Evaporite Karst in Calatayud, Iberian Chain

Abstract

The Cenozoic sedimentary fill of Calatayud Graben, an intramontane basin within the Iberian Chain, includes an evaporitic sequence around 500 m thick with significant halite and glauberite units in the subsurface. Interstratal dissolution of the salt-bearing evaporites has generated megacollapse structures covering up to 12 km2 in which Neogene sediments have subsided as much as 200 m. The Quaternary alluvium related to the present-day fluvial systems shows sharp changes in thickness locally reaching more than 100 m. The thickened terrace deposits fill basins several kilometres long generated by dissolution-induced synsedimentary subsidence. The area offers the opportunity to examine excellent exposures of subsidence structures and paleosinkholes that illustrate the mechanisms involved in sinkhole development (sagging, collapse, and suffosion). Dissolution and hydrocompaction subsidence has caused extensive structural damage in Calatayud city, including outstanding historical buildings. On November 2003, a collapse sinkhole undermined the foundation of a five-storey building, leading to its demolition, involving around 5 million euro of direct losses.