The pictures display the 3 sinkholes of 5-8 meters of diameter evryone that align east-west in one crop on the basis of northern slope of Puig de Sanç, left side of stream of Tordell by the neighbourhood of Joncarets, in Suria. They are known as the basinholes of Joncarets. Their depth varies. As the pictures are seen, nr.1 is cylindrical and 8 meters depth, nr.2 is funnel shaped and its deeper than 25-30 meters bottom can’t be clearly seen, and nr.3 is cylindrical as nr.1 although only 4-5 meters depth. The sinkhole nr.1 is the youngest, it appeared in 04.12.2000. West from sinkhole nr.3, one smash of the land of just 1 meter depth so far insinuates another one.
The sinkholes of Joncarets are placed in the south, riding side of the big inverse fault of Tordell. The sinkholes align parallel to the fault plane that on surface is located several hundred of meters north. The materials are grey sandstones and mudstones from period Eocene that lay above the gypsum that reaches surface in Joncarets which again is above the salts from geological formation Cardona. The whole south side of the fault of Tordell rides above the more modern red mudstones of period Oligocene. The gypsum and the salts of south side spread through the plane of the fault in a diapir structure that’s similar to that of valley of salt of Cardona.
The sinkholes of Joncarets must result from karstic cavities by dissolution of gypsum rock that can’t be so in depth, and the sudden collapse of the ceiling. Their circular shape, the collapse events not as frequent as the ones that in 1999 and 2000 brought chaos in La Coromina (Cardona) in salt material as well as the stratigraphic position of the gypsum above the salt, all views suggest that the original karstic cavities are into gypsum, less soluble than salts. Nevertheless, since original cavities can’t be seen, some role of the salts can’t be disregarded yet. Perhaps the deeper sinkhole nr.2 is a narrow entrance to an unexplored, white and beautiful cave in gypsum; who knows!
Most likely process is alive, therefore the area risks of new collapses.
[photos Jordi Badia, January 2016]