The fabric of the Culm conglomerates in the eastern parts of the Nizký Jesenik and Drahany Uplands, eastern margin of the Bohemian Massif, the Czech Republic

Abstract

The fabric of the Culm conglomerates was studied by geometrical strain analysis methods in the eastern parts of the Nízký Jeseník and the Drahany Uplands on the eastern margin of the Bohemian Massif. The shapes and orientations of pebbles were used as strain markers and the average final ellipsoids (Shimamoto & Ikeda, 1976) were calculated (final fabric ellipsoids representing both depositional and deformational influence on the sediments). The geometric strain analysis shows a predominantly depositional or only partially deformational fabric. Only at some sites in the eastern part of the Nízký Jeseník Uplands a deformational fabric of the conglomerates occurs. But there is evidence of a very weak effect of ductile shortening in the Drahany Upland probably connected with rotation of the more rigid pebbles in the viscous graywacke matrix of the conglomerates. The orientations of the long axes of the final fabric ellipsoids are more or less uniform. The long axes are predominantly orientated N-S to NE-SW in the eastern parts of the Nízký Jeseník and the Drahany Uplands, which means nearly parallel to the major structures of the Variscan orogen in this region.