The origin, typology, spatial distribution and detrimental effects of the sinkholes developed in the alluvial evaporite karst of the Ebro River valley downstream of Zaragoza city (NE Spain)

摘要: Three types of sinkhole have been mapped in a 50 km2 stretch the Ebro River valley downstream Zaragoza: large collapse sinkholes, shallow subsidence depressions and small cover-collapse sinkholes. The sinkholes relate to karstification evaporitic bedrock that wedges out abruptly downstream, giving way shale substratum. Twenty-three up m diameter by 6 deep, commonly hosting saline ponds, identified floodplain. They attributed upward stoping dissolutional cavities formed within rising groundwater flows. Twenty-four were These may reach 850 length structurally controlled interstratal soluble beds (halite or glauberite? gypsum) flow progressive settlement overlying overburden sediments. A total 447 cover-collapse, dropout, recognized perched alluvial level along southern margin valley. result from propagation voids through mantle caused downward migration detrital sediments into voids. majority these 1·5–2 diameter, are induced human activities. Over karstic bedrock, there is significant increase density downstream. This interpreted as being wedging convergence lines aquifer. this area, locally with probability occurrence higher than 140 sinkholes/km2/year, cause substantial damage linear infrastructures, buildings agriculture, they might eventually loss lives. Copyright © 2006 John Wiley & Sons, Ltd.