Analiza tektoniczna uskoków w okolicy Lipna i Sierpca wyznaczonych metodą sejsmiczną

Abstract

TECTONIC ANALYSIS OF SEISMICALLY CONTROLLED FAULTS IN THE VICINITIES OF LIPNO AND SIERPC Summary The paper presents results of tectonic analysis of faults and fold structures in the area of Lipno and Sierpc (NE part of the Warsaw Syncline). For that area, there were compiled structural maps of seismic reflectors correlated with the Permian (P), Triassic (T) and Jurassic (J), in the scale 1:100,000, using time and depth seismic reflection data of J. Żaruk (1970). The Cretaceous (K) reflector was omitted because of less satisfactory correlation with a lithostratigraphic horizon. The obtained structural maps show two major brachyanticlines: Lipno (Fig. 2) and Sierpc (Fig. 3). The forms, 16-20 km in length, are disarticulated into the second-order ones with NNW - SSE oriented main axes. Moreover, the brachy-folds are curved by NNW - SSE, NNE - SSW and NE - SW oriented faults. Faults which curve brachyfolds are obliquely oriented in relation to fold axes, often leading to their displacement t SW (see Figs. 2, 3). In my opinion, the origin of the Lipno and Sierpc fold forms and major faults in the Permo- Mesozoic cover in this area is mainly related to wrench movements taking place along major faults of the Teisseyre-Tornquist Line. I interpret en echelon arrangement of the brachyfolds as a result of sinistral wrench movements along NW -SE oriented faults of the Teisseyre-Tornquist Line, connected with Laramie compression (Figs. 4A, 6B). Reorientation of regional stress field reflects a change in compression. Signs of Alpine compression acting towards the Teisseyre-Tornquist Line were dextral wrench movements. The latter resulted in origin of oblique-slip faults in the Lipno and Sierpc area, partly using synsedimentary faults (Figs. 4B, 6C).