Acta Musei Moraviae

Research of Permian-Carboniferous sediments of the southern part of the Boskovice Graben; an overview (Part 2. Geology and Petrography).

An overview of geological and petrologic research of the southern part of the Boskovice Graben summarizes the knowledge and points out an attention to some unsolved problems. Basement of the Boskovice Graben form Moravian and Moldanubian Zone crystalline complexes and in the eastern part also Culmian sediments. Sedimentation in the basin had a fluvial to lacustrine character. Upper Carboniferous breccias and Balinka conglomerates represent the start of deposition, locally substituted by coarse-grained sandstones. Basal conglomerates along the western margin of the basin contain pebbles of crystalline rocks of adjacent West Moravian crystalline complex together with numerous clasts of Culmian greywackes. They pass gradually upwards into gray and locally red-brown sandstones intercalated by aleuropelites, conglomerates and several coal seams, accompanied coal claystones and organic component-rich pelocarbonates with cyclic arrangement. The whole sequence belongs to the Rosice Formation. The Permian-Carboniferous boundary is located several tens of meters above the I. coal seam (the uppermost seam). Brown-red colored sandstones and aleuropelites belonging to the Padochov Formation form the dominant part of the overlying Permian sediments. Gray pelites and unique micritic clayey limestones and dolomitic pelocarbonates appear episodically. Particularly dark bituminous shale and marl (“combustible shales”), rich fossils of Lower Permian in age (Zbýšov and Říčany horizons) are conspicuous. Coarse-grained arkose to feldspar-rich sandstone or cyclic alternation of sandstoneconglomerate–siltstone beds represent the overlying deposits. Red-brown fine-grained sandstones, siltstones, slates and finally coarse-grained arkoses were recognised in their superposition. Claystones, siltstones and sandstones of the Veverská Bítýška Formation represent the topmost part of the succession. Very coarse-grained Rokytná conglomerate consisting of greywacke and limestone boulders are developed in the eastern rim of the basin where they consitute an equivalent of whole sediment complex developed in the western and central part of the Boskovice Graben. Rokytná conglomerates are product of episodic flood sedimentation (fan-conglomerates) associated with the uplift of the western margin Thaya-Ivančice (Brno) pluton. Descriptions of conglomerates, sandstones and aleuropelites and as well as a brief characteristics of bituminous sediments, hard coal, (pelo)carbonates and (sub)volcanic rocks are given.