Hypogene Karst in Macedonia

Abstract

Research on hypogene karst in Macedonia is quite a recent topic, with systematic study of some areas starting only few years ago, although certain caves with genetic characteristics attributable to hypogene speleogenesis have been described before. Hypogene karst is presently known from three areas: Mariovo, Katlanovo and Krcin. All of the registered examples are connected to hydrothermal karstification in pre-Cenozoic rocks, along the boundaries of Neogene basins formed within the South Balkan extensional system (northern part of the Aegean extensional regime). Deep circulating meteoric waters were heated due to the increased geothermal gradient, discharging mostly along faults at basin boundaries, with subsequent evolution of the hypogene karst systems governed by the lowering of the base level due to valley incision, thus controlling spring positions. Best studied is the hypogene karst in Mariovo, where hydrothermal karstification is locally combined with ghost-rock weathering (in dolomitic marble and dolomite, e.g., Karsi Podot Cave and Allchar ore deposit), and sulfuric acid speleogenesis (e.g., Provalata Cave, likely connected to the nearby coal basin; or due to oxidation of metal sulfides, i.e., Allchar ore deposit/Kožuf thermal springs). At Katlanovo Spa, where hypogene karst is developed in marble, thermal springs are found at the bottom of the valley discharging water from deep faults, with thick travertine deposits found also at higher elevation. A similar situation is found in the southern parts of Krcin Mountain, with thermal springs discharging from both limestone (Banjiste Spa) and evaporites (Kosovrasti Spa), and a number of caves with hot air circulation located above the Banjiste Spa.