Geomorphology and hydrogeology of an exposed evaporite dome: the Dumre karst area, Central Albania

Abstract

The Dumre area, located in Central Albania, is distinguished by a landscape whose main features consist of low altitude, mosaic and irregular relief, and the presence of a large number of depressions with lakes. These features result from karst development related to the presence of a tectonically affected dome of Triassic evaporite rocks, mainly gypsum. Gypsum karstification has operated since the Pliocene, and the present-day geomorphological appearance of the area indicates an advanced, mature stage of karst development. Signs of this maturity include the widespread occurrence of large depressions, many of which are water-filled, forming lakes, the occasional presence of gypsum hills in the form of monadnocks, a thick “coating” of residual sediments largely isolating the karstic gypsum substrate from precipitation and surface waters, and the fragmentary pattern of a degraded river network. The karst character of the relief is largely “camouflaged” by clastic terrigenous and residual deposits of considerable thickness which cover the gypsum and form a caprock. At the present stage, the caprock is being strongly reshaped and eroded. Chemical analyses show a mean dissolved gypsum content of 1.9 g/l and mean dissolved NaCl content of 0.4 g/l. The mean flow rate of subaqueous springs is calculated as 1.84 m³/s. The density of gypsum is 2.3, and that of rock salt is 2.17, thus the total volume of gypsum dissolved each year is 47,420 m³ and of rock salt 10,680 m³, making a total volume of dissolved material released by the subaqueous springs in one year of 58,100 m³. This corresponds to a cubic void of side length 38.7 m.