The Ve?erná-?árka cave system (KuchyňaOre?any Karst, Malé Karpaty Mountains, Slovakia) – tectonically controlled phreatic speleogenesis in the marginal part of block mountains

摘要

The Ve?erná-?árka cave system is the longest underground site of the Kuchyňa-Ore?any Karst (Malé Karpaty Mountains, western Slovakia). Although its length is only 58 m, it is a site of remarkable interest in terms of speleogenesis that was strongly controlled by tectonic structure of the Middle Triassic limestone (Fatric Unit). Morphologically, the studied cave system represents a branched cave, formed by linear, and in some places intersecting passages. Their direction is strongly linked with two systems of steep parallel and crossing tectonic failures of N–S and NW–SE direction. Phreatic morphologies of passages show that the cave system originated by dissolution of limestone along these tectonic discontinuities, in several places the cave passages were enlarged by the destruction of parallel rock partitions. Probably, waters of deeper circulation ascended along steep tectonic fractures. Since these waters were relatively saturated, limestone mostly dissolved in the zone of mixing with seeping rainwater. A dense network of steep parallel and intersecting tectonic fractures allowed to diffuse groundwater circulation without much concentration of water flow into one or more main conduits. The absence of water table notches, ceiling cupolas as well as blind oval chimneys indicate that the caves formed below or just below the former piezometric surface of groundwater and without its significant oscillations, e.g. in the shallow phreatic zone. The estimated Pliocene (or late Pliocene?) age of the cave system (lying at an altitude of 413–419 m asl.) is determined based on its location above the recent hydrographic network (60 m above the floor of the valley) and by the remains of the Plio-Pleistocene planation surface located at 250–350 m asl. in the adjacent part of the Malé Karpaty Mountains.