Geologiczne warunki występowania konkrecji fosforytowych w pstrych marglach węglowieckich (górna kreda) Karpat Środkowych

Abstract

GEOLOGICAL CONDITIONS OF OCCURRENCE OF PHOSPHORITIC CONCRETIONS IN THE WĘGLÓWKA VARIEGATED MARLS (UPPER CRETACEOUS OF THE MIDDLE CARPATHIANS)In this paper the authors present the results of their investigations on phosphoritic concretions appearing in the area of the Middle Flysch Carpathians. These concretions are being found in the Węglówka variegated marls (Upper Cretaceous Chalk) of the Silesian and Subsilesian unit. They are developed in ellipsoidal, loaf-like or spherical shape, of 5 do 60 cm. in diameter; in exceptional cases their diameter is smaller. Most frequent are concretions of 20 to 40 cm. in diameter. These phosphoritic concretions are characterized by great weight and hardness. On their surface they are covered by a thin coating of manganese oxides which, however, often is obliterated. Their fracture reveals an ivory-grey colour. A chemical analysis of the phosphoritic concretions, carried out by W. Narębski (1958), showed a high content of P2O5 fluctuating between 17.86 and 28.06% and, moreover, a marked amount of carbonates of Ca, Mn, Mg and F. The principal component appearing in the phosphoritic concretions is carbonate fluorapatite; its amount varies betwe 51 and 82%.The phosphoritic concentrations appear chiefly in one of the varieties of the Węglówka variegated marls, i.e. in the grey-green marls. On the basis of microfaunal investigations, J. Liszkowa M. Sc. and S. Geroch M. Sc. have determined the age of the marl beds in which the phosphoritic concretions appear, as being Maastrichtian - Danian. These concretions are being found on at least 3 horizons; two of them have been identified in the part of the Węglówka variegated marls representing the Maastichtian - the third horizon in the marls resenting the Danian.The greatest concentration of phosphoritic concretions has been found at Bezmiechowa Górna and Olszanica. The occurrence of these concretions has been followed up on an area extending over about 200 kilometers (from Janowice on the Dunajec river as far as Olszanica near Ustrzyki Dolne).In the authors' opinion these concretions may be connected with the volcaniam of the Laraminian phase. The occurrence of phosphoritic concretions on such an extensive area, their high content of fluorapatite and their abundant appearance at Bezmiechowa Górna and Olszanica might indicate that these deposits may be of industrial significance.