Krk Island located in the Dinaric karst is characterized by somehow contradictory, yet undefined depressions of linear geometry. A comprehensive spatial analysis considering over 900 linear features ...has served as a testing ground for revealing the specific circumstances required for the occurrence of linear morphology on the surface of rather pure karst typically characterized by dolines. Morphologic characteristics, spatial distribution and direct field evidence imply that linear features of different appearance are the outcome of, to the different stages reshaped, karstified, lithologic and tectonic structures. Due to specific regional climate conditions, they have been subsequently modified by the sporadic, fluvial processes of different degrees of intensity. Recently, such linear features hold dry valley- or dry gorge-like appearance. This example from the Dinarides gives the insight into possible circumstances that may cause a temporal surface runoff and consequentially result in the existence of an apparent fluvial surface morphology even in rather pure karst conditions. This knowledge is valuable for understanding other karst areas expressing temporal fluvial activity or imprints of past fluvial processes.
We characterize the fracture pattern, including both meso-scale joints and macro-scale faults, within the central sector of Sierra de las Nieves (Betic Cordillera, S Spain), which contains one of the ...largest karstification systems in Europe. Structural data were compared with the direction pattern of the karstic conduit network of the largest caves. Carbonate rocks were deformed in a collisional setting and exposed at the surface since the early Miocene. Normal and normal–oblique faults trending NW–SE to WNW–ESE are the most prominent brittle structures, having formed coevally with shorter NE–SW normal to normal–dextral after the main thrusting phase. In addition, two main open joint sets striking NW–SE and NE–SW developed on a broad scale. Orthogonal normal faults and open joints suggest an extensional setting characterized by horizontal minimum (S3) and intermediate (S2) stress axes of similar magnitudes that intermittently shifted their positions during the middle-to-late Miocene. Vertical water flow coming from direct recharge sectors tends to infiltrate across these high-dipping faults, mainly concentrating at fault intersections, thus favoring sub-vertical conduit formation within the vadose zone. Horizontal paleo-phreatic levels are perched linked to the recent uplift undergone by the sector, giving us the opportunity to analyze the incidence of fractures at the phreatic zone. Joint sets determine the hydraulic anisotropy within the former phreatic levels. Because our study illustrates the primary role of diverse tectonic structures during massive multiphase cave development above and below the water table, it could contribute to better constraining of the models of karstic conduit formation.
•Diverse tectonic structures control massive multiphase cave development.•Fault intersections favored sub-vertical conduit formation within the vadose zone.•Horizontal paleo-phreatic levels are perched linked to the uplift undergone by the sector.•Joint sets determine the hydraulic anisotropy within the former phreatic levels.
Between the Guapiara Plateau and the Paranapiacaba Range, Southern Brazil, there are karst systems that are under constant pressure from anthropic advancement of various natures, such as mining of ...carbonate rocks, forestry, agriculture, and human settlement itself. Karst systems develop differently in both geomorphological compartments. At the Guapiara Plateau the karst is not very expressive with scattered and rare karst features in all carbonate bodies covered by this study. The most cushioned relief, with relatively low hydraulic gradients and the short time of exposure of the carbonate rocks did not allow the full development of a karst system at the plateau. At Paranapiacaba Range, the most rugged relief, associated with high hydraulic gradients, purer carbonates and longer exposure of the carbonate rocks, allows karst features to be more concentrated, and greater development in relation to the plateau. This study presents the karst vulnerability and environmental zonation based on geologic and geomorphologic aspects, using EPIK and KDI methods. At the Guapiara Plateau, the karst vulnerability is low and human settlement is more expressive, with little risk to the system and the people who settled there. At Paranapiacaba Range the presence of karst features is constant and concentrated so the vulnerability is very high, but the presence of protected areas to guarantee the preservation of this type of system and the low occupancy and human interference. This study can contribute to public policies for future land use, minimizing any impacts on the karst region.
The cenotes near Mt Gambier are circular, cliffed, collapse dolines containing water-table lakes up to 125
m deep, floored by large rubble cones. They lie in a flat, coastal plain composed of ...mid-Tertiary limestone. Most of the deepest cenotes are concentrated in two small areas located along trends sub-parallel to the main joint direction in the limestone. The cenotes do not connect to underwater phreatic passages, and water chemistry data confirm that they are not part of an interconnected karst network. They formed by collapse into large chambers (up to >
1 million m
3) that extended 125
m or more below the land surface. Several cenotes have actively growing stromatolites on the sub-vertical walls that started growing at ∼
8000
years BP.
The caves that collapsed to form the deep Mt Gambier cenotes are much larger than shallow and deep phreatic caves in the area, and do not connect into deep phreatic systems. They were not formed by freshwater/seawater mixing, responsible for many of the well-known Yucatan cenotes, because they are not associated with locations of the mixing zone during previous high sea levels, and are much larger than caves presently forming along the mixing zone near Mt Gambier. Instead dissolution was most likely due to a process whereby acidified groundwater containing large amounts of volcanogenic CO
2 ascended up fractures from the magma chambers that fed the Pleistocene–Holocene volcanic eruptions in the area; deep reservoirs of volcanogenic CO
2 occur nearby.
Cave dissolution could have been due to release of CO
2 during the Mt Gambier eruption ∼
28,000
years ago, followed by collapse to form cenotes during the low sea levels of the Last Glacial Maximum ∼
20,000
years ago. The cenotes then flooded ∼
8000
years ago as sea level rose, and stromatolites began to grow on the walls.
The increasing awareness of some local and international authorities has promoted the appearance of new legislation and the rising of research works focused in the prevention of damage to the ...cultural heritage in karstic caves. Nevertheless, karstic areas usually imply complex studies, and a universal methodology is very difficult to establish. This work exposes the basic methodology for the geological risk assessment in archaeological site and/or rock art bearing karstic caves getting a strategy that provides flexibility to adjust specific methods according to the conditions of different cases. The integrated use of basic geological (mapping, petrology, stratigraphy…) and geotechnical (rock mass quality analytical methods and indexes) techniques used in engineering geology is proposed. Those techniques permit the geological characterization of the rock mass, the hazard identification and the analysis and the geological risk assessment of the research area. Obtained geological risk areas could be included in protection areas that could be used as the basis for the selection of the areas where further investigations and the application of prevention/mitigation measures would have a better cost/benefit ratio. The geological risk should be considered together with other type risk evaluations in order to define effective protection areas.
Discrete underground drainage conduits in quartz sandstones are far less common than in limestones. This paper provides field evidence from the quartzose Precipice Sandstone in the Carnarvon Range of ...south-central Queensland, Australia, for tubular underground drainage networks similar in many ways to limestone conduits. Diameters range from less than 1 or 2 cm to over 1.5 m, most display a near-circular to oval cross-section that seems to suggest phreatic or epiphreatic development, and the internal surfaces of many are case-hardened by secondary silica deposits. A number of the region's perennial springs appear to be fed by such tubes.
The dominant vertical jointing of the quartz sandstone and relatively high permeability of the sandstone are important controls on tube formation. Solutional weathering of the sandstone is widespread, and is followed by the removal of loosened sand grains by flowing underground water, the process of ‘arenisation’. Tube development would appear to have been happening for a very long time, and may still be occurring. A model for tube network formation is proposed.
These findings highlight our potentially poor understanding of groundwater flow within some quartz sandstones, and may have important groundwater management implications.
Coastal caves throughout the Caribbean basin have provided critical environmental settings for diverse human activities spanning many cultural periods and have ranged from ceremonial, mortuary or ...ritualistic applications to the practical uses of such shoreline structures within the context of past subsistence strategies and subsequent post-contact commercial exploitation. Coastal caves can harbor significant cultural resources, serving as repositories of archaeological and historical materials as well as providing critical physiographic components of cultural development in the Puerto Rican islands. However, anthropogenic uses of coastal cave sites of the Puerto Rico mainland have received limited attention in comparison to the numerous archeologically and geologically significant cave and karst sites located in the island interior. The comparative distribution and diversity of coastal cave rock art forms can serve as indicators of anthropogenic uses, forming an important baseline data set contributing to a more complete understanding of long-term cultural uses of littoral sites. This study integrates an overview of anthropogenic influences on Puerto Rican coastal karst landforms with their distinctive geomorphologies, correlating defined examples of cave structures with associated pre-contact and post-contact uses, contemporary human impact, and applied management/preservation strategies.
The Monte Corchia cave system, one of the most famous and popular caves in Italy, has in recent times been the subject of investigation on its speleothems as paleoclimate archives. This paper ...describes the geology, geomorphology and water chemistry of the cave system with the aim to elucidate the processes that have generated these speleothems and the properties they contain that are so useful for paleoclimatology. Some general conclusions can be drawn: i) the Corchia system is a cave developed over different altitudes during progressive uplift of the mountain chain in which it is located, probably under drainage conditions very different to those of the present. This has allowed the development of a large (ca. 60 km) and deep (-1187 m) karst system; ii) the dewatering phases have left the deepest chambers far away from clastic input and with long drip pathways; iii) the peculiar geological context has permitted the water to intercept and dissolve a significant source of U (still unknown) that facilitates radiometric dating; iv) in the last 1 Ma at least, no significant changes have occurred in the relief and in the epikarst, in the sense that speleothems have grown under very similar conditions. In addition the extremely low Ca concentration of drip waters have permitted low speleothem growth rates and, at least for the “Galleria delle Stalattiti”, the zone under paleoclimate studies,a stable plumbing system (i.e. chemistry and stable isotopes of drip waters) has produced calcite close to isotopic equilibrium.
The Mannute Caves (Salento, Italy) are a karst system that can only be reached using vertical rope techniques for caving and, hence, are not suitable for tourist visits because of their ...inaccessibility. New texture, geochemistry and age data of a peculiar type of carbonate accretion known as ‘bulky stalactites’ are presented here. Based on previous topographic surveys and observations on calcareous tufas, new geological data enables us to infer the palaeo-environmental history of the Mannute Piccola Cave. The present location of the bulky stalactites, close to the entrance of the cave, is in disagreement with an accretion process which requires sciophilous conditions. Based on U-Th dating, the growth of the bulky stalactites can be shown to have occurred in the Holocene and ended abruptly when the entrance of the cave was enlarged, probably due to a rockslide. The growing demand for geotourism in Salento suggests that management guidelines are required for coastal cave attractions, along with strategies to protect and evaluate the Mannute Piccola Cave as a potential geosite. Improved geological knowledge of the cave should be seen as a preliminary stage for geoheritage promotion through information communication technology (ICT) strategies, with the aim being to integrate the site within regional networks for cultural heritage enjoyment.
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