Ритми формування каньйоноподібних долин Придністров’я на прикладі Смотрицького каньйону

Abstract

In order to determine the age and conditions of formation of the Smotrich Canyon, geological, geomorphological and palynological studies were carried out, the results of which revealed that the formation of the Smotrich River valley consists of rhythms caused by the formation of terrace terraces of the Dniester River and the laying of its left (Podolsk) tributaries during the Dneprovsky degradation period glaciation. The beginning of the formation of canyonlike valleys with incision into the ancient Paleozoic rocks can be attributed to three stages; 1 - the Ice Age (Tyasminsk loess), 3 - to the Mikulinsky interglacial (Prilukskaya fossil soil). These stages correspond to the formation cycles of the lower terraces of the Dniester and the terraces of the Smotrich river. During the Valdai glacial epoch, accumulation of loess strata took place under periglacial conditions in the cold tundro-forest-steppes and the formation of fossil soils with signs of permafrost during inter-stage warming during the spread of coniferous and birch forests (sometimes with a mixture of deciduous species) of forest-steppes and swamps For the Holocene epoch (10000 - 100 y.a.), phases of warming and an increase in precipitation and humidity of the climate were established on the basis of spore-pollen data, especially in the optimally humid and warm conditions of the Atlantic period (8000–4500 y.a.), which led to the intensification of errosion processes and the further design of the canyon walls. In the Holocene, the Smotrych River meandered along the bottom of the canyon, washing up the banks, forming and eroding the ledges of the 1-2nd above-floodplain (inner cannon) socle terraces, small fragments of which survived only on the convex banks of the meanders. In the modern canyon, the levels of the 1st floodplain terrace are clearly visible, with high and fragmentary low floodplains. Deep erosia prevails in the mainstream, as evidenced by bedrock outcrops, rapids, microsouples, micro-waterfalls and bystrins (swimmenstreams). The formation of the canyon continues, as the longitudinal profile of the Smotrich bed has not been developed and depends on the main erosion basis - the level of the Dniester River, the longitudinal profile of the bed is also far from equilibrium. Now the Smotrych River continues to develop a channel equilibrium profile with a predominance of undermining the banks and canyon walls between reservoirs, the levels of which are local bases of erosion.