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.