Ancient valleys of the Ukrainian shield

Abstract

Ancient valleys of the Ukrainian shield present linear erosional depressions formed in the Precambrian basement and on the shield slopes-in the Prejurassic strata. The valleys are 200-250 m long, 3-5 km wide (sometimes to 10 km) and 100-120 m deep. The valleys are filled with alluvial-usually coal-bearing- deposits of Bajocian-Bathian, Aptian-Albian, of the Middle Eocene and Early Miocene alternated with thin marine deposits of different age. The valleys are adjacent distinctly to fracture zones, primarily of meridional or latitudinal direction. Most valleys appeared and formed in the Middle Jurassic, some of them inherited the position of Prejurassic valleys. Some valleys of the Early Devonian are also indicated. A great role of ancient valleys is marked for the transportation of material from the Ukrainian shield on its slopes and to the neighbouring region where sedimentational series formed with certain metallogenic features.