From a river valley to a ria: evolution of an incised valley (Ria de Ferrol, north-west Spain) since the Last Glacial Maximum
Cartelle, V.; García-Gil, S. (2019). From a river valley to a ria: evolution of an incised valley (Ria de Ferrol, north-west Spain) since the Last Glacial Maximum. Sedimentology 66(5): 1930-1966. https://dx.doi.org/10.1111/sed.12565
In: Sedimentology. Wiley-Blackwell: Amsterdam. ISSN 0037-0746; e-ISSN 1365-3091, meer
The evolution of incised valleys is an important area of research due to the invaluable data it provides on sea-level variations and depositional environments. In this article the sedimentary evolution of the Ría de Ferrol (north-west Spain) from the Last Glacial Maximum to the present is reconstructed using a multidisciplinary approach, combining seismic and sedimentary facies, and supported by radiocarbon data and geochemical proxies to distinguish the elements of sedimentary architecture within the ria infill. The main objectives are: (i) to analyse the ria environment as a type of incised valley to evaluate the response of the system to the different drivers; (ii) to investigate the major controlling factors; and (iii) to explore the differentiation between rias and estuaries. As a consequence of the sea-level rise subsequent to the Last Glacial Maximum (ca 20 kyr bp), an extensive basin, drained by a braided palaeoriver, evolved into a tide-dominated estuary and finally into a ria environment. Late Pleistocene and Holocene high-frequency sea-level variations were major factors that modulated the type of depositional environments and their evolution. Another major modulating factor was the antecedent morphology of the ria, with a rock-incised narrow channel in the middle of the basin (the Ferrol Strait), which influenced the evolution of the ria as it became flooded during Holocene transgression. The strait acted as a rock-bounded ‘tidal inlet’ enhancing the tidal erosion and deposition at both ends, i.e. with an ebb-tidal delta in the outer sector and tidal sandbanks in the inner sector. The final step in the evolution of the incised valley into the modern-defined ria system was driven by the last relative sea-level rise (after 4 kyr bp) when the river mouths retreated landward and a single palaeoriver was converted into minor rivers and streams with scattered mouths in an extensive coastal area.
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