Budowa geologiczna rejonu Niedrzwicy

Abstract

GEOLOGICAL STRUCTURE OF THE NIEDRZWICA REGION

Summary

Recently, a Carboniferous-Devonian anticlinal form was investigated in the region of Lublin by means of seismic and during works. Owing to bitumen traces ascertained in this area, the structure seems to be of interesting importance.
The Niedrzwica anticline (Figs. 3–7) runs from NW to SE and represents a bipartite structure. Its lower part is built up of Devonian formations, and the upper one consists of Carboniferous deposits. Between the Carboniferous and Devonian a distinct angular un conformity occurs, amounting to approximately 20°.
Geological data concerning the anticline under consideration are directly obtained from the bore holes Niedrzwica IG-l and Bystrzyca IG-J. The uppermost formations of the Upper Devonian are the oldest recognized deposits building the anticline. So far unknown in the Lublin region, they are characterized by dips amounting to about 30°, locally in fault zones even 90°.
The Devonian formations are represented by two lithological series. The lower (not pierced) series is developed as dark grey nodular limestones with scarce brachiopod fauna. These are of Lower Famennian age. The upper series, the so-called Niedrzwica beds (Upper Famennian–Strunian) is built up of characteristic parallelly laminated clay- dolomite marls with subordinate intercalations of arenaceous limestones, marly sandstones and dolomitic marls. Here are found representatives of brachiopods, goniatites, pelecypods and crinoids, as well as abundant flora remains.
At the bottom of the Carboniferous there occurs a series of tuffogene sandstones and of diabases (Tournaisian – Lower Visean?). Higher up, there rest limestones with marine fauna, sandstones, siltstones and claystones with flora, forming several cyclothems (upper part of the Visean and Namurian A and B). Towards the top of the section marine deposits gradually disappear in favour of limnic formations. Along the anticlinal axis, the Carboniferous formations are represented by the Visean and Lower Namurian, in synclines also by the deposits that belong to the upper part of the Namurian and to the Westfalian. Dips of the Carboniferous formations do not exceed 15°. Manifestations of bitumens, appearing in the form of petroleum seepages, were observed mainly in nodular limestones of Devonian age. The top of the anticline is cut off by the horizontally resting formations of Upper Jurassic and Upper Cretaceous age.