Gypsum Karst in the CrotoneProvince (Calabria, Southern Italy)

Povzetek

Področje Kalabrije v južni Italiji predstavlja izreden primer krasa v sadri, ki vključuje tudi evaporitne kamnine triasne do miocenske starosti. Triasni evaporiti se pojavljajo v sekvenci debeli okrog sto metrov na področju obmorskega hrbta na zahodni obali Kalabrije. Na drugi strani pa evaporiti mesinske starosti obširno izdanjajo na vzhodu, v krotonskem bazenu. Pričujoči prispevek opisuje glavne značilnosti krasa v sadri (od površinske kraške morfologije do razvoja jam) na vzhodnem predelu Kalabrije. Krotonski bazen je med najbolj zanimivimi področji evaporitnega krasa v Italiji: tam najdemo različne površinske kraške oblike kot so vrtače, slepe doline, zaprte depresije, globoke in ozke soteske, kjer zasledimo intenzivna pobočna gibanja. Številni vhodi jam so na dnu vrtač. Jama Grave Grubbo, dolga prek 2.500 m, je ena daljših jam v Italiji v evaporitih. Na raziskovanem področju je prišlo do številnih sprememb, še posebno zaradi kmetijske dejavnosti in zaradi nezadostne pozornosti lokalnih oblasti do te izjemne pokrajine. Posebna vrednost krasa v sadri v Kalabriji še ni v celoti ovrednotena. Prišlo je namreč do onesnaženja številnih jam in posledično do znižanja kakovosti vode, ki teče v kras.

The Calabria region of southern Italy presents remarkable examples of gypsum karst, involving evaporite rocks ranging in age from Trias to Miocene. Triassic evaporites are limited to a sequence of about one hundred meters of thickness in the Coastal Chain, on the western Calabrian coast. Messinian evaporites, on the other hand, extensively crop out to the east, in the Crotone Basin. The present contribution intends to describe the main features of gypsum karst in the latter area, from the surface karst morphology to the development of caves. The Crotone Basin is among the most interesting areas as regards evaporite karst in Italy: a variety of surface karst landforms is there present, including dolines, blind valleys, closed depressions, and deep and narrow canyons intensely affected by slope movements. Many caves are located at the bottom of the dolines, as Grave Grubbo which, with a length over 2,500 meters, is one of the longest Italian caves in evaporites. The study area has experienced several transformations, mostly due to agricultural activity and to scarce attention paid by local administrators toward this unique naturalistic landscape. The high value of Calabrian gypsum karst is thus not fully exploited, and several cases of degradation of the caves have been registered, even with consequences for the quality of water flowing in the karst systems.