The Black Sea level during the period of the catastrophic river runoff

Sidorchuk, A.; Borisova, O.

Авторы: Sidorchuk A., Borisova O.
Сборник: INQUA 2019
Тезисы
Год издания: 2019
Место издания: https://app.oxfordabstracts.com/events/574/program-app/authors
Аннотация: O-3207 The Black Sea level during the period of the catastrophic river runoff Aleksey Sidorchuk 1, Olga Borisova 2 1 Moscow State University, Moscow, Russian Federation. 2 Institute of Geography RAS, Moscow, Russian Federation Abstract The remnants of the palaeo-channels much larger than the modern ones are widespread in the floodplains of lowland rivers in the Black Sea basin on the East European and Pannonian plains. Palynological studies of palaeo-rivers alluvium make it possible to locate the climatic and hydrologic region-analogues of the landscapes at the time of their development, from 16 to 19 ka BP. These analogues allowed reconstruction of the former surface runoff of the large Late Glacial rivers, as well as the total volume of flow to the Black Sea from the East European and Pannonian plains, using the transform functions.The mean annual water yield from this territory for several thousand years was up to 700-800 km3 and reached 2800 км3 per year for a few decades during the extreme runoff stage. This huge river runoff was the main factor of the Black sea level rise in that period. The flow velocity calculations, lithological composition of deposits and morphology of the Bosporus and Dardanelles straits shows that these canals were cleaned of loose sediments by this powerful flow, and the basement rocks were exposed. There is an uncertainty in the position of the highest rock sill, as the maximum rock surface altitude is similar in the Dardanelles and in the Bosporus (about -75…-80 m). We assume that the rock sill in the Dardanelles was formerly higher than at present (about -70 m), and was lowered down to its modern position by the powerful flow through the canal. When the ocean level was lower than the rock sill in the Dardanelles, the level of the Black Sea was controlled by flow hydraulics on this sill. The spillway flow theory was used to calculate the water level on the rock sill using discharge, critical velocity of rock erosion initiation and cross-section geometry. At the stage of the maximum discharge (the “hydrocratic” transgression of the Black Sea), sea level was about -62…-64 m. Later on, with diminishing discharge it decreased to -66…67 m. Since about 14 ka BP, when the ocean level rose above the altitude of the Dardanelles rock sill, the new stage of the “eustatic” transgression has begun. The level of the Black Sea was then controlled by the ocean level and remained close to it ever since. This study was funded by Russian Federation program “The Evolution and Transformation of Erosion–Channel Systems under Changing Environment and Human impact.”
Добавил в систему: Борисова Ольга Кимовна

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