Spatial distribution, morphometry and subsidence acitvity due to evaporite disolution in a collapse sinkhole field (Ebro Valley, Zaragoza)

Abstract

In the Ebro Depression, a sinkhole field covering 0.25 km with 158 collapse dolines has been studied. The subsidence features are related to the intraestratal dissolution of evaporite sediments mantled by a thin alluvial cover. Both, the elongation and alignment of the sinkholes is markedly controlled by a regional joint set trending N130-140E. Based on a detailed map elaborated in the field, the morphometry and spatial distribution of the sinkholes have been analysed. A mean value of land lowering due to solution-induced subsidence has been estimated. The activity of the sinkhole field has been assessed through periodic field surveys. The continuous precipitation record supplied by a soil erosion experimental plot located 2 km apart has allowed to prove the relevant role that storm events play in the generation of collapse sinkholes. A single storm event of 47,6 mm, lasting 48 minutes, with a maximum intensity of 108 mm/h triggered 13 sinkholes.