Mezoskopowe struktury kwiatowe w dolno paleozoicznych utworach NE obrzeżenia GZW - rezultat transpresyjnego ścinania w strefie dyslokacyjnej Kraków - Myszków (Hamburg - Kraków)

Jerzy Żaba

Abstrakt


MESOSCOPIC FLOWER STRUCTURES IN THE LOWER PALEOZOIC DEPOSITS OF THE NE BORDER OF THE UPPER SILESIA COAL BASIN - A RESUIT OF THE TRANSPRESIONAL SHEARING IN THE KRAKÓW – MYSZKÓW (HAMBURG - KRAKÓW) DISLOCATION ZONE (SW POLAND)

Summary

Meso-scale positive flower structures have been observed in cores from unmetamorphosed to slightly metamorphosed Silurian flysch sequence in two boreholes located in the NE margin of the Upper Silesian Coal Basin in the vicinities of Myszków (Ż-63) and Zawiercie (RK-6). The boreholes were drilled within the major Hamburg-Kraków fault zone. The flower structures developed in rocks subjected to sinistral shear documented by low angle Riedel and P shears, strike-slip duplexes combined with reverse-slip movements on steep mesofaults. The formation of flower structures was preceded by folding (as evidenced by minor folds) and was succeeded by extensional event (resulting in formation of dilatation veins, jogs and bends). Determination of orientational parameters for one of the drill cores (RK -6) enabled assessment of principal stress directions as well as the directions of shortening and extension. The results derived from the examination of drill cores suggest sinistral motion along the Hamburg-Krak6w fault zone, accompanied by an uplift of the Małopolska relative to the Upper Silesian Massif. The fault zone was subjected to transpressional regime at that time approximately E - W shortening direction. Flower structures have not been observed in rocks younger than Silurian (Ludlow). The age of formation of the flower structures is inferred as the turn of Silurian and Devonian.