Surface Karst Landforms Research Articles

An inception framework hypothesis for karst development in the Burren, Ireland

The Inception Horizon Hypothesis (IHH) postulates that certain stratigraphic horizons in a limestone sequence, combined with structural surfaces such as joints, provide a framework for cave development. Although subsurface and surface karst landforms are fundamentally linked, the IHH has not yet been extended to surface karstification. We tested this extension of the IHH in the world-renowned Burren karst due to its stratigraphic and structural simplicity. We used very high-resolution remote sensing datasets and detailed fieldwork to develop an updated map of the Burren's surface karst features, combined with a 3D geological model containing over 60 km of mapped cave passages.Our analysis shows that karstic connectivity between the surface and subsurface is primarily provided by a suite of vertically-persistent calcite and silica-rich veins, which form a non-stratabound fracture system across the Burren. The flow pathways provided by these veins then intersect the following inception horizons: (i) boundaries between distinct lithological units in the limestone sequence; (ii) crinoidal cycle tops, and more sporadically chert lenses, within one of those units (the Slievenaglasha Formation); (iii) thin horizons of non‑carbonates (‘clay wayboards’) within another unit (the Aillwee member). At the surface, the same horizons have been preferentially exploited by glacial processes, creating surfaces from which meteoric waters now recharge the subsurface and form new surface karst depressions and other karst landforms. Our new inception framework for karstification thus provides a new basis for understanding surface and subsurface connectivity in the karst critical zone in the Burren landscape, and it provides new geological insight into the functioning of carbonate critical zones more generally.

Groundwater Resources in a Complex Karst Environment Involved by Wind Power Farm Construction

The need to produce energy from clean energy sources has caused public administrations and private companies to look for suitable places. The windiness detected in the eastern area of the Matese karst massif (southern Italy) has favored the construction of wind farms to produce electricity from clean energy sources. During the installation of the first wind turbines, some alterations in the supply of drinking water, fed by the springs of this area, were attributed by the population to this installation. Therefore, in order to assess whether there has been an impact produced by the wind farms on the quality of groundwater, a detailed hydrogeological study was developed. Karst hydrogeological features of the area were mapped, focusing on endorheic areas, sinkholes and karst springs. Artificial tracer tests were then carried out to investigate groundwater flow circulation and connection between surface karst landforms and springs. Chemical and physical characteristics of the groundwater were monitored during the construction of the wind farms and, for the following months, by infield measurements and laboratory analysis of spring water samples. This study highlights that wind farms mainly develop along the boundary of endorheic areas, which are important recharge zones for groundwater resources, and are directly connected to the major karst springs through sinkholes and a dense network of karst conduits. The results of the monitoring did not reveal any anomalies in the quality of the water and, therefore, any alterations cannot be attributed to the wind farms. Our investigation appears useful for a better understanding of the possible actual and future effects of the wind farms on both groundwater circulation and spring water quality in this karst area.

A model of karst systems of the Usturt plateau (Middle Asia)

The issues relating to the structure and development of desert karst is currently one of the least studied problems. The goal of the research efforts presented in this paper was to create a model of karst systems in the Usturt Plateau and, primarily, of the systems formed by the prevailing numerous surface karst landforms. The model is based on the following main assumptions: the process of emergence of the karst phenomena is probabilistic and occurs independently at non-intersecting sites; the probability of emergence of one depression at a reference site depends only on its area. The increase of the dimensions of a karst landform is a random process that occurs independently of other karst landforms, its speed is governed by random factors, and it is directly proportionate to the existing dimensions of the landform. The model does not assume constancy of climatic characteristics. The testing was conducted at several reference sites of the Usturt Plateau. The research allowed us to reach the following conclusions: the karst depressions of the Usturt Plateau, which are the typical forms of desert karst, are governed by the Poisson distribution of their centres and by the lognormal distribution of their dimensions, similar to the karst depressions in a humid climate. The results may be used in assessments of karst hazard for linear and areal structures, as well as for small-dimensional structures.

Surface Karst Landforms of the Notranjska region (south-western Slovenia)

The distribution and characteristics of surface karst landforms in the Notranjska region, exemplifi ed in the Cerknisica and Rak river catchment, is presented. The geomorphology of the examined area, with respect to on the micro-, meso- and macro- forms division, is described. The course and dynamics of morpho- genetic and geological processes are analyzed. A geotourist route linking the described landforms of surface karst is proposed.

Landforms of mountainous karst in the middle latitudes: reflections, trends and research problems

Research into the landforms of karst highlands in the middle latitudes began in the “Classical Karst” in the 19th century and has been marked by alternating periods of progress and stability since. In the beginning, the elementary morpho-types were recognized, in particular the circular closed depression defined as the “karst doline”. Later the mid-latitude karst forms were compared with those of other climatic zones, especially tropical humid karst. In recent decades many papers have been published on the morphometry, the fillings, and models of the evolution of the surface karst landforms. It has been emphasized that in the mid-latitude karsts the morphogenesis is the result not only of karst solution but also of several other weathering processes such as cryoclastic (frost) action and other periglacial processes. Examination of the main scientific journals dealing with karst and other geomorphology shows that present day research in karst areas is mostly concerned with very specific subjects, such as speleogenesis, hydrogeology, sedimentology, geochemistry, mineralogy, cave biology, unusual landforms: only a minority of papers focus on karst surface landforms, and among these only a few attempt organic and comprehensive studies of the entire assemblage of relief forms in a karst morpho-unit. In reality, it is evident that the surface landform complex in a karst morpho-unit has to be considered in its entirety and that only such an integrated approach to this complex entity may bring significant progress in understanding. The landforms may be considered from different point of views, but always as a part of a holistic approach, in particular: a) in the geodynamic context of the evolution of the particular mountain group, b) as part of a complex geo-ecosystem, c) in the framework of models based on modern geomorphological concepts. Such comprehensive studies carried out by multi- and inter-disciplinary research teams applying the most modern techniques and methodologies will present stimulating challenges not only for progress in karstology but also in all the environmental sciences.

Investigation of Structure of Various Surface Karst Formations in Limestone and Dolomite Bedrock with Application of the Electrical Resistivity Imaging

Karst landforms are developed in different kind of rocks and in different structural settings. Authors are presenting some results of profile measurement of Electrical resistivity imaging in some dolines and collapse dolines that developed in lime­stone and dolomite in Slovenia. Selected features are examples of surface karst landforms whichcould be morphologically de­fined as typical of its kind. For electrical resistivity imaging data collection was used SuperSting R1/IP earthresistivity meter. Electrical resistivity imaging method was applied for researchof material characteristics beneathsurface of karst landforms. Materials withhigher portion of water as fractured bedrock or clay are less resistant to electrical current than unfractured bed­rock. Application of the ERI method has turned out as appro­priate for detailed investigation of surface karst landforms.

Erratic judgements: re‐evaluating solutional erosion rates of limestones using erratic‐pedestal sites, including Norber, Yorkshire

The re‐interpretation of surface karst landforms in Northern England has led to a re‐examination of well‐known erratic‐pedestal sites that were the origin for karst denudation rates applied extensively, on the supposition that erratics protect underlying limestone from rainwater solution. Height of the pedestal has been used to calculate long‐term solutional‐lowering, as much as 50 cm in 15 ka (33.3 mm/ka) from UK sites. The sites include Norber and Scar Close, Yorkshire, UK. This paper shows that the sites have been misinterpreted, in particular at Norber where the erratics lie on a pre‐existing structurally stepped surface. Norber and several other sites also experience much mechanical weathering, in relatively weak, well‐fractured limestones, a process which must be distinguished from solution. Sites in strong, less‐fractured limestones demonstrate lower rates, which are sounder indications of land surface lowering. Some pedestals have been confirmed as partly resulting from solutional weathering in surrounding soil and vegetation. Re‐evaluation reduces solution rates to 3–13 cm in 15 ka. Applying such rates has profound implications for understanding limestone landscapes, challenging orthodox views.

The influence of bedrock‐derived acidity in the development of surface and underground karst: evidence from the Precambrian carbonates of semi‐arid northeastern Brazil

AbstractVery extensive cave systems are developed in Precambrian Una Group carbonates in the Campo Formoso area, eastern Brazil. In contrast, the area is largely devoid of significant surface karst landforms, as would be expected given its semi‐arid climate. The caves in the area display many morphological features characteristic of deep‐seated hypogenic caves, such as lack of relationship with the surface, ramiform/network pattern, abrupt variations of passage cross‐sections and absence of fluvial sediments, but do not show evidence of vertical passages marking the ascending path of acidic water nor present extensive gypsum or acid clay mineral deposits. Hydrochemical analyses of present‐day ground water indicate that oxidation of bedrock sulphide is an active process, and sulphuric acid may be the main agent driving carbonate dissolution in the area. A shallow mode of speleogenesis is thus proposed, in which sulphuric acid produced through the oxidation of sulphide beds within the carbonates controls cave initiation and development. Moreover, the geological situation of the area in an ancient stable passive margin precludes the possibility of deep‐seated sources of acidity.Under dry climate, due to the absence of recharge, solutional landforms will be largely subdued in the surface. Hypogenic processes, if present, are likely to predominate, producing a landscape characterized by a marked disparity in the comparative degree of development between surface and underground landforms. Rates of karst landform development have traditionally been analysed through a climatic perspective, runoff being the main controlling factor in promoting karst development. This view needs to be reassessed in the light of the growing awareness of the importance of climate‐independent processes related to hypogenic sources of acidity. Copyright © 2003 John Wiley & Sons, Ltd.

Towards the prediction of subsidence risk upon the Chalk outcrop

Summary Surface karst landforms such as solution pipes, swallow holes and dolines are well developed on the Cretaceous chalk outcrop in Britain. The local frequency of these solution features on the chalk can be as high as on any of the best developed karst areas on other British limestones. However, the overall frequency of solution features for major regions of the chalk outcrop is much lower. Solution pipes, swallow holes and dolines often represent an engineering hazard because of metastable conditions, which, if disturbed, can result in ground subsidence. The research described here is aimed at producing a model to predict areas of subsidence risk upon the chalk outcrop. Considerations for the prediction of subsidence risk are outlined with preliminary analysis for two areas.