Hydrochemizm strefy hipergenicznej na Wyżynie Miechowskiej

Abstract

Hydrochemical charactristic of the hypergenic zone of the Miechów Upland The hydrochemical investigations reported here covered four out of five aquifers present on the area, of the Miechów Upland. Water samples were collected from wells and spring's at 209 localities, providing material for a hydrochemical characteristics of the hypergenie zone. Twelwe water classes were distinguished, and their occurrence within the individual aquifers is presented in Fig. 2. The Upper Jurassic aquifer comprise thin-bedded limestones of Kimmeridgian age and rocky limestones of Rauraeian age, in which crevice waters occur. This aquifer is exposed at the surface on a small area in the western part of the studied region. Farther east the Jurassic aquifer plunges under an impervious roof of glauconitic marls of Santonian age, and acquires an artesian character. The chemical composition of waters expressed by the modified Kurlov’is formula (the arithmetic mean of contents of the individual ions is given in parentheses, and the minimal and maximal values outside the parentheses) is given in the Polish text (formula 1). The Senonian aquifer occurs on the major part of the investigated area. It is composed of marls, siliceous cherty, marls and gaizes. Several waterbearing horizons are present, formed above intercalations of impervious soft marls occurring within the Senonian lithological complex. It is estimated that the Senonian rocks are storing and conducting waters down to the depth of 80—120 m, while at greater depth they are practically dry. Unit well capacities range from 0.3 to 74.2 m3/h/m of depression. The infiltration amounts to 16.7 per cent of the annual rainfall. The mineralization of water has a simple character, with abundant bicarbonate and calcium ions. More rarely three ions: bicarbonate, magnesium and calcium are present in abundance. The composition expressed by the modified Kurlov’s formula is given in the Polish text (formula 2). The Miocene aquifer comprises three water-bearing horizons, occurring in sands of the sub-Lithothamnium beds, in calcareous sandstones and sands of the Lithotamnium beds, and in gypsum of the Gypsum beds. The water occurring in sands has a low mineralization, and the ionic composition of the dry residue is simple. Instead, the waters of the calcareous sandstones have a higher mineralization, ranging up to 1369 mg/1 of dry residue, with three or four abundant ions. The highest mineralization is present in the water of the gypsum water-bearing horizon. The ionic composition (given in the Polish text, formula 4) show little variation. The rapid exchange of waters in the gypsum karst prevents a higher mineralization. The Pleistocene aquifer comprises two water-bearing horizons, one occurring in loess, the other in fluvioglacial sands and gravels. The mineralization and the ionic composition is variable as indicated by the wide range of content of various ions (see formula 6, Polish text). The highest mineralization of water was noted in lloesis. This is caused by the fine- -grained nature of the rook favouring solution of mineral particles, and by the slow filtration of water. In the fluvioglacial rocks, where the exchange of water is more rapid the water mineralization is several times smaller.