Stan rozpoznania sejsmicznego utworów paleozoiku w zachodniej Polsce z uwzględnieniem efektywności metody refleksyjnej

Abstract

Seismic investigations of palaeozoic rocks in Western Poland taking into consideration the effectiveness of seismic reflaction method In the area under study, only Zechstein deposits from the Palaeozoic rocks are within the scope of seismic methods. Within the Zechstein, the boundaries of Z1 and Z3, in some regions also of Z2, cyclothems may be traced. From older formations reflections were obtained in few cases, e.g from the Rotliegendes on the Foresudetic monocline, and from the Devonian in the area of the Pomeranian anticlinorium and Szczecin synclinorium. Reflection boundaries of the Zechstein complex are connected with high-velocity sets of anhydritic and carbonate beds that occur at the individual cyclothem interfaces and are separated by salt bodies. The northern part of the Foresudetic monocline as well as the south- -eastern part of the Pomeranian anticlinorium and Szczecin synclinorium are in the deeper portion of the Zechstein basin, where the thickness of the Werra cyclothem salts is insignificant and the reflections from anhydritic and carbonate beds of the Werra and Stassfurt cyclothems interfere, giving an interferated multiphase reflection. The southern part of the Foresudetic monocline and the northwestern part of the Pomeranian anticlinorium are situated in the coastal zone of the Zechstein basin, in which the thickness of the Werra cyclothem rock salt separating high-velocity sets of the Stassfurt and Werra cyclothems, increases. This makes the reflection split into two bunches: lower (boundary Zl) and upper (boundary Z2). The reflection boundary Z3, which just as Zl is recorded almost all over the area in question, is connected with anhydritic and carbonate beds of the Leine cyclothem. In the nearest-shore part of the Zechstein basin, where the thickness of Stassfurt salts is small, Zl and Z2 reflections interfere giving a common reflection. A characteristic feature of Zl boundary is its unconformity with the overlying boundaries, this being due to salt tectonics in the Stassfurt and Werra cyclothems.