revealed the production of ~ 9 Mg ha-1yr-1 of sediments from degraded soils, while 2.0 Mg ha-1yr-1 are produced from soils having received the conservation protocol, a lower value than the geological rate as established in the literature. The sediments transported in the karst are poorly sorted compared to those in the rivers and an increase in the particulate load during floods (<7 against ~500 mg/L).

There is still a lack of evidence about the origin of the water and sediments circulating in this karst system. Further studies on fresh sedimentary deposits in the recent sinkholes may help to better quantify recent paleo-environmental modifications and the effects of anthropogenic activities upstream.

Keywords: GIS; Geochronology; Blind valleys; C14;  Fluviokarst

How to cite: Uagoda, R., Hussain, Y., Caldeira, D., Moraes Nogueira, A., Fonseca, M. R., and da Silva Tavares, A.: Hydrosedimentological study of a covered fluviokarst in the Brazilian Cerrado, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-423, https://doi.org/10.5194/icg2022-423, 2022.

The analyzed active sinkhole is located on the outer bank of a meander of the Ebro River, affecting the Alcalá de Ebro village and a flood-control embankment dike. Between 1927 and 1957 the Ebro River channel experienced a major shift of 500 m until its present position abutting the village. The development of the sinkhole, around 100 m long, is related to dissolution of cavernous salt-bearing evaporites (i.e., halite and glauberite) underlying the unconsolidated alluvium. It experiences progressive sagging subsidence punctuated by the catastrophic occurrence of nested collapses in the village and the dike since 2007, leading to the demolition of a building and recurrent high-risk and uncertainty situations during floods. The sinkhole has been partially treated with a number of costly remediation measures, including shallow injection of polyurethane foam, compaction grouting and the installation of geogrids. Subsurface information on the spatial extent of the dissolution and subsidence phenomena has been obtained by boreholes, electrical resistivity tomography and ground-penetrating radar. Surface deformation at the site has been monitored utilizing multiple techniques, including: (1) several lines of high-precision leveling since 2015; (2) terrestrial laser scanner since 2014; (3) distributed strain and temperature sensing in optical fiber based on BOTDA since 2019; and (4) Structure from Motion Photogrammetry with drone images since 2020. The available surface displacement data provide an opportunity to: (1) compare the performance of the different techniques and identify their strengths, weaknesses and complementarity for sinkhole monitoring; (2) analyze the impact of floods and the associated water-table rises and drops on the activity of the sinkhole; and (3) assess the performance of remediation measures by comparing subsidence data before, during and after their application. Regarding the latter point, surface displacement data indicate that some measures significantly reduced subsidence activity (compaction grouting reaching the karstification zone), whereas other measures (shallow injection of polyurethane foam) aggravated the situation (subsidence acceleration and expansion). Moreover, the location of some treatments shows a significant offset with respect to the active subsidence area (i.e., inadequately sited without displacement data). The rapid sagging subsidence occurring at the present time on a paved area 11 m across is ascribed to a large cavity spanned by a geogrid, which eventually might produce a damaging catastrophic collapse. Precisely identifying the area affected by sinkhole subsidence and characterizing the spatial and temporal patterns of the surface displacement is essential for assessing the associated hazard and designing effective remediation measures. The most suitable monitoring techniques largely depend on the subsidence mechanisms (sagging vs. collapse), displacement regime (progressive vs. episodic), subsidence rates, and characteristics of the area.

How to cite: Gutiérrez, F., Sevil, J., Sevillano, P., Zarroca, M., Roqué, C., Comas, X., Desir, G., Guerrero, J., García-Arnay, Á., Preciado-Garbayo, J., Martínez, J. J., and Benito-Calvo, A.: Multi-approach monitoring of a high-risk sinkhole in the Ebro Valley, Spain using high-precision leveling, terrestrial laser scanner, photogrammetry, and BOTDA distributed optical fiber sensing, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-85, https://doi.org/10.5194/icg2022-85, 2022.

For seldom investigated Brazilian caves, detailed non-invasive mapping is crucial for environmental, ecological, and geological investigations. However, the Cerrado region of Brazil hosts covered karst (underlain by a thick clayey layer) which makes its non-invasive mapping difficult using the readily available tools. In this study, we applied a geophysical technique to establish the linkage (continuity) among the three caves named Trimba, Pasto de Vaca I, and Pasto de Vaca II in the environmentally protected area of River Vermelho, Goias, Brazil.

Our analysis started with the optimization of the electrode array geometry and its depth of penetration in the area. A forward model was chosen based on the site where the river enters the cave and soil-clay-carbonate lithological contacts are exposed on the surface. As there are well-developed drainage networks and cave development is attributed to fluvial influences that still have subsurface water flows in most of the places. Therefore, buried streams were also considered in the numeral approximation study. Findings from the numerical simulation indicated that the best results could be obtained using either the dipole-dipole, pole-dipole, or Wenner-Schlumberger array configurations, with an inter-electrode spacing of 2.5 meters.

Hence, a dipole-dipole array of electrodes was selected to acquire the DC electrical resistivity data. Considering the objective of the study, the measurements were carried out using 72 electrodes were spaced 2.5 m apart and arranged in seven electrical resistivity tomography (ERT) profiles perpendicular to the one end of Trimba cave, covering the entire length of Pasto de Vaca I and the beginning of Pasto de Vaca II cave marked on existent caves topography.

In the first stage of resistivity data processing, a manual inspection and consequent removal of bad data points to improve the inversion results were conducted seeking a possible reduction in root mean square error. The inversion models, represented through 2D sections, indicated anomalous resistivity areas, interpreted as regions of subsurface cavity. Additionally, a geomodeling approach was used for improving the presentation of the inversion results (resistivity variables) in 3D. The latter revealed anomalous zones present on all profiles, attributed to the presence of a subsurface cavity.

The geophysical results made it possible to detect the continuity of the same cave from north to south, contrary to the previously held assumption about the existence of three individual caves. Results encourage the integrated application of geophysical techniques for further detailed investigations.

Keywords: Cerrado; Electrical Resistivity; Array optimization, Geomodeling

How to cite: Neuhauss Aguiar, A. C., Hussain, Y., Rodrigues Borges, W., and Uagoda, R.: Continuity among three-consecutive Brazilian caves established by a geophysical approach, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-424, https://doi.org/10.5194/icg2022-424, 2022.

Karstified carbonate formations are among the most complex geomorphological structures due to their high spatial heterogeneity and intricated internal structure. Studying these specific environments is highly challenging and usually requires sophisticated, costly instruments and procedures.

Therefore, one of the most applied methodologies is the analysis of the springs' discharge. Its detailed analysis is a valuable method for understanding aquifer hydrodynamics and inferring information about the internal structure of karst systems. Many previous studies stated that the analysis of single karst springs could provide very useful information as spring flow carries an imprint of the global karst massif hydrodynamics and, consequently, of its physical characteristics.

Understanding karst underground features from a hydrogeomorphological perspective is crucial due to the high vulnerability of karst aquifers to contamination and its enormous importance as a freshwater reservoir, particularly in the present climate change scenario under the Mediterranean climate. 

The study area is the northern sector of Sicó karst massif located in the central-western region of Portugal. The massif's structure comprises limestone mountains and plateaus supported by the well-karstified Middle Jurassic units. This part of the karst massif corresponds to a karst aquifer of about 100 Km², which essentially drains through several temporary and perennial springs at the western shore. The recharge area is dominated by a plateau with covered karst in the central part, where diffuse recharge is dominant, and exhumed karst in the west part, where concentrated recharge occurs.

This study aims to infer Sicó karst massif physical characteristics from their hydrogeological functioning by applying well-known methodologies focused on the springs' discharge time series. The combined methodological approach used in the present investigations includes (i) time series analysis on rainfall and discharge (correlation and spectral analysis), (ii) recession curve hydrograph analysis (quantitative parameters from Mangin method and recessional equations from Malík & Vojtková master recession curve method), and (iii) spring outflow physicochemical variations analysis (electrical conductivity, temperature, Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃^-, Cl^-, SO₄^-2, NO₃^- ). The data were logged at the main spring (Olhos d'Água do Anços) every 20 minutes by a multiparameter gauge station from 2010. More recently, water samples were collected and examined in the laboratory. 

The results revealed a bimodal and heterogeneous hydrogeological behavior with: (i) rapid circulation through highly transmissive channels in the vadose zone (important quick flow component and turbulent circulation), and (ii) high non-linearity, slow vadose circulation (delayed flow), and ample storage capacity (dominance of baseflow). In terms of physical characteristics, these outputs allow inferring the duality of the massif corresponding to (i) very karstified sectors and a structured drainage network that quickly drains the unsaturated zone and (ii) less karstified sectors (with lower hydraulic conductivity – small fractures, fissures, pores) and a thick and deep saturated zone retaining and storing large amounts of water.

Although some documented limitations of each method, this combined methodological perspective has proved to supply precious information related to a karst system's complexity, evolution, and physical properties.

Keywords: Karst; spring discharge analysis; hydrodynamic functioning; Sicó karst massif; Portugal

How to cite: Paiva, I., Cunha, L., Sofio, S., and Ribeiro, A.: Understanding karst massif physical characteristics from the analysis of springs natural responses: a combined methodological approach, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-372, https://doi.org/10.5194/icg2022-372, 2022.

Karst systems are composed of complex underground structures of pores, fissures, fractures, and conduits of diverse sizes and forms. An intricated network of caves and drainage systems, developed by karstification of rocks with a high degree of dissolution, is the most distinctive feature of these singular systems. The dissolution process is responsible for the widening of rock fissures and fractures, enabling the permeability and, consequently, the karst network's evolution — the more interconnected and more developed, the greater the system's karstification degree. Factors such as geological and geomorphological context, rock chemical and stratigraphic composition, rock-water interaction, underground flow dynamics, and climatic conditions are determinants to assess the degree of karstification.

The study area is located in the são Miguel river basin, in the southwest of the state of Minas Gerais, Brazil, a typical karst relief marked by the presence of sinkholes, dolines, karst springs, and caves. This region comprises carbonate rocks from the Sete Lagoas Formation (Bambuí Group), where some karstic systems were developed. From a hydrogeological point of view, this geological formation corresponds to a complex karst aquifer.

This work aimed to determine the degree of karstification of three karst systems (east, west, and south) in the São Miguel river basin from a geomorphological and hydrological perspective by the association of different methods widely applied in karst regions: (i) karst spring hydrograph analysis, (ii) dye tracer tests, and (iii) GIS model to identify the potential of karstification.

Methodologically, the hydrographs and particularly the recession curves of three karst springs (S1, S2, and S3) were analyzed to identify the internal characteristics of the systems. These springs constitute the karst systems' exutories and were monitored from November 2019 to November 2020. Dye tracers tests with Rhodamine WT and Uranina were applied during the dry and rainy seasons to calculate the quantitative parameters of the underground flow (velocity and dispersivity). Finally, a field mapping of regional and local structural geology, geomorphology, and speleology was performed in order to identify and limit the areas with higher karstification potential. These regional features served as parameters for the parametric analysis through geoprocessing in GIS software.

The results of spring hydrograph analysis, particularly the first stages of the recession curve, revealed that the east and south systems have a high degree of karstification, with concentrated recharge, circulation in a turbulent regime, and rapid drainage through the unsaturated zone.

From the dye tracers technique, it was possible to map the most probable routes of the three karst systems and demonstrate that the south system presented the highest velocity values (fast flow), and the east system presented the highest seasonal variations of flow parameters. The western system presented the lowest velocities, greater dispersivity, and lower seasonal variation than the other karst system. The investigation of the karstification potentiality showed that the east system was the most karstified, proved by the presence of dolines, cave entrances, and the absence of surface drainage.

This study confirms that the association of different methodological approaches is quite valuable for determining the degree of karstification of karst systems.

How to cite: Assunção, P., Paiva, I., Galvão, P., Marques, T., Schuch, C., and Fleming Marshall, P.: Inferring the regional karstification degree from a multi-method approach in Pains region, MG, Brazil, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-642, https://doi.org/10.5194/icg2022-642, 2022.

In karst coastal areas, speleothems preserved in karst caves were widely used to date the seashore emersion, as well as to infer its uplifting rate. Likewise, speleothems would be also used to approach rates of coastal subsidence. Landscape evolution and tectonic driving of Southern Spain is being investigated by relief GIS-analysis, geomorphological indicators, fault analysis and geochronology in the framework of the Spain-funded project titled “Morphomed” (PID2019-107138RB-I00). In the Westernmost Mediterranean Sea, Granada coast shows carbonate cliffs interrupted by bays and inlets filled by delta, alluvial fan and other deposits. Alluvial sediments were deposited on marine terraces located below sea level according to previous gravity and seismic studies. Cliffs barely preserve sediments such as landslides, alluvial fan deposits and karst deposits within fracture caves. Karst deposits comprise speleothems and cave detrital infills, containing fossils of continental gastropods (probably genus Iberus). A total of fifteen speleothems collected in a transect from sea level to 220 m altitude, were dated by the ²³⁸U-²³⁰Th method in Jiaotong University (China). The dating revealed ages older than 650 ka for speleothems located throughout the transect from the cliff bottom to the higher altitude areas. Field observations and datations points out the occurrence of a Chibanian karst in Granada cliff coast, but with a lack of any documented uplifting evidence (e.g., Upper Pleistocene-Holocene speleothems / raised marine deposits). This fact clashes with the occurrence of well-developed marine terraces and clear emerged Quaternary marine deposits reported in nearby shore areas sited to the West (Malaga coast) and to the East (Almeria coast) of the study area. Altogether, preliminary results suggest the relative subsidence of Granada coast since at least the Chibanian, which agrees the occurrence of submerged marine terraces and the tectonic setting defined by previous works.

How to cite: Ballesteros, D., Pérez-Mejías, C., Moreno-Sánchez, M., Reyes-Carmona, C., Azañón, J. M., Booth-Rea, G., Pérez-Peña, V., Moreno, D., González-Ramón, A., Cheng, H., Galve, J. P., and Ruano, P.: Coastal subsidence based on speleothem ages: preliminary evidence from Granada coast (Spain), 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-230, https://doi.org/10.5194/icg2022-230, 2022.

Automatic methods for detecting and delineating relief features allow remote and low-cost mapping, which has an outstanding potential for large-scale spatial analysis and calculation of morphometric characteristics of karst depressions in remote, forested and hard to cross areas. Besides geomorphology, detection methods can be also useful for wildlife ecology and similar research. We applied a filled-DTM (digital terrain model) method using LiDAR (Light Detection and Ranging) data to automatically detect dolines and other karst depressions in a rugged terrain of the Dinaric Mountains, Slovenia. For the dolines we calculated basic morphometric and morphological characteristics such as surface area, diameter, depth, slope, ruggedness and others.
To demonstrate its applicability for wildlife research, we applied it 1) in a preliminary study (Menišija plateau and Logatec-Begunje plain test area, NW Dinaric Mountains) in combination with GPS-telemetry data to assess the selection of these features by the Eurasian lynx (Lynx lynx) and 2) to analyse what characteristic are typical for those dolines where lynx killed ungulates (whole Dinaric Mountains of Slovenia).
In preliminary study we found that lynx selected for habitats in the vicinity of karst depressions, among which they preferentially used larger karst depressions. Lynx also regularly killed ungulate prey near these features. For whole Dinaric Mountains 202 kill sites were identified, among which 32.2% (n=65) were located inside dolines or in their close vicinity. Analysing the characteristics of those dolines where lynx kill sites were identified, we found that also these dolines were larger than mean and median surface area, depth, and diameter of all dolines in the Dinaric Mountains. The median with standard error of surface area of the dolines where the lynx caught its prey is 1,141.4 ± 703.2 m², has diameter of 38.8 ± 11.3 m, and is 5.2 ± 1.9 m deep. The maximum slope in these dolines ranges from 20.4 to 56.3°, which could indicate the formation of smaller walls, rocky outcrops and karren fields. Morphometric and morphological characteristics of dolines could influence success of lynx hunting.
Habitat selection for karst depressions and high proportion of killed ungulate inside or in close vicinity of dolines illustrate that karstic features could play an important role in the ecology of lynx

Key words: Karst depressions, GIS, LiDAR, geomorphology, Eurasian lynx (Lynx lynx), kill sites, microhabitat characteristics, Dinaric mountains, telemetry, spatial ecology

How to cite: Čonč, Š., Oliveira, T., Breg Valjavec, M., and Krofel, M.: Dolines as microhabitat relief feature and their importance for Eurasian lynx (Lynx lynx) ecology, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-60, https://doi.org/10.5194/icg2022-60, 2022.

Geomorphology of exposed epigene karst (EK) is determined by meteoric recharge from the surface, which creates characteristic solution landforms (karren, dolines, ponors, poljes, uvalas, etc.) conveying surface runoff to the conduit systems. In covered EK, collapse and subsidence forms are also common.  On a larger scale, EK favors the formation of plateau-topped massifs as the internal drainage diminishes fluvial erosion.

In contrast, hypogene karst (HK) is driven by rising flow from underlying aquifers or cross-formational fracture/conduit systems recharged from deep-seated sources and/or distant areas. It commonly develops without direct relationships with the surface. In the artesian type of HK (in confined multistory aquifer systems under a gravity-driven circulation regime), karstification is supported by upward leakages between aquifers in zones of piezometric lows, generally corresponding to topographic lows. Thus, there is an oblique relationship between landscape and karst systems in this type of HK. In the endogenous type of HK, solution cavities are commonly associated with cross-formational fluid-conducting fracture zones (fracture-vein fluid systems).  Hypogene caves are documented at depths up to 8 km (Tarim basin, China). With uplift and denudation, hypogenically karstified units are brought into the shallow subsurface and karst systems start receiving the surface expression. Assuming a long-term denudation rate at 1000 mm/kyr (the order typical for orogenic areas), a karstified unit at depth of 2 km can receive the surface exposure since the beginning of the neotectonic period (ca. 2 myr).

Landscape features of HK are peculiar and may occur as isolated forms but often as characteristic complexes that are commonly distributed by clusters. In hydrogeologically active HK, it is first expressed as rising flow features (vent orifices and mineral or clastic mounds). Outstanding examples are hydrothermal springs in Yellowston, USA and Lusi mud volcano in Phillipines.  Further expression of HK systems occurs as collapse sinkholes (shafts) forming over substantial solution cavities or breccias pipes. Examples are numerous from areas with varying geodynamic settings (Western Canadian Basin; Konya Basin, Turkey; Dead Sea area, Israel; Zacaton area, Mexico; Gambier volcano area, Australia). Rift conduits, when intercepted by the surface, give rise to «earth fractures» and slot canyons (Colorado Plateau; South Africa). Where intervals with extensive stratiform hypogene caves are brought to the shallow subsurface, unroofing and decomposition of these caves causes the formation of dense sinkhole fields and «rock cities». With further uplift, cliffs are often formed along karst rifts, displaying characteristic solution features of rising flow in walls.

Three complexes of landscape HK features can be identified, often representing successive stages of the geomorphological evolution: (1) rising discharge complex - vent orifices and mineral or clastic mounds; (2) areal exhumation complex - collapse sinkholes and shafts, subsidence depressions, cave unroofing features (dense sinkhole fields, rock cities), rock arches and windows, earth fractures, slot canyons, exhumation of mineralized features (sandstone, silica, and carbonate chimneys and mounds); (3) cliff complex - rock shelters, amphitheaters, tafoni, honeycomb surfaces, cavernous zones, half-tubes in the scarps. The geomorphology of HK is distinctly different from EK geomorphology by both, characteristic feature assemblages and evolution tracks.

How to cite: Klimchouk, A.: The singularity of hypogene karst geomorphology, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-71, https://doi.org/10.5194/icg2022-71, 2022.

During the Quaternary, many coastal parts of the world experienced deposition of elongated shore-parallel dunes, often formed from reworked shallow-marine biogenic carbonate sediments or ooids. These dunes cement rapidly, many of the early Holocene dunes are already cemented, and are termed aeolian calcarenite or aeolianite. Carbonate dune systems are found in a wide variety of environments world-wide, but they are most extensive between 20° and 40° latitudes in both hemispheres.

Internally the dunes typically show large-scale aeolian cross-bedding deposition discontinuities marked by palaeosols or, less commonly, shallow-marine or swamp sediments. The general topography comprises subdued ridges and swales, which are remnants of the original coastal carbonate dunes. Karst development on such dune ridges is dependent on several interrelated conditions. The ridge must have a sufficiently high proportion of soluble material that is pure enough for the solution processes not to be impeded by insoluble residue left after solution has occurred. The higher the proportion of carbonate the more likely karst features will develop. Adequate and aggressive moisture must be available for dissolution but due to the high rock porosity and permeability the percolation of water is not dependent on the presence of fractures. Similarities exist with karst formed in geologically young marine calcarenites as the main lithological characteristics of both types of rocks are similar: high permeability and matrix porosity, and weak cementation.

Compared to older and more lithified limestones, the surface karst on coastal dune limestone is less well-developed due to the limited consolidation of the rock. Karst features such as collapse dolines and caves are similar to those developed in older, better cemented limestones, but have specific morphological characteristics: two common plan forms; simple single linear passages or chambers and single-level spongework maze systems, and vary in length from a few metres to several kilometres of passage. There are distinctive karst features e.g., solution pipes (vertical dissolutional tubes), ceiling bell holes, and the presence of root moulds and/or rhizomorphs. Some caves have extensive arrays of speleothems. Most have walls and ceilings with moonmilk.

Karst formation in coastal dune limestone begins concurrently with cementation/lithification; in geological terms, these karst processes are rapid, occurring over thousands of years. The early phase is generally characterised by caprock formation with cave development being limited to shallow caves beneath the caprock. Solution pipes can form during this phase, even within still unconsolidated sand. The late phase is characterised by a sufficient level of cementation to support extensive cave formation.

ACKNOWLEDGEMENT: We acknowledge the financial support of Slovenian Research Agency (P6-0101; I0-0031; N1-0162; J6-3142).

How to cite: Lipar, M., White, S. Q., and Ferk, M.: Quaternary Coastal Dune Limestone Karst, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-44, https://doi.org/10.5194/icg2022-44, 2022.

Poljes, characterized by extremely flat floors, are the largest depressions that develop in karst terrains. Although there has been much research about poljes in carbonate karst settings, references to these landforms in evaporite areas are anecdotic. This work documents poljes developed in the Sivas gypsum karst of Turkey, describing their neotectonic context and characteristics, and inferring their variable origins and evolutionary paths. Two different morphostructural zones can be distinguished in the area related to differential uplift associated with the active Sivas Thrust: (1) a more rapidly rising ridge associated with the thrust front, corresponding to a hanging-wall antiform controlled by an inferred footwall ramp; and (2) a low-lying area in the trailing zone of the antiformal ridge that controls the path of the Kızılırmak River, and where the poljes are located. Detailed geomorphological mapping revealed 13 flat-floored poljes with areas ranging from 1 to 8 km² and variable geometries in plan (i.e. elongated, subcircular, irregular). The bottom of the depressions is situated within the water-table oscillation zone (epiphreatic zone), locally lying below the floodplain of the Kızılırmak River, and typically host permanent or ephemeral lakes. Therefore, these basins can be considered as active base-level poljes. The poljes are mostly drained by ponors or swallow holes that commonly correspond to flood-water caves, generally with entrances at the foot of retreating gypsum scarps. Cartographic relationships indicated that poljes in the region can be initiated from: (1) flat-bottom and low-gradient relict valleys; (2) abandoned valley sections; and (3) coalescing bedrock collapse sinkholes. The evolution and enlargement of the poljes is mainly related to solutional undercutting and slope retreat, notably at lake margins, together with corrosional lowering controlled by the regional base level. In contrast with most of the poljes described in carbonate karst regions, the gypsum poljes of Sivas do not show any control by tectonic structures.

How to cite: Gökkaya, E. and Gutiérrez, F.: Origin and evolution of poljes in the Sivas gypsum karst, Turkey, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-225, https://doi.org/10.5194/icg2022-225, 2022.

Gunung Pulai and Gunung Baling (~500m a.s.l.) form the southern end of a crescent shaped ridge to the north of the town of Baling, in Kedah. This landscape is the result of karstification of the coarse sparry marble of the Baling Group, and an example of tropical karst remnant towers (karstinselberge) which are common in Peninsular Malaysia in areas with much thicker limestone. Together with the neighboring hill to the northwest, the limestone complex is possibly the remnant of a doline (a circular feature with a depression in the middle), with a diameter of about 4km. The crescent topography is formed possibly by collapse of more than half of its northwestern limb. Baling Formation comprises a variety of argillaceous, calcareous and arenaceous strata in which argillaceous beds are predominant. The Lower Silurian limestone occurs as bands, lenses or compounds of lenses measuring from a few mm to 1.6km, with the nearest distinct karst outcrop is about 10km away to the southeast. The Baling karst is the most distinct karst landscape in this area and exhibits a typical tropical karst tower despite its relatively thin strata. It hosts at least 21 caves, which are part of a system of channels and conduits draining rainwater from the ridge into Sungai Ketil. Using GIS, geomorphological analysis is carried out in an attempt to describe the landscape and its possible origin and evolution.

Glossary; gunung:mountain, sungai:river

How to cite: Muhammad, R. F., Zaidi, M. A. A., Daud, M. F. M., Ngasri, M. A. H., and Fatt, N. T.: Possible origin and evolution of the crescent-shaped karst in Baling, Kedah, West Malaysia, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-708, https://doi.org/10.5194/icg2022-708, 2022.

Sinkhole development causes significant economic losses in many karst regions worldwide. Very often, the subsidence damage is related to sinkholes induced by various types of human activity that involve alterations in the surface and/or underground hydrological systems. One of the most striking examples of human-induced sinkhole hazard is found in the rapidly evolving eogenetic salt karst of the Dead Sea. Here, the decline of the lake level caused by the use of the water in the catchment (diversion from the Jordan River) and the lake basin (pumping to evaporation ponds) has resulted in the lakeward displacement of the brackish water - fresh water interface and the development of thousands of sinkholes since 1980s. The sagging and collapse sinkholes developed in the mud flats and gravelly alluvial fans at the lake margins tend to form tightly packed alignment and clusters. These can evolve by various processes (new sinkhole occurrence, lateral growth by mass wasting, coalescence) into expanding compound subsidence depressions as much as thousands of square meters in area. Sinkhole damage in the area includes the destruction of human structures (e.g., roads, touristic facilities, dikes in the evaporation ponds) and accidents involving the shallowing of people. The extremely high activity of the sinkhole areas not only pose a major threat, but also offers and exceptional opportunity to study quantitatively their spatial and temporal evolution. The results of the analyses have implications for hazard assessment (e.g., distribution of new sinkholes, probability of occurrence, frequency-size relationships). This work analyses the geomorphological evolution between 2005 and 2021 of an area on the western shore of the Dead Sea south of the Nahal Darga alluvial fan, including several sinkhole clusters and hundreds of new sinkholes. Time-lapse cartographic inventories have been produced using aerial and satellite imagery from multiple dates, high-resolution photogrammetric models produced using aerial photographs taken from drones, and field surveys. The quantitative analysis of the sinkholes (e.g., morphometry) and their evolution patterns have been carried out coupling GIS and R software environments.

How to cite: Sevil, J. and Gutiérrez, F.: Morphometry, distribution, and evolution of sinkholes on the western shore of the Dead Sea, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-82, https://doi.org/10.5194/icg2022-82, 2022.

Subglacial carbonate deposits have been exposed on the lee sides of small protuberances on a bare polished and striated limestone bedrock surface in the immediate vicinity of the disappearing small glaciers in the south-eastern Alps (N Slovenia and NE Italy). The uranium-thorium dating of these carbonates indicates that they were deposited during the Last Glacial Maximum (LGM) and Younger Dryas (YD). The small glaciers in the Slovenian Alps (i.e., the Triglav and Skuta glaciers) are generally considered relicts of the Little Ice Age that were not continuously present due to the warm Holocene Climatic Optimum (HCO). If these glaciers had completely melted during the HCO, the the subglacial carbonates of the LGM and YD would have been exposed to frost weathering and would have had little chance of being preserved to the present day. While it has been postulated that subglacial carbonates are not very resistant to such weathering, no direct data have been available to date. Therefore, the objective of our study was to determine the rate of freeze-thaw weathering of subglacial carbonate deposits. Freeze-thaw analysis was performed in a controlled freeze-thaw chamber under dry and wet conditions. Preliminary results after 56 freeze-thaw cycles indicate an average mass loss of 2.13%. According to the high-altitude meteorological station adjacent to the Triglav Glacier, there is an average of 19 freeze and thaw cycles per year when there is no snow cover, indicating an average mass loss of 0.73% per year and a total mass loss in about 2000 years. These laboratory results suggest that the subglacial carbonates would likely have weathered in the absence of glaciers during the HCO and thus can be considered indicative of the recently exposed ice- or glacier-free surface for the first time since their deposition.

How to cite: Zorn, M., Lipar, M., Ferk, M., Cof, K., and Čretnik, J.: Subglacial carbonate deposits - a new source for studying the presence of glaciers in a glaciokarstic environment, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-698, https://doi.org/10.5194/icg2022-698, 2022.

Slovenian region Kras, a low carbonate plateau located in the south-western part of Slovenia, represents a part of the Classical Karst area with numerous and diverse surface and underground geomorphological karst features, unique in their appearance and size. More than 1.500 known caves, and the numerous more to be discovered, furnish an extensive system of habitats for various representatives of subterranean fauna, including many endemic species. Equally important is carbonate surface that determines a great biodiversity of this area. Karst landscape has already been recognized as a unique natural and cultural heritage at the international level. The paper discusses the efficiency of integration of nature heritage and biodiversity conservation measures into the huge construction projects in the Kras region. Already built new motorways and current constructions of the new track of the Divača - Koper railway line and new logistic centre in Sežana town, intensively encroach on environmentally sensitive karst landscape and ecosystem. The national legislation in Slovenia has established a comprehensive framework for systematic protection of the environment and nature. A solid framework for systematic regulation of nature protection integrated into the spatial planning and sectorial planning is provided. The building permit issued on the sides of substantive nature conservation values determine nature protection conditions and obligations for the investor and contractors before, during construction and even after if necessary. Active cooperation is provided between the investor, contractors, and the professional service for nature conservation. The permitting process complies with national and European nature conservation legislation. The investor is obliged to ensure regular observation of protected areas, affected by construction works and the implementation of mitigation measures. Regular speleological and geological supervision in case new cartological or geological features appear during the construction is carried out in collaboration with the Karst Research Institute and Slovene geological Survey. Diverse specialists monitor flora, fauna and habitat types on construction sites before, during and after construction in order to detect the potential negative impact on which they propose new mitigation measures. The conference will highlight the effective integration of nature protection legislation and nature protection control in the field in large construction projects from their planning to construction, some examples of long-standing practice of the Institute of the Republic of Slovenia for Nature Conservation will be presented. 

How to cite: Stupar, M., Cernatič Gregorič, A., and Ličen, A.: Nature Conservation and Construction Projects in the Kras Region (Slovenia), 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-267, https://doi.org/10.5194/icg2022-267, 2022.

Carbonate karst covers only approximately 5% of mainland Portugal’s land surface, with the most expressive landscapes associated to Middle Jurassic units and corresponding to the Sicó and Estremadura massifs in the central region. Multiple and complex phases of karstification were recognized, controlled by tectonics and climate. A discontinuous Meso-Cenozoic siliciclastic cover was responsible for organizing a fluvial network, as demonstrated by a set of suspended dry/blind valleys and canyons that cut the carbonate reliefs. This fluviokarst testifies how the fluvial network tries to follow the progressive and differentiate post-Jurassic tectonic uplifts of the massifs, mainly during Plio-Quaternary.

Despite this scientific knowledge, the timing of karst landscape evolution over Plio-Quaternary, including the quantitative constraints on the tectonic uplifts and long-term fluviokarst incision rates, remains poorly documented. A multi-scalar approach was used to combine geomorphological regional studies (massifs and entrenched valleys level) and local analysis of siliciclastic sediments preserved in selected caves/rock-shelters. New data were produced using a combination of intersecting sedimentological, geomorphological, geochemical, and geochronological analyses of karst record (forms and deposits).

Several types of clastic cave sediments, such as filtrates, fluvial, aeolian and marine deposits, were identified and compared with the local post-Jurassic siliciclastic covers through facies analysis. An extensive dating program of the siliciclastic fraction, relying on the ¹⁰Be and ²⁶Al cosmogenic nuclides, yield burial ages ranging from ~1.2 to 3.0 Ma.

Facies architecture of the siliciclastic sediments preserved in some small caves/rock-shelters (at an altitude of 360 m), opened on the structurally controlled western border of the Sicó massif, as well as on the slopes of the nearby Poio Novo fluviokarst valley, allow a genetic correlation with marine and aeolian deposits that, at an altitude of ca. 120 m, materialize a mainly Pliocene coastal plain. The obtained ²⁶Al/ ¹⁰Be data confirm a late Pliocene/early Pleistocene chronology for these karst infilling (from 2.3 ± 0.7 Ma to 1.5 ± 0.3 Ma), allowing to estimate local simple linear tectonic uplifts ranging from 0.08 to 0.2 mm/yr for the lasted ~3.0 Ma, being so in agreement with the more empirical values previously admitted by Soares (2006), Cabral (1995), and Ferreira (1991).

Furthermore, these marine and aeolian clastic cave sediments, previously found and describes for the Sicó massif by Cunha (1990), were already recognized in a similar topographic position on the western edge of the Serra de Candeeiros (Daveau, 1973, 1976), permitting to consider a similar uplift history also for the Estremadura massif.

Finally, in addition to strengthening the knowledge on karst landscape evolution, this study highlights the potential of clastic cave sediments as data archives for understanding local/regional morphotectonics.

How to cite: Dimuccio, L., Cunha, L., Braucher, R., and Bourlés, D. L.: Plio-Quaternary morphotectonic evolution recorded in the clastic cave sediments of Sicó massif (central Portugal), 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-351, https://doi.org/10.5194/icg2022-351, 2022.