The origin of sediments inside collapse dolines of Postojna karst (Slovenia)
Uroš Stepišnik - (33/1,2004)
Several hundred collapse dolines are recorded on the Slovenian karst surface. Their floors are covered with boulders, scree or a soil layer. In ponor karst areas, where water transports significant amount of allochtonous material, many collapse doline floors are made level by deposits of loamy sediment. This discussion relates to a detailed study of 15 collapse dolines near the Postojna cave system. Loamy sediment appears within several neighboring collapse dolines and covers their floors at approximately the same altitude. The sediment level preserved in the collapse dolines is commonly at the same elevation as flood loam deposits within nearby caves. It transpires that the flattening of the collapse doline floors is a result of flooding inside the karst that extended above the original floors of the collapse dolines. It is possible to predict some of the sedimentation dynamics inside the karst on the basis of the elevations of the loamy sediments within the collapse dolines. On the other hand, it is also possible to find out about collapse doline development by studying the processes inside cave systems.