Zoloushka Cave (Ukraine–Moldova)—A Prime Example of Hypogene Artesian Speleogenesis in Gypsum

Abstract

Zoloushka Cave, the third longest gypsum cave in the world (92 km) and the world’s largest gypsum cave by volume (>0.7 million cubic meter), is an outstanding example of a large maze cave formed in a multi-story artesian aquifer system due to the upward leakage between the aquifers across a soluble unit. Although local settings and evolution caused some peculiar features in speleogenesis, as compared to other large maze caves in Western Ukraine, these singularities provide further insights on variants and mechanisms of both regional and general models of hypogene artesian speleogenesis. The cave is located in the area where the host aquifer system is generally confined until present, but in one of the more uplifted tectonic blocks where the gypsum was partially incised by the nearby valley of the Prut River during the Holocene and rapidly drained due to the quarry operations since 1946. The cave experienced considerable modifications and transformations in the course of the recent transition to unconfined conditions and subsequent artificial dewatering. The geomorphological breaching of the confined aquifer system in the cave area occurred in the Holocene, i.e., later than in the area where most other large maze caves in the region are located. A relatively stable position of the water table in the upper part of the gypsum during most of the Holocene caused pronounced widening of passages, which determined the anomalously large size of passages and high indices of areal karstification in some regions of the cave. The most intense development of conduits occurred in areas where the input of freshwater from the lower aquifer was more abundant. Quarry operation and accompanying groundwater withdrawal during the last 70 years caused drastic and rapid transformations in the cave environment.