Osady triasowe na pograniczu mezozoicznej osłony Gór Świętokrzyskich i synklinorium brzeżnego

Abstract

TRIASSIC DEPOSITS AT THE BOUNDARY OF THE MESOZOIC COVER OF THE ŚWIĘTOKRZYSKIE MTS. AND THE MARGINAL SYNCLINORIUMSummaryAt the boundary of the Mesozoic cover of the Świętokrzyskie Mountains and tine marginal synclinorium (Fig. 1), Triassic deposits are known only from bore holes. They rest here on a dislocated Palaeozoic surface and on the Zechstein formations. The Triassic deposits we represented here by all their stratigraphical members. The thickness of these deposits varies, ranging from about 1000 metres in the area of the Mesozoic cover of the Świętokrzyskie Mountains, to about 250 metres in the area of the Lublin , synclinorium adjacent from the north-east. The changes in ·thickness took place along an enormous dislocation line (dislocation zone Iłża – Nowe Miasto) that makes a boundary between the marginal synclinorium (a part of the European platform) and the Middle-Polish anticlinorium.It results from the observations of the lithological development of the deposits considered (Figs. 2 and 3) that during the sedimentation of the Triassic deposits, the area under consideration was covered with several basins characterized by approximate environmental conditions. At the time of the Lower Buntsandstein this was a shallow-water basin in which marine influences were expressed in the form of intercalations of limestones and dolomites. They reached the area of Middle Europe through the same ways as at the Zechstein time, coming from north-west. The basin of the Middle Buntsandstein was somewhat shallower, where formations of flowing waters prevailed. Frequently, the basin passed into shallow, drying up flood areas.In Roethian and Muschelkalk, the area under consideration was covered by shallow sea. At first, at the Lower Roethian time the sea invaded the Świętokrzyskie Mountains area, whereas in the Lublin synclinorium only the uppermost member of the Roethian may be observed. Both Keuper and Roethian deposits were formed under similar conditions of a fresh-water basin.Fauna that has so far been found in the Triassic deposits of the region considered is analogous to that observed to occur in the other areas, particularly within the northern margin of the Świętokrzyskie Mountains.It results from an analysis of thickness distribution that the thickness of the individual Triassic members varies. The present authors are of the opinion that these variations may be due to the previous vertical movements of the Triassic substratum. The displacement of the individual Palaeozoic blocks took place along several zones that correspond to the dislocations ascertained to occur at present in the Mesozoic formations and to run in a NW–SE direction.