The gravel fill beneath the lacustrine sediments of the Ljubljansko barje

Abstract

The subsidence area of Ljubljansko barje - the Ljubljana Swamp, drained at present, was filled during Pleistocene and Holocene by fluvial and lacustrine sediments. The basement consists in Southern, western and central parts of Upper Triassic dolomite nad Jurassic limestone, and in northern and eastern parts of Triassic and Permo-Carboniferous shaly mudstone and sandstone. The bottom of the basin in the eastern part of Barje is deeper than in the western part. South of Ljubljana the rocky bottom is more than 150 meters deep. Numerous depressions are filled with fluvial gravelly and sandy sediments which form about 75 % of the entire surface of the Barje. The gravel beds are percolated by ground water which occurs in the major part of Barje under artesian pressure. The gravel aquifers below lacustrine clays are recharged in part by water of small rivers, and for the major part by the karstic aquifer. Owing to relatively good protection from polution from the surface, the ground water of gravel aquifers in Barje represents an important source of drinking water.