A genetic classification of sinkholes illustrated from evaporite paleokarst exposures in Spain (original) (raw)
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We show that clusters of karst sinkholes can occur on carbonate hypogene karst terrains. Unlike common doline karst of dissolution origin, the studied sinkholes form mainly by sagging and collapse. Thermal survey, OSL dating and morphologic analysis during quarrying and excavations are applied to study the sinkholes at the Ayyalon karst, Israel. The thermal survey shows the spatial pattern of rising warm water plumes, whose temperature is N 2°C warmer than the surrounding aquifer water. These plumes dissolve the limestone, creating large voids and maze caves. Mass wasting forms surface sinkholes mainly by sagging and collapse. Both types of deformation often occur within the same depression. Lack of hydrologic connection between the surface and underground voids constrain drainage and promote rapid accumulation of colluvium, dust and pedogenic clays. These have filled the sinkholes up to their rim before the late Holocene. OSL dating constrains the rate of sediment accumulation within the sinkholes. The average filling rate (thickness divided by elapsed time) is~47 mm ka −1 for the last 53 ± 4 ka in Sinkhole 1, while in Sinkhole 2 ("Nesher Ramla karst depression"), the rate is~61 mm ka −1 from 200 to 78 ka, and~173 mm ka −1 since~78 ka. Between~170 and 78 ka, Sinkhole 2 was intensively used by Middle Paleolithic hominins. The studied sinkholes may be considered as a type locality for hypogene sinkhole terrain on carbonate rocks.
Geomorphology, 2009
A detailed sinkhole map has been produced in a stretch of the Ebro Valley (40.8 km 2 ) including the western sector of Zaragoza city (NE Spain). During the last few decades, around 70% of the original sinkhole area has been filled with anthropogenic sediments causing the disappearance of 137 ha of wetlands. The interstratal karstification of salts (halite and glauberite) and a WNW-ESE-trending joint set have played a major control in the development of sinkholes. Three morphometric types of sinkholes have been differentiated, each attributed to a specific subsidence mechanism inferred from the paleosinkholes exposed in the surrounding of Zaragoza city; sagging of bedrock and cover, collapse of bedrock and cover, and collapse of cover material related to the downward migration of particles through dissolutional conduits. Each type of sinkhole is characterised by a distinctive behaviour in terms of controlling factors, spatio-temporal distribution and kinematics, and consequently the proposed differentiation may have a practical utility. The vast majority of the subsidence damage identified in the area occurs within the boundaries of pre-existing sinkholes identifiable in old aerial photographs and topographical maps. This fact demonstrates that the application of preventive planning strategies based on detailed geomorphological maps would have allowed avoidance of most of the large financial losses caused by subsidence in the area, of the order of hundreds of thousands of euros per year.
Earth Surface Processes and Landforms, 2007
ABSTRACT Three types of sinkhole have been mapped in a 50 km2 stretch of the Ebro River valley downstream of Zaragoza: large collapse sinkholes, large shallow subsidence depressions and small cover-collapse sinkholes. The sinkholes relate to the karstification of evaporitic bedrock that wedges out abruptly downstream, giving way to a shale substratum. Twenty-three collapse sinkholes, up to 50 m in diameter by 6 m deep, and commonly hosting saline ponds, have been identified in the floodplain. They have been attributed to the upward stoping of dissolutional cavities formed within the evaporitic bedrock by rising groundwater flows. Twenty-four large shallow subsidence depressions were mapped in the floodplain. These may reach 850 m in length and were formed by structurally controlled interstratal karstification of soluble beds (halite or glauberite? and gypsum) by rising groundwater flow and the progressive settlement of the overlying bedrock and overburden sediments. A total of 447 small cover-collapse, or dropout, sinkholes have been recognized in a perched alluvial level along the southern margin of the valley. These sinkholes result from the upward propagation of voids through the alluvial mantle caused by the downward migration of detrital sediments into dissolutional voids. The majority of these sinkholes, commonly 1·5–2 m in diameter, are induced by human activities. Over the karstic bedrock, there is a significant increase in sinkhole density downstream. This is interpreted as being a result of the evaporitic bedrock wedging out and the convergence of the groundwater flow lines in the karstic aquifer. The collapse sinkholes in this area, locally with a probability of occurrence higher than 140 sinkholes/km2/year, cause substantial damage to the linear infrastructures, buildings and agriculture, and they might eventually cause the loss of human lives. Copyright © 2006 John Wiley & Sons, Ltd.
Evaporite karst and sinkholes: a synthesis on the case of Camaiore (Italy)
Environmental Geology, 2008
In 1995 a sinkhole suddenly formed at Camaiore (Tuscany, Italy), causing destruction or heavy damages to several houses and resulting in the evacuation of many people. To understand the causes, for the formation and evolution of the collapse, surface and underground geologic features were investigated and reconstructed on the basis of geologic and geognostic surveys. The sinkhole area is underlain by thick alluvial deposits that cover a bedrock consisting of the Calcare cavernoso formation. This formation results from hydration and dissolution of Triassic evaporites and has a characteristic spongy and vacuolate texture. The bedrock contains karst cavities, generally filled by breccia and/or alluvial materials. Thus, the sinkhole disaster could be ascribed to deep collapse of a cave in the bedrock, and might be considered a distant effect of ancient karst phenomena in evaporites.
Collapse sinkholes in the carbonate massifs of Central and Southern Apennines
Acta Carsologica, 2012
This study focuses on karst collapse sink�oles of t�e sout�ern and central Apennines region (Italy), and �as t�e aim of outlining and discussing t�e factors w�ic� contribute to t�e occurrence of collapse p�enomena. By t�e analysis of t�e mor-p�ometrical/morp�ological features of t�e about 600 initially identified sink�oles, about 50% were interpreted as collapse sink�oles related to karst p�enomena, w�ic� are t�e object of t�is study. These were geo-referred and organised in a data base, in w�ic� information on t�e geological-structural and �ydrogeological features of areas affected by t�e collapses was also reported. The collapse sink�ole inventory was paralleled by an analysis of t�e distribution of t�e main mineral springs (H 2 S-and CO 2 -ric� waters), of travertine bodies and of extensional faults wit� late quaternary activity, w�ic� were all considered significant to t�e study due to t�e interrelations linking travertines, karst solution processes, CO 2 -ric� waters and faults. Furt�ermore, wit� t�e aim of investigating t�e role of seismic s�aking in t�e occurrence of t�e collapses, t�e karst collapse sink�ole distribution was compared wit� t�e distribution of stronger �istorical eart�quake epicentres. The results of t�is regional scale synt�esis suggests a possible key to t�e interpretation of karst collapse p�enomena. The latter, in fact, appear correlated to t�e combination of peculiar conditions, w�ic� may be envisaged in t�e presence of active faults and mineral waters. The study, in particular, suggests t�at karst collapse sink�oles result from en�anced dissolution p�enomena related to t�e rising of fluids of deep origin, for w�ic� active
Sinkholes are one of the most hazardous phenomena due to their occurrence and unpredictability. In the Friuli Venezia Giulia Region (northeast Italy), the presence of outcropping, mantled or capped evaporites is the main predisposing factor for these phenomena. Even if evaporites do not exceed 1% of the entire regional territory, their presence causes catastrophic events mainly in the Carnian alpine valleys. Chalks are included in the Bellerophon Formation (Late Permian) and in the Raibl one (Upper Carnian). These weak rocks are mainly located in the valley bottoms and not at the top of the mountains. Even if, in correspondence of the northern ridges of Sauris municipality, several sinkholes have been observed. In detail, north of Sauris, quartz sandstones and micasiltstones belonging to the Werfen Formation (Triassic) are widely present. These rocks, capping evaporitic ones, belonging to the Bellerophon Formation, are jointed and characterized by a secondary permeability. Over time...
Sagging and collapse sinkholes over hypogenic hydrothermal karst in a carbonate terrain
We show that clusters of karst sinkholes can occur on carbonate hypogene karst terrains. Unlike common doline karst of dissolution origin, the studied sinkholes form mainly by sagging and collapse. Thermal survey, OSL dating and morphologic analysis during quarrying and excavations are applied to study the sinkholes at the Ayyalon karst, Israel. The thermal survey shows the spatial pattern of rising warm water plumes, whose temperature is N 2°C warmer than the surrounding aquifer water. These plumes dissolve the limestone, creating large voids and maze caves. Mass wasting forms surface sinkholes mainly by sagging and collapse. Both types of deformation often occur within the same depression. Lack of hydrologic connection between the surface and underground voids constrain drainage and promote rapid accumulation of colluvium, dust and pedogenic clays. These have filled the sinkholes up to their rim before the late Holocene. OSL dating constrains the rate of sediment accumulation within the sinkholes. The average filling rate (thickness divided by elapsed time) is~47 mm ka −1 for the last 53 ± 4 ka in Sinkhole 1, while in Sinkhole 2 ("Nesher Ramla karst depression"), the rate is~61 mm ka −1 from 200 to 78 ka, and~173 mm ka −1 since~78 ka. Between~170 and 78 ka, Sinkhole 2 was intensively used by Middle Paleolithic hominins. The studied sinkholes may be considered as a type locality for hypogene sinkhole terrain on carbonate rocks.
2011
Collapse sinkholes distribution in the carbonate massifs of central and southern Apennines This study focuses on karst collapse sink�oles of t�e sout�ern and central Apennines region (Italy), and �as t�e aim of outlining and discussing t�e factors w�ic� contribute to t�e occurrence of collapse p�enomena. By t�e analysis of t�e mor-p�ometrical/morp�ological features of t�e about 600 initially identified sink�oles, about 50% were interpreted as collapse sink�oles related to karst p�enomena, w�ic� are t�e object ACTA CARSOLOGICA 40/1-2011 96 ANTONIO SANTO, ALESSANDRA ASCIONE, SOSSIO DEL PRETE, GIUSEPPE DI CRESCENZO & NICOLETTA SANTANGELO faults represent preferred pat�ways, and favoured by t�e presence of a relatively s�allow water table. In t�e collapse events, an important role is possibly played by seismic s�aking.
Sinkhole development in the Sivas gypsum karst, Turkey
The extensive gypsum karst of Sivas, Turkey is one of the most outstanding examples of bare gypsum karst in the world. It displays a number of remarkable geomorphic features, including: (1) two stepped planation surfaces cut-across folded gypsum developed during an initial phase of slow base level deepening punctuated by periods of stability; (2) unusual deeply entrenched gypsum canyons related to a subsequent phase of rapid fluvial incision and water table lowering; (3) a polygonal karst of superlative quality mainly developed in the upper surface; (4) relict valleys disrupted by sinkholes in the lower erosional surface; (5) a large number of bedrock collapse sinkholes mostly associated with the lower surface; and (6) numerous cover subsidence sinkholes developed in the valley floors. This work analyses the spatial distribution, characteristics and evolution of the sinkholes within the broad Plio-Quaternary geomorphological and paleohydrological evolution of the epigene karst system dominated by autogenic recharge. A cartographic sinkhole inventory has been produced in an area covering 2820 km 2 with morphometric data and including 295 bedrock collapse sinkholes and 302 cover subsidence sinkholes. The different sinkhole types show a general spatial zonation controlled by the hydrogeological functioning of the different sectors: (1) solution sinkholes (polygonal karst) in the upper recharge area; (2) bedrock collapse sinkholes in the lower denudation surface and close to the base level, where well developed caves are inferred; and (3) cover subsidence sinkholes, with high densities probably associated with areas of preferred groundwater discharge. The morphology of the bedrock collapse sinkholes, varying from small cylindrical holes to large and deep tronco-conical depressions with gentle slopes reflect to geomorphic evolution of these sinkholes that reach exceptionally large hectometre-scale diameters. Their evolution, involving substantial enlargement and deepening, is attributed to the solutional removal as solute load of large volumes of gypsum by downward vadose flow. This type of morphological evolution with significant post-collapse solutional denudation differs from that observed in carbonate rocks characterised by lower solubility and erodibility. The analysis of historical imagery reveals that bedrock collapse sinkholes currently have a very low probability of occurrence and that buried cover subsidence sinkholes are used for urban development creating risk situations.