Valleys and terraces formation in the course of fluvial morphogenesis within the area of the last ice sheet (a case study of the Batlic region)

Abstract

Valleys formation was controlled by a complicate temporal and spatial pattern of the earthcrust movements (both of glacioisostatic and tectonic origin), by frequent changes in local base levels formed by meltwater proglacial lakes, by changes in the World Ocean level which opened and closed intermittently the connection with ancient Baltic basins (the latter were a base level for Baltic rivers during the finiglacial and postglacial time), a certain effect on the valleys formation had changes in rivers discharge after ten water supply form the ice sheet had been stopped and pro glacial lakes drained. Under conditions of environments being highly changeable the terrace formation process was complex, with individual features in each valley. Often a large number of terraces was developed. Three cycles of active terrace formation are distinguished (Pre-Allerod, Allerod - Boreal and middle and late Holocene).