ASGP (2009), vol. 79: 159-168

ARTESIAN ORIGIN OF A CAVE DEVELOPED IN AN ISOLATED HORST: A CASE OF SMOCZA JAMA (KRAKÓW UPLAND, POLAND)

Michał GRADZIŃSKI (1), Jacek MOTYKA (2) & Andrzej GÓRNY (3)

1) Institute of Geological Sciences, Jagiellonian University, Oleandry 2a, 30-063 Kraków, Poland, e-mail: michal.gradzinski at uj.edu.pl
2) Faculty of Geology, Geophysics and Environmental Protection, AGH, University of Science and Technology, Al. Mickiewicza 30, 30-059 Kraków, Poland, e-mail: motyka at agh.edu.pl
3) Geological Museum, AGH, University of Science and Technology, Al. Mickiewicza 30, 30-059 Kraków, Poland, e-mail: a.gorn at op.pl

Gradziński, M., Motyka, J. & Górny, A., 2009. Artesian origin of a cave developed in an isolated horst: a case of Smocza Jama (Kraków Upland, Poland). Annales Societatis Geologorum Poloniae, 79: 159-168.

Abstract: The cave of Smocza Jama located in the centre of Kraków is developed in the Wawel Horst built of Upper Jurassic limestone and surrounded by grabens with Miocene clays. The cave is composed of two series: the old one has been known for ages and the new one was discovered when an artificial shaft was mined in 1974. The new series comprises small chambers separated by intervening thin walls while the old series consists of three connected together spatial chambers. The cave abounds in extensively developed solution cavities – cupolas and ceiling pockets. The internal fine-grained deposits, predominantly representing clay fraction are built of illite, mixed layer illite-smectite, kaolinite and iron oxides. They are probably the residuum after dissolution of Jurassic limestone. The cave originated in phreatic condition due to water input from below. The new series represents juvenile stage of cave evolution. The water rose through fissure-rifts located in chamber bottoms, circulated convectionally within particular chambers, finally led to bleaching of intervening walls, and hence to connection of the neighbouring chambers. The evolution of the old series is far more advanced. The rounded solution cavities imply that the cave was formed by water of elevated temperature. The lack of coarse-grained fluvial deposits, Pleistocene mammal remains and Palaeolithic artefacts prove that the cave was isolated since its inception till Holocene time. The cave originated due to artesian circulation, when the Wawel Horst was covered by imper- meable Miocene clays. A foreland basin with carbonate basement, filled with fine-grained molasse-type deposits seems to be particularly favourable for the development of artesian caves.