Fluvial terrace formation and controls in the Lower River Danube, SE Romania

Abstract

The Black Sea climatically-driven level change is the main control of the Lower Danube incision and aggradation in the long-term subsiding setting of the Eastern Romanian Plain. The interglacial episodes of aggradation suggest a decreasing fluvial accommodation. While T4 terrace fill partially buried the cut terrace T5 in the upstream part of the studied area (Lower Danube-Argeş-Dâmboviţa), younger deposition did not compensate the previous incisions. Black Sea level fallings during glaciations were followed by Lower Danube incisions which propagated upward through knickpoints. Loess deposits can be correlated with these periods. Five episodes of incision were recognized based on terrace levels T5 to T1. Their ages and of the covering loess were obtained through optically stimulated luminescence (OSL) and were correlated with MIS 6 – MIS 3 and classic glacial chronological events (latest Rissian-middle Würmian). The maximum limiting age of Danube oldest terrace (T5) in the studied area is 141 ± 25 kyr, while of the youngest (T1) is 50 ± 6 kyr. The equivalent terraces on tributaries are younger. The time delays between terrace incisions on the Lower Danube system were estimated. The 32.7–15.9 kyr Danube floodplain deposits and the 5 kyr forests buried up to 7 m under Argeş floodplain suggest that younger than 44–40 kyr terraces may be buried.