Geomorphologic evolution of the Danube at the Iron Gates (Carpathian Mts, Romania)

The Iron Gates gorge, where the Danube River cuts through the Carpathian Mountains, represents a key corridor for understanding fluvial dynamics in Central and Southeast Europe. This study presents new insights into the formation and Quaternary evolution of the Lower Danube Gorge through high-resolution morphometric analyses and relative and absolute dating of terrace sequences within the gorge and the downstream alluvial plain.

The earliest fluvial terraces, located at elevations between 270 and 320 m, mark the initial phase of river incision. Terraces T8 to T5 formed during this period and are correlated with mid–late Pliocene fine alluvial deposits and late Pliocene–early Quaternary coarser alluvial fan sediments downstream. The transition from upper (T8–T5) to lower terraces (T4–T1) in the gorge mirrors a comparable sequence in the Danube lowlands, where 7–8 alluvial terraces are identified, representing the shift from upper deltaic and alluvial fan deposits to the lower Danube plain.

This longitudinal correlation highlights a regional change from lateral fluvial erosion and downstream vertical aggradation to dominant fluvial incision and terrace formation during the Middle–Late Quaternary, influenced by ongoing tectonic uplift and glacial–interglacial climate cycles. Fossil assemblages support a Late Pliocene–Early Quaternary age for the upper terraces, while newly obtained OSL dates for the younger terraces at the gorge exit (T3–T1) correspond to Marine Isotope Stages 3–1.

The results reinforce the antecedent drainage model for the Danube at the Iron Gates, suggesting episodic incision superimposed on an actively uplifting landscape.

Acknowledgments: This research was funded by the ChronoCarp project (Contract no. 760055/23.05.2023, project code CF 253/29.11.2022, PNRR-III-C9 2022-I8).